Light Regulatilon of the Synthesis of Ribulose 1,5-Bisphosphate Carboxylase and Fructose 1, 6-Bisphosphatase Effect of Jasmonic Acid Methyl Ester on the Photosynthesis of Rice Seedlings Response Characteristics of Plant Growth and Leaf Photochemical Activity of Sugar Beet Seedlings to Different Nitrogen Application Levels Differences of Photosynthetic Characteristics and Low Light-tolerance in Seedlings of Four Pepper Cultivars Differences of Photosynthetic Characteristics and Low Light-tolerance in Seedlings of Four Pepper Cultivars