ISSN:
1399-3054
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
Notizen:
Seedlings of Scots pine (Pinus sylvestris L.) were grown on perlite for 21 days under controlled conditions. Apart from the water control, KNO3 (15 mM), (NH4)2SO4 (7.5 mM), and NH4NO3 (15 mM) were offered to study the effects of a high nitrogen supply on nitrogen assimilation. In some experiments 1.3 mM potassium was added to the basic ammonium solutions. In labelling studies nitrate and ammonium were 2.3 atom%15N-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 NH4+, 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.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1399-3054.1992.tb04706.x
