适度水分胁迫下增硝对不同基因型水稻苗期生长及生理特性的影响

Effect of ratio of nitrate to ammonium on physiological characteristics of rice genotypes at seedling stage under moderate water stress

以不同基因型代表性稻种(冈优527、扬稻6号、中旱3号、农垦57)为材料,采用水培试验,进行不同水分胁迫程度和不同氮素形态的处理,分析了水分胁迫及氮素形态对不同基因型水稻生长发育的影响及其生理机制。研究结果表明:正常水分供应条件下,适当地提高硝态氮肥的比例(铵硝配比为50∶50),不影响各营养器官净光合速率(Pn),并能促进水稻叶及根中硝态氮含量增加,但硝态氮肥比例>50%,会导致各生理及代谢指标的显著降低,不利于不同基因型水稻的生长;而适度的水分胁迫下,适当增加硝态氮比例(铵硝配比50∶50)相对于非水分胁迫、纯铵态氮肥处理,更有利于提高功能叶Pn,促进渗透调节物质的积累,能发挥以水促肥的优势,进而促进水稻的生长。此外,不同基因型水稻生长在适度水分胁迫下对增硝营养的响应程度差异显著,籼稻与粳稻相比,杂交籼稻和常规籼稻相比,常规粳型旱稻与常规粳型水稻相比,前者在净光合速率、氮素吸收利用上均表现出更为明显的优势,同品种耐旱性规律一致。

Rice genotypes including Gangyou 527, Yangdao 6, Zhonghan 3 and Nongken 57 were grown under different water stress conditions and treated with ammonium and nitrate at various ratios to investigate the effects of water stress and nitrogen forms on growth, nitrogen absorption and physiological characteristics of rice. The results indicated that, under normal water condition, moderate decrease in the ratio of ammonium/nitrate （50：50） could increase nitrate content in the leaves and roots of rice, while the net photosynthetic rate （Pn） was not affected. However, when the proportion of nitrate N was higher than 50%, the physiological and metabolic indexes decreased significantly and the growth of rice seedlings was inhibited. Under moderate water stress condition, the ratio of ammonium/nitrate at 50 ： 50 was more beneficial to increase Pn of top three leaves, to promote the accumulation of compatible osmolytes, to improve the nitrogen uptake and to boost the growth of rice seedlings, as compared with that treated with normal water and 100% ammonium N, Moreover, under moderate water stress condition, the responses of different rice genotypes to increasing nitrate N differed from each other significantly. In terms of Pn and nitrogen use efficiency, indica rice was superior to japonica rice; similarly, hybrid indica rice was superior to inbred indica rice, and japonica upland rice was better than japonica paddy rice. No difference was observed in drought tolerance within the same rice genotype.