结实期水分胁迫对不同氮肥水平下水稻产量及其品质的影响

以生产上广泛使用的3个水稻品种为材料，研究了结实期适度水分胁迫对不同氮肥水平下稻米产量及其品质的影响.结果表明，正常施氮水平下，水分胁迫使3个品种籽粒产量降低11.6%～14.7%，虽整精米率有所提高，但垩白度却显著增加(18.7%～33.1%)，外观品质变劣；而高氮水平下，水分胁迫处理的产量增加18.8%～22.2%，垩白粒率和垩白度分别降低15.3%～37.2%和13.7%～29.9%，外观品质变优.稻米RVA谱特征值和米饭质地也明显受到结实期土壤水分和施氮水平的影响.正常施氮水平下，水分胁迫处理的最高粘度和崩解值(扬稻6号除外)要低于水层灌溉处理，而其消减值却明显高于水层灌溉处理，水分胁迫使得正常施氮处理的米饭口感较硬，弹性较差，粘性降低，且咀嚼有渣感.而高氮水平下，水分胁迫利于米粉糊化过程中早期粘度的上升，最高粘度增加，崩解值也明显高于水层灌溉，消减值却明显减小，米饭的硬性和凝聚性减小，松弛性和粘附性增大，米饭质地有变优的趋势.

Effects of water stress during grain-filling period on rice grain yield and its quality under different nitrogen levels

To examine the effects of nitrogen (N) supply and water stress on rice grain yield and its quality, a pot experiment was conducted at Yangzhou University. Three rice cultivars were grown under two N levels (high N and normal N) from initial heading, and two water conditions (well watering and water stress) were installed for each of the two N levels from flowering to maturity. The results showed that when the plants of test cultivars were grown under normal N level, water stress markedly reduced the grain-filling percentage and grain weight, resulting in a significant decrease of grain yield by 11.6% to approximately 14.7%. Though the head-milled rice had a slight increase, the percentage of chalkiness was significantly increased by 18.7% to approximately 33.1%, which resulted in an inferior performance in grain-apparent quality. In contrast, when the plants were grown under high N level, water stress increased the grain yield by 18. 8% to approximately 22.2% because of the increase of grain-filling percentage and grain weight. As compared with well watering, water stress decreased the percentages of chalky grain and chalkiness by 15.3% to approximately 37.2% and 13.7% to 29.9%, respectively, which improved the performance of grain-apparent quality. The pronounced effects of N application and water treatment were observed on the RVA profile and cooked quality. Under both two N levels, water stress decreased the peak viscosity and breakdown (except for Yangdao 6) while increased the setback. According to the performance in the indices of cooked quality, the palatability became poor when subjected to water stress under normal N level, as the result of the increase of hardness and cohesiveness. In contrast, under high N level, water stress availed the ascending of viscosity at the early stage when rice flours were pasting, peak viscosity and breakdown were increased, and setback was decreased, suggesting that the palpability got well. It was concluded that mild water stress during grain-filling period was benefit for the development of high quality grain when rice plants were grown under high N level.