以生产上广泛使用的水稻(Oryza sativa)品种‘汕优63’、‘扬稻6号’和‘武育粳3号’为材料,研究了水分胁迫对结实期水稻籽粒蛋白质积累及营养品质的影响。结果表明:正常施氮水平下,花后10~20 d的水分胁迫提高了谷氨酰胺合成酶(Glutamine synthetase,GS)和谷氨酸合酶(Glutamate synthase,GOGAT)活性,提高了籽粒自身利用无机氮合成氨基酸的能力,从而利于籽粒内蛋白质的积累,而高氮水平下,水分胁迫降低了籽粒自身合成氨基酸的能力。以重量为基数的蛋白质含有率在整个灌浆过程中呈“V”型消长,正常施氮水平下,水分胁迫明显提高了花后15 d至成熟期蛋白质含有率,而高氮水平下,水分胁迫处理的蛋白质含有率明显低于水层灌溉。与水层灌溉相比,水分胁迫提高了正常施氮水平下精米中醇溶蛋白和谷蛋白含量,但却明显降低了高氮水平下精米中醇溶蛋白和谷蛋白含量。水分胁迫对稻米中赖氨酸含量的影响因品种、植株的氮营养水平的不同而不同,水分胁迫显著降低了两种氮肥水平下‘汕优63’中赖氨酸含量,但却明显提高‘扬稻6号’中赖氨酸含量;而‘武育粳3号’于两种氮肥水平下表现恰好相反,正常施氮水平下赖氨酸含量略有升高;而高氮水平下赖氨酸含量明显降低。

Aims Soil drying is an important factor threatening rice production in China, and there has been much recent research on the development of grain yield and quality in rice grown under shortages of water. The objective of this study is to examine the effects of soil moisture and N supply levels on rice grain N accumulation and nutrient quality.
Methods We conducted a pot study using three rice cultivars and varying in N content to examine physiological characteristics for N accumulation and distribution to grains during the grain-filling period in response to water stress and N supply exposure at heading stage.
Important findings The activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) involved in N metabolism were enhanced by mild water stress at 10-20 DAA (days after anthesis) under normal N level, and abilities to synthesize amino acids were improved, which promoted the accumulation of N and elevated the protein content in grains. However, the activities of GS and GOGAT were negatively affected by mild water stress with exposure to high N level, which resulted in decreased synthesis of amino acids. The dynamic changes of the ratio of protein to grain weight presented a “V" type during grain-filling. Water stress improved the ratio of protein to grain weight from 15 DAA to harvest under normal N level, but the ratio was decreased by water stress under higher N level when compared with well-watered treatments. Changes of four component parts of protein subjected to water stress varied with nitrogen levels and cultivars. Compared to well-watered treatment, the water-stressed treatment had higher contents of prolamine and glutelin under normal N level, but the contents of prolamine and glutelin subjected to water stress were significantly less than those in the well-watered treatment under higher N level. Water stress affected the lysine content of grains, and varied with cultivars and N supplies. Lysine contents of `Shanyou63' under two N levels were decreased by water stress, but were increased in `Yangdao6'. The variation observed in enzymes involved in N metabolism and partitioning at grain filling to grains of the rice imposed by water stress at heading indicated that plant genotypes influence N accumulation and protein components of grains and subsequent nutrient quality.