| 1. |
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| 2. |
- Pawlik, B, et al.
(författare)
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pH-dependent cadmium transport inhibits photosynthesis in the cyanobacterium Synechocystis aquatilis
- 1993
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Ingår i: Environmental and Experimental Botany. - 0098-8472 .- 1873-7307. ; 33:2, s. 331-337
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Tidskriftsartikel (refereegranskat)abstract
- Short-term (5-120 sec) transport of cadmium (Cd-109) into cells of the unicellular cyanobacterium Synechocystis aquatilis was studied using a rapid filtration technique. The transport was strongly pH-dependent, occurring at pH 7, but not at pH 5.5, and was also observed in long-term (40 min) experiments. For this process the optimum pH was approximately 7.5; uptake was considerably reduced at lower pHs. The entrance of cadmium disturbed photosynthetic activity and related processes. At pH 7, cadmium (8.9 muM) decreased CO2 fixation by about 55%, inhibited carbonic anhydrase activity (completely in intact cells, by 65%, in cell-free extracts) and photosynthetic O2-evolution by about 50%. At pH 5.5 no effects were observed.
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| 3. |
- Asplund, Johan, et al.
(författare)
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Soil fertility and charcoal as determinants of growth and allocation of secondary plant metabolites in seedlings of European beech and Norway spruce
- 2016
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 131, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- Climate-change is predicted to drive a migration of European beech (Fagus sylvatica) into the boreal Norway spruce (Picea abies) zone. Still, the mechanisms underpinning beech success on novel soils is little understood. Further, projected increasing summer temperatures will increase risk of fire and subsequent charcoal deposition. Here we investigate how soil type and presence of charcoal affect growth and key plant traits of beech and spruce seedlings.Beech and spruce seedlings were grown in pots with forest soils of beech- or spruce origin to which beech- or spruce derived charcoal was added. Concentrations of phenolic compounds, carbon (C) and nitrogen (N) were analysed separately for root, stem, and leaf tissues.Our spruce forest soil contained more N than the beech forest soil, and both beech- and spruce seedlings grew bigger in spruce forest soil. Beech seedlings also had overall lower tissue concentrations of phenolic compounds when grown in spruce soil. For both species, shoots and roots displayed opposite phenolic responses. The addition of charcoal had no effect on growth, while effects on phenolic compounds were largely idiosyncratic.Our results indicate that beech expansion is not limited by soil factors in the study area, nor is it facilitated by increased levels of charcoal.
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| 4. |
- Dahlberg, C. Johan, et al.
(författare)
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Correlations between plant climate optima across different spatial scales
- 2020
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 170
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Tidskriftsartikel (refereegranskat)abstract
- Identifying the factors determining the abundance and distribution of species is a fundamental question in ecology. One key issue is how similar the factors determining species' distributions across spatial scales are (here we focus especially on spatial extents). If the factors are similar across extents, then the large scale distribution pattern of a species may provide information about its local habitat requirements, and vice versa. We assessed the relationships between landscape and national optima as well as landscape and continental optima for growing degree days, maximum temperature and minimum temperature for 96 bryophytes and 50 vascular plants. For this set of species, we derived landscape optima from abundance weighted temperature data using species inventories in central Sweden and a fine-grained temperature model (50 m), national optima from niche centroid modelling based on GBIF data from Sweden and the same fine-grained climate model, and continental optima using the same method as for the national optima but from GBIF data from Europe and Worldclim temperatures (c. 1000 m). The landscape optima of all species were positively correlated with national as well as continental optima for maximum temperature (r = 0.45 and 0.46, respectively), weakly so for growing degree days (r = 0.30 and r = 0.28), but sometimes absent for minimum temperature (r = 0.26 and r = 0.04). The regression slopes of national or continental optima on local optima did not differ between vascular plants and bryophytes for GDD and Tmax. However, the relationship between the optima of Tmin differed between groups, being positive in vascular plants but absent in bryophytes. Our results suggest that positive correlations between optima at different spatial scales are present for some climatic variables but not for others. Moreover, our results for vascular plants and bryophytes suggest that correlations might differ between organism groups and depend on the ecology of the focal organisms. This implies that it is not possible to routinely up- or downscale distribution patterns based on environmental correlations, since drivers of distribution patterns might differ across spatial extents.
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| 5. |
- Ekelund, Nils, et al.
(författare)
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Changes in chlorophyll a fluorescence in Euglena gracilis and Chlamydomonas reinhardtii after exposure to wood-ash.
- 2007
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 59:1, s. 92-98
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Tidskriftsartikel (refereegranskat)abstract
- Recycling of wood-ash to boreal forests has been suggested to prevent depletion of essential soil nutrient or reduce the negative effects of acidification of surface waters. This study investigated the effects of different concentrations of wood-ash (5, 10 and 12.5 mg l-1 diluted in cultivating medium) on chlorophyll a fluorescence in Euglena gracilis and Chlamydomonas reinhardtii. The green alga C. reinhardtii was more susceptible to wood-ash solutions than the flagellate E. gracilis. Two different forms of wood-ash solutions were tested. In the first solution no adjustment of pH was made. In the second, the pH was adjusted to 7. Wood-ash forms a very strong alkaline reaction if no adjustment of pH is made. The results show that no negative effect on fluorescence yield, electron transport rate (ETR), photochemical quenching (qP) or non-photochemical quenching (NPQ) was observed in E. gracilis. In contrast, C. reinhardtii displayed strong inhibition at concentrations of 10 and 12.5 mg l-1 with non-adjusted pH. The negative effects of high pH on the photosynthetic capacity in C. reinhardtii could either be related to the destruction of the ∆pH across the thylakoid or other parts in the photosynthetic systems that are negatively affected by changing pH. Elevated pH levels in aquatic ecosystems constitute a major environmental stress factor to the phytoplankton community and may lead to loss of diversity among primary producers. If wood-ash application was to become general practice in or near aquatic ecosystems the ash may need to be treated accordingly to avoid rapid changes in pH.
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| 6. |
- Figueiredo, Duarte
(författare)
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OsICE1 transcription factor improves photosynthetic performance and reduces grain losses in rice plants subjected to drought
- 2018
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 150, s. 88-98
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Tidskriftsartikel (refereegranskat)abstract
- Drought is a major environmental threat to agriculture sustainability. We have characterised the role of OsICE1, a basic helix-loop-helix (bHLH) transcription factor from rice (Otyza saliva L.), in response to drought. OsICEI gene is constitutively expressed in roots and shoots of rice seedlings grown under control conditions, as well as in response to low temperature, high salinity, and ABA. Nevertheless, in response to drought, OsICE1 is up-regulated in roots. Plants over-expressing OsICE1 (OsICEI-OX) show improved drought tolerance at both vegetative and reproductive stages, whereas OsICE1 silenced plants (OsICE1-RNA1) show decreased drought tolerance in the same phenological stages. Under drought, OsICE1-0X plants show improved net photosynthetic rates and stomatal conductance to water vapour, as well as higher photochemical efficiency of photosystem II and tolerance to photo-inhibition, as compared to the WT and OsICEI-RNAi. In addition, under severe drought, OsICEI-OX plants show lower grain yield losses than WT, while OsICE1-12NAi plants show the highest grain losses. OsICE1-OX and OSICE1-RNAi plants do not differentially respond to ABA, and drought-inducible genes are more responsive in OsICEI-RNAi and less in OsICE1-OX plants (as compared to WT), suggesting that OsICE1 has a central role modulating molecular responses to drought in an ABA-independent way. This role might be mediated by OsWsi18, a LEA encoding gene up regulated in OsICE1-OX rice plants and known to enhance membrane stability under drought.
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| 7. |
- García, María B., et al.
(författare)
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Rocky habitats as microclimatic refuges for biodiversity. A close-up thermal approach
- 2020
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 170
-
Tidskriftsartikel (refereegranskat)abstract
- In the present scenario of climatic change, climatic refugia will be of paramount importance for species persistence. Topography can generate a considerable climatic heterogeneity over short distances, which is often disregarded in macroclimatic predictive models. Here we investigate the role of rocky habitats as microclimatic refugia by combining two different analyses: exploring a thermal mechanism whereby rocky habitats might serve as refugia, and examining if the biogeographic pattern shows a high abundance of relict, endemic and peripheral species. The thermal profile of two populations of relict and endemic plant species occurring in Pyrenean cliffs was investigated by infrared images and in situ temperature data-loggers. Despite occurring in crevices of a south oriented slope, Androsace cylindrica showed a narrower daily range of temperature than the surrounding matrix, thereby avoiding extreme high temperatures. Borderea chouardii, of tropical ancestors, also occurred in patches where temperatures were buffered during the growth season, experiencing lower mean temperatures than the surrounding matrix and nearby areas during the warmer part of the day, and similar temperatures during the colder. The rocky habitats of both species, therefore, reduced temperature ranges and exposition to extreme climatic events. Compared to other habitats, the rocky ones also harboured a very high fraction of both endemics and peripheral plant populations according to the largest vegetation dataset available in the Pyrenees (18,800 plant inventories and 400,000 records). Our results suggest an association between the habitats of relicts, endemics and species at their distribution limit, driven by a stabilizing effect of rocky habitats on extreme temperatures. Given the important role of rocky habitats as hotspots of singular and unique plants, their characterization seems a sensible first step to identify potential refugia in the context of climate change.
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| 8. |
- Imran, Muhammad, et al.
(författare)
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Exogenous Melatonin mediates the regulation of endogenous nitric oxide in Glycine max L. to reduce effects of drought stress
- 2021
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 188
-
Tidskriftsartikel (refereegranskat)abstract
- Drought stress retards plant growth and yield. Melatonin and nitric oxide (NO) have demonstrated their potential role against abiotic stresses; however, the underlying molecular mechanism by which they interact and extend drought stress tolerance has not been fully elucidated. Herein, the current study was performed to establish the optimum beneficial concentration of MT and NO in combating drought stress and later understand its responses at biochemical, and molecular levels. Results showed exogenous MT, and sodium nitroprusside (SNP as NO donor) have counteracted drought-induced growth inhibition of soybean (Glycine max L.) by increasing plant biomass, photosynthesis efficiency and water content and reducing reactive oxygen species accumulation. MT and NO treatments showed reduced lipid peroxidation and improved defense responses via significantly higher antioxidant enzyme activities than control during drought. Surprisingly, endogenous abscisic acid (ABA) contents and gene expression of its synthesis and ABA-responsive proteins and their promoters were significantly decreased in drought by MT + NO. This was coupled with an increase in endogenous MT levels. In endo-NO regulations, S-nitrosoglutathione was increased, but L-NAME (NO inhibitor) and cPTIO (NO scavenger) decreased the S-nitrosothiol (SNO) contents, which was followed by the increased expression of NO-synthesis-related-genes by MT + NO. Interestingly, MT + NO-induced drought stress tolerance was coupled with increased expression of transcription factors such as GmWRKY27 and GmMYB174. Conclusively, the physiological, antioxidant, and molecular analysis showed that MT triggers downregulated NO accumulation, promoting tolerance against drought stress.
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| 9. |
- Imran, Qari Muhammad, et al.
(författare)
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Transcriptome wide identification and characterization of NO-responsive WRKY transcription factors in Arabidopsis thaliana L.
- 2018
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 148, s. 128-143
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Tidskriftsartikel (refereegranskat)abstract
- WRKY transcription factors are important plant-specific regulatory genes characterized by one or two conserved WRKY domain(s) usually followed by a zinc-finger motif. In this study using Arabidopsis thaliana, the RNA-Seq based transcriptomic analysis showed differential expression of 33 genes encoding WRKY TFs in response to the nitric oxide (NO) donor S-Nitrosocysteine (CySNO). Interestingly, 93.9% of these TFs were up-regulated with at least 2-fold change, suggesting their putative involvement in NO mediated gene regulation. GO- analysis of all the 33 transcriptomic elements showed their putative involvement in biological processes such as abiotic stress tolerance and defense against fungal pathogens (89.39 fold enrichment). Analysis of the NO-responsive AtWRKY TFs promoter region revealed the presence of the cis-acting elements such as ABRE, EIRE, ERE, and MBS involved in osmotic stress response, maximal elicitor-mediated activation, and drought-stress regulation. The analysis of NO-responsive AtWRKY TF motifs and their comparison with rice, soybean, and tomato orthologs suggested that members of the WRKY family belonging to the same group shared similar motifs and phylogenetic tree suggested that these TFs were highly conserved. Validation of transcriptomic data through quantitative real time-PCR showed a high correlation coefficient (0.85) indicating the high reliability and similarity of both types of analysis. Comparison of the NO-responsive and non-responsive WRKYs showed the presence of tyrosine (T) and cysteine (C) residues at a distance of 7 residues from the WRKYGQK motif which may serve as potential targets for modification by NO via tyrosine nitration and S-nitrosylation. We also validated the response of WRKYs through in vivo analysis using atwrky62 loss of function mutant and the results indicated a negative role of AtWRKY62 in plant growth. Furthermore, atwrky62 showed significantly less SNO contents compared to wild type plants indicating putative role of AtWRKY62 in NO metabolism.
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| 10. |
- Jensen, Anna M., et al.
(författare)
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Effects of above- and below-ground competition from shrubs on photosynthesis, transpiration and growth in Quercus robur L. seedlings
- 2011
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 71:3, s. 367-375
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Tidskriftsartikel (refereegranskat)abstract
- For a tree seedling to successfully establish in dense shrubbery, it must maintain function under heterogeneous resource availability. We evaluated leaf-level acclimation in photosynthetic capacity, seedling-level transpiration, and seedling morphology and growth to gain an understanding of the effects of above- and below-ground competition on Quercus robur seedlings. Experimental seedlings were established in a typical southern Swedish shrub community where they received 1 of 4 competition levels (above-ground, below-ground, above- and below-ground, or no competition), and leaf-level responses were examined between two growth flushes. Two years after establishment, first-flush leaves from seedlings receiving above-ground competition showed a maximum rate of photosynthesis (Amax) 40% lower than those of control seedlings. With the development of a second flush above the shrub canopy,Amax of these seedlings increased to levels equivalent to those of seedlings free of light competition. Shrubby competition reduced oak seedling transpiration such that seedlings exposed to above- and below-ground competition showed rates 43% lower than seedlings that were not exposed to competition. The impaired physiological function of oak seedlings growing amid competition ultimately led to a 60–74% reduction in leaf area, 29–36% reduction in basal diameter, and a 38–78% reduction in total biomass accumulation, but root to shoot ratio was not affected. Our findings also indicate that above-ground competition reduced Amax, transpiration and biomass accumulation more so than below-ground competition. Nevertheless, oak seedlings exhibited the ability to develop subsequent growth flushes with leaves that had an Amax acclimated to utilize increased light availability. Our findings highlight the importance of flush-level acclimation under conditions of heterogeneous resource availability, and the capacity of oak seedlings to initiate a positive response to moderate competition in a shrub community.
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| 11. |
- Jensen, Anna M., 1978-, et al.
(författare)
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High-light acclimation in Quercus robur L. seedlings upon over-topping a shaded environment.
- 2012
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 78, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- High developmental plasticity at the seedling-level during acclimation to the light environment may be an important determinant of seedling establishment and growth in temperate broadleaf forests, especially in dense understories where spatial light availability can vary greatly. Pedunculate oak (Quercus robur L.) seedlings were raised beneath a range of artificial light environments (high light, partial high light and low light) to examine morphological and photosynthetic acclimation to vertically stratified light availability. Acclimation observed at the seedling level included changes in proportional distribution of biomass and leaf area ratio to enhance either light gathering under low light availability or reduction of moisture stress under high light availability. Seedling-level acclimation was partially driven by plasticity at the flush level, but plasticity of traits determining flush morphology, such as leaf number, area, and mass, was largely controlled during bud formation rather than during shoot development. Therefore, flush-level acclimation was restricted when shoots elongated from a shaded environment into a high light environment. In contrast, traits influencing leaf-level acclimation, such as leaf thickness, specific leaf area, and pigment concentrations appeared to be driven primarily by the prevailing light environment during leaf development. The plastic response in leaf traits to light environments during shoot development enabled immediate acclimation of photosynthetic capacity to the prevailing light environment. In conclusion, oak seedlings displayed a large phenotypical plasticity on multiple levels that maximized whole seedling performance.
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| 12. |
- Kolzenburg, Regina, et al.
(författare)
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Marginal populations show physiological adaptations and resilience to future climatic changes across a North Atlantic distribution
- 2021
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 188
-
Tidskriftsartikel (refereegranskat)abstract
- Rising levels of anthropogenic carbon dioxide (CO2) in the atmosphere over the past several decades has resulted in a changing climate and is projected to further fuel global climate change in future centuries. Key components of climate change in the ocean are ocean acidification (decreasing pH and carbonate ion concentration [CO32-]) and rising sea surface temperatures. While several studies have investigated the effect of these climatic changes on a single population, very few studies have addressed effects on populations living at the margins of their species distribution and the full distributional range. This gap in knowledge impedes the determination of detailed predictions for most species’ futures. Over the course of four months, we investigated physiological changes (primary production, respiration, calcification and growth rates) of 6 populations of the intertidal ecosystem engineer and articulated coralline alga Corallina officinalis to future climatic conditions (low pH (∌7.8); T+3 °C; as well as the combination of low pH and T+3 °C). The populations (n = 2 per geographical location) represent the northern (Iceland) and southern (Spain) margins, as well as the centre (England) of the species distribution in the NE Atlantic. Here, we show that southern and central populations are already living closer to their thermal and stress limits, while Northern populations appear to be the most resilient to environmental changes. We present data confirming light calcification to be the most valuable physiological process which is prioritized in populations throughout the geographical gradient in the NE Atlantic. We found elevated temperature to have a greater effect on populations than pCO2. Investigating and monitoring organism physiology and structure under these extreme environmental conditions provides important information to predict their acclimatisation and resilience to future environmental conditions and potential changes in their distribution.
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| 13. |
- Kumar, S. Anil, et al.
(författare)
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Beyond just being foot soldiers : osmotin like protein ( OLP ) and chitinase ( Chi11 ) genes act as sentinels to confront salt, drought, and fungal stress tolerance in tomato
- 2016
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 132, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- Osmotin like protein (OLP) and chitinase (Chi11) belong to pathogenesis-related (PR) class of proteins and are induced during both biotic and abiotic stresses. Transgenic tomato was developed with OLP and Chi11 via in vitro and in planta transformation methods. Transgenes integration and transcript levels were confirmed by multiplex PCR, DNA blot, and multiplex reverse transcriptase PCR. Homozygous T2 transgenics when evaluated for salt, drought, and fungal stresses showed enhanced tolerance compared to untransformed controls (UC). Transgenics showed enhanced endochitinase activity and root biomass under normal conditions. Transformants also displayed higher proline content, K+, relative water content, chlorophyll fluorescence, total biomass, vascular conductivity, and fruit yield than the UC under stress conditions. Co-immunoprecipitation revealed that Chi11 co-expresses with phosphofructokinase2 (PFK2), which may play a role in enhanced root biomass. qPCR analysis resulted in higher transcript levels of OLP, Chi11, and PFK2 in transgenics as compared to the untransformed controls. Our findings suggest the use of multiples genes to confer multiple stress tolerance for enhanced crop productivity. This work unveils a new molecular player PFK2, which may play a role in enhanced root biomass.
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| 14. |
- Malnoë, Alizée
(författare)
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Photoinhibition or photoprotection of photosynthesis? : update on the (newly termed) sustained quenching component qH
- 2018
-
Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 154, s. 123-133
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Forskningsöversikt (refereegranskat)abstract
- Non-photochemical quenching (NPQ) of chlorophyll fluorescence is a valuable feature for the study of photosynthetic organisms’ light utilization and dissipation. However, all too often NPQ is simply equated with the harmless dissipation of excess absorbed light energy as heat. This is not always the case as some processes cause NPQ without thermal dissipation. Photoinhibitory quenching, qI, is sustained NPQ that continuously depresses the commonly used fluorescence parameter “quantum yield of photosystem II (PSII)”, or Fv/Fm, and is often viewed as a result of PSII core inactivation due to D1 damage. Inactivated PSII cores might have a photoprotective role but that is not the topic of the present review. Instead, this review focuses on a sustained photoprotective antenna quenching component, which we have termed qH, and summarizes the recently uncovered molecular players of this sustained form of NPQ.
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| 15. |
- Mellerowicz, Ewa
(författare)
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Pectinous cell wall thickenings formation-A response of moss protonemata cells to lead
- 2009
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 65, s. 119-131
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Forskningsöversikt (refereegranskat)abstract
- The findings substantiate previous hypotheses that lead ions can be sequestered in cell walls and point to the possibility that capacity for lead binding might increase in cell response to lead. (C) 2008 Elsevier B.V. All rights reserved.
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| 16. |
- Moritz, Kim, et al.
(författare)
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Roe deer prefer mixed-sex willow stands over monosexual stands but do not discriminate between male and female plants
- 2018
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Ingår i: Environmental and Experimental Botany. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0098-8472 .- 1873-7307. ; 146, s. 62-67
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Tidskriftsartikel (refereegranskat)abstract
- Male and female plants of dioecious species often experience differential herbivory, possibly due to differences in defences such as secondary metabolite composition or nutritional quality. These plant sex effects on herbivory have been extensively studied for plant individuals, but not for stands/populations. For mobile herbivores, such as deer, stands may be a more relevant scale to study than individual plants. We predicted that male Salts viminalis plants should be subject to more extensive roe deer (Capreolus capreolus) browsing than female plants due to weaker defence in male plants. Furthermore, we expected that mixed-sex stands should experience more damage than monosexual stands due to positive effects of diet mixing on browsing by generalists. We tested for differences in roe deer browsing in plots that were either monosexual male or female, or a mix of male and female plants in a replicated field experiment. Roe deer browsing was estimated after one growth season with heavy herbivory. We also measured plant secondary metabolite concentrations and nitrogen content in leaves from all experimental clones to test the assumption that the sexes differed in defence or nutrients. Mixed-sex plots were more extensively browsed than monosexual plots. However, there was no difference in browsing between male and female plant individuals within mixed-sex plots or between monosexual plots. Plant secondary metabolite profiles differed between male and female plants, while nitrogen content did not. Our findings suggest that the diversified plant secondary metabolite contents of mixed-sex plots may have led to more extensive herbivory. Higher browsing of plant sex mixes may impact both natural and commercial S. viminalis stands with different sex ratios.
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| 17. |
- Nabi, Rizwana Begum Syed, et al.
(författare)
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Nitric oxide regulates plant responses to drought, salinity, and heavy metal stress
- 2019
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Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 161, s. 120-133
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Tidskriftsartikel (refereegranskat)abstract
- Plants are exposed to diverse abiotic stresses like drought, heat, salinity, and high-metal concentrations at different stages of their life cycle. As protection against stress, plants release signaling molecules that initiate a cascade of stress-adaptation responses leading either to programmed cell death or plant acclimation. Nitric oxide (NO) is a small but important redox signaling molecule that in plants is involved in a diverse range of physiological processes including germination, development, flowering, senescence, and abiotic stress. Although the exact role of NO in plants remains unclear and is species dependent, various studies have suggested a positive correlation between NO accumulations in stress in plants. In this article, we review and discuss the biosynthesis of NO, sources and exogenous application of NO donors under drought, salt, and heavy metal stress. A review of publications indicated that, in general, application of exogenous NO alleviates the negative stress effects in plants and improves antioxidant activity in most plant species. In addition, S-nitrosylation and tyrosine nitration are two NO-mediated posttranslational modification. All these factors are important in protecting plants from diverse stresses and vary with the species. Furthermore, to determine precise mechanisms of action of NO is expected to help in efficient utilization of crop cultivation under stress conditions.
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| 18. |
- Nunes, P., et al.
(författare)
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The leaf of Agapanthus africanus (L.) Hoffm. : A physical-chemical perspective of terrestrialization in the cuticle
- 2023
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- Although Agapanthus africanus (L.) Hoffm. is one of the most popular ornamental species in both hemispheres, it has an extremely restricted wild occurrence (Cape province, South Africa). This contradiction between gener-alized ornamental application and natural distribution was the basis for the analytical approach adopted in the present work. We hypothesized that characteristic features of the cuticular waxes were adopted by this species to help it cope with severe dehydration associated with marine salinity on account of the short distance of the wild populations to the sea. A comprehensive morpho-anatomical, histological and physical-chemical analysis was performed on the epicuticular and intracuticular layers of the adaxial and abaxial surfaces of leaves of specimens of A. africanus. The adaxial epicuticular surface is hydrophilic and the abaxial epicuticular surface exhibits globally hydrophobic behavior. The main chemical compounds detected in the wax layers of both surfaces of the leaf are the short-chain monocaprylin monoglyceride (C8), and very long-chain 1-hexacosanol (C26) and 1-octa-cosanol (C28) alcohols. While monocaprylin is particularly abundant in the intracuticular layers, the epicuticular adaxial surface revealed the highest concentration of both alcohols. We demonstrate that the smart combination of these two classes of molecules with opposite water affinity endows the A. africanus leaf cuticle with a unique water management system combining the efficient entrapment of water in the disordered alpha-gel phase formed by monocaprylin and the high resistance to water transport provided by ordered domains composed of tightly packed, all-trans alkyl chains of the above pair of alcohols. The remarkable structural similarity existing between the monocaprylin alpha-gel and the mucilage of algae is an evidence of the terrestrialization process.
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| 19. |
- Nyquist, Johanna, et al.
(författare)
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Response of two wetland plant species to Cd exposure at low and neutral pH
- 2009
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 65:2-3, s. 417-424
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Tidskriftsartikel (refereegranskat)abstract
- Emerged and submerged plants are used in treating various metal-containing wastewaters, such as stormwater (neutral pH) and acid mine drainage (low pH). The aim was to investigate the appearance of a set of possible mechanisms to detoxify Cd in plants and whether their appearance differ due to the surrounding pH and/or plant type. One emergent (Carex rostrata) and one submerged (Elodea canadensis) macrophyte were exposed to 0, 0.05, and 0.5 μM Cd for 3 d in hydroponic solutions at pH 3.5 and 6.9. We analysed cadmium accumulation, thiol-rich peptide concentrations and cell wall-bound Cd in plants, organic acid content and pH change in surrounding water cation exchange capacity (CEC) of plant tissue. Both plant species accumulated Cd in their tissues, and thus did not exclude it and C. rostrata decreased the relative Cd distribution to its shoots with increasing Cd addition. In both species, Cd was immobilized through cell wall binding, and thiol-rich peptides synthesized in the presence of Cd that may participate in Cd binding. In addition, E. canadensis increased its CEC by synthesizing new metal-binding sites in the cell walls. Organic acid composition in surrounding water did not change with Cd addition and had no effect on Cd detoxification. However, E. canadensis increased the surrounding pH from pH 3.5 in the presence of Cd; the surrounding pH did not, however, influence the detoxification mechanisms.
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| 20. |
- Nyquist, Johanna, et al.
(författare)
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Uptake of Zn, Cu, and Cd in metal loaded Elodea canadensis
- 2007
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Ingår i: Environmental and Experimental Botany. - 0098-8472 .- 1873-7307. ; 60:2, s. 219-226
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Tidskriftsartikel (refereegranskat)abstract
- Since uptake of metals in submerged plants can have a positive effect on the total remediation efficiency in a wetland it is important to investigate factors that possibly can have an effect on uptake of metals. In this short term study we investigated whether the tissue concentration of Zn, Cu and Cd influenced further uptake by metals in Elodea canadensis. Stress effects in response to metal exposure were also investigated. Plants were first loaded with metals for 48 h followed by a metal exposure period of 72 h. Metals in plant tissue and stress effects on plants were analysed both prior to, and after exposure. The results showed that tissue concentration of Zn and Cu did not have effect on further uptake, however for Cd it did have an effect. During Cd exposure accumulated Cd started to leak out of the plants where a decreased leakage could be seen with increased exposure concentration of Cd. The degree of metals binding to the cell wall could explain the influence of tissue concentration on uptake. These results are relevant to the phytoremediation technology area, where it is of great importance to achieve knowledge of commonly used plant species in treatment wetlands to optimise treatment of polluted areas.
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| 21. |
- Poborilova, Zuzana, et al.
(författare)
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DNA hypomethylation concomitant with the overproduction of ROS induced by naphthoquinone juglone on tobacco BY-2 suspension cells
- 2015
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 113, s. 28-39
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Tidskriftsartikel (refereegranskat)abstract
- Juglone, 5-hydroxy-1,4-naphthoquinone, is a naturally occurring plant secondary metabolite with allelopathic and cytotoxic properties. The cytotoxic effect of juglone and changes at the level of DNA methylation were investigated on a plant cell model, tobacco BY-2 cell suspension culture. We found that juglone in a concentration-dependent manner inhibits cell growth and causes creation of reactive oxygen species (ROS) that were visible mainly in nucleus, nucleolus, cytoplasm, and plasma membrane. Analysis of the changes in DNA methylation level using Luminometric Methylation Assay showed that juglone at the concentrations of 60 and 80 mu m causes hypomethylation of DNA. Decrease in DNA methylation was confirmed by the more sensitive technique, confocal immunofluorescence microscopy, already at 30 mu m, and was accompanied by significant overproduction of hydrogen peroxide, hydroxyl radicals, and superoxide anion radicals. The highest percentage of the signs of programed cell death, especially apoptic-like bodies that indicate DNA fragmentation was observed at 30 mu m of juglone. On the basis of results we suggest that overproduction of ROS is the main mechanism that causes hypomethylation of DNA, which may contribute to the initiation of the programmed cell death.
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| 22. |
- Ramesh, Vetukuri
(författare)
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Overexpression of an autophagy-related gene DiATG3 from Davidia involucrata improves plant thermotolerance by enhancing the accumulation of polyamines and regulating genes in calcium and MAPK signaling pathways
- 2023
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 208
-
Tidskriftsartikel (refereegranskat)abstract
- Autophagy, a conserved eukaryotic mechanism for degrading intracellular constituents, plays prominent roles in plant abiotic stress tolerance. This study aimed to isolate an autophagy-related gene DiATG3 from a cool-adapted endangered plant species, dove tree (Davidia involucrata Baill.), and to investigate the physiological functions and regulatory mechanisms of DiATG3 for improving heat tolerance. DiATG3 was found to mainly localize to cytoplasm and possess the N-terminal domain, the catalytic domain with the HPC motif, and the C-terminal domain with the FLKF motif. Elevated transcript level of DiATG3 was detected in D. involucrata treated with heat stress. The constitutive overexpression of DiATG3 in Arabidopsis led to elevated levels of autophagy and conferred tolerance under heat stress. Furthermore, this thermotolerant phenotype was associated with improved photo-synthetic capacity, higher antioxidant enzyme activities, and increased accumulation of polyamines. Tran-scriptome analysis suggest that activated calcium signaling and mitogen-activated protein kinase (MAPK) cascade may act as a central hub necessary for DiATG3-mediated heat tolerance. In addition, DiATG3 over -expression resulted in up-regulated expression of stress-related genes including heat shock factor A3 (AtHSFA3), dehydration-responsive element-binding protein 2C (AtDREB2C), AtWRKY26, and AtWRKY33 after heat treatment. Our study could yield insights into the engagement of plant autophagy during abiotic stress responses and contribute to breeding and engineering thermotolerant endangered plant species.
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| 23. |
- Sjulgård, Hanna, et al.
(författare)
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Reversible and irreversible root phenotypic plasticity under fluctuating soil physical conditions
- 2021
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 188
-
Tidskriftsartikel (refereegranskat)abstract
- Roots grow in a highly heterogeneous physical environment due to the spatial complexity of soil structure. Thereby, the root growth zone repeatedly experiences soil physical stress such as hypoxia or increased penetration resistance. To mimic the highly variable physical environment surrounding the root growth zone, we subjected pea and wheat seedlings to periodic soil physical stress. One day of soil hypoxia or increased penetration resistance reduced root elongation rate of both species by at least 20 %. Upon stress release, root elongation rate of pea could recover within one day, while no such recovery occurred in wheat. Similarly, the diameter of the root elongation zone in pea increased by 15 % and 20 % due to hypoxia and increased penetration resistance, respectively, but decreased again once the stresses were released. In contrast, the diameter of the elongation zone of wheat roots started to decrease with the onset of soil physical stress and this trend continued upon stress release. Hence, root responses to short-term soil physical stress were reversible in pea and irreversible in wheat, indicating reversible and irreversible root phenotypic plasticity, respectively. This suggests that strategies to cope with periodic soil physical stress may vary among species. The differentiation between reversible and irreversible phenotypic plasticity is crucial to advance our understanding on soil exploration, resource acquisition, whole plant growth, and ultimately crop yield formation on structured soil.
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| 24. |
- Skorzynska-Polit, E, et al.
(författare)
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Calcium modifies Cd effect on runner bean plants
- 1998
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Ingår i: Environmental and Experimental Botany. - 0098-8472 .- 1873-7307. ; 40:3, s. 275-286
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Tidskriftsartikel (refereegranskat)abstract
- The effect of different Ca concentrations in the growth medium on the toxicity of 25 mu M CdSO4 was studied in runner bean plants (var. Piekny Jas) at two different growth stages of primary leaves. In young plants growing in a medium with low level of Ca a treatment with Cd for 12 days resulted in Ca accumulation in roots, a strong reduction of the leaf area, a decreased monogalactosyl diacylglycerol/digalactosyl diacylglycerol ratio and efficiency of the photosynthetic apparatus. In leaves of older plants growing under the same conditions, and surviving Cd treatment, a high accumulation of Ca but a low one of Cd, chlorosis of leaves, a decrease of the ratio monogalactosyl diacylglycerol/digalactosyl diacylglycerol and photosynthetic activity were shown. At a high level of Ca in the nutrient medium plant roots showed a remarkably high specificity to accumulate Cd but the toxic effect of the metal on plant growth parameters and content of pigments was decreased. No changes were observed in the level of galactolipids, but changes in fluorescence quenching were recorded. Calcium deficit enhanced the effect of Cd toxicity, including primary photochemistry, whereas excess Ca reduced toxic effects, while it is increasing the nonphotochemical quenching of excitation energy. (C) 1998 Elsevier Science B.V. All rights reserved.
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| 25. |
- Srivastava, Akanksha, et al.
(författare)
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Regulatory role of LexA in modulating photosynthetic redox poise and cadmium stress tolerance in the cyanobacterium, Anabaena sp. PCC7120
- 2022
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 195
-
Tidskriftsartikel (refereegranskat)abstract
- Strategies developed by organisms to overcome disruption in redox poise of photosynthetic electron transport chain (pETC) are important for its survival under abiotic stress. The process needs to be tightly regulated for optimal functioning. While the redox poising processes are well known in cyanobacteria, understanding of their regulatory network is lacking. Since LexA is one of the known global regulators of stress response in the cyanobacterium Anabaena sp. PCC7120, its role in pETC redox poising was investigated using cadmium (Cd) as an abiotic stressor to disrupt photosynthesis. Assessment of the photosynthetic responses of recombinant Anabaena strains, AnlexA+ (LexA-overexpressing) and AnpAM (vector control), under unstressed and Cd-stressed conditions using transmission electron microscopy (TEM) and chlorophyll a fluorescence, indicated that some pETC redox poising responses, including PSII photodamage, energy dissipation, PSI photoprotection, and NDHmediated cyclic electron flow were decreased in AnlexA+ under unstressed conditions. Disturbance in pETC redox poise during Cd stress observed in Anabaena was accentuated upon overexpression of LexA. The decreased photodamage of PSII and increased photoinhibition of PSI in AnlexA+ in the presence or absence of Cd stress, correlated well with the changes in pETC complexes observed in blue native (BN)-PAGE and the regulation of over 70 of the 90 pETC component genes by LexA demonstrated through transcript, electromobility shift assay (EMSA), and bioinformatics studies. In a nutshell, LexA has been identified as one of the regulators involved in the streamlining of pETC redox poising responses under normal growth and during abiotic stress through transcriptional regulation of some of the redox-controlled pETC component genes.
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| 26. |
- Sun, Yujie, et al.
(författare)
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A comparative analysis of cytosolic Na+ changes under salinity between halophyte quinoa (Chenopodium quinoa) and glycophyte pea (Piswn sativwn)
- 2017
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 141, s. 154-160
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Tidskriftsartikel (refereegranskat)abstract
- Sodium (Na+) uptake into the halophyte quinoa (Chenopodium quinoa Willd.) plants was compared with the uptake into pea (Pisum sativum L.), and related to changes in cytosolic pH and potassium (K+) concentration in plant tissues. The total uptake of Na+ and K+ in roots and shoots was analyzed and compared with net ion fluxes at the root xylem parenchyma, determined by ion-specific microelectrodes in a non-invasive way. The cytosolic changes of Na+ concentration, [Na-cyt(+)], and pH, pH(cyt), were measured by fluorescent probes, specific to Na+ and H+, using a dual-wavelength fluorescence microscopy. These changes were monitored in protoplasts after cultivation with or without 100 mM NaCl, and after addition of NaC1 to the protoplasts. Roots and shoots of quinoa controls contained much higher K+ levels than pea roots and shoots, and the K+ levels increased even more after salinity treatments in quinoa. The cytosolic uptake of Na+ in quinoa protoplasts was transient if less than 200 mM NaCl was added, while in pea the Na+ concentration increased even upon addition of 50 mM Na+ and gradually increased with time. Saline conditions during cultivation increased pH(cyt) of both species. However, with a direct addition of NaCl to control protoplasts only a small increase was seen in pea pH(cyt) while in quinoa this increase was much larger. The different reactions of pH(cyt) to salinity when NaCl was added to salinity-treated seedlings may reflect an increased proton pump activity in quinoa, while this activation is lacking in pea. ABA addition to the root xylem parenchyma cells induced a net efflux of K+ and acidification of the xylem. On the other hand, 20 mM NaC1 addition induced a net flux of protons in both species, and a net K+ flux in pea, but not in quinoa, probably since such a low concentration is not a stress for quinoa. It is suggested that salinity tolerance in quinoa is achieved by a faster removal of Na+ from the cytosol and a high K+ concentration in roots and shoots under salinity, resulting in a high K+/Na+ ratio, and that this mechanism is driven by a higher proton pump activity, compared with glycophytic pea species.
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| 27. |
- Waldmann, Patrik
(författare)
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Plant adaptation to metal polluted environments—Physiological, morphological, and evolutionary insights from Biscutella laevigata
- 2016
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 127, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Polluted soils promote rapid plant adaptation to high concentrations of trace metal elements. Biscutella laevigata is a little investigated pseudometallophyte that appears promising to study these evolutionary processes and advance understanding beyond existing model species, but its metal tolerance is insufficiently understood. We determined the zinc tolerance level and various plant responses to environmentally relevant zinc concentrations in ten metallicolous and non-metallicolous B. laevigata populations from southern Poland. In a two-phase hydroponic experiment, we scored multiple morphological and physiological traits (e.g. biomass, visible stress symptoms, element content in foliage) and assessed phenotypic variability within plant families. The structure of these quantitative traits was compared to that of neutral molecular markers to test, whether natural selection caused population differentiation in zinc tolerance. While zinc tolerance was species-wide (i.e. enhanced in all genotypes compared to a zinc sensitive reference species), we found congruent trends toward higher tolerance in metallicolous compared to non-metallicolous plants. The most indicative parameters for these differences were dry shoot biomass, dry root biomass, and particularly effective photosystem II yield. We found that enhanced zinc tolerance in metallicolous populations is driven by divergent selection in response to metal contamination. In addition, analyses of genotype x environment interaction indicated that this differentiation is heritable. These findings promote diploid accessions of B. laevigata as zinc tolerant but non-hyperaccumulating organisms to study plant adaptation to contaminated environments. Remarkably, tolerance differences between edaphic types emerged already at an environmentally relevant zinc concentration of 150 mu M. This opens an unusual perspective on plant adaptation that should be tested in other non-hyperaccumulating species. (C) 2016 Elsevier B.V. All rights reserved.
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| 28. |
- Weih, Martin
(författare)
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Synthesis and future research directions linking tree diversity to growth, survival, and damage in a global network of tree diversity experiments
- 2018
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 152, s. 68-89
-
Tidskriftsartikel (refereegranskat)abstract
- Despite considerable research demonstrating that biodiversity increases productivity in forests and regulates herbivory and pathogen damage, there remain gaps in our understanding of the shape, magnitude, and generality of these biodiversity-ecosystem functioning (BEF) relationships. Here, we review findings from TreeDivNet, a global network of 25 tree diversity experiments, on relationships between levels of biodiversity and (a) tree growth and survival and (b) damage to trees from pests and pathogens. Tree diversity often improved the survival and above- and belowground growth of young trees. The mechanistic bases of the diversity effects on tree growth and survival include both selection effects (i.e., an increasing impact of particular species in more species-rich communities) and complementary effects (e.g. related to resource differentiation and facilitation). Plant traits and abiotic stressors may mediate these relationships. Studies of the responses of invertebrate and vertebrate herbivory and pathogen damage have demonstrated that trees in more diverse experimental plots may experience more, less, or similar damage compared to conspecific trees in less diverse plots. Documented mechanisms producing these patterns include changes in concentration, frequency, and apparency of hosts; herbivore and pathogen diet breadth; the spatial scale of interactions; and herbivore and pathogen regulation by natural enemies. Our review of findings from TreeDivNet indicates that tree diversity experiments are extending BEF research across systems and scales, complementing previous BEF work in grasslands by providing opportunities to use remote sensing and spectral approaches to study BEF dynamics, integrate belowground and aboveground approaches, and trace the consequences of tree physiology for ecosystem functioning. This extension of BEF research into tree-dominated systems is improving ecologists' capacity to understand the mechanistic bases behind BEF relationships. Tree diversity experiments also present opportunities for novel research. Since experimental tree diversity plantations enable measurements at tree, neighbourhood and plot level, they allow for explicit consideration of temporal and spatial scales in BEF dynamics. Presently, most TreeDivNet experiments have run for less than ten years. Given the longevity of trees, exciting results on BEF relationships are expected in the future.
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| 29. |
- Xia, Shaopan, et al.
(författare)
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Silicon accumulation controls carbon cycle in wetlands through modifying nutrients stoichiometry and lignin synthesis of Phragmites australis
- 2020
-
Ingår i: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 175, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- Silicon (Si) is one of the most abundant elements in the Earth’s crust but its role in governing the biogeochemicalcycling of other elements remains poor understood. There is a paucity of information on the role of Si in wetlandplants, and how this may alter wetland C production and storage. Therefore, this study investigated Si distribution,nutrient stoichiometry and lignin abundance in Phragmites australis from a wetland system in China tobetter understand the biogeochemical cycling and C storage. Our data show that Si content (ranging between0.202% to 6.614%) of Phragmites australis is negatively correlated with C concentration (38.150%–47.220%).Furthermore, Si content was negatively antagonistically related to the concentration of lignin-derived phenols inthe stem (66.763–120.670 mg g-1 C) and sheath (65.400–114.118 mg g-1 C), but only a weak relationship wasobserved in the leaf tissue (36.439–55.905 mg g-1 C), which is relevant to the photosynthesis or stabilizationfunction of the plant tissues. These results support the notion that biogenic Si (BSi) can substitute lignin as astructural component, due to their similar eco-physiological functions, reduces costs associated with ligninbiosynthesis. The accumulation of BSi increased total biomass C storage and nutrient accumulation due togreater productivity of Phragmites australis. On the other hand, BSi regulated litter composition and quality (e.g.,nutrient stoichiometry and lignin) that provide a possibility for the factors affecting litter decomposition. Thuscompeting processes (i.e., biomass quantity vs quality) can be influenced by Si cycling in wetlands.
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| 30. |
- Yong, Jean W.H
(författare)
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Glutamate over-accumulation may serve as an endogenous indicator of tricarboxylic acid (TCA) cycle suppression under NH4+ nutrition in wheat (Triticum aestivum L.) seedlings
- 2020
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472 .- 1873-7307. ; 177
-
Tidskriftsartikel (refereegranskat)abstract
- Soil excess ammonium (NH4+) has serious negative effects on crop growth and yield formation. Most studies of NH4+ stress have addressed only the effects of free NH4+, failing to recognize changes in nitrogen (N) assimilation products. Hydroponic experiments were conducted using 5 mM NH4+ or nitrate (NO3-) forms of N in two wheat cultivars that differed in NH4+ tolerance (NH4+-sensitive AK58 and NH4+-tolerant XM25). To evaluate the effects of NH4+ assimilation products on plant growth, 1 mu M L-methionine sulfoximine (MSO, an inhibitor of glutamine synthetase) and 1 mM glutamate (a primary N assimilation product) were added to the N source solutions. NH4+ treatments significantly reduced plant biomass in both cultivars, but to a greater extent in AK58. These inhibition effects were alleviated by MSO and strengthened by the application of glutamate. The free NH4+ concentration was increased under NH4+ conditions and was enhanced by the application of MSO. Amino acids levels were significantly greater in both cultivars; however, XM25 showed a lower glutamate concentration and a lower ratio of (glutamate + glutamine) to (aspartic acid + asparagine) than AK58. Under NH4+ conditions, levels of tricarboxylic acid (TCA) cycle intermediates and adenosine triphosphate were decreased due to inhibited pyruvate kinase activity; this inhibition was enhanced by the application of glutamate, but relieved by MSO. These results show that, aside from the large amounts of free NH4+ in wheat tissues, as a primary N assimilation product, the over-accumulated glutamate is also involved in interrupting TCA cycle metabolism under NH4+ stress, leading to reduced plant growth.
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| 31. |
- Falkengren-Grerup, Ursula, et al.
(författare)
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Uptake capacity of amino acids by ten grasses and forbs in relation to soil acidity and nitrogen availability
- 2000
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Ingår i: Environmental and Experimental Botany. - 0098-8472. ; 44:3, s. 207-219
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Tidskriftsartikel (refereegranskat)abstract
- Uptake capacity of organic nitrogen was studied in solution experiments on eight grasses and two forbs growing in acid soils with relatively high nitrogen mineralisation in southern Sweden. Uptake of a mixture of amino acids (alanine, glutamine, glycine), that varied between 1.6 and 6.3 mu mol g(-1) dw root h(-1), could not be explained by soil data from the species' field distributions (pH, total carbon and nitrogen, potential net mineralisation of ammonium and nitrate). The ratio between organic and inorganic nitrogen (methylamine) uptake was < 0.05 for the forbs, higher for the grasses with a maximum of 1.42 for Deschampsia flexuosa. The ratio was negatively correlated with measures related to soil acidity (Ellenberg's R-value, soil nitrate and total carbon) but not, as hypothesised, with the total amount of mineralised nitrogen. The total demand on nitrogen by all components of the ecosystem would probably have described the extent to which competition among and between plants and microbes induced nitrogen limitation. In a methodological study two grasses were exposed to pH 3.8, 4.5 and 6.0 and to 50, 100 and 250 mol l(-1) of three amino acids. Uptake was also compared between intact plants and excised roots. The treatment response varied considerably between the species which stresses the importance of studying intact plants at field-relevant pH and concentrations. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 32. |
- Musil, Charles F, et al.
(författare)
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How substantial are ultraviolet-B supplementation inaccuracies in experimental square-wave delivery systems?
- 2002
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Ingår i: Environmental and Experimental Botany. - 0098-8472. ; 47:1, s. 25-38
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Tidskriftsartikel (refereegranskat)abstract
- Square-wave (SQW) ultraviolet-B (UV-B: 280–315 nm) radiation supplementation systems continue to be used in outdoor experimental locations due to the economically restrictive installation and maintenance costs, and technical expertise required to effectively operate more advanced modulated (MOD) delivery systems. However, continued yet contentious criticisms of SQW delivery systems risk creating prejudices as to the validity of plant responses measured in these with potentially negative repercussions on future UV-B experimentation. Consequently, we quantified the magnitude of UV-B supplementation inaccuracies in our typical outdoor step-wise SQW delivery system using 7-year records of computer-modeled and instrument-measured solar UV-B irradiances and synchronous measurements of total solar (300–3000 nm) radiation and daily sunshine duration. Both broad- and narrow-band instrument measurements confirmed that our step-wise SQW delivery system rendered larger total daily supplemental UV-B exposures (time-integrated UV-B irradiances) than a MOD delivery system on only substantially overcast days (25% or less daily sunshine duration). These larger supplemental UV-B exposures were augmented with increased magnitude of the added artificial UV-B supplement. However, their ranges did not exceed those in a MOD delivery system by more than 10% for added UV-B supplements of realistic magnitude (30% or less above background), except on virtually completely overcast days (5% or less daily sunshine duration). Also, our step-wise SQW delivery system rendered higher photon flux ratios of UV-B/total solar radiation than a MOD delivery system on only substantially overcast days, the ranges of which were also augmented with increased magnitude of the added artificial UV-B supplement. However, these features were restricted to high solar angles, since with reduced solar angle these higher photon flux ratios also included progressively less overcast days. Nevertheless, ranges of photon flux ratio increases were well below reported thresholds inhibiting to plant growth at all solar angles for the added artificial UV-B supplements of realistic magnitude, except on virtually completely overcast days. Results point to an under-estimation of clear-sky UV-B irradiance by the computer-encoded semi-empirical model commonly utilized to predict background and supplemental UV-B irradiances for SQW delivery systems. They confirm the superiority of MOD delivery systems in providing more realistic conditions of UV-B increases but likewise demonstrate little justification on balance for branding results derived from all field-based SQW delivery systems as exaggerated where sensible irradiation protocols and realistic UV-B supplements are applied. This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription.
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| 33. |
- Bouksila, Fethi, et al.
(författare)
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Assessment of soil salinization risks under irrigation with brackish water in semiarid Tunisia
- 2013
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 92, s. 176-185
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Tidskriftsartikel (refereegranskat)abstract
- The salinity problem is becoming increasingly widespread in arid countries. In semiarid Tunisia about 50% of the irrigated land is considered as highly sensitive to salinization. To avoid the risk of salinization, it is important to control the soil salinity and keep it below plant salinity tolerance thresholds. The objective of the present study was to provide farmers and rural development offices with a tool and methodology for predicting, monitoring of soil salinity for a better agronomical strategy. The experiments were carried out in the highly complex and heterogeneous semiarid Kalâat Landalous irrigated district of Tunisia. The field and laboratory measurements of soil and water properties were conducted in 1989 and 2006 at different observation scales (2900 ha, 1400 ha, 5200 m long transect, and soil profiles). Seventeen years of reclamation of a saline and waterlogged soil led to the reduction of average electrical conductivity of the soil saturated paste extract (ECe), measured at 5 soil depths (from 0 to 2 m) below the plant salt tolerance threshold and the dilution of groundwater salinity from 18.3 to 6.6 dS m−1. The variation in soil salt storage (ΔMss = Mss2006 − Mss1989) in the vadose zone was negative, equal to about −145 × 103 ton (≈−50 ton ha−1). During the same period, the salt balance (Siw–Sdw) estimated from the input dissolved salt brought by irrigation water (Siw) and output salts exported by the drainage network (Sdw) was equal to −685 × 106 kg and the Sdw was 945 × 106 kg. Under irrigation and efficient drainage, the soil salinization could be considered as a reversible process. At the transect scale, the high clay content and the exchangeable sodium percentage was negatively correlated to saturated hydraulic conductivity. The textural stratification, observed at soil profile scale, favors accumulation of salt in the soil. Based on the findings related to the multiscale assessment of soil salinity and groundwater properties, soil salinization factors were identified and a soil salinization risk map (SRU) was elaborated. The shallow groundwater constitutes the main risk of soil salinization. This map can be used by both land planners and farmers to make appropriate decisions related to crop production, and soil and water management.
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| 34. |
- Danielsson, Helena, et al.
(författare)
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An ozone response relationship for four Phleum pratense genotypes based on modelling of the phytotoxic ozone dose (POD)
- 2013
-
Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 90, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- In the last decade extensive research has focused on the development of dose–response relationships based on stomatal plant ozone uptake (phytotoxic ozone dose, POD). So far most work has concentrated on crops and forest trees. This study provides a flux-based dose–response function for timothy (Phleum pratense), a widespread grassland species, which can be used in risk assessment for ground-level ozone. In 1996 and 2001 timothy was exposed in open-top chambers to ozone concentrations ranging from around 10 nmol mol−1 in the charcoal filtered treatments up to 60 nmol mol−1 in the fumigated treatments (08:00–20:00) in. In 1996 there was a negative effect of ozone on biomass production in the non-filtered treatment while in 2001 no such ozone effect in the non-filtered treatment could be seen. Measurements of stomatal conductance on four timothy genotypes in 2001 were used to calibrate a Jarvis-type multiplicative stomatal conductance model. The maximum conductance varied between the genotypes, from 477 to 589 mmol O3 m−2 s−1 (projected leaf area). The model includes functions describing the reduction of stomatal conductance of senescing leaves and the direct effects on stomatal conductance by light, temperature and water vapour pressure deficit. A function describing ozone induced senescence of the leaves was included since exposure to ozone is known to cause premature senescence. The function for ozone was applied when it suggested ozone to be more limiting to stomatal conductance than phenology. To avoid overestimation of stomatal conductance in days with high VPD, a function reflecting the effect on leaf water potential on stomatal conductance was included. Comparison between modelled and measured conductance for the four timothy genotypes resulted in an r2 value at 0.57 and a very small average deviation of observed from modelled values. The calibrated stomatal conductance model was used to estimate the accumulated POD, i.e. the accumulated stomatal flux of ozone, of the plants in the 1996 and 2001 experiments. The strongest relationship between ozone relative effects on biomass was obtained when POD was accumulated from 105 degree days after emergence to 1000 degree days after emergence, and integrated using an uptake rate threshold of 7 nmol m−2 s−1 (POD7). The response relationship between biomass and POD7 resulted in an r2 value of 0.71 over all four genotypes. This r2 value was somewhat higher than for the corresponding relationship based on the accumulated ozone exposure over 40 nmol mol−1 (AOT40; r2 = 0.66). With an uptake rate threshold at 7 nmol m−2 s−1, ozone concentrations above ∼20 nmol mol−1, contribute to reduce the biomass production of timothy if meteorological conditions promote maximum stomatal conductance.
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| 35. |
- Pleijel, Håkan, 1958, et al.
(författare)
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Differential ozone sensitivity in an old and a modem Swedish wheat cultivar - grain yield and quality, leaf chlorophyll and stomatal conductance
- 2006
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 56:1, s. 63-71
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Tidskriftsartikel (refereegranskat)abstract
- Field-grown crops of one modem ('Dragon') and one 100-year old ('Lantvete') wheat (Triticum aestivum L.) cultivar were exposed to charcoal-filtered air (CF) or non-filtered air plus additional ozone (NF+) in open-top chambers (n = 6). Ambient air plots (11 = 3) were used to monitor the effects of the chamber enclosure. Quantitative (ear weight, harvest index and 1000-grain weight), as well as qualitative (grain concentration of N. P. K, Ca, Mg, Cd), aspects of crop yield were studied. In addition, the chlorophyll content of the top leaf was followed during the 10-week-long ozone exposure and flag leaf stomatal conductance was monitored. Ear weight was negatively affected by ozone. The effect was smaller in the lower yielding 'Lantvete' compared to the modem cultivar 'Dragon'. A similar ozone effect was found for the harvest index and 1000-grain weight. The difference between cultivars was small for 1000-grain weight, with harvest index significantly lower in 'Lantvete' compared with 'Dragon'. The crude protein concentration of the grain was higher in 'Lantvete', and was enhanced by ozone exposure. No significant treatment or cultivar effects were observed on grain Ca and Cd concentrations, but the greatest chamber effect was on Cd, which was considerably higher in grain from treatment chambers compared with ambient air (possibly due to the higher rate of transpiration in the plants enclosed in the chambers). There were strong differences with respect to grain P, K and Mg concentration between cultivars; 'Lantvete' exhibiting higher concentrations than 'Dragon' in all cases, apart from K. Weak, but significant, increases in grain P, K and Mg concentrations were evident in O-3-treated plants. The chlorophyll concentration of the flag leaf was negatively affected by ozone exposure after approximately I month, but chlorophyll content declined faster in 'Dragon' than 'Lantvete'. Flag leaf chlorophyll concentration was significantly lower in 'Lantvete' compared with 'Dragon' before onset of ozone effects in NF+ and during most of the experiment in CF. Stomatal conductance was also significantly lower in 'Lantvete' than in 'Dragon'. The most important conclusion drawn from the present study is that the 'older' cultivar, 'Lantvete', was less affected by ozone than the modem, bred cultivar, 'Dragon'. This observation might to a large extent be explained by the higher stomatal conductance exhibited by the modern wheat cultivar. The result is consistent with earlier investigations for Greek wheat cultivars, and suggests that the findings reported by others, based on vegetative growth, may extend to grain yield. Growth dilution effects (i.e. the lower observed concentration of an element at higher biomass yield) may explain observed differences between cultivars, and between ozone treatments, in the level of various elements, except for potassium. (c) 2005 Elsevier B.V. All rights reserved.
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| 36. |
- Podgórska, Anna, et al.
(författare)
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Respiratory burst oxidases and apoplastic peroxidases facilitate ammonium syndrome development in Arabidopsis
- 2021
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- Ammonium-nitrogen (NH4+) nutrition is linked to metabolic over-reduction for plants. The characteristic symptom of sole NH4+ nutrition is growth suppression, signifying this condition as the ammonium syndrome. In the present study, we investigated the mechanism of perception of high NH4+ conditions in Arabidopsis thaliana plants by examining apoplastic reactive oxygen species (ROS) metabolism. Major enzyme activity and a special pattern of expression of NADPH-dependent respiratory burst oxidases (RBOH) was found in Arabidopsis individuals cultured under NH4+ as the sole nitrogen source. This oxidative burst is independent of RBOHD/F expression and does not activate typical intracellular signalling pathways. In addition, elevated superoxide dismutase and apoplastic secretory peroxidase activities contributed to hydrogen peroxide (H2O2) accumulation in plants exposed to NH4+ nutrition. Consequently, higher H2O2 contents were determined in the extracellular space and were localised cytochemically. H2O2 is a substrate for cell wall cross-linking peroxidases, which showed enhanced activity in the presence of NH4+. Increase of cell wall polymerisation, could in turn inhibit cell elongation and slow down growth, as observed under NH4+ toxicity.
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| 37. |
- Simin, Tihomir, et al.
(författare)
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Volatile organic compound emission in tundra shrubs : Dependence on species characteristics and the near-surface environment
- 2021
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Ingår i: Environmental and Experimental Botany. - : Elsevier BV. - 0098-8472. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- Temperature is one of the key abiotic factors during the life of plants, especially in the Arctic region which is currently experiencing rapid climate change. We evaluated plant traits and environmental variables determining leaf temperature in tundra shrubs and volatile organic compound (VOC) emissions with field measurements on deciduous tundra shrubs, Salix myrsinites and Betula nana, and evergreen Cassiope tetragona and Rhododendron lapponicum. Higher leaf-to-air temperature difference was observed in evergreen, compared to deciduous shrubs. Evergreen shrubs also showed continuously increasing photosynthesis with increasing temperature, suggesting high thermal tolerance. For the deciduous species, the optimum temperature for net photosynthesis was between our measurement temperatures of 24 °C and 38 °C. Air temperature and vapor pressure deficit were the most important variables influencing leaf temperature and VOC emissions in all the studied plants, along with stomatal density and specific leaf area in the deciduous shrubs. Using climate data and emission factors from our measurements, we modelled total seasonal tundra shrub VOC emissions of 0.3–2.3 g m−2 over the main growing season. Our results showed higher-than-expected temperature optima for photosynthesis and VOC emission and demonstrated the relative importance of plant traits and local environments in determining leaf temperature and VOC emissions in a subarctic tundra.
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| 38. |
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