| Thermo-tolerance of modern high-yielding Indica and Japonica and hybrid rice varieties were researched. According to high-temperature disorder in heading to flowering and high temperature damage in productive phase, studying high-temperature reaction and physiological characteristics of fertilization and enrichment in order to definite the relationship between breed characteristics of rice pollen behavior and thermo-tolerance formation in heading to flowering. Analysis the effects of high temperature in productive phase towards seed setting growth and yield formation. Main results were as follows:(1) In experiment varieties and combinations, modern Japonica varieties showed better thermo-tolerance in heading to flowering, while two-line hybrid rice worse. In this experiment, the Wuxiangjing 14 and Ningjing 1 had better thermo-tolerance than hybrid rice, and even better than conventional indica Yangdao 6. Two-line hybrid rice Yangliangyou 6 showed weaker thermo-tolerance in a low heat stress, the fertilization rate compared with other materials down to a very low level. Three-line hybrid indica Shanyou 63 had a strong resistance under a weaker heat stress in flowering stage, but the resistance fell rapidly under high heat stress.(2) There were two heat stress reaction type before and after flowering. The first, pollen enriching process before flowering had higher response than fertilization process after flowering, such as Shanyou 63; the second, fertilization process after flowering had higher response than pollen enriching process before flowering, such as Yangliangyou 6, Yangdao 6 and Ningjing 1.(3) The pollen number in anther of experiment materials showed that hybrid rice has a higher level of pollen number per anther. There was no significant correlation between pollen enrich number and fertilization under heat stress. It meant that rice thermo-tolerance in flowering stage wasn't affected by pollen production capacity.(4) Heat stress made anther dehiscent coefficient significantly declined. And with the high temperature treatment time prolonged, anther dehiscent coefficient declined more significantly, and this trend was even significant under 39℃heat stress. In the condition of higher heat stress, anther dehiscent of hybrid rice might be more easily locally inhibited, and mainly spread pollen with poricidal dehiscence. Ningjing 1 could keep longitudinal cracking for a longer time under stronger heat stress. In the condition of heat stress, the pollen number on rice stigma was significantly fewer than control under natural temperature, and with high temperature treatment time prolonged, the pollen number reduces even more. These showed that pollen cracking characteristics has a greater influence on rice thermo-tolerance in flowering stage, the bigger the anther cracking coefficient, the more the number of pollen on stigma, and the stronger the thermo-tolerance.(5) High temperature treatment in productive phase caused yield dramatically reduced. The effect of high-temperature treatment in early productive phase was greater than that in middle productive phase. Rice matter production in productive phase under heat stress reduced significantly. Heat stress in early productive phase also inhibited the rate of the translocation of the storage material in the stem-leaf sheath. But after long time heat stress, it was higher than control under nature temperature. Photosynthesis rate of flag leaf under high-temperature treatment reduced significantly, but it showed higher thermo-tolerance in early stage of photochemical reaction.(6) Heat stress treatment seriously inhibited dry matter accumulation of endosperm. On superior grains, mainly in grain growth in the latter part of the enriched material was significantly inhibited. For inferior grains, there was obvious growth retardation in early filling stage, grain weight reduction more serious than superior grains. Because of grain development being inhibited, unfulfilled grains significantly increased, seed setting rate reduced seriously.
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