Effects Of Nitrogen Application On Drought-resistance Capability Of Potato Seedlings (Solanum Tuberosum L)

To identify the influence of different nitrogen level on the performs of potato seedlings under drought stress, Chuanyu 117 which was widely cultivated in Sichuan province was chose as the material and adopted by sand culture measurement. Determining the growth situation, photosynthetic characteristics, blade plasma membrane system, osmotic regulation substances and protective enzyme system, leaf ultrastructure and potato yield, we try to reveal the drought resistance mechanism of early nitrogen application on potato seedlings through morphological characterizes, photosynthetic physiology, osmotic regulation, antioxidant metabolism, cell structure and physiological response. The main results were as follows:The results showed that the height, leaf area and L/T of potato increased with the increase of nitrogen concentration, while potato plant height, leaf area and leaf and L/T was inhibited by drought stress in comparison to more than normal water supply. Increased nitrogen relieved the inhibition of plant height and L/T, enhanced biomass accumulation to root under drought stress.Increasing nitrogen application can improve the photosynthetic capacity of potato, and slowing photosynthetic capacity decreased under moderate drought stress, but had no obvious effect on the potato photosynthesis under severe drought stress. Within high nitrogen levels, the potato leaf chlorophyll content and photosynthetic rate increased first and then decreased with the increase of nitrogen concentration. The decline degree of chlorophyll content and photosynthetic rate of heavy and moderate water stress treatment lower to of normal water treatment is minimum when the nitrogen concentration was 1.26 g/L.Drought stress could lead to increase the MDA content, but the MDA content decreased with the increase of nitrogen concentration. Compared to other nitrogen level, the MDA content of high nitrogen potato seedlings increased was the least rise in drought stress treatment as compared to CK, which illustrated that increasing nitrogen application could inhibit membrane lipid peroxide under drought stress, and make maintain potato leaf the cell membrane structure and function at relatively stable. However, with the increase of nitrogen concentration, the MDA content of different water treatments decreased firstly and then increased, the increasing range extent of MDA content of drought stress to CK appeared decreased firstly and then increased, and the smallest increase appeared in the nitrogen concentration of 1.26 g/L. It is showed that appropriately increase nitrogen application can effectively restrain the increase of potato plants of the membrane lipid peroxidation levels and the membrane permeability of potato seedlings under drought stress.Increased nitrogen application levels could promote pro content, soluble sugar, soluble protein content of potato leaves under drought stress. Pro content, soluble sugar, soluble protein content in high nitrogen treatment was significantly higher than that of other nitrogen treatment, so as to that effectively reduced the cell osmotic potential and maintain turgor pressure, and improved the plant osmotic regulation ability and drought resistance ability.Increasing nitrogen application could improve the ability of active oxygen metabolism enzyme, and reducing the damage of reactive oxygen species on the cell structure and function. However, with the increase of nitrogen concentration, the POD activity of different water treatment increased firstly and then decreased, the POD activity increasing range extent of drought stress treatment to CK appeared increased firstly and then decreased, and the biggest increase appeared in the nitrogen concentration of 1.26g/L.Drought stress causes potato mesophyll cell deepen damaged as the stress degree. Increased nitrogen levels can reduce chloroplasts and mitochondria damage under drought stress. With the increase of nitrogen concentration, the chloroplasts and mitochondria damage under drought stress appeared reduced firstly and then aggravated, and the lightest damaged degree appeared in the nitrogen concentration of 1.26 g/L.With the increase of nitrogen application, the potato yield under different water treatments appeared increased, and the yield under normal water conditions is greater than that under drought stress. The potato production of the high nitrogen treatment were higher than that of other nitrogen treatment, showing that increasing nitrogen application can promote the improvement of the potato yield under drought stress to some extent.In conclusion, increased nitrogen levels could reduce adverse effects of drought stress on growth and photosynthesis of potato seedlings, and could improve the gas exchange, the absorption and utilization of light energy, thus enhanced photosynthetic apparatus'adaptability to drought environment. It also improved the activities of antioxidase and the osmotic regulation substances content, thus reduced the damage of reactive oxygen species on the cell structure and function. The results showed that nitrogen supply at the early stage of potato growth helped potato seedlings to develop effective resistances to drought. However, with the increase of nitrogen concentration, the drought resistance of potato increased firstly and then decreased, excessive nitrogenous fertilizer could reduce the drought resistance of potato, which the strongest drought-resistant ability appeared in the nitrogen concentration of 1.26 g/L.