Study on photosynthetic characteristics in shoot-growing stage of Camellia oleifera clones.

Taking Camellia oleifera clones,including high-yield varieties,moderate-yield varieties and common varieties,as materials and using the Li-6400 portable photosynthesis system,the diurnal dynamics of net photosythetic rate(Pn),transpiration rate,and light response curves of net photosynthetic rate(Pn) in the shoot-growing stage of Camellia oleifera were compared and studied.The results showed that:(1) The diurnal variation of net photosynthetic rate(Pn) presented a single peak curve and a double peak curve,the single peak curve existed in the high-yield and moderate-yield varieties,while the double peak curve existed in the common varieties,and the common varieties appeared an obvious midday depression.There were significantly differences of Pn among the three types of varieties,which provided references for high photosynthetic efficiency breeding of Camellia oleifera.(2)The diurnal variation curve of transpiration rate presented a single peak curve and the diurnal variation curve of WUE presented a U-shaped pattern.(3)The maximum net photosynthetic rate(Pnmax) was 8.404-10.879 μmol CO2·m-2·s-1,light saturation point varied from 305 to 318 μmol·m-2·s-1 and light compensation point varied from 24 to 53 μmol·m-2·s-1.(4) Stomatal conductance(Cond),intercellular CO2 concentration(Ci) and air relative humidity were the dominant factors influencing the Pn of high-yield varieties.However,the dominant factors were stomatal conductance(Cond) for moderate-yield varieties,and Cond and Ci for common varieties.