Study On Mechanism Of High Temperature Response Of Photosynthesis In Super Hybrid Rice And Their Parental Lines

Temperature is one of the main ecological factors that effect rice growth and development,the change of which will arose the rice complicated physiological and biochemical response.Simultaneous measurement of the responses of leaf gas exchange and modulated chlorophyll fluorescence to light and CO₂ concentration to determine a wide range of key biochemical and biophysical limitations on photosynthesis in vivo.Using both theoretical and experimental evidence, we describe the temperature response of instantaneous net CO₂ assimilation rate(A)in terms of these limitations,evaluate possible limitations on A at elevated temperatures arising from heat-induced variations of Rubisco kinetic parameters,and compare the difference of photosynthetic rate among the varieties.The results show that:(1)Mesophyll conductance in flag leaves of super hybrid rice and their parent line was determined via measurements of gas exchange, coupled with modulated chlorophyll fluorescence,we found that mesophyll conductance of Y58S was si higher than other varieties, and pionted out that Raising mesophyll conductance is an efficiency way to improve photosynthetic rate of super hybrid rice.(2)Using both theoretical and experimental evidence,we found that Rubisco capacity is the predominant limitation on photosynthesis at high growth temperature.(3)Compare with pei'ai 64S,the higher stomatal conductance,apparent quantum yield of carbon assimilation and electron transport rate,may be the physiological basis for photosynthetic efficiency of Y58S in high levels.