The Influences Of Drought Hardening And Continuous Cropping Regulation On The Growth And Resistance Physiology Of Potato

Potato(Solanum tuberosum L.) is one of the most common and important economical crops, and widely cultivated in our country and even the world. Potato planting areas in our country most distribute in arid and semi-arid areas, water shortage is one important environment factor which limiting potato tuber yield and quality. With the expansion of potato cultivation area and intensive management, there is an evident phenomenon of potato continuous cropping, and causes serious harms to potato production. How to alleviate the damage of drought stress and continuous cropping obstacle on potato production becomes one problem which needs to be solved urgently. For this reason, this paper was to investigate the effects of drought hardening and continuous cropping regulation through the indexes of resistance physiology and growth of potato, to improve the cultivation measures and physiology mechanism understanding under continuous cropping and drought conditions, so as to provide the theoretical and technical support for the healthy and sustainable development of potato production in our country. Studies in this paper are described as follows:1. The influence of drought stress and drought hardening on the growth and development, resistance physiology and leaves microstructure of potato seedlings were studied, and the mechanism of drought hardening improving drought resistance of the potato seedlings was elucidated in this chapter. The results showed that the drought stress caused an adverse effect on the potato seedlings, yet drought hardening could alleviate it, for example, drought hardening alleviated the decrease of water content, net photosynthetic rate and chlorophyll content, relatively increased the water utilization efficiency, inhibited the increase of MDA content of the potato seedlings leaves under the drought stress. Furthermore, drought hardening improved the activities of antioxidant enzymes, the content of osmotic regulatory substances and even the content of ABA and polyamines of the potato seedlings leaves. The results also indicated that potato leaves thickness decreased under drought stress, palisade tissue,spongy tissue and ratio of palisade tissue and spongy tissue changed very significantly, but drought hardening could revise this changes. Through the above changes the transpiration of the leaves reduced and the leaves water content reduction was alleviated under subsequent drought stress. In the other way, through improving the contents of polyamines, ABA, osmotic regulatory substances and the activities of antioxidant enzymes, the drought resistance of the potato seedlings was enhanced. So it could be concluded that drought hardening had a positive role in improving potato drought resistance through the changes of the resistance physiology, and even the leaves microstructure.2. The study was to elucidate the impact of continuous cropping obstacle on potato resistance physiology and leaves microstructure. Based on soils’ different continuous cropping years, combined with potato growth and leaves anatomy structure, the resistance physiology of potato was discussed. The results indicated that organic matter content and available phosphorus content of potato rhizosphere soil decreased with the increase of continuous cropping years, the content of nitrogen and soil p H value raised. Soil enzymes including alkaline phosphatase, urease, sucrose invertase and catalase activities gradually reduced, especially in cropping 6 years. The amount of soil bacteria and actinomycetes decreased, the amount of fungi increased and then decreased. Continuous cropping obstacles caused by deterioration of soil environment occurred, inhibited potato growth, plant height, root length, aboveground biomass and plant tuber weight increased in cropping three years and then decreased in 6 years, the stems crude gradually reduced, even for 6 years. Meanwhile, with the increase of continuous cropping years, potato leaves’ s photosynthesis reduced, MDA content increased, resulting in the accumulation of peroxide, antioxidant enzyme activity weakened and caused the further damage of reactive oxygen, then the potato resistance weakened, affected potato growth in general. The leaves anatomical structure showed that leaves thickness, palisade tissue thickness decreased, ratio of palisade tissue and sponge tissue also declined significantly. Therefore, this paper explained the effects of potato continuous cropping obstacles in the two aspects of resistance physiology and anatomical structure, which is important for the understanding of the mechanism about potato continuous cropping obstacles.3. To explore the influence of oil-sunflower rotation on the growth and resistance physiology of different continuous cropping potato, compared with potato before planting quinoa, 4 years continuous cropping potato, 1 year rotation oil-sunflower after 4 years continuous cropping potato, 6 years continuous cropping potato, 1 year rotation oil-sunflower after 6 years continuous cropping potato of the same test field was chosen, changes of soil properties, soil enzymes activities and soil microorganism quality were measured. Then planted potato in this experimental field, measured their photosynthesis, antioxidant enzyme activities and potato growth indicators. The results showed that with the increase of continuous cropping years, potato soil rhizosphere p H value increased and tended to alkalinity in general, the content of organic matter and available phosphorus decreased, alkali-hydrolyzable nitrogen content increased. Soil enzyme activities were negatively correlated with continuous cropping years and were lowest in the 6 years continuous cropping. The amount of soil bacteria and actinomycetes, ratio of bacteria and fungi(B/F) decreased, but fungi number increased. The deterioration of potato rhizosphere soil environment resulted reduction of potato growth and chlorophyll content, leaves photosynthesis decreased, MDA content increased, SOD activity decreased, the production of O2-. accelerated. Rotation oil-sunflower significantly improved the content of organic matter, available phosphorus and alkali-hydrolyzable, increased soil enzyme activities, the amount of bacteria and B/F, reduced the numbers of fungi, improved soil microenvironment, promoted the potato growth and development, increased relative chlorophll content, photosynthesis, reduced MDA content, increased SOD activity and reduced the production rate of O2-.. It could be seen that rotation oil-sunflower alleviated membrane lipid peroxidation and free radical damage, enhanced antioxidant capacity, and even for rotation oil-sunflower in 4 years continuous cropping was of benefit to alleviate potato continuous cropping obstacles.Based on the above research, we could draw the conclusions as below:(1) Drought stress inhibited potato growth, resulted the decrease of leaves water content and net photosynthesis rate, drought hardening could relatively increase the leaves water content of potato seedlings under drought stress, enhanced the leaves’ chlorophyll content and net photosynthesis rate, increased the content of osmotic regulatory substances, PAs and ABA, improved the antioxidant enzymes activities. The changes mentioned above improved potato drought resistance, thus alleviated the inhibition of drought stress on potato seedlings growth and development.(2) Potato continuous cropping resulted in the aggravation of soil physiological and chemical properties, the decrease of soil enzymes activities, and even the inhibition of potato normal growth, continuous cropping also caused net photosynthesis rate decrease, and the increase of MDA content and reactive oxygen level. Rotation oil-sunflower could alleviate the deterioration of soil physicochemical property and biological property caused by continuous cropping, ameliorated soil’s environment, so as to promote the potato growth and development.