Effects of Shading on Net Photosynthetic Rate and Chlorophyll Fluorescence Parameters of Leaf in David Maple(Acer davidii Franch.)

The shoot growth and the pigment content,net photosynthetic rate,transpiration rate and chlorophyll fluorescence of leaf under different shading treatments(0%,15%,35% and 50%)were investigated in david maple seeding.The results showed that the pigment content,net photosynthetic rate,minimal fluorescence(Fo),conversion efficiency of primary light energy(Fv/Fm)of PSⅡ and photochemical quenching coefficient(qP)were enhanced,but the non-photochemical quenching coefficient(qN)was decreased as shading increased.The diurnal variation curve of net photosynthetic rate had two peaks under 0% and 15% shading treatments,while there was only one peak under 35%and 50% shading treatments.The diurnal variations of Fv/Fm showed increase-decrease-increase curve under 0% and 15% shading treatments,and kept stable in 35% and 50% shading treatments.It is concluded that 50% shading suitable for the growth of david maple seedlings.