摘要:地表臭氧浓度增高情形下水稻减产，米质呈变劣趋势，但稻米热力学特征值的变化及其与生长季、品种以及籽粒着生部位的关系均不清楚。本研究利用自然光气体熏蒸平台，以8个水稻品种为材料，设置高臭氧浓度为100 nL·L-1，对照浓度为9 nL·L-1。连续两年系统研究了高臭氧浓度熏蒸对成熟稻穗不同部位糙米热力学特性（DSC）的影响。与对照相比，臭氧胁迫使稻米热焓值极显著下降4.15%，但对糊化起始温度、糊化峰值温度、糊化终止温度、DSC曲线峰宽和峰高均无显著影响；2017年度稻米热焓值、糊化峰值温度、糊化起始温度和峰高极显著大于2016年，但DSC曲线峰宽表现相反；稻米所有6个DSC特征值的品种间差异均达极显著水平。从稻穗不同位置看，所有测定参数均表现为稻穗上部>中部>下部，除糊化起始温度外差异均达极显著水平。方差分析表明，臭氧×年度对热焓值、糊化峰值温度和糊化终止温度的影响均达显著或极显著水平，臭氧×品种对糊化峰值温度、糊化终止温度、DSC曲线峰宽和峰高均有极显著影响，而臭氧×部位仅对DSC曲线峰宽有显著影响。以上数据表明，稻米淀粉DSC热力学参数因生长季、供试品种以及籽粒着生部位而异，臭氧胁迫环境下稻穗不同部位稻米的热焓值总体上均呈下降趋势，表现为更易糊化的特点。
关键词:臭氧胁迫/
水稻/
基因型差异/
强弱势粒/
热力学特性(DSC)/
稻米品质
Abstract:As a strong oxidant, ozone pollution not only threatens human health but also negatively affects plant life. Elevated concentrations of ground-level ozone reduces rice yield and tends to deteriorate grain quality traits, including appearance, nutritional value and taste. However, the effect of ozone stress on the thermodynamic characteristics (DSC) of rice starch in respect of growth season, variety, and grain position on a panicle is not well-known. In this study, a glasshouse-type gas fumigation platform was used to examine how ozone stress affected the DSC of rice grains located at different positions on a panicle. Plants of eight rice varieties were exposed to ozone fumigation from the plant tilling stage until plant maturity. Two levels of ozone concentration, 100 nL·L-1 and 9 nL·L-1 were applied to rice plants as ozone stress treatment and control, respectively. At harvest, according to their positions on a panicle, rice grains were separated into three groups:superior grains, inferior grains, and medium grains, according to their position in a panicle-upper part, lower part and middle part of panicle. The DSC values of rice starch from the different groups were measured. The study showed that ozone stress significantly reduced the enthalpy value of brown rice by 4.15% compared with the control, but it had no significant effect on the gelatinization starting temperature, the peak gelatinization temperature, the gelatinization termination temperature, and the peak width and peak height of the DSC curve. In 2017, the enthalpy value, gelatinization peak temperature, gelatinization starting temperature, and peak height of brown rice were significantly higher than the values in 2016. However, the opposite trend was observed for the peak width of the DSC curve. There were significant differences among rice varieties in respect of the DSC characteristic values of rice starch. All the DSC values of grains at different positions on a panicle were in the order of upper part > middle part > lower part, and the differences were statistically significant, apart from the case of the gelatinization starting temperature. Results of ANOVA revealed significant ozone by year interactions for enthalpy value, gelatinization peak temperature, and gelatinization termination temperature, and significant ozone by variety interactions for gelatinization peak temperature, gelatinization termination temperature, and peak width and peak height of the DSC curve. Meanwhile, ANOVA revealed significant ozone by grain position interactions only for the peak width of DSC curve. The findings demonstrated that the DSC thermodynamic parameters of rice grains varied with the growing season, the varieties tested, and the grain position on a panicle. Ozone fumigation during the rice growing season reduced the enthalpy value of grains at different positions on a panicle, which indicated ozone-stressed rice grains are prone to gelatinization.
Key words:Ozone stress/
Rice/
Genotypic variation/
Superior and inferior grains/
Thermodynamic characteristics/
Rice quality
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