结实期相对高温对稻米淀粉粘滞性谱及镁、钾含量的影响

Effects of relatively high temperature at grain-filling stage on rice grain's starch viscosity profile and magnesium and potassium contents

选用武育粳3号(粳稻)和扬稻6号(籼稻)两个水稻品种,利用人工气候室在水稻灌浆结实期进行控温试验,设置全结实期相对高温、结实前期相对高温、结实后期相对高温、全结实期适温(对照,日均温23℃)对照4个处理,探讨结实期不同时段相对高温(日均温度30℃)对稻米淀粉粘滞性谱和Mg、K等元素含量的影响.结果表明:结实期相对高温使武育粳3号和扬稻6号淀粉粘滞性谱特征值发生改变,其中糊化开始温度、冷胶粘度、回复值和消减值升高,最高粘度、热浆粘度和崩解值下降;结实期相对高温促进了米粉中Mg、K、N含量的提高,特别是K含量的大幅提高,使稻米中Mg/K和Mg/(N.AC.K)明显降低;而2个水稻品种的直链淀粉含量(AC)对相对高温的反应截然相反,武育粳3号的AC降低、扬稻6号的AC升高.全结实期相对高温对稻米淀粉粘滞性谱和Mg、K等元素含量的影响最大,结实前期其次,结实后期的影响较小,开花后20d内是稻米淀粉粘滞性谱和Mg、K等元素含量受温度影响的关键时期.Mg/K和Mg/(N.AC.K)与淀粉粘滞性谱特征值显著相关,可以作为稻米食味品质评价的参考指标.

With rice cultivars Yangdao 6 （Indica） and Wuyujing 3 （Japonica） as test materials, the effects of relatively high temperature （RHT, mean temperature 30 ℃） at grain-filling stage （GFS） on the starch viscosity profile and magnesium （Mg） and potassium （K） contents of rice grain were studied in a phytotron. Four temperature treatments were installed, i. e. , RHT at whole GFS, RHT at early GFS and optimum temperature at later GFS, optimum temperature at early GFS and RHT at later GFS, and optimum temperature （ CK, mean temperature 23℃） at whole GFS. The results showed that RHT at GFS significantly influenced the characteristic values of rice grain＇ s starch viscosity profile, e. g. , the values of gelatinization temperature, final viscosity, consistency, and setback increased, while those of peak viscosity, hot viscosity, and breakdown decreased, with Yangdao 6 and Wuyujing 3 followed the similar pattern. The RHT increased the contents of Mg, K, and N, especially of K, resulting in a marked decrease of Mg/K and Mg/（N · AC· K） in the grain. The grain＇ s amylase content （ AC ） of the two cultivars showed contrasting in response to temperature treatments. Wuyujing 3 performed decrease, while Yangdao 6 exhibited increase in AC values. The RHT at whole GFS affected the starch viscosity profile and the Mg and K contents most greatly, followed by the RHT at early GFS, and the RHT at later GFS. The period within 20 days after flowering was the key period during which temperature affected the grain＇ s starch viscosity profile and Mg and K contents. The Mg/K and Mg/ （N· AC · K） in rice grain significant correlated with the characteristic values of starch viscosity profile, which could be used as the reference indices of rice eating quality.