Study On Physiological Characteristics Of Rice Under Farmland Water Level Management

Based on the experiential data, the change rules of the rice physiological indexes under different water level management were analyzed, the best water level management mode for the growth of rice were looked for. Analyzed the diurnal Changes, the change rules in different growth periods and the relation of the environment factors about rice' leaf water potential, stomatal conductance, transpiration rate, net photosynthetic rate, and chlorophyll fluorescence characteristics.The results showed that under different water lever management the rice' leaf water potential, stomatal conductance, transpiration rate, net photosynthetic rate, conversion efficiency of primary light energy(Fv/Fm) and PS II and photochemical quenching coefficient(qP) all assumed the rules that reduced in water controlled period and rose after the water level become normal, but the minimal fluorescence(Fo) assumed the opposite rule. All the chlorophyll fluorescence characteristics change scope increased with the enlargement of the stress degree and the advancement of the stress lasting. The conversion efficiency of primary light energy(Fv/Fm)'s diurnal variation was a "V" type curve, the leaf water potential,stomatal conductance, transpiration rate, net photosynthetic rate, PS II and photochemical quenching coefficient(qP)'s diurnal variation were parabola or "M" type curve. Leaf temperature is the most tremendous influence factor to the transpiration rate, the next is photosynthetically active radiation, air humidity is the smallest influence factor. Leaf water potential, stomatal conductance, transpiration rate, net photosynthetic rate, and chlorophyll fluorescence characteristics are easiest to be influence by photosynthetically active radiation, soil (leaf) temperature to be next, air humidity (relative humidity) to be smallest.Under -100mm water level condition in the elongation and booting stage for 3 days, under -100mm and 200mm water level condition in earring period for 4 days, the rice net photosynthetic rate (Pn), efficiency of primary light energy(Fv/Fm) and PS II and photochemical quenching coefficient(qP) were higher than the normal water level conditions. The adjustment ability and the adaptive capacity of rice has strengthened, the SP II react centre shut off proportion reduced, the electron's transfer ability improved, the photosynthesis strengthened. It indicated that it was good for the growth of rice to light drought in the elongation and booting stage or to light drought or appropriate flood in earring period.