Effects Of Drought Stress On Tolerant Plants-Soil System In Shanxi Industrial And Mining Regions

Taking the tolerant plants of Lolium multiflorum, Agropyron desertorum, Poaannua and Medicago sativa as experimental plants, and the raw loess, mellow soil and coal gangue in the Industrial and Mining areas of Shanxi Province as the experimental soil matrix, physiological response characteristics of tolerant species and soil system under drought stress were conducted in green house. The treatments consisted of three levels of drought:normal soil moisture (75-80%of field capacity levels), slight drought (55-60%of field capacity levels), and severe drought (35-40%of field capacity levels). The effect of drought stress on the plant overground biomass, antioxidant enzyme activity, the diversity of soil microbial community and plant photosynthesis-characteristic were studied by the methods of the continuous extraction method, biochemical technology, denaturing gradient gel electrophoresis (PCR-DGGE) etc. The main results were as follows:(1) Overground biomass of the four tolerant herbaceous plants under heavy drought stress was significantly lower than that under normal water condition and slight drought stress in three kinds of soil matrix (P<0.05). It indicated that the plant growth was limited by heavy drought stress. While Overground biomass of Agropyron desertorum and Poaannua under heavy drought stress was higher than those under normal water condition and slight drought stress in mellow soil, which indicated that these two species had high tolerance to drought stress under the condition of sufficient soil nutrition.(2) The SOD activity of the four tolerant herbaceous plants increased with increasing levels of drought stress in three soil matrix, while the POD activity had no significantly increased except Medicago sativa in raw loess under severe drought stress. MDA content of the four species increased with increasing levels of drought stress. The results suggested that all the plants suffered oxidative damage and they could enhance their antioxidant capacity by increasing activties of antioxidant enzyme under differnet levels of drought stress.(3) DGGE bands of soil microbial community of four tolerant herbaceous plants in three kinds of soil matrix was significantly different under different water treatment. Soil microbial diversity of Lolium multiflorum in different soil matrix was as follows:mellow soil≈coal gangue with raw loess> raw loess. Soil microbial diversity of Agropyron desertorum in different soil matrix was as follows:mellow soil> raw loess> coal gangue with raw loess. However, Poaannua grown in different soil matrix had little change in the diversity indices. Soil microbial diversity for most plants was generally lower under drought stress than normal water condition except that Lolium multiflorum grown in coal gangue with raw loess and Medicago sativa grown in three kinds of soil were just reversed. In addition, Medicago sativa grown in three kinds of soil had high diversity indices under drought stress.(4) The net photosynthesis rate of four tolerant species of herbaceous plants grwed in three kinds of soil matrix under normal water condition was higher than under drought stress. It was highest for Lolium multiflorum grown in mellow soil under slight drought stress when the net photosynthesis rate of this species in drought stress or three kinds of soil matrix was compared, followed by grown in coal gangue with raw loess under heavy drought stress. For Agropyron desertorum and Poaannua, the net photosynthesis rate varied very little. While for Medicago sativa grown in coal gangue with raw loess and raw loess, the net photosynthesis rate were both high under slight drought stress.In total, the growth of Lolium multiflorum grown in mellow soil and coal gangue with raw loess was beeter than in raw loess, and the effect of slight drought stress on this species were much small. Agropyron desertorum could grow well in mellow soil under heavy drought stress, or in coal gangue with raw loess under slight drought stress. Poaannua could grow well on three soil matrix under drought stress. And Medicago sativa grown in coal gangue with raw loess had high resistance to heavy drought stress.