灌浆温度和氮肥及其互作效应对稻米贮藏蛋白组分的影响

灌浆结实期温度与氮肥施用量是影响稻米品质的两个重要生态因子,尤其是与稻米蛋白含量及米饭食味关系密切。本文以多个水稻主栽品种为材料,通迆灌浆结实期的人工控温试验、大田长期定位点的施氮处理试验和盆栽条件下的温氮两因素复合处理试验,探讨了水稻灌浆结实期温度对稻米贮藏蛋白含量与组分影响及其有别于氮肥处理效应的差异觃律,幵分析了温度与氮肥两个因素对稻米贮藏蛋白及其组分影响的交互作用特点。结果表明,高温胁迫和增施氮肥均引起水稻籽粒总蛋白及其谷蛋白组分含量(%)的显著增加,但两者对稻米醇溶蛋白影响却存在明显差别。其中,高温处理引起醇溶蛋白含量显著下降,提高稻米谷蛋白/醇溶蛋白比值,而增施氮肥引起稻米谷蛋白和醇溶蛋白含量明显增加,但对谷蛋白/醇溶蛋白比值与贮藏蛋白各亚基的组成比例影响相对较小。在高温处理下,谷蛋白的57kD前体亚基组分含量有所提高,而37kD酸性亚基和22kD碱性亚基随温度处理的差异变化却因品种而异,且高温处理对水稻籽粒蛋白绝对含量(mg grain~(–1))的影响程度也进没有其对蛋白相对含量(%)的影响明显。高氮×高温处理组合对稻米总蛋白与谷蛋白含量的影响程度显著大于单一高温或高氮处理,但在高氮水平下由高温引起稻米醇溶蛋白含量的下降幅度却小于其低氮对照,有利于稻米醇溶蛋白含量在不同温度处理下的相对稳定。

Individual and combined effects of air temperature at filling stage and nitrogen application on storage protein accumulation and its different components in rice grains

Air temperature during grain-filling stage and application amount of nitrogen fertilizer are two of most important factors affecting rice grain quality, which largely related to grain protein content and cooking palatability. In this paper, the difference in grain protein content and its composition was investigated using different rice varieties, with different temperature treatments under artificial controlled condition and three nitrogen application levels in a long-term experiment field. Meanwhile, another experiment of two factors (temperature and nitrogen) in pot condition was conducted to clarity the interaction effects of temperature and nitrogen on grain protein content and its components. The higher temperature (HT) and heavier N application (HN) significantly enhanced the total protein content and glutelin accumulation in rice grain. However, HT differed obviously from HN in their impact on grain prolamin. HT significantly decreased grain prolamin concentration and markedly enhanced the ratio of glutelin to prolamin in rice grains, while HN increased in grain glutelin and prolamin contents had smaller effects on ratios of glutelin to prolamin and the proportion of subunit compositions in grain storage proteins. Furthermore, HT had a marked impact on the glutelin composition in rice grains, with the significant increase in 57 kD pro-glutelin amount. However, the effect of HT on 37 kD α-glutelin and 22 kD β-glutelin was greatly variable among different rice varieties. The varying extent of grain protein amount per grain (mg grain^-1) affected by HT was much smaller than that of grain protein content (%). The combined effect of HT and HN on the total storage protein and glutelin accumulation in rice grain was much greater than the individual effect of HT and HN. The dropping extent of grain prolamin content under HT appeared to be smaller for HN relative to LN, suggesting that appropriate N application was beneficial to keep the relatively stable content of grain prolamin composition under the fluctuating temperature for rice growth.