近地层臭氧浓度增高对稻米品质的影响: FACE研究

利用稻田开放式空气中臭氧浓度增加(FACE,Free Air gas Concentration Enrichment)平台,以常规粳稻‘武粳15’和杂交粳稻‘陵风优18’为供试材料,设置大气背景臭氧浓度(Ambient)和高臭氧浓度(比Ambient增高21%,模拟21世纪中叶臭氧浓度)两个水平,研究臭氧胁迫对大田生长水稻成熟期稻米加工、外观、蒸煮/食味和营养品质的影响及其种间差异。结果表明,近地层臭氧浓度增高使稻米糙米率、精米率和整精米率均不同程度下降,其中精米率降幅达显著水平。与Ambient相比,臭氧胁迫使两品种稻米垩白米率、垩白大小和垩白度平均分别增加15.0%(P=0.10)、42.0%(P0.05)和60.5%(P0.05)。臭氧胁迫使稻米胶稠度平均降低7.1%(P0.05),但对两品种稻米直链淀粉和糊化温度均无显著影响。稻米RVA谱测定结果显示,臭氧胁迫对稻米最高黏度值、崩解值、冷胶黏度值、消减值和回复值均无显著影响。臭氧胁迫使两品种稻米蛋白质浓度呈增加趋势,但均未达显著水平。方差分析表明,多数情况下,两品种间稻米诸品质性状存在显著差异,但品种与臭氧的互作对所有测定指标均无显著影响,说明两品种稻米品质对臭氧胁迫的响应无明显差异。本试验在开放稻田条件下运行,适度臭氧胁迫使稻米垩白明显增加,胶稠度显著下降,但对其他米质指标影响较小,两品种趋势一致。

Effect of elevated surface layer ozone concentration on grain quality of two rice cultivars - A FACE study

AbstractTropospheric ozone has been assumed to be the most phytotoxic air pollutant, which has created a severe concern for environmental pollution due to its negative impact on crop production. However, high ozone concentration also affects crop quality, which has so far not been treated in sufficient detail. Rice (Oryza sativa L.) is one of the most important food crops in the world, providing a significant proportion of human daily dietary needs. The accurate assessment of the impact of elevated concentration of surface layer ozone on rice quality is critical for reducing uncertainties in predicting future global food security. Using a Free-Air gas Concentration Enrichment (FACE) facility in Xiaoji Town (which is in Jiangdu County, Jiangsu Province, China), we conducted a field experiment to investigate the impacts of ozone stress on rice grain quality, including processing quality, appearance quality, cooking/eating quality and nutritional quality. Two rice cultivars (a conventional japonica cultivar ‘Wujing 15’ and a hybrid japonica cultivar ‘Lingfengyou 18’) were exposed to either ambient or elevated ozone concentration (ca. 21% above ambient values) from tillering to harvest. The results showed that elevated ozone resulted in a small decrease in brown rice percentage, milled rice percentage and head rice percentage, with the effect on milled rice percentage significant at the 0.05 level. Averaged across the two cultivars, elevated ozone concentration increased chalky grain percentage, area of chalkiness and degree of chalkiness by 15.0% (P= 0.10), 42.0% (P< 0.05) and 60.5% (P< 0.05), respectively. On average, elevated ozone concentration decreased gel consistency by 7.1% (P< 0.05), while no significant effect was observed on amylose concentration and gelatinization temperature for both cultivars. Measurements of RVA profile (Rapid Visco Analyser) indicated no significant changes in maximum viscosity, breakdown, cold viscosity, setback, and return due to elevated ozone. Elevated ozone concentration caused a non-significant increase in grain protein concentration for both cultivars. Analysis of variance indicated that in most cases, the effect of cultivar differences was significant. However, the interaction of ozone with cultivar was not detected for the tested traits of grain quality, suggesting that the response to ozone stress was similar for the two rice cultivars. The open-air field experiment suggested that moderate high ozone environment greatly increased grain chalkiness and significantly decreased gel consistency, but had little effect on other quality parameters of both cultivars.