Effects of shades on the photosynthetic characteristics and chlorophyll fluorescence parameters of Urtica dioica Responses of growth and chlorophyll florescence of Emmenopterys henryi seedlings to different light intensities Chlorophyll fluorescence characteristics of photosystem Ⅱ of two cultivated poplars seedlings Characteristics of Photosynthesis and Thermal Dissipation in Mentha haplocalyx Briq.in Qinghai Effects of NaCl and Drought Stress on Quality and Chlorophyll Fluorescence Parameters of Kentucky Bluegrass Photosynthetic Physiological Characteristics and Ultrastructure of Salvinia natans Leaves under Cr6+ Stress Daily Change of Photosynthesis and Chlorophyll Fluorescence of Dendrobiumhuoshanense Influence of Drought Stress on Plant Growth and Photosynthetic Traits in Maize Seedings