| 1. |
- Aguetoni Cambui, Camila, et al.
(författare)
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Patterns of Plant Biomass Partitioning Depend on Nitrogen Source
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) availability is a strong determinant of plant biomass partitioning, but the role of different N sources in this process is unknown. Plants inhabiting low productivity ecosystems typically partition a large share of total biomass to belowground structures. In these systems, organic N may often dominate plant available N. With increasing productivity, plant biomass partitioning shifts to aboveground structures, along with a shift in available N to inorganic forms of N. We tested the hypothesis that the form of N taken up by plants is an important determinant of plant biomass partitioning by cultivating Arabidopsis thaliana on different N source mixtures. Plants grown on different N mixtures were similar in size, but those supplied with organic N displayed a significantly greater root fraction. (15)N labelling suggested that, in this case, a larger share of absorbed organic N was retained in roots and split-root experiments suggested this may depend on a direct incorporation of absorbed amino acid N into roots. These results suggest the form of N acquired affects plant biomass partitioning and adds new information on the interaction between N and biomass partitioning in plants.
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| 2. |
- Franklin, Oskar, et al.
(författare)
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The carbon bonus of organic nitrogen enhances nitrogen use efficiency of plants
- 2017
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 40, s. 25-35
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Tidskriftsartikel (refereegranskat)abstract
- The importance of organic nitrogen (N) for plant nutrition and productivity is increasingly being recognized. Here we show that it is not only the availability in the soil that matters, but also the effects on plant growth. The chemical form of N taken up, whether inorganic (such as nitrate) or organic (such as amino acids), may significantly influence plant shoot and root growth, and nitrogen use efficiency (NUE). We analysed these effects by synthesizing results from multiple laboratory experiments on small seedlings (Arabidopsis, poplar, pine and spruce) based on a tractable plant growth model. A key point is that the carbon cost of assimilating organic N into proteins is lower than that of inorganic N, mainly because of its carbon content. This carbon bonus makes it more beneficial for plants to take up organic than inorganic N, even when its availability to the roots is much lower - up to 70% lower for Arabidopsis seedlings. At equal growth rate, root:shoot ratio was up to three times higher and nitrogen productivity up to 20% higher for organic than inorganic N, which both are factors that may contribute to higher NUE in crop production.
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| 3. |
- Gruffman, Linda, et al.
(författare)
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Cultivation of Norway spruce and Scots pine on organic nitrogen improves seedling morphology and field performance
- 2012
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 276, s. 118-124
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen availability exerts a significant control on biomass allocation of plants including Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris (L)) in boreal forest ecosystems. Recent studies suggest, however, this control differs for inorganic and organic nitrogen sources. The importance of the chemical form of nitrogen (inorganic or organic) for the morphology and growth of conifer seedlings was studied during production of seedlings in a forest nursery and subsequently in a field trial in northern Sweden. Seedlings were supplied with two different nutrient solutions; an inorganic conventional fertilizer and an organic, amino acid-based fertilizer. Seedlings cultivated on the organic nitrogen source displayed larger root systems resulting in a higher root: shoot ratio than did seedlings cultivated on the inorganic nitrogen source. The proportion of fine roots to lateral roots and the root tip proportion colonized by mycorrhiza were positively affected by the organic nitrogen source. Norway spruce seedlings cultivated on organic nitrogen displayed significantly increased shoot growth compared to seedlings cultivated on inorganic nitrogen. Our results suggest that the chemical form of nitrogen influences the allocation of biomass in conifer seedlings. The shift in allocation of resources to root biomass further leads to a competitive advantage in field conditions, resulting in a significant increase in shoot growth one year following transplant. (C) 2012 Elsevier B.V. All rights reserved.
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| 4. |
- Gruffman, Linda
(författare)
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Nitrogen nutrition and biomass distribution in conifers : aspects of organic and inorganic nitrogen acquisition
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objectives of the work presented in this thesis were to increase our understanding of how different chemical forms of nitrogen (N) affect the growth and biomass distribution of conifer seedlings and hence their establishment and performance in field. Growth studies of Scots pine (Pinus sylvestris (L.)), Norway spruce (Picea abies (L.) Karst.) and the model plant Arabidopsis (Arabidopsis thaliana, ecotype Col-0) showed that plants can grow at similar (or higher) rates on organic N sources to those on the inorganic N sources ammonium (NH4+) and nitrate (NO3-). Cultivation on arginine also improved the field performance of Norway spruce seedlings by increasing their current-year shoot growth, despite smaller initial shoot length. Moreover, plants supplied with organic N distributed a relatively larger proportion of their biomass to root structures than controls with similar total biomass and N contents grown on inorganic N sources. Detailed studies on Arabidopsis revealed that an increase in the root:shoot ratio coincided with high retention of organic N in the roots, implying that the site of assimilation may be of importance for the short-term distribution of biomass. Further, studies on Scots pine seedlings deprived of carbohydrates suggested that the uptake, reduction and assimilation of NO3- are highly dependent on recent photoassimilates and that use of organic N may have considerable energetic benefits for plants, especially under conditions that limit carbohydrate supplies. The results from the studies underlying this thesis highlight the potential role of organic N in the nutrition of conifer seedlings, the links between seedling nutrition, morphology and field performance, and effects of organic N on biomass distribution. They suggest that organic N may serve as an alternative or complement to inorganic N sources in seedling production, and may help attempts to improve seedling establishment in the field.
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| 5. |
- Gruffman, Linda, et al.
(författare)
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Plant nitrogen status and co-occurrence of organic and inorganic nitrogen sources influence root uptake by Scots pine seedlings
- 2014
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 34, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Insights into how the simultaneous presence of organic and inorganic nitrogen (N) forms influences root absorption will help elucidate the relative importance of these N forms for plant nutrition in the field as well as for nursery cultivation of seedlings. Uptake of the individual N forms arginine, ammonium (NH4+) and nitrate (NO3-) was studied in Scots pine (Pinus sylvestris (L.)) seedlings supplied as single N sources and additionally in mixtures of NO3- and NH4+ or NO3- and arginine. Scots pine seedlings displayed a strong preference for NH4+-N and arginine-N as compared with NO3--N. Thus, NO3- uptake was generally low and decreased in the presence of NH4+ in the high-concentration range (500 mu M N), but not in the presence of arginine. Moreover, uptake of NO3- and NH4+ was lower in seedlings displaying a high internal N status as a result of high N pre-treatment, while arginine uptake was high in seedlings with a high internal N status when previously exposed to organic N. These findings may have practical implications for commercial cultivation of conifers.
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| 6. |
- Hedwall, Per-Ola, et al.
(författare)
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Interplay between N-form and N-dose influences ecosystem effects of N addition to boreal forest
- 2018
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 423, s. 385-395
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) addition effects on boreal forest ecosystem are influenced by an interplay between N-form and N-dose. We hypothesize that trees take up organic N more efficiently than inorganic N and that unwanted side-effects of organic N are smaller. We predicted that 1) the tree growth response to arginine (ARG) addition is larger than to ammonium-nitrate (AN) and, 2) understory vegetation and ectomycorrhizal (EcM) changes following ARG addition are smaller than following AN addition.We investigated the effects of AN and ARG addition (50 and 150 kg N ha(-1)) during five years on tree growth, understory vegetation and EcM fungi in a Pinus sylvestris L. forest (c 50 years old) in northern Sweden.N addition increased tree growth and changed understory vegetation composition with few significant differences between AN and ARG. Differences in responses mainly occurred for the bryophyte Pleurozium schreberi which decreased more from ARG, and for EcM sporocarps, which sharply declined from AN, but not from ARG.We found very few differences in responses between AN and ARG addition with the exception of EcM and bryophytes. These species groups have several key functions in boreal forests and the differences in responses merits further investigations.
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| 7. |
- Lim, Hyungwoo, et al.
(författare)
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Organic nitrogen enhances nitrogen nutrition and early growth of Pinus sylvestris seedlings
- 2021
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 42, s. 513-522
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Tidskriftsartikel (refereegranskat)abstract
- Boreal trees are capable of taking up organic nitrogen (N) as effectively as inorganic N. Depending on the abundance of soil N forms, plants may adjust physiological and morphological traits to optimize N uptake. However, the link between these traits and N uptake in response to soil N sources is poorly understood. We examined Pinus sylvestris L. seedlings' biomass growth and allocation, transpiration and N uptake in response to additions of organic N (the amino acid arginine) or inorganic N (ammonium nitrate). We also monitored in situ soil N fluxes in the pots following an addition of N, using a microdialysis system. Supplying organic N resulted in a stable soil N flux, whereas the inorganic N resulted in a sharp increase of nitrate flux followed by a rapid decline, demonstrating a fluctuating N supply and a risk for loss of nitrate from the growth medium. Seedlings supplied with organic N achieved a greater biomass with a higher N content, thus reaching a higher N recovery compared with those supplied inorganic N. In spite of a higher N concentration in organic N seedlings, root-to-shoot ratio and transpiration per unit leaf area were similar to those of inorganic N seedlings. We conclude that enhanced seedlings' nutrition and growth under the organic N source may be attributed to a stable supply of N, owing to a strong retention rate in the soil medium.
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| 8. |
- Oyewole, Olusegun Ayodeji, et al.
(författare)
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Soil diffusive fluxes constitute the bottleneck to tree nitrogen nutrition in a Scots pine forest
- 2016
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 399, s. 109-120
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Tidskriftsartikel (refereegranskat)abstract
- In nutrient poor environments, plant nitrogen (N) acquisition is governed by soil diffusive fluxes and root uptake capacities. However, the relationship between these two processes is not well understood. We explored a way of comparing the processes, enabling identification of the limiting factor for tree N acquisition.The study comprised N-fertilized and N-limited Scots pine stands, and measurements of uptake capacities of detached tree roots and of induced soil diffusive fluxes (through in-situ microdialysis) done at the onset and the end of the growing season.Soil N fluxes were higher at the onset than at the end of the growing season and amino acids comprised a larger fraction of N than inorganic N. N fertilization reduced root uptake capacities of NH4 (+), glycine and NO3 (-) but not of arginine. For all N compounds except NO3 (-), diffusive fluxes were significantly lower than root N uptake capacities.Our results suggest that soil N supply in both, N-fertilized and N-limited forest stands, is dominated by amino acids, thus being the major component of plant-available N. Uptake of N appears more constrained by the diffusive fluxes of N compounds rather than root uptake capacity, except for NO3 (-).
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| 9. |
- Palmroth, Sari, et al.
(författare)
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Organic nitrogen uptake of Scots pine seedlings is independent of current carbohydrate supply
- 2013
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 33, s. 590-600
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Tidskriftsartikel (refereegranskat)abstract
- In boreal forests, seedling establishment is limited by various factors including soil nitrogen (N) availability. Seedlings may absorb N from soil in a variety of inorganic and organic forms; however, the energy and thus carbohydrate requirements for uptake and assimilation of N vary with N source. We studied the importance of current photoassimilates for the acquisition and allocation of different N sources by Scots pine (Pinus sylvestris (L.)) seedlings. Girdling was used as a tool to impair phloem transport of photoassimilates, and hence gradually deprive roots of carbohydrates. Seedlings were cultivated in a greenhouse on equimolar N concentrations of one of the N sources-arginine, ammonium or nitrate-and then girdled prior to a pulse-chase uptake experiment with isotopically labeled N sources. Girdling proved to be efficient in decreasing levels of soluble sugars and starch in the roots. Uptake rate of arginine N was highest, intermediate for ammonium N and lowest for nitrate N. Moreover, the uptake of arginine N was unaffected by girdling, while the uptake of the two inorganic N sources decreased to 45-56% of the ungirdled controls. In arginine-treated seedlings, 95-96% of the acquired arginine N resided in the roots, whereas a significant shift in the N distribution toward the shoot was evident in girdled seedlings treated with inorganic N. This spatial shift was especially pronounced in nitrate-treated seedlings suggesting that the reduction and following incorporation into roots was limited by the availability of current photoassimilates. These results suggest that there are energetic benefits for seedlings to utilize organic N sources, particularly under circumstances where carbohydrate supply is limited. Hence, these putative benefits might be of importance for the survival and growth of seedlings when carbohydrate reserves are depleted in early growing season, or in light-limited environments, such as those sustained by continuous cover forestry systems.
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