Effects of Low Light Intensity on Gas Exchange and Chlorophyll Fluorescence Characteristics of Capsicum Seedlings

The effects of low light(75-100 μmol·m-2·s-1)on photosynthetic gas exchange,chlorophyll fluorescence and chlorophyll contents in seedlings of different Capsicum were studied.The results showed that under low light,net photosynthetic rate(Pn),dark respiration rate,night respiration rate,actual photochemical efficiency of PSⅡin the light(ФPSⅡ),electron transport rate(ETR),photochemical quenching(qP) and excitation energy to PSⅡphotochemistry decreased,whereas the heat dissipation increased and no significant changes in maximal photochemical efficiency of PSⅡ in the dark(Fv/Fm).From the response curve of ФPSⅡ to light intensity,it was seen that with the increase of light intensity,there was a faster decrease in ФPSⅡ.The response curve of ETR to light intensity indicated that Capsicum grown under low light had lower saturate electron transport rate light and saturation point of electron transport rate,as compared with those grown under normal light.The SPAD value of leaves in Capsicum decreased which mean that the synthesis of chlorophyll was inhibited under low light.Capsicum with lower net photosynthesis decreasing,higher Fv/Fm and ETR may possess potential low light-tolerance.