小麦花后弱光对籽粒淀粉积累和相关酶活性的影响

2005—2007年选用小麦品种济麦20和山农1391, 在大田试验条件下研究了花后不同阶段弱光对籽粒淀粉积累、淀粉粒分布及相关酶活性的影响。结果表明, 花后不同阶段弱光显著降低成熟期籽粒淀粉积累量, 但提高了籽粒直链淀粉含量。花后不同阶段弱光使籽粒A型淀粉粒比例显著增加, B型淀粉粒比例显著降低。不同阶段弱光处理对籽粒淀粉积累的影响程度不同, 灌浆中期的效应大于灌浆前期。Logistic方程拟合籽粒淀粉积累进程发现, 花后弱光对籽粒淀粉积累量的影响, 主要是通过影响其平均积累速率与活跃期积累速率, 而不是积累持续期。花后弱光显著降低小麦磷酸蔗糖合酶(SPS)、蔗糖合酶(SS)和腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)的活性。灌浆前期弱光使束缚态淀粉合酶(GBSS)、可溶性淀粉合酶(SSS)活性高于对照或与对照无显著差异, 而灌浆中期弱光使这两种酶的活性均显著低于对照。灌浆前期弱光减少了淀粉合成底物的供应, 系旗叶SPS活性、籽粒SS及AGPase活性下降所致; 而灌浆中期弱光除淀粉合成底物减少外, 籽粒淀粉合酶活性亦降低。

Effect of Shading after Anthesis on Starch Accumulation and Activities of the Related Enzymes in Wheat Grain

Low light intensity as a result of cloudy or rainy days often occurs during the grain filling of winter wheat (Triticum aestivum L.) in Huanghuai region of China, largely affecting grain yield and starch accumulation. Many investigators have de- monstrated the effects of shading on photosynthesis, dry matter accumulation, grain yield and its components of winter wheat. However, there are few reports on the effects of shading on starch synthesis in wheat grain. In the present experiment, two wheat cultivars Jimai 20 and Shannong 1391 were used for the mechanism study on starch synthesis response to shading in grains. The black nets were over the wheat canopy to reduce light intensity to 10% in the early (6–9 d after anthesis, S1) and middle (16–19 d after anthesis, S2) grain filling stages. The starch accumulation, starch granule distribution, and activities of enzymes involved in starch synthesis were examined during grain development of winter wheat. The results showed that shading after anthesis remarkably reduced starch accumulation, and significantly increased the amylose content in ripe grains. The amount of starch accumulation showed an order of control (CK)>S1>S2. Shading significantly increased and reduced the volume percents of A-type starch granule and B-type starch granule, respectively. Logistic simulation and correlation analysis showed that it was mean starch accumulation rate and the starch accumulation rate in actively-increasing period, but not starch accumulation duration affected by shading to reduce grain starch accumulation. The activities of sucrose phosphate synthase (SPS), sucrose synthase (SS) and adnosine diphosphate glucose pyrophosphorylase (AGPase) in shading treatments were significantly lower than those in control. The activities of granule bounded starch synthase (GBSS) and soluble starch synthase (SSS) under shading stress at early grain filling were higher than those in control or no significant difference with those in control. However, the activities of GBSS and SSS under shading stress at middle grain filling were significantly lower than those in control. The results suggested that there are less the substrate for starch accumulation, caused by low activities of SPS, SS, and AGPase in S1 treatment, and both less the substrate and the low activities of starch synthase (GBSS and SSS) in S2 treatment.