Drought tolerance and acclimation in Pinus ponderosa seedlings: the influence of nitrogen form

Abstract Drought is a limiting factor to forest regeneration and restoration, which is likely to increase in intensity and duration under future climates. Nitrogen (N) nutrition is related to drought-resistance mechanisms in trees. However, the influence of chemical N form (inorganic and organic N) on physiological traits related to drought resistance has been sparsely studied in conifer seedlings. We investigated the effect of N forms on morpho-physiological traits of Pinus ponderosa Dougl. ex Laws. seedlings and subsequent influences in drought tolerance and acclimation. One-year-old seedlings were fertilized during 10 weeks at 9 mM N with different N forms [either NH4+, NO3− or organic N (amino acids mixture)] in their second year of growth. After fertilization, we measured traits associated with intrinsic drought tolerance (shoot water relations, osmotic regulation, photosynthesis and cell membrane stability). Seedlings were then subjected to an 8-week drought period at varying drought intensities to evaluate plant acclimation mechanisms. We demonstrated that P. ponderosa seedlings could efficiently use amino acids as a primary N source, showing similar performance to those grown with inorganic N forms. Nitrogen form influenced mainly drought-acclimation mechanisms rather than intrinsic drought tolerance. Osmotic potential at saturation (Ψπsat) was marginally affected by N form, and a significant relationship between proline concentration in needles and Ψπsat was found. During acclimation, seedlings fertilized with organic N minimized needle senescence, retained more nutrients in the oldest needles, had maximum increments in proline concentration and hastened the development of water-use efficiency mechanisms compared with those fertilized with inorganic N sources. Our results suggest an improved physiological drought acclimation of organic N-fertilized seedlings.

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Arabidopsis and Lobelia anceps access small peptides as a nitrogen source for growth

Functional Plant Biology ◽

10.1071/fp11077 ◽

2011 ◽

Vol 38 (10) ◽

pp. 788 ◽

Cited By ~ 25

Author(s):

Fiona M. Soper ◽

Chanyarat Paungfoo-Lonhienne ◽

Richard Brackin ◽

Doris Rentsch ◽

Susanne Schmidt ◽

...

Keyword(s):

Amino Acids ◽

Nitrogen Source ◽

Biomass Accumulation ◽

Organic N ◽

Amino Acid Residues ◽

Growth Responses ◽

Small Peptides ◽

Inorganic N ◽

Metabolic Products ◽

Species Specific

While importance of amino acids as a nitrogen source for plants is increasingly recognised, other organic N sources including small peptides have received less attention. We assessed the capacity of functionally different species, annual and nonmycorrhizal Arabidopsis thaliana (L.) Heynh. (Brassicaceae) and perennial Lobelia anceps L.f. (Campanulaceae), to acquire, metabolise and use small peptides as a N source independent of symbionts. Plants were grown axenically on media supplemented with small peptides (2–4 amino acids), amino acids or inorganic N. In A. thaliana, peptides of up to four amino acid residues sustained growth and supported up to 74% of the maximum biomass accumulation achieved with inorganic N. Peptides also supported growth of L. anceps, but to a lesser extent. Using metabolite analysis, a proportion of the peptides supplied in the medium were detected intact in root and shoot tissue together with their metabolic products. Nitrogen source preferences, growth responses and shoot–root biomass allocation were species-specific and suggest caution in the use of Arabidopsis as the sole plant model. In particular, glycine peptides of increasing length induced effects ranging from complete inhibition to marked stimulation of root growth. This study contributes to emerging evidence that plants can acquire and metabolise organic N beyond amino acids.

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Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

Biogeosciences Discussions ◽

10.5194/bgd-8-11311-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 11311-11335 ◽

Cited By ~ 4

Author(s):

E. Gioseffi ◽

A. de Neergaard ◽

J. K. Schjoerring

Keyword(s):

Amino Acids ◽

Nutrient Solution ◽

Inorganic Nitrogen ◽

N Uptake ◽

Organic N ◽

Arable Soils ◽

Inorganic N ◽

N Losses ◽

Total N ◽

N Source

Abstract. Soil-borne amino acids may constitute a nitrogen (N) source for plants in various terrestrial ecosystems but their importance for total N nutrition is unclear, particularly in nutrient-rich arable soils. One reason for this uncertainty is lack of information on how the absorption of amino acids by plant roots is affected by the simultaneous presence of inorganic N forms. The objective of the present study was to study absorption of glycine (Gly) and glutamine (Gln) by wheat roots and their interactions with nitrate (NO3–) and (NH4+) during uptake. The underlying hypothesis was that amino acids, when present in nutrient solution together with inorganic N, may lead to down-regulation of the inorganic N uptake. Amino acids were enriched with double-labelled 15N and 13C, while NO3– and NH4+ acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO3– and NH4+ did not differ from each other and were about twice as high as the uptake rate of organic N when the different N forms were supplied separately in concentrations of 2 mM. Nevertheless, replacement of 50 % of the inorganic N with organic N was able to restore the N uptake to the same level as that in the presence of only inorganic N. Co-provision of NO3– did not affect glycine uptake, while the presence of glycine down-regulated NO3– uptake. The ratio between 13C and 15N were lower in shoots than in roots and also lower than the theoretical values, reflecting higher C losses via respiratory processes compared to N losses. It is concluded that organic N can constitute a significant N-source for wheat plants and that there is an interaction between the uptake of inorganic and organic nitrogen.

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Potential organic and inorganic N uptake by six Eucalyptus species

Functional Plant Biology ◽

10.1071/fp06045 ◽

2006 ◽

Vol 33 (7) ◽

pp. 653 ◽

Cited By ~ 51

Author(s):

C. R. Warren

Keyword(s):

Amino Acids ◽

N Uptake ◽

N Cycling ◽

Organic N ◽

Eucalyptus Species ◽

Inorganic N ◽

South Eastern ◽

Eastern Australia ◽

Relative Abundances ◽

South Eastern Australia

There are no published studies of organic N uptake by species of south-eastern Australia (e.g. Eucalyptus) despite several studies of ecosystem N cycling. This study examines uptake of nitrate, ammonium and glycine (an amino acid) by six species of 16-year-old Eucalyptus growing at two plantations (‘common gardens’). By using two plantations, one xeric / oligotrophic and one mesic / eutrophic, I was able to disentangle genotypic from phenotypic differences in preference for N forms. Measurements were made on three separate occasions during spring. N uptake was examined in situ with attached roots placed in uptake solutions containing equimolar 100 μmol L–1 concentrations of 15N-nitrate, 15N-ammonium and 2-13C215N-glycine. Water and KCl extracts were used to determine the relative abundances of nitrate, ammonium and amino acids at the two plantations. Nitrate dominated at the eutrophic site, but was nearly absent at the oligotrophic site. N at the oligotrophic site was dominated by ammonium and amino acids which were present in similar concentrations. The rate of uptake of ammonium (6.3 ± 0.4 μmol g h–1; mean ± s.e., n = 108), was faster than glycine (3.4 ± 0.2), which was faster than nitrate (0.62 ± 0.07). Plant ‘preference’ for N forms did not vary between sites despite large differences in the relative abundances of N forms (nitrate v. ammonium v. amino acids). Hence, there was little evidence for acclimation of Eucalyptus species to differences in the relative availability of N forms. This study suggests the possibility for considerable organic N uptake in the field. Previous studies of ecosystem N cycling in south-eastern Australia have only examined inorganic N. The N cycle in south-eastern Australia needs to be revisited with a new perspective, one that considers inorganic N and organic N.

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Effects of long-term soil warming on nitrogen fluxes in forest soils

10.5194/egusphere-egu2020-7551 ◽

2020 ◽

Author(s):

Erich Inselsbacher ◽

Jakob Heinzle ◽

Andreas Schindlbacher

Keyword(s):

Amino Acids ◽

Global Warming ◽

Soil Temperature ◽

Organic N ◽

Soil N ◽

Inorganic N ◽

Soil Warming ◽

N Fluxes

Forests are the main contributors to the global terrestrial carbon (C) sink but several studies suggest that global warming could significantly reduce their CO2 mitigation potential. The capacity of forest plants to sequester C is closely linked to soil nitrogen (N) availability, a major control of plant growth and ecosystem functioning. An increase of soil temperature caused by global change is critically affecting soil N supply rates, both directly by increasing diffusive N fluxes in the soil solution and indirectly by accelerating soil N turn-over rates. In recent short-term laboratory incubation studies, an increase in soil temperature has not only led to a significant increase in diffusive N fluxes but also to a concomitant shift in N quality available for plant uptake towards a higher portion of inorganic N forms compared to small organic N forms such as amino acids. However, until now long-term effects of soil warming on soil N fluxes have not been studied. Here, we present first results from a study on soil N availabilities at the long-term soil warming experimental site Achenkirch (Austria) in the Limestone Alps. This site is one of the few in situ climate manipulation experiments operational for more than 10 years and has already provided a wealth of novel insights into the potential effects of global warming on forest ecosystem responses. Applying in situ microdialysis, we estimated diffusive fluxes of inorganic N and amino acids along the growing season in soils warmed by resistance heating cables since 2005 (+4 &#176;C compared to control plots) and control soils. Fluxes of all N forms were highly variable within each subplot (2 x 2 m) and reflected the high heterogeneity of soils at this forest site. Interestingly, fluxes of amino acids were less variable than of nitrate or ammonium throughout the year, indicating comparably stable protein depolymerization rates. In summary, long-term soil warming affected diffusive N fluxes but less than other factors operating on smaller (< 1 cm) scales.

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Different characteristics of nitrogen utilization between lupin and soybean: can lupin utilize organic nitrogen in soils?

Canadian Journal of Botany ◽

10.1139/b05-136 ◽

2006 ◽

Vol 84 (1) ◽

pp. 20-27 ◽

Cited By ~ 6

Author(s):

Toshihiro Watanabe ◽

Miwa Okamoto ◽

Seiji Misawa ◽

Masaru Urayama ◽

Mitsuru Osaki

Keyword(s):

Amino Acids ◽

Ammonium Sulphate ◽

Farmyard Manure ◽

White Lupin ◽

Organic N ◽

Cluster Roots ◽

Inorganic N ◽

Available N ◽

Microbial Decomposition ◽

Glycine Uptake

It is well known that lupin forms cluster roots, which help in dissolving insoluble P in soils. In nonleguminous species, cluster roots also appear to contribute to the utilization of organic N in soils. In white lupin ( Lupinus albus L.), however, the characteristics of its organic N utilization have not been studied. Therefore, we examined whether white lupin can utilize organic N in soils. Soybean ( Glycine max (L.) Merr.), which does not form cluster roots, was used as a control plant. Seedlings of lupin and soybean were cultivated in soils with different N sources (non-N, ammonium sulphate, ammonium sulphate plus cattle farmyard manure, or cattle farmyard manure). The rate of glycine uptake by excised roots was determined in a hydroponic experiment to investigate the ability of lupin and soybean to directly utilize amino acids. Nitrogen accumulation in soybean corresponded to the decrease in inorganic N in the soils. In contrast, N accumulation in lupin was higher than the decrease in inorganic N in the soil, especially with the cattle farmyard manure treatment, indicating that lupin derived more N from an organic N source. Wheat ( Triticum aestivum L.) cultivated with lupin in a pot accessed more available N than wheat with soybean or wheat in monoculture, suggesting that lupin roots themselves or the lupin rhizosphere microorganisms were able to decompose organic N in soils. Excised roots of lupin, especially cluster roots, exhibited higher rates of glycine uptake than roots of soybean. In conclusion, lupin decomposed organic N in the rhizosphere and was able to absorb amino acids from decomposition in addition to any inorganic N produced by further microbial decomposition.

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Co-occurrence of organic and inorganic N sources influences asparagine uptake and internal amino acid profiles in white clover

10.1101/577114 ◽

2019 ◽

Author(s):

Weronika Czaban ◽

Jim Rasmussen

Keyword(s):

Amino Acids ◽

Amino Acid ◽

White Clover ◽

Uptake Rate ◽

Essential Amino Acids ◽

Organic N ◽

Inorganic N ◽

Total N ◽

Amino Acid Profiles ◽

N Status

AbstractDirect plant uptake of organic nitrogen (N) is important for plant N nutrition, but we lack knowledge of how the concentration of external N forms (organic and inorganic) -influence organic N uptake and plant N status. We investigated the uptake of the amino acid asparagine (Asn) in white clover in the presence of different nitrate (NO3-), Asn, and total N concentrations. White clover seedlings were for one week exposed to combinations of NO3-(3-30 µmol N kg-1sand DW) and Asn (3-30 µmol N kg-1sand DW), where after the Asn uptake rate was determined by addition of13C4-Asn. Shoot and root Asn content and amino acid profiles were also analyzed. Increasing external NO3-and total N concentrations decreased13C4-Asn uptake rates and internal clover Asn content. Furthermore, total N affected clover amino acid profiles from non-essential amino acids at low N doses to the dominance of essential amino acids at increasing N doses. Asn uptake rate in white clover is reduced by increasing inorganic N, but not by increasing organic N concentrations. Furthermore, plant amino acid profiles are likely to be a more sensitive indicator of N supply and descriptor of the N status.

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Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

Biogeosciences ◽

10.5194/bg-9-1509-2012 ◽

2012 ◽

Vol 9 (4) ◽

pp. 1509-1518 ◽

Cited By ~ 42

Author(s):

E. Gioseffi ◽

A. de Neergaard ◽

J. K. Schjoerring

Keyword(s):

Amino Acids ◽

Nutrient Solution ◽

Inorganic Nitrogen ◽

N Uptake ◽

Organic N ◽

Arable Soils ◽

Inorganic N ◽

N Losses ◽

Total N ◽

Uptake Rates

Abstract. Soil-borne amino acids may constitute a source of nitrogen (N) for plants in various terrestrial ecosystems but their importance for total N nutrition is unclear, particularly in nutrient-rich arable soils. One reason for this uncertainty is lack of information on how the absorption of amino acids by plant roots is affected by the simultaneous presence of inorganic N forms. The objective of the present study was to study absorption of glycine (Gly) and glutamine (Gln) by wheat roots and their interactions with nitrate (NO3−) and ammonium (NH4+) during uptake. The underlying hypothesis was that amino acids, when present in nutrient solution together with inorganic N, may lead to down-regulation of the inorganic N uptake, thereby resulting in similar total N uptake rates. Amino acids were enriched with double-labelled 15N and 13C, while NO3− and NH4+ acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO3− and NH4+ did not differ from each other and were generally about twice as high as the uptake rate of organic N when the different N forms were supplied separately in concentrations of 2 mM. Nevertheless, replacement of 50% of the inorganic N with organic N was able to restore the N uptake to the same level as that in the presence of only inorganic N. Co-provision of NO3− did not affect glycine uptake, while the presence of glycine down-regulated NO3− uptake. The ratio between 13C and 15N were lower in shoots than in roots and also lower than the theoretical values, reflecting higher C losses via respiratory processes compared to N losses. It is concluded that organic N can constitute a significant N-source for wheat plants and that there is an interaction between the uptake of inorganic and organic N.

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Adaptations to nitrogen form: comparing inorganic nitrogen and amino acid availability and uptake by four temperate forest plants

Canadian Journal of Forest Research ◽

10.1139/x11-090 ◽

2011 ◽

Vol 41 (8) ◽

pp. 1626-1637 ◽

Cited By ~ 17

Author(s):

R.J. Metcalfe ◽

J. Nault ◽

B.J. Hawkins

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Glutamic Acid ◽

Temperate Forest ◽

Picea Sitchensis ◽

Organic N ◽

Inorganic N ◽

Short Term ◽

Shrub Species ◽

Dry Biomass

There are few examinations of the relative availability and plant uptake of inorganic N and amino acid N in temperate forest regions. We determined the availability of amino acid N and inorganic N in soils under two shrub species ( Vaccinium ovalifolium Sm. versus Rubus spectabilis Pursh) on three sites near Jordan River, British Columbia, over a growing season. We compared biomass production of the two shrubs and two conifers ( Picea sitchensis (Bong.) Carr. and Pseudotsuga menziesii (Mirb.) Franco var. menziesii) when given inorganic N (20:80 or 80:20 NH4+–NO3–) or organic N (glycine and glutamic acid) and assessed short-term uptake (24 h) of 15N-labelled NH4+, NO3–, glycine, or glutamic acid by the four species. Water-extracted soil concentrations of NH4+ were up to 1.5 times greater than NO3– averaged across sites. Concentrations of amino acid N and inorganic N were similar on soils under Rubus , but the amino acid N to inorganic N ratio was up to 2.4:1 in soils under Vaccinium . Soils dominated by Rubus had up to twice the NO3–-N and two thirds the amino acid N concentrations of soils dominated by Vaccinium, averaged across sites and Rubus had relatively high short-term 15NO3– uptake. The dry biomass of conifers was approximately four times greater when supplied mainly with NH4+ compared with NO3–, but biomass of the two shrub species was similar in both inorganic N treatments. All plants had comparable rates of short-term 15N uptake from amino acids and inorganic N, suggesting that amino acids could contribute to the N nutrition of these temperate species; however, dry biomass of all four species grown with amino acids was less than one half that of plants grown with inorganic N.

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