The Carboxylation Rate of Rubisco and Activity of Carbonic Anhydrase in Plants from a Subtropical Forest Grown at Different Light Intensity Study on Diurnal Photosynthetic Characteristics in Different Alfalfa Leaf Layers in Loess Plateau Effects of Oligochitosan on Photosynthetic Parameter of Brassica napus Seedlings under Drought Stress Diurnal Variation in Photosynthesis of Differently Directional Leaves in Hybrid Hazels (Corylus heterophylla×Corylus avellana)