STUDIES ON PHOTOSYNTHETIC CHARACTERISTICS IN RICE HYBRID PROGENIES AND THEIR PARENTS I. CHLOROPHYLL CONTENT, CHLOROPHYLL-PROTEIN COMPLEX AND CHLOROPHYLL FLUORESCENCE KINETICS Exogenous betaine improves photosynthesis of Lycium barbarum under salt stress Comparison on Characteristics of the Fast Chlorophyll Fluorescence Induction Kinetics between Pinus Species and Populus Species Comparison of Growth and Photosynthesis in Response to Salt Stress in Populus Hybridization Clones and Their Parent Species