| 91. |
- Torres Jimenez, Maria Fernanda, et al.
(författare)
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Functional and historical drivers of leaf shape evolution in Palms (Arecaceae)
- 2023
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Ingår i: Global Ecology and Biogeography. - 1466-822X. ; 32:9, s. 1495-1507
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Tidskriftsartikel (refereegranskat)abstract
- Aim Leaves display a remarkable variety of shapes, each with potential ecological advantages in specific climates. While the relations between leaf shape and either climate or height have been relatively well studied in eudicots, the macroecological drivers of shape remain poorly known in monocots. Here, we investigated the associations between climate and plant height with the evolution of leaf shape in a clade with high species and morphological diversity.Location Global.Time period Cretaceous to contemporary.Major taxa studied Palms (Arecaceae).Methods We apply a Bayesian phylogenetic mixed model to test for associations between climate and leaf shape (all - entire-leaved, pinnate-dissected, palmate-dissected and costapalmate). We further reconstruct the ancestral leaf shape using multistate speciation and extinction models and compare the frequency of shapes with global temperatures through time.Results We find that plant height associates with dissected leaves and that annual precipitation associates with pinnate shapes. The ancestral leaf shape is unclear, but early diversification was dominated by pinnate-dissected palms, which has remained the most species-rich form of leaves throughout palm history.Main Conclusions Palms that are tall and live in humid regions are more likely to have pinnate leaves. Through geological time scales, temperature did not play an obvious role in determining leaf shapes. This study contributes to our understanding of how the diversity of leaf shapes is linked to biological and climatic factors.
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| 92. |
- Uddling, Johan, 1972, et al.
(författare)
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Biomass reduction of juvenile birch is more strongly related to stomatal uptake of ozone than to indices based on external exposure
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:28, s. 4709-4719
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Tidskriftsartikel (refereegranskat)abstract
- In order to test the hypothesis that ozone-induced limitation of biomass production in juvenile silver birch (Betula pendula Roth) is driven by stomatal uptake of ozone (O-3) rather than external exposure, biomass reduction was related to the cumulative uptake of O-3 through stomata over an uptake cut-off threshold of x nmol O-3 m(-2) s(-1) (CUO > x), to the accumulated exposure to O-3 over a threshold of y nmol mol(-1) during daylight hours (daylight AOTy) or during 24 h (24 h AOTy), and to the sum of daytime concentrations exceeding 60 nmol mol(-1) (SUM06). The analysis included data from nine different experiments conducted in Sweden, Finland and Switzerland. Stomatal uptake of O-3 was estimated using a stomatal conductance (g,) model including g, response functions for photosynthetic photon flux density, water vapour pressure deficit of the air and air temperature. Experiment-specific maximum g(s) (g(max)) as well as g(s) in darkness (g(dark)) were assessed through local measurements. Biomass reduction Was more strongly related to CUO > x than to SUM06 and daylight or 24 h AOTy, but the difference between CUO > x and 24 h AOTy was small. The better performance of CUO > x was dependent on the use of site- and experiment-specific g(max) and g(dark) values, and there was a positive relationship between g(max) and biomass reduction per unit AOT40. Daylight AOTy and SUM06 could not account for the growth limiting impact of nocturnal O-3 uptake in the Swiss experiments. A sensitivity analysis revealed that the CUO > x estimates were largely insensitive to the estimate of the conductance for non-stomatal leaf surface deposition of O-3, as a result of turbulent conditions at the experimental plots. In summary, we conclude that CUO > x was more successful in accounting for the variation in biomass reduction in juvenile birch as compared to indices based on external exposure, if g(max) and g(dark) were locally parameterised. (C) 2004 Elsevier Ltd. All rights reserved.
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| 93. |
- Uddling, Johan, 1972, et al.
(författare)
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Changes in stomatal conductance and net photosynthesis during phenological development in spring wheat: implications for gas exchange modelling
- 2006
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Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 51:1, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- Gas exchange was measured from 1 month before the onset of anthesis until the end of grain filling in field-grown spring wheat, Triticum aestivum L., cv. Vinjett, in southern Sweden. Two g (s) models were parameterised using these data: one Jarvis-type multiplicative g (s) model (J-model), and one combined stomatal-photosynthesis model (L-model). In addition, the multiplicative g (s) model parameterisation for wheat used within the European Monitoring and Evaluation Programme (EMEP-model) was tested and evaluated. The J-model performed well (R-2=0.77), with no systematic pattern of the residuals plotted against the driving variables. The L-model explained a larger proportion of the variation in g (s) data when observations of A (n) were used as input data (R-2=0.71) compared to when A (n) was modelled (R-2=0.53). In both cases there was a systematic model failure, with g (s) being over- and underestimated before and after anthesis, respectively. This pattern was caused by the non-parallel changes in g (s) and A (n) during plant phenological development, with A (n) both peaking and starting to decline earlier as compared to g (s) . The EMEP-model accounted for 41% of the variation in g (s) data, with g (s) being underestimated after anthesis. We conclude that, under the climatic conditions prevailing in southern Scandinavia, the performance of the combined stomatal-photosynthesis approach is hampered by the non-parallel changes in g (s) and A (n), and that the phenology function of the EMEP-model, having a sharp local maximum at anthesis, should be replaced by a function with a broad non-limiting period after anthesis.
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| 94. |
- Uddling, Johan, 1972, et al.
(författare)
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Crop quality under rising atmospheric CO2
- 2018
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Ingår i: Current Opinion in Plant Biology. - : Elsevier BV. - 1369-5266. ; 45, s. 262-267
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Forskningsöversikt (refereegranskat)abstract
- © 2018 Elsevier Ltd Crops grown under elevated CO2 (eCO2) typically exhibit enhanced yields but at the same time decreased nutritional quality. The latter effect has often been explained as a growth dilution phenomenon, but this cannot be the only process involved since crop nutrient concentrations are decreased also when production is unaffected by eCO2. We review the current knowledge on eCO2 effects on crop nutritional quality with focus on the current understanding of the possible mechanisms and processes causing these effects. Emphasis is on crop nitrogen (N) and protein concentrations but effects on other nutrients and how they compare with those on N are also covered.
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| 95. |
- Uddling, Johan, 1972, et al.
(författare)
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Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings
- 2007
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Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 91:3, s. 37-46
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Tidskriftsartikel (refereegranskat)abstract
- Relationships between chlorophyll concentration ([chl]) and SPAD values were determined for birch, wheat, and potato. For all three species, the relationships were non-linear with an increasing slope with increasing SPAD. The relationships for birch and wheat were strong (r(2) similar to 0.9), while the potato relationship was comparatively weak (r(2) similar to 0.5). Birch and wheat had very similar relationships when the chlorophyll concentration was expressed per unit leaf area, but diverged when it was expressed per unit fresh weight. Furthermore, wheat showed similar SPAD-[chl] relationships for two different cultivars and during two different growing seasons. The curvilinear shape of the SPAD-[chl] relationships agreed well with the simulated effects of non-uniform chlorophyll distribution across the leaf surface and multiple scattering, causing deviations from linearity in the high and low SPAD range, respectively. The effect of non-uniformly distributed chlorophyll is likely to be more important in explaining the non-linearity in the empirical relationships, since the effect of scattering was predicted to be comparatively weak. The simulations were based on the algorithm for the calculation of SPAD-502 output values. We suggest that SPAD calibration curves should generally be parameterised as non-linear equations, and we hope that the relationships between [chl] and SPAD and the simulations of the present study can facilitate the interpretation of chlorophyll meter calibrations in relation to optical properties of leaves in future studies.
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| 96. |
- Uddling, Johan, 1972, et al.
(författare)
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Interacting effects of elevated CO2 and weather variability on photosynthesis of mature boreal Norway spruce agree with biochemical model predictions
- 2012
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 32:12, s. 1509-1521
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Tidskriftsartikel (refereegranskat)abstract
- According to well-known biochemical and biophysical mechanisms, the stimulation of C3 photosynthesis by elevated atmospheric CO2 concentration ([CO2]) is strongly modified by changes in temperature and radiation. In order to investigate if a static parameterisation of the commonly used Farquhar et al. model of photosynthesis (i.e. without CO2-induced seasonal or thermal acclimation of photosynthetic capacity) can accurately predict these interactions in mature boreal Norway spruce (Picea abies (L.) Karst.) during the frost-free part of the growing season, shoot gas exchange was continuously measured on trees during their second/third year of exposure to ambient or doubled [CO2] inside whole-tree chambers. The relative CO2-induced enhancement of net photosynthesis (An) at a given temperature remained stable over the study period, but increased strongly with temperature and radiation, in agreement with predictions by the model. Light-saturated An (+67% at 20 C), dark respiration (+36%) and intercellular to ambient [CO2] ratio (ci/ca; +27%) were significantly increased by CO2 treatment. Stomatal conductance (gs) was not significantly affected. Our results demonstrate that the Farquhar et al. model of photosynthesis has the capability to predict interactions between [CO2] and seasonal weather variability on An in Norway spruce during the non-frost growing season without accounting for CO2-induced seasonal and/or thermal photosynthetic acclimation. However, stomatal model assumptions of reduced gs and constant ci/ca under rising atmospheric [CO2] did not hold.
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| 97. |
- Uddling, Johan, 1972, et al.
(författare)
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Leaf and canopy conductance in aspen and aspen-birch forests under free-air enrichment of carbon dioxide and ozone
- 2009
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 29:11, s. 1367-1380
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Tidskriftsartikel (refereegranskat)abstract
- Increasing concentrations of atmospheric carbon dioxide (CO2) and tropospheric ozone (O-3) have the potential to affect tree physiology and structure, and hence forest feedbacks on climate. Here, we investigated how elevated concentrations of CO2 (+ 45%) and O-3 (+ 35%), alone and in combination, affected conductance for mass transfer at the leaf and canopy levels in pure aspen (Populus tremuloides Michx.) and in mixed aspen and birch (Betula papyrifera Marsh.) forests in the free-air CO2-O-3 enrichment experiment near Rhinelander, Wisconsin (Aspen FACE). The study was conducted during two growing seasons, when steady-state leaf area index (L) had been reached after > 6 years of exposure to CO2- and O-3-enrichment treatments. Canopy conductance (g(c)) was estimated from stand sap flux, while leaf-level conductance of sun leaves in the upper canopy was derived by three different and independent methods: sap flux and L in combination with vertical canopy modelling, leaf C-13 discrimination methodology in combination with photosynthesis modelling and leaf-level gas exchange. Regardless of the method used, the mean values of leaf-level conductance were higher in trees growing under elevated CO2 and/or O-3 than in trees growing in control plots, causing a CO2 x O-3 interaction that was statistically significant (P <= 0.10) for sap flux-and (for birch) C-13-derived leaf conductance. Canopy conductance was significantly increased by elevated CO2 but not significantly affected by elevated O-3. Investigation of a short-term gap in CO2 enrichment demonstrated a + 10% effect of transient exposure of elevated CO2-grown trees to ambient CO2 on g(c). All treatment effects were similar in pure aspen and mixed aspen-birch communities. These results demonstrate that short-term primary stomatal closure responses to elevated CO2 and O-3 were completely offset by long-term cumulative effects of these trace gases on tree and stand structure in determining canopy- and leaf-level conductance in pure aspen and mixed aspen-birch forests. Our results, together with the findings from other long-term FACE experiments with trees, suggest that model assumptions of large reductions in stomatal conductance under rising atmospheric CO2 are very uncertain for forests.
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| 98. |
- Uddling, Johan, 1972, et al.
(författare)
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Measuring and modelling leaf diffusive conductance in juvenile silver birch, Betula pendula
- 2004
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Ingår i: Trees-Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890. ; 18:6, s. 686-695
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Tidskriftsartikel (refereegranskat)abstract
- Leaf diffusive conductance for water (g(l)) and twig xylem pressure (psi(xt)) was measured in juvenile silver birch, Betula pendula, under field conditions in southern Sweden. Data from one site were used to parameterise two different multiplicative models for g(l) (dependent data), and measurements from another site were used to validate these models (independent data). In addition, experiments were performed in controlled environments to validate the g(l) response functions used in the models. The driving variables in the D-model were photosynthetic photon flux density, air temperature and water vapour pressure deficit of the air (D-a), while the DH-model also included the accumulated hours after sunrise each day with D-a above a certain threshold (H). Both models satisfactorily predicted the variation in g(l) in dependent as well as in independent data, and the g(l) response functions used were supported by the experiments in controlled environments. The DH-model was more successful in predicting g(l) than the D-model by accounting for the observation that g(l) was lower at higher H under similar weather conditions. There was a considerable variation in maximum g(l) during the season, as well as between the two sites. On relatively warm and dry days psi(xt) rapidly declined during the morning and then stabilized around a constant value until the late afternoon, with the stomatal regulation effectively preventing psi(xt) from decreasing below this value. We suggest that these models could be used to simulate the g(l) in juvenile birch if maximum g(l) is locally estimated and if the response functions are not extrapolated beyond the climate range for this study.
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| 99. |
- Uddling, Johan, 1972, et al.
(författare)
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Measuring and modelling stomatal conductance and photosynthesis in mature birch in Sweden
- 2005
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923. ; 132:1-2, s. 115-131
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Tidskriftsartikel (refereegranskat)abstract
- Stomatal conductance (g(s)), net photosynthesis (A(n)) and twig water potential (Psi(t)) were measured in mature silver birch (Betula pendula) during 3 years in southern Sweden. Measurements from 2 years were used to parameterise three different gs models and measurements from a 3rd year were used to validate these models. Two different multiplicative stomatal models were used. In one of these, the gs response function for the water vapour pressure deficit (D) was fixed, while in the other the g, sensitivity to D increased with the accumulated time after sunrise with D above a certain threshold value. Furthermore, one combined stomatal-photosynthesis model (L-model) was used. The L-model was run either by using observations of photosynthesis as input data, or by predicting g(s) and photosynthesis simultaneously from environmental data. The model used to predict photosynthesis was parameterised from measurements of the photosynthetic responses to the photosynthetically active radiation, CO2 and temperature. The stomatal response functions of the L-model were parameterised using observations of photosynthesis as input data in order to make them independent of the performance of the photosynthesis model. The difference in model performance between the two multiplicative models was relatively small. The multiplicative stomatal models and the L-model were similarly successful in predicting g(s) when the L-model was driven by observations of photosynthesis. However, the L-model was considerably less successful when photosynthesis was predicted. Photosynthesis was systematically under- and overestimated at high and low Psi(t), respectively, causing errors in the prediction of g(s). In most situations, measurements of photosynthesis are not available and g(s) must be predicted from environmental data. In such cases, we conclude that the two multiplicative models are more successful in predicting gs in mature silver birch than the combined stomatal-photosynthesis model. (c) 2005 Elsevier B.V. All rights reserved.
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| 100. |
- Uddling, Johan, 1972, et al.
(författare)
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Ozone impairs autumnal resorption of nitrogen from birch (Betula pendula) leaves, causing an increase in whole-tree nitrogen loss through litter fall
- 2006
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Ingår i: Tree Physiology. - 0829-318X. ; 26:1, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- Saplings of one half-sib family of birch, Betula pendula Roth, were exposed to three ozone concentrations (non-filtered air (NF); non-filtered air + 10-20 nmol O-3 mol(-1) (NF+); non-filtered air + 40-60 nmol O-3 mol(-1) (NF++)) in open-top chambers during two growing seasons from 1997 to 1998. Shed leaves were collected regularly during both growing seasons and, in 1998, the dry mass (DM) and nitrogen (N) concentrations ([N]) of the shed leaves were measured to quantify the total amount of N lost through litter fall. Dry mass and [N] were also determined in mid-August for attached, mature and non-senescent leaves, in order to estimate autumnal leaf N resorption efficiency and proportional leaf DM decrease. Net photosynthetic capacity was measured during August and September 1998, in a population of leaves that emerged in mid-July. Photosynthesis declined with increasing leaf age in the NF++ treatment, whereas it remained high throughout the measurement period in the NF and NF+ treatments. In both years, leaves abscised prematurely in the NF++ treatment, whereas this effect was only significant in 1998 in the NF+ treatment. There was a strong linear relationship between proportional leaf shedding and daylight ozone exposure above a threshold of 40 nmol mol(-1) (daylight AOT40) during the growing season. The resorption of N was significantly impaired by ozone, and the smaller autumnal decrease in leaf DM in elevated ozone concentrations suggested that the bulk resorption of leaf DM was also inhibited. Nitrogen resorption efficiencies were 81. 73 and 63% and leaf mass decreases were 45, 36 and 30% in the NF, NF+ and NF++ treatments, respectively. Compared with the NF treatment, total N loss through litter fall was increased by 16 and 122% in the NF+ and NF++ treatments, respectively. We conclude that ozone impaired N resorption from birch leaves before abscission, causing a substantial increase in whole-tree N loss through litter fall.
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