Effect of phosphorus on activities of enzymes related to nitrogen metabolism in flag leaves and protein content of wheat grains

Effect of phosphorus on the activities of enzymes related to nitrogen metabolism in flag leaves, and protein content in grains of wheat cultivars with different end-use quality were studied under field conditions. The studied enzymes include nitrate reductase (NR), glutamine synthetase (GS), endop eptidase (EP) and carboxyp eptidase (CP). Field experiment was conducted at the Experiment Station of Shandong Agricultural University in Taian, Shandong from 2005 through 2006. Two cultivars, strong gluten cultivar JM20 and weak gluten cultivar SN1391, were selected and three phosphorus application levels, P2O5 0, 135 and 225 kg/ha were set up. Results indicated that the effects of phosphorus application rates on enzyme activities and protein content varied with wheat cultivars. Both the enzyme activities and protein content in strong gluten wheat JM20 were promoted with increasing of phosphorus application rate, but declined in the weak gluten wheat SN1391. The un-unique response of different wheat cultivars on phosphorus should be fully considered during the process of developing P application strategy.