灌浆期高温胁迫对甜玉米籽粒糖分积累和蔗糖代谢相关酶活性的影响

为明确高温对甜玉米籽粒产量和品质的影响，以甜玉米厦甜1号和粤甜16为材料, 人工授粉3 d后, 利用人工气候室分别进行昼间高温(HT)35℃和正常气温(CK)处理, 研究了甜玉米籽粒灌浆过程中粒重、糖分积累和蔗糖代谢相关酶活性的动态变化。结果表明, 与正常气温相比, 高温缩短甜玉米灌浆进程, 显著降低粒重、含水量, 提高皮渣率。在最佳采收期(水分含量为68%~74%)甜玉米鲜百粒重分别下降了20.8% (厦甜1号)和16.4% (粤甜16)。在甜玉米籽粒灌浆过程中可溶性糖和蔗糖的含量随授粉后时间先升高后降低, 高温处理不利于可溶性糖和蔗糖积累, 籽粒中糖分含量降低, 淀粉含量升高。籽粒中蔗糖的合成与分解主要由磷酸蔗糖合成酶(SPS)和蔗糖合成酶(SS)催化, SS催化反应是可逆的。高温明显降低SPS和SS合成方向活性, 提高SS分解方向活性, 导致糖分含量降低, 品质变劣。高温缩短两品种SS(合成方向)活性峰值出现的时间, 而对于SPS活性峰值出现时间厦甜1号被缩短, 粤甜16 为不变。

Effects of Heat Stress During Grain Filling on Sugar Accumulation and Enzyme Activity Associated with Sucrose Metabolism in Sweet Corn

With the trends of global warming, the extreme high temperature stress often happens during crop grain filling in the world. Heat stress has been an important factor limiting grain yield and quality. To determine the effects of heat stress on fresh kernel yield, quality and enzyme activities of sucrose metabolism, we carried out an experiment was carried out in artificial phytotron using two sweet corn cultivars (Xiatian 1 and Yuetian 16) with two typical temperature treatments (high temperature, HT and control, CK) during grain filling. The results indicated that the growth process of sweet corn was accelerated, but the weight and quality of kernel was decreased seriously under high temperature. The weight of 100-fresh-kernel and kernel water content were markedly reduced, but content of pericarp was increased. At the optimum harvest stage of fresh ear (with kernel water content 68%–74%), the fresh kernel weight of the two cultivars was reduced significantly by 20.8% (Xiatian 1) and 16.4% (Yuetian 16) under higher temperature respectively. The contents of soluble sugar and sucrose first increased and then decreased during the grain filling stage. High temperature was not favorable to sugar accumulation, resulting in sucrose content decrease and starch content increase. Sucrose phosphate synthetase (SPS) and sucrose synthetase (SS) play an important role in sucrose synthesis and degradation. SS catalyzes the interconversion of sucrose. Heat stress decreased the activities of SPS and SS (synthetic) and increased the activity of SS (cleavage), which inevitably leads to a depression in sucrose content and a reduction in kernel quality. The maximum SS (synthetic) activity in process of grain filling of two sweet corns appeared earlier under high temperature, while that of SPS activity appeared earlier in Xiatian 1 and did not in Yuetian 16.