Effect Of Drought Stress On Anatomical Structure And Physiological Characteristics In Solanum Nigrum

This experiment used potted Solanum nigrum which was in vegetative growth stage as test material. This experiment studied the effect of drought stress on anatomical structure of root and stem and leave of Solanum nigrum. At the same time, this experiment also determined the growth indices and physiological indices and photosynthetic characteristics of the Solanum nigrum under drought stress. By studying the anatomical structure and physiological and photosynthesis indices under the drought stress, we hoped to explore the mechanism of adapting to drought of Solanum nigrum and to provide the theoretical basis for the further research. Studies shows:1. Drought stress had certain effect on the anatomical structure of the Solanum nigrum. The total thickness of leaves, palisade tissue thickness, spongy tissue thickness was trended to increased and then decreased with drought stress increasing. And the ratio to palisade tissue and spongy tissue became bigger. Both the diameter of vessels in main vein of leaf and the thickness of catheter wall became bigger. The diameter of vessels in xylem of stem became bigger, but the thickness of catheter wall became smaller. Both the diameter of vessels of root and the thickness of catheter wall became bigger.2. Drought stress had significantly effected on the growth and development conditions of the Solanum nigrum. With drought stress increasing, the plant height, leaf length and leaf width decreased. Under the severe drought, they decreased 47%,28.71% and 24.29% respectively, which was significant. With drought stress increasing, the total biomass, the biomass of root, stem and leaf also decreased. The effect of drought stress on the biomass of stem, leaf was more than the biomass of root. Under drought stress conditions, the biomass was decreased, but Solanum nigrum had distributed more biomass to root system. Therefore, the root to shoot ratio were increased.3. Drought stress had varies degrees effected on the physiological of the Solanum nigrum. Proline accumulation of Solanum nigrum under drought stress and the change of soluble sugars, soluble protein and malondiadehyde were same as proline. But water content in plant tissue and chlorophyll content were decreased with increasing of drought stress. The highest of proline were observed under severe drought was three times almost under normal water. Solube sugar accumulated significantly, solube protein also accumulated under water stress. It can keep low malondiadehyde content.This showed that the drought tolerance of Solanum nigrum was better. Under drought stress conditions, SOD activity was increased, but POD activity and CAT activity was trended to increased and then decreased. Under the severe drought, they also increased 26.71% and 19.55% respectively.4. Drought stress had differently effected on the photosynthetic characteristics of the Solanum nigrum. With drought stress increasing, the net photosynthetic rate, stomatal conductance and transpiration were decreased. Intercellular CO2 concentration was trended to decreased and then increased with drought stress increasing. While the water use efficiency was trended to increased and then decreased. The main reason caused the decreasing of the net photosynthetic rate was stomatal limit under light drought and moderate drought treatments, while the decreasing of the net photosynthetic rate was mainly caused by non-stomatal limit under severe drought treatment.A conclusion can be got from this research that drought stress had certain influence to the anatomical structure, growth, physiological and photosynthetic characteristics of Solanum nigrum. Under drought stress conditions, Solanum nigrum increased the content of proline to keep its normal physiology from being hurt from drought stress. At the same time, Solanum nigrum adjusted its stomatal movement, increased its stomatal conductance, and enhanced its water use efficiency to decrease the hurt to photosynthesis from drought stress. At the same time, anatomical structure had certain changes to adapt the drought stress.