Photosynthetic Characteristics in Fruit-growing Stage of Camellia oleifera Clones

In July,during the rapid-growth period of fruit of oil-tea camellia(Camellia oleifera),diurnal changes of net photosynthetic rate(Pn),transpiration(Tr),water use efficiency(WUE) of three clones(XL67、XL1 and CK) were measured comparatively with LI-6400P portable photosynthetic system.The results showed that the diurnal changes of Pn of XL67 and CK were in unimodal curves,but that of XL1 was in a bimodal curve.Different peak value and occurring time were different among the clones tested.Midday depression phenomenon of photosynthesis was observed in all clones.The values of Pn of XL67,XL1,and CK were 6.97,6.30 and 5.72 μmol·m-2·s-1,respectively,and there were significant differences between them.Diurnal changes of Tr presented as unimodal curve while diurnal changes of WUE presented as a U curve.The maximun net photosynthetic rates of three clones were 9.79 to 14.20 μmol·m-2·s-1,the light saturations of three clones were 409 to 540 μmol·m-2·s-1,and the light compensation points of three clones were 58 to 82 μmol·m-2·s-1.Main factors which influenced Pn were analysed by multivariate stepwise regression.