The Physio-ecological Mechanisms For Water Deficit Compensatory And Water-saving Effect During The Period Of Late-tillering In Rice

The growth of crop could be compensated when it is rewatered after water stress. The losses which it suffered during drought period will be made up, or even be excessive compensated if the water treatment is appropriate. The mechanisms of water deficit compensation and water- saving in crop are meaningful for applying in agriculture. We set different moisture gradient and densities to study the molecular physio-ecological responses of rice to water deficit and rehydration during the period of late-tillering. The inner mechanisms of compensatory water-saving are explored in this paper.The water treatments of this research are divided into three levels, which are well-watered,5-day drought and 10-day drought. The densities were 15 plants,45 plants and 90 plants in every square metre. We measured morphological indices such as tillers number, height, biomass, grain yield, physiological indicators such as photosynthesis, transpiration, stomatal conductance, water use effeciency, molecular indicators such as the activity of RuBP carboxylase and PEP carboxylase and so on. The results are as follows.(1) The invalid tillers and growth of rice could be reduced through the regulation of watering. The water use effeciency and grain yield could be improved. We measured the number of tillers during the period of water stress and rehydration. The aboveground biomass of water treatment groups were lower than the control after the harvest of rice, but the grain yield were a small amount of lower or even higher than the control. The harvest index of water treatments were all higher than the control.(2) The compensatory effect and threshold were significant in the physio-ecological aspects after appropriate water deficit during the period of late-tillering in rice. The photosynthesis, transpiration rate and stomatal conductance in excess of the threshold exposure were significantly lower, the number of tillers reduced, the growth of shoot biomass was inhibited, root biomass and root to shoot ratio increased during water stress period. The photosynthesis, transpiration rate and stomatal conductance increased, the aboveground biomass compensated in some extent, belowground biomass and root to shoot ratio decreased after the resumption of water.(3) The photosynthetic circle of C4 could be induced by the water stress and rehydration in rice. The activities of RuBP carboxylase and PEP carboxylase increased during the period of water deficit. The activities of RuBP carboxylase and PEP carboxylase were still higher than the control in a certain period after water recoverWe find that the water deficit compensatory effect of 10-day drought in density of 45/m2 was the best by the treaments of water and densities during the period of late-tillering in rice. The changeable mechanisms of experiment parameters such as photosynthetic indices and activities of enzymes provide a theoretical support for the study of water deficit compensatory effect and water-saving technology in rice.