Effects of Light Intensity on Photosynthesis and Physiological Characteristics in Seedlings of Camellia pubipetala

Potted 3-year-old seedlings of Camellia pubipetala were grown in 10%,25%,50% and 100% natural light intensity,and the effects of light intensity on photosynthesis and physiological characteristics of C.pubipetala seedlings were studied.It will provide scientific basis for exsuit conservation and population recovery in C.pubipetala.(1)It has been found that with the increasing light intensity,the maximum net photosynthetic rate(Pmax),light saturation point(LSP) and apparent quantum yield(AQY) all decreased,while light compensation point(LCP) increased.The Pmax and AQY in 10% and 25% light were significantly higher than that in 50% and 100% light.(2)The contents of total chlorophyll(Chl),chlorophyll a(Chl a),chlorophyll b(Chl b) and carotenoid(Car) in leaves all decreased with increasing light intensity,while Car/Chl enhanced with stronger irradiance.(3)The chlorophyll a fluorescence parameters Fm,Fv,Fv/F0,Fv/Fm all decreased under high light,and Fm,Fv,Fv/Fm in 100% light were significantly lower than that in other three treatments,while these 3 parameters had no significantly difference in 10%,25%,50% light.(4)The contents of malondialdehyde(MDA) and proline(Pro) in leaves increased in strong light,and in 100% light,these two indexes were significantly higher than that in other three treatments,the contents of MDA in leaves was significantly higher in 50% light than that in 10% and 25% light.(5)There was no photoinhibition in 25% natural light intensity of C.pubipetala.While in 50% natural light intensity,its photoinhibition was mainly caused by reversible deactivation of PSⅡ reaction center.In 100% natural light intensity,the reaction center of PSⅡ was seriously destroyed,and there was a light oxidation in C.pubipetala.We concluded that C.pubipetala is a shade-tolerant plant,but it can bear a certain degree of strong light(50% light intensity).So the protect measure of moderate intermediate cutting upper layer trees could be adopted in over crown closure forest so as to increase forest light transmittance,which improve flowering and seed setting rate of the plant,and promote the natural regeneration of C.pubipetala population.C.pubipetala is suitable for growing in opening shade environments in ex-suit conservation.