Abstract: Soil water stress is the major ecological factor limiting grain quality formation of wheat,while elucidating the physiological mechanism and regulation principles of this formation is of important significance for understanding grain quality physiology and guiding wheat cultural management.In this paper,a cement pool culture experiment was conducted to study the effects of nitrogen supply rate on nitrogen metabolism and grain protein accumulation of two wheat varieties differed in grain protein content under drought and waterlogging.Three water treatments were established from anthesis to maturity,i.e.,waterlogging,drought,and moderate water supply (CK).In each treatment,two nitrogen levels of 120 and 240 kg·hm^-2 were implemented.Compared with CK,both drought and waterlogging significantly reduced the nitrate reductase (NR) activity in flag leaf,and the contents of total nitrogen and free amino acid in leaf,stem and sheath.Drought increased,while waterlogging reduced the contents of total nitrogen and free amino acid in stem and sheath,and that of protein in grain.Under drought and waterlogging,nitrogen supply increased the NR activity in flag leaf,the total nitrogen and free amino acid contents in leaf,stem and sheath,and the free amino acid and protein contents in grain.Both drought and waterlogging stress reduced grain yield and protein yield.Nitrogen supply increased grain yield under CK and drought,but reduced it under waterlogging,illustrating that nitrogen supply could obviously regulate the nitrogen metabolism and grain protein accumulation of wheat from anthesis to maturity under drought or waterlogging.

Key words: Ecosecurity, Scale, Urban area, Regional ecosecurity pattern, Construction