Effect of Shade on Photosynthesis, Specific Leaf Weight, Leaf Chlorophyll Content, and Morphology of Young Peach Trees

Abstract One-year-old peach [ Prunus persica (L.) Batsch cv. Redhaven] trees were grown outdoors under 4 different shade levels (100%, 36%, 21%, and 9% of full sun). Shoot length, internode length, and node number were unaffected by shade, but heavy shade (9% full sun) reduced stem diameter 24%. Compared to those in full sun, average leaf areas were increased 18%, 30%, and 20% by 36%, 21%, and 9% shade, respectively. Shading caused a more horizontal leaf orientation and lower specific leaf weight. Both average and maximum photosynthetic rate per unit area or per mg chlorophyll decreased with shading, but increased with shading when expressed per unit dry weight. Chlorophyll content per unit leaf area increased with shading, but stomatal resistance was unaffected. Leaves from shade treatments became light-saturated between 400 and 600 µEs -1 m -2 ; full-sun leaves became light-saturated at 700-900 µEs -1 m -2 .