A Physiological Study on Pre-harvest Sprouting in Rice Studies on Genetic Effects of Sterile Cytoplasm in Hybrid Rice(Oryza sativa L.Ssp.Sinica) EFFECTS OF Ca2+ ON PHOTOREDUCTION ACTIVITY OF ISOLATED CHLOROPLASTS AND RELATIONS TO CALMODULIN RELATIONSHIP BETWEEN NITRATE REDUCTASE ACTIVITY AND YIELD CHARACTER OF HYBRID RICE DURING GROWTH AND DEVELOPMENT