Effects Of Reservoir Water Operation On Rice's Some Physiological Characteristics And Yield Characters At Different Growth Stages

A pot experiment was carried out and the effects of reservoir water operation upon tillering dynamics, chlorophyll levels, leaf area, dry matter, root vigor, free proline content of leaf, stem bleeding saps, photosynthesis characteristic parameters and yield indicators of rice at different growth stages were studied systematically.The results indicated that:1. Maintaining a shallow layer of field at the returning green stage is beneficial to the growth and development of seedlings.2. Serious drought at early tillering will reduce the number of seedlings tillering, while mild drought at late tillering is more advantageous to increase the effective tillers of rice.3. Tillering stage is a critical period to lay the basis of chlorophyll levels. Drought at the tillering stage of rice directly causes the descendant of the chlorophyll level of functional leaves. The booting stage requires more water than other period, recovering water at booting stage can increase chlorophyll level of leaves quickly and substantially. Soil moisture condition at full heading stage can also influence the chlorophyll level of rice leaves, adequate water will improve the chlorophyll level of functional leaves effectively.4. The expansion of rice leaf will be restricted because of suffering drought at the tillering stage. The rice suffered drought at tillering stage, its leaf area could be compensated greatly, even bigger than the rice that does not suffer from drought at tillering stage, if it is re-watered at booting stage. Rice is very sensitive to water conditions at the booting stage, and it is the critical period of leaf area size of rice.5. The soil moisture condition of rice at tillering stage determines dry matter accumulation of rice. Re-watering at booting stage can increase dry matter weight of rice greatly, if rice suffered from drought at tillering stage, but it is difficult to return to level of not suffered drought at tillering stage. The dry matter accumulating could be slowed down if rice is subjected to drought during the booting stage. Suffering from drought does not cause a decline of dry matter accumulation during the full heading stage and milky stage.6. The rice roots can adapt to drought best from returning green stage to before jointing booting, It is easy to lead to premature senescence of rice roots if soil drought at later growth stages.7. The proline content of rice will be increased by suffering drought at tillering stage, while it will be increased more and bring serious injury to rice plants at booting stage. There is high water requirement of rice at full heading stage, subjected to drought during this period will hurt rice plants, but the extent of damage is small.8. The stem bleeding saps of rice subjected to drought at tillering stage is more than that of rice which is not subjected to drought, mild drought will increase the vitality of rice roots; Drought at the booting stage will decrease the stem bleeding sap of rice tender stem and reduce the vitality of rice roots, rice is very sensitive to drought at booting stage, during this period water requirement of rice is very large; Keeping a shallow layer of field at the full heading stage can increase the bleeding sap of rice tender stem and raise the vitality of rice roots.9. Rice is most sensitive to water at the booting stage, during this period subjected to drought will greatly reduce rice's leaves photosynthesis; rice in full heading stage is less sensitive to water than rice in booting stage, but it is also a period of large water requirement, if rice is subjected to drought at this growth stage can also affect the photosynthesis of rice leaves; At milky stage, rice is slow to soil moisture conditions, the effect of drought on rice leaf photosynthesis is little.10. Subjected to drought at the tillering stage will seriously impede the growth of rice and reduce the height of rice plants, re-watering at booting stage can stimulates plant growth, but the potential of grow taller is not large. Subjected to drought at the tillering stage will reduce the rice panicles, the effect of drought on rice panicles at the booting stage and full heading stage is little. Mild drought in the tillering stage cannot bring any harm to rice spikelet differentiation, instead it can raise the seed setting rate of rice, but serious drought in booting stage will greatly reduce rice yield and seed setting rate. Subjected to drought at the tillering stage will reduce the thousand kerner weight of rice, mild drought in the late tillering stage is help to increase the thousand kerner weight of rice, reservoir operation at the booting stage also increase the thousand kerner weight of rice.