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

TY - JOUR

T1 - Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

AU - Gioseffi, Elena

AU - de Neergaard, Andreas

AU - Schjørring, Jan Kofod

PY - 2012

Y1 - 2012

N2 - 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 (NO 3 -) and ammonium (NH 4 +) 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 NO 3 - and NH 4 + acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO 3 - and NH 4 + 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 NO 3 - did not affect glycine uptake, while the presence of glycine down-regulated NO 3 - 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.

AB - 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 (NO 3 -) and ammonium (NH 4 +) 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 NO 3 - and NH 4 + acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO 3 - and NH 4 + 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 NO 3 - did not affect glycine uptake, while the presence of glycine down-regulated NO 3 - 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.

U2 - 10.5194/bg-9-1509-2012

DO - 10.5194/bg-9-1509-2012

M3 - Journal article

SN - 1726-4170

VL - 9

SP - 1509

EP - 1518

JO - Biogeosciences

JF - Biogeosciences

ER -