Effects of shade treatments on the photosynthetic capacity, chlorophyll fluorescence, and chlorophyll content of Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diels et Gilg was grown under full sunlight and moderate and high levels of shade for one month to evaluate its photosynthetic and chlorophyll fluorescence response to different light conditions. The results showed that T hernsleyanum attained greatest leaf size and P-n when cultivated with 67% shade. Leaves of seedlings grown with 90% shade were the smallest. Leaf color of plants grown under full sunlight and 50% shade was yellowish-green. The P-n value increased rapidly as PPFD increased to 200 pmol m(-2) s(-1) and then increased slowly to a maximum, followed by a slow decrease as PPFD was increased to 1000 mu mol m(-2) s(-1). ion was highest for the 67% shade treatment and the LSP for this shade treatment was 600 mu mol m(2) s(-1). Full sunlight and 50% shade treatments resulted insignificant reduction of ETR and qP and increased NPQ, Chl a, Chl b and total chlorophyll content increased and Chl a/b values decreased with increased shading. Results showed that light intensity greater than that of 50% shade depressed photosynthetic activity and T hernsleyanum growth. Irradiance less than that of 75% shade limited carbon assimilation and led to decreased plant growth. Approximately 67% shade is suggested to be the optimum light irradiance condition for T hernsleyanum cultivation. (C) 2008 Elsevier B.V. All rights reserved.