Differences In Canopy Temperature Among Different Mid-season Rice Varieties And Its Relationships With Yield And Heat Resistance

The study was conducted in the science and technology park of Jiangxi Agricultural University in 2013-2015. 21 varieties of middle rice were used as materials in 2013 to screen the canopy temperature, ear temperature and those depressions with gas from booting stage to milking stage, and study the change rule of temperature and those relationships with yield. In 2014, selected two typical varieties on the basis of 2013,compared those population characteristics, leaf anatomical structure and physiological characteristics then analyzed the mechanism of canopy temperature differentiation of middle rice. A pot experiment of two rice varieties with high temperature treatment started in 2015, observed leaf temperature, ear temperature and related physiological traits, preliminary explored the relationships between canopy temperature and heat resistance of middle rice and their heat-resistant mechanism. The main results are as follows:The day canopy temperature depression, gas spike temperature depression were positively correlated with rice yield at different times, which day canopy temperature depression was significantly correlated at milking stage. Through cluster analysis, all varieties can be divided into low temperature, medium temperature and high temperature type three types.Net photosynthetic rate and transpiration rate of low temperature type variety were significantly higher than that of high temperature type variety at heading stage, but stomatal conductance and intercellular CO2 concentration without significant difference.Compared to high temperature type variety, the leaf chlorophyll of low temperature type variety was in slow decomposition rate at heading and milking stage. Low temperature type variety had high canopy light transmittance rate and leaf area index was significantly lower than that in the high temperature type variety, but with high dry matter translocation rate in mature period. Stomatal area of low temperature type variety was significantly higher than that of high temperature type varieties, the leaf vascular bundle area without significant difference. Catalase(CAT) activity of low temperature type variety at booting stage was lower than that of high temperature type variety, peroxidase(POD), superoxide dismutase(SOD) activities and malondialdehyde content had nodifference; the activities of antioxidant enzymes at heading stage showed no significant difference.Both natural and high temperature conditions, temperature of flag leaf and spike were consistent with air temperature and lower than air temperature; the difference of gas leaf and gas spike temperature depression were not obvious in varieties; but accumulation of gas spike temperature depression in varieties were obvious under natural condition.High temperature at heading stage significantly reduced seed setting rate of rice, varieties of seed setting rate, high temperature stress index had no significant difference. Gas leaf and gas spike temperature depression and heat resistance of middle rice had no obvious correlation. Under the natural condition, the varieties with low air spike temperature difference had higher net photosynthetic rate and transpiration rate. The soluble sugar and protein content in leaves were higher, and the CAT activity was stronger. The extreme high temperature had a serious effect on the metabolism of rice, and different varieties showed different heat resistance mechanisms.