棉花氮素利用效率动态调控机理的探讨

Understanding the mechanisms of nitrogen(N) use efficiency in plants under low N supply is crucial to improve crop productivity. This study aimed to elucidate the potential mechanisms involved in N uptake, assimilation and its utilization associated with morphology, photosynthesis and growth of different cotton genotypes i.e. N-efficient(HM-2270,GH-Uhad) and N-inefficient(Z-50,FH-444) grown under low-N (0.5 mmol•L-') and high-N(5.0 mmol•L-1) conditions. HM-2270 produced maximum root and shoot dry weight, while minimum root and shoot dry weight was observed for FH-444 and Z-50. Likewise, highest leaf area, epidermal cells area(EPCA), stomatal density(SD) and stomatal index on adaxial surface was noted for HM-2270, while maximum SD on abaxial surface and highest no. of epidermal cells and greater EPCA exhibited by GH-Uhad and FH-444 respectively, on both surfaces under all conditions. Higher intercellular carbon dioxide concentration was found in FH-444. However N-efficient genotypes behaved alike for net photosynthetic rate, transpiration rate, stomatal conductance and chlorophyll content, but significantly differ from N-inefficient genotypes. In addition, the activities of ribulose-1,5-bisphosphate carboxylase/oxygenas, sucrose phosphate synthase, nitrate reductase, and glutamine synthetase were higher in HM-2270, followed by GH-Uhad in both N regimes. The N supply induced the expression of nitrate transporters (NRT1.1, NRT 2.1 and NRT 2.2) in tested genotypes after 6 to 24 h of N treatments. Maximum peaks for transporter's expression were observed in N-efficient genotypes and they maintained the expression for longer time as compared with N-inefficient genotypes. In conclusion, the above mentioned N responses mediate the developmental plasticity related to efficient N uptake. High enzymatic activities and sustainingphotosynthesis contribute to N-homeostasis and plant growthunder different N concentrations.