Effects of Water Stress on growth, nutrition and physiological indices of Hemarthria compressa

As one of artificial pasture in Southwest China, Hemarthria compressa often suffers from drought due to frequently occurred dry spells. A green house pot experiment was carried out to study the effects of drought on the growth, nutrition and physiological indices of Hemarthria compressa under light, middle and serious water stresses. The control was established with normal water supply. The results indicate that the aboveground growth is inhibited and the biomass is reduced by 20-34% under the middle and serious droughts compared to those of the control, while underground growth is not significantly affected. As a result, the ratios of root to shoot are increased which benefit to improve the drought resistance. The absorptions of N, P and K are decreased significantly under the water stresses, which are possibly related to the drop of the root activity. The accumulations of nutrients in the aboveground are significantly reduced under the water stresses; while those of the roots are not affected. These results indicate that the nutrient distributions in the plants are changed. Notably, the K contents of roots are significantly increased under droughts, with the highest value of 36% compared with the control. K plays an important role in improving osmotic pressure of root cells, and promotes the moisture absorption. Moreover, the relative water contents of leaves, chlorophyll contents and root activities are reduced at different scales. The reductions are one of possible reasons to decrease photosynthetic rate, absorption of nutrients and the yield of pasture. However, the proline content is increased 1.7 times compared with the control, which is higher than the decrease of other physiological indices. Hence, the accumulation of proline might be regarded as the protective biochemical reaction produced by the plant, especially under the light water stress.