Characterization on the physiological traits of plants and yield formation capacity upon water- and N-saving conditions in wheat (T. aestivum L.)

Improving water and nitrogen (N) use efficiencies of the Triticum aestivum species contributes to the sustainable agriculture worldwide. In this study, we investigated the physiological traits of plants and the yield formation capacity of winter wheat treated with deficit irrigation together with N-saving condition. Compared with OI-ON (optimum irrigation, OI together with optimum nitrogen, ON), treatment DI-DN (deficit irrigation, DI combined with deficient N (DN, N120) led to decreased contents of chlorophyll, nitrogen (N), and osmolytes, Pn, and the activities of SOD and POD in leaves at various stages together with reduced yields in Jimai 585 and Shimai 22, two cultivars with contrast drought stress responses. The moisture contents in soil profile planted by tested cultivars showed significant reduction under OI-ON with respect to those under DI-DN, suggesting the positive impact of elevated soil water consumption on plant physiological and agronomic traits. The drought-tolerant cultivar Shimai 22 displayed much more improvement on the physiological and agronomic traits, WUE, and NUE than drought-sensitive cultivar Jimai 585 under DI-DN, due to effective usage for soil water and N storage. Yields and grain weights under DI-DN were positively correlated with chlorophyll and osmolytes contents, Pn, and antioxidant enzyme activities, suggesting that the improved physiological traits under DI-DN contributed to the elevated yield for the drought-tolerant cultivar. Two nitrate transporter (NRT) family ones TaNRT2.1 and TaNRT2.2 and TaPYR3 and TaPYR6, two abscisic acid receptor (PYR) family genes exhibited induced transcripts upon DI-DN in wheat cultivars, with more abundance in Shimai 22 than in Jimai 585. Transgenic analysis on the differential genes confirmed their functions in mediating plant drought and N deprivation responses, suggesting that distinct PYR and NRT family members mediate drought and N deprivation adaptation in wheat plants. Our investigation provided insights into high WUE and NUE cultivation of winter wheat under the limited-water and N-saving management.