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Assimilation of nitrate and ammonium by the Scots pine ( Pinus sylvestris ) seedling under conditions of high nitrogen supply
Author(s) -
Flaig Holger,
Mohr Hans
Publication year - 1992
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1992.tb04706.x
Subject(s) - scots pine , ammonium , chemistry , nitrate , nitrogen , potassium , ammonium nitrate , nitrogen assimilation , potassium nitrate , asparagine , botany , amino acid , biochemistry , pinus <genus> , biology , organic chemistry
Seedlings of Scots pine ( Pinus sylvestris L.) were grown on perlite for 21 days under controlled conditions. Apart from the water control, KNO 3 (15 m M ), (NH 4 ) 2 SO 4 (7.5 m M ), and NH 4 NO 3 (15 m M ) were offered to study the effects of a high nitrogen supply on nitrogen assimilation. In some experiments 1.3 m M potassium was added to the basic ammonium solutions. In labelling studies nitrate and ammonium were 2.3 atom% 15 N‐enriched. It was found that over the 21‐day period approximately three times more ammonium‐N was taken up than nitrate‐N. However, nitrate and ammonium, applied simultaneously, were taken up to the same extent as if they were applied separately (additivity). The presence of K + in the medium did not affect N‐uptake. Among the soluble N‐containing compounds nitrate, ammonium and 8 amino acids were quantified. It was found that assimilation of nitrate can cope with the uptake of NO − 3 under all circumstances. Neither free nitrate nor ammonium or amino acids accumulated to an extent exceeding the values of water‐grown seedlings. On the other hand, in case of high ammonium supply considerably more nitrogen was taken up than could be incorporated into nonsoluble N‐containing substance (‘protein’). The remaining nitrogen was found to accumulate in intermediary storage pools (free NH 4 + , glutamine, asparagine, arginine). Part of this accumulated N could be incorporated into protein when potassium was offered in the nutrient solution. It is concluded that potassium is a requirement for a high rate of protein synthesis not only in crop plants but also in conifers.