The Preliminary Study of Xantha Mutants in Oncidium LEAF SENESCENCE AND PROTECTIVE ENZYME ACTIVITIES OF A XANTHA MUTANT RICE(Oryza sativa L.) THE DIURNAL VARIATION OF PHOTOSYNTHESIS OF A XANTHA MUTANT IN RICE(Oryza sativa L.) Research on Physiological Basis of Xantha Rice Mutant Functional Leaves Senescence Photosynthesis and Chlorophyll Fluorescence Characters of Xantha Wheat Mutants Chloroplast Ultra-structure of a Xantha Wheat Mutant Response of High-temperature Stress on Photosynthetic Characteristics and Chloroplast Ultrastructure of Flag Leaves in Xantha Rice Mutant