Abstract
This study was conducted to examine the effect of temperature on heterosis in photosynthetic characteristics in F1 hybrid rice (Oryza Sativa L.) from a thermo-sensitive genie male sterile line. At the active tillering stage, photosynthetic parameters were measured at 5 temperature levels (20, 25, 30 35 and 40°C), and chlorophyll fluorescence quenching was measured at 25°C in the F1 hybrid and its parents. Within a temperature range of 20-35°C, CO2 exchange rate and other photosynthetic characters viz., stomatal conductance and transpiration rate were lower in the F1 hybrid than the male parent. On the other hand, at 40°C, these characters were higher in the F1 hybrid than in parents. Non-photochemical quenching in the F1 hybrid was higher than that in parent cultivars, whereas no significant differences in effective quantum yield of photosystem II, electron transport rate or photochemical quenching were observed between the F1 hybrid and parent cultivars. It is considered that the positive heterosis for CO2 exchange rate at higher temperature was due to the higher stomatal conductance and the higher non-photochemical quenching.
