Effects of Shading Stress and Light Recovery on the Photosynthesis Characteristic and Chlorophyll Fluorescence Characteristic of Fragaria Ananassa Duch. cv. Toyonoka

Light is an important resource for plant growth and development, crops need to change their physiological characteristics to different light environments. Fragaria ananassa Duch. cv. Toyonoka. is an important economic plant which is widely planted at home. A greenhouse experiment was conducted from April 2010 with different sun-shading treatment, 85% (CK), 60% (T1), 35% (T2) and 10% (T3). After 7 days of shading stress, the physiological characteristics were slowly recovered. The results showed that (1) Under shading condition, Light saturation rate (Amax), Apparent Quantum Yield (AQY), Carboxylation Efficiency (CE), dark respiration (Rd), Light Saturation Point (LSP) and Light Compensation Point (LCP) became lower. (2) The maximal fluorescence (Fm), light energy transformation efficiency of PS II (Fv/Fm), actual photochemical efficiency of PS II in the light (Yield), photochemical quenching coefficient (qP) declined with shading stress increase. (3) There were significant difference in the chlorophyll fluorescence parameters among different treatment groups by the end of sun-shading treatment (p<0.05). After the light was recovered, the physiological characteristics could rapidly recover under low shading stress and moderate shading stress, while in severe shading stress the physiological characteristics hardly recover.