Temperature thresholds during the rice （Oryza sativa L.） cycle development have been reported to affect plant metabolism Therefore, this study aimed to evaluate the effects of the above-optimal temperature on photos...Temperature thresholds during the rice （Oryza sativa L.） cycle development have been reported to affect plant metabolism Therefore, this study aimed to evaluate the effects of the above-optimal temperature on photosynthetic and morphometric parameters in two contrasting irrigated rice genotypes （BRS Quer^ncia--sensitive and Nagina 22 （N22）~tolerant）. Plants of both genotypes were grown in rhizotrons and always maintained under two temperature conditions： Out--under environmental temperature conditions, and In--rhizotrons inside a plastic structure, which increased the temperature about 3 ~C to 5 ~C above the external one. In the genotype N22, there was an increase （twofold higher） in CO2 assimilation in plants cultivated under elevated temperature （In）. In BRS Quer^ncia, the stomatal conductance （gs） and transpiration rate （E） decreased upon high temperature. The rise in the temperature also negatively impacted in the modulated fluorescence parameters in both genotypes. Increases in root dry weight （RDW） and shoot dry weight （SDW） were also observed in the genotype N22 when compared to BRS Quer^ncia upon temperature rise. In general, the N22 genotype showed greater response to the above-optimal temperature due to its intrinsic thermotolerance traits over BRS Quer^ncia. Thus, N22 appeared as a potential donor of heat tolerance genes aiming to obtain new cultivar to face current global wanning.展开更多
文摘Temperature thresholds during the rice （Oryza sativa L.） cycle development have been reported to affect plant metabolism Therefore, this study aimed to evaluate the effects of the above-optimal temperature on photosynthetic and morphometric parameters in two contrasting irrigated rice genotypes （BRS Quer^ncia--sensitive and Nagina 22 （N22）~tolerant）. Plants of both genotypes were grown in rhizotrons and always maintained under two temperature conditions： Out--under environmental temperature conditions, and In--rhizotrons inside a plastic structure, which increased the temperature about 3 ~C to 5 ~C above the external one. In the genotype N22, there was an increase （twofold higher） in CO2 assimilation in plants cultivated under elevated temperature （In）. In BRS Quer^ncia, the stomatal conductance （gs） and transpiration rate （E） decreased upon high temperature. The rise in the temperature also negatively impacted in the modulated fluorescence parameters in both genotypes. Increases in root dry weight （RDW） and shoot dry weight （SDW） were also observed in the genotype N22 when compared to BRS Quer^ncia upon temperature rise. In general, the N22 genotype showed greater response to the above-optimal temperature due to its intrinsic thermotolerance traits over BRS Quer^ncia. Thus, N22 appeared as a potential donor of heat tolerance genes aiming to obtain new cultivar to face current global wanning.
