EFFECTS OF LOW POTASSIUM STRESS ON PHOTOSYNTHETIC CHARACTERISTICS AND ANTIOXIDANT SYSTEMS IN DIFFERENT POSITION LEAVES OF RICE PLANTS Changes in Reactive Oxygen Species and Antioxidative Defense Mechanism in Tomato Leaves under Low Potassium Stress Some agronomic and nutritional characteristics for potassium efficient rice genotypes under low potassium stress Overexpression of Millet Transcription Factor Gene SiNAC45 to Response of Low Potassium Stress and ABA Treatment in Transgenic Arabidopsis Physiological Characteristics of Delaying Leaf Senescence in Maize Inbred Lines Tolerant to Potassium Deficiency