臭氧胁迫对稻穗不同部位糙米直链淀粉含量和RVA谱特征值的影响

近地层臭氧浓度升高使水稻产量下降,但臭氧胁迫对稻米品质的影响及其强弱势粒差异尚不清楚.本研究以8个不同类型水稻品种为供试材料,利用自然光气体熏蒸平台,设置对照(9 nL·L^-1)和高浓度臭氧(约100 nL·L^-1)处理,研究臭氧胁迫对稻穗不同部位糙米直链淀粉含量和RVA谱特征值的影响.结果表明: 与对照相比,臭氧处理使糙米直链淀粉含量、最高粘度、热浆粘度、崩解值和冷胶粘度分别下降5.9%、7.6%、5.9%、11.6%、2.9%,消减值和糊化温度分别增加24.9%和1.0%,均达显著水平.稻米直链淀粉含量和所有RVA特征参数的品种间差异均达极显著水平.稻穗不同部位稻米直链淀粉含量、最高粘度、热浆粘度、崩解值、冷胶粘度从大到小依次为强势粒>中势粒>弱势粒,消减值则表现相反.绝大多数情形下,臭氧与年度或臭氧与品种间的互作对稻米直链淀粉含量和RVA谱的影响达显著水平;尽管稻米RVA特征值对臭氧胁迫的响应多表现为稻穗上部略小于中部和下部,但臭氧与部位间的互作均未达显著水平.表明中等强度的臭氧胁迫使水稻食味品质明显变劣,变劣的程度因生长季和供试品种而异,籽粒着生位置受臭氧胁迫的影响较弱.

Effects of ozone stress on amylose content and starch RVA profile in grains located at diffe-rent positions on a panicle

The increase of ground-level ozone concentration significantly reduces rice yield, but its effect on grain quality in association with the positions on a panicle was largely unknown. The effects of ozone stress on amylose content and RVA profile of rice grains located at different positions of panicles were studied by using a sunlit gas fumigation platform. Eight varieties representing different types of rice were fumigated under ambient (9 nL·L^-1) or elevated ozone (100 nL·L^-1) concentrations from transplanting until maturity. The results showed that elevated ozone treatment significantly reduced amylose content, maximum viscosity, hot viscosity, breakdown and cold viscosity by 5.9%, 7.6%, 5.9%, 11.6%, 2.9%, respectively, but increased the setback and gelatinization temperature by 24.9% and 1.0%. There were significant differences among varieties for amylose content and all parameters in RVA profile. The grains located at different positions on a panicle differed in amylose content, maximum viscosity, hot viscosity, breakdown and cold viscosity. The superior grains located at the upper part of a panicle had the highest value and the inferior grains located at the lower part of a panicle had the lowest value. However, the setback in RVA profile showed a different trend, with the superior grains having the lowest setback but inferior grains having the highest setback. In most cases, there were significant interactive effects of ozone by year or ozone by variety on amylose content and RVA profile. No significant ozone by grain position interaction on RVA profile was found, although the responses of superior grains to ozone stress was slightly smaller than those of inferior grains or grains located at the middle part of a panicle. The results demonstrated that ozone fumigation of 100 nL·L^-1 during rice growing season deteriorated rice quality, with the magnitude of deterioration varying with growth seasons and varieties and little impacts of grain positions on a panicle.