Effects Of Drought Stress On Potato Starch Accumulation And Enzyme Activities

Drought is a worldwide problem and one of the most serious natural disasters in the world.Drought stress has a serious impact on growth and development of plants,leading to a series of physiological changes in plants.In this study,pot experiment of two treatments of soil moisture content of 30%-40%(drought)and 60%-70%(normal)was carried out with high-starch potato variety Kexin 22 and low-starch variety Kexin 19 as test materials,.The effects of drought stress on potato growth were studied on dry matter content,yield,starch and content and accumulation of starch,starch synthesis and starch synthase activity.The effects of drought stress on the mechanism of starch synthesis were discussed,which may provide the theoretical basis for drought tolerance breeding of potato.The results showed that:1.Under drought stress conditions,the plant height,stem diameter,branch number,and stolon number and length of the two varieties were significantly decreased.The growth indexes showed a single peak change,but the chlorophyll content increased slightly.2.Under the conditions of drought stress,the fresh weight and root dry weight of the two varieties decreased to some extent,and the fresh weight and dry weight of the leaves decreased in different degrees.The fresh and dry weights of the stem were also reduced to some extent,with root fresh weight be more obvious.3.Under the conditions of drought stress,the growth of potato tubers was inhibited,and the dry matter content of Kexin 22 was decreased by 7.04%.The dry matter content of Kexin 19 was decreased by 3.42% and the high starch variety Kexin.22 was more obvious.The yield of low-starch variety Kexin 19 was higher than that of high-starch cultivar Kexin 22.But under the drought stress,the yield of Kexin 22 and Kexin 19 decreased by 28.73% and 21.84%,respectively,which indicated that variety Kexin 22 was more influenced by water stress.The drought tolerance coefficient was 0.7126 for Kexin 22,and 0.7816 for Kexin 19.The drought tolerance index was 0.5338 for Kexin 22,and 0.9777 for Kexin 19.4.Under drought stress,the content of crude starch,amylose and amylopectin in Kexin 22 was decreased by 13.21%,6.39% and 14.21%,respectively,while the content of crude starch,amylose,and amylopectin in Kexin 19 was decreased by 8.95%,8.49%,and 8.96%,respectively.Under drought stress,the accumulation of crude starch,amylose and amylopectin of Kexin 22 was decreased by 29.11%,39.14% and 24.65%,respectively,while the accumulation of crude starch and amylose,and amylopectin of Kexin 19 was decreased by 28.35%,29.28% and 28.08%,respectively.Under drought stress conditions,the rate of accumulation of crude starch,amylose and amylopectin of Kexin 22 was decreased by 38.67%,38.00% and 39.69% respectively,while the accumulation rate for Kexin 19 was decreased by 35.76%,32.56% and 32.43%,respectively.5.Activity of four enzymes(AGPase,GBSS,SSS,SBE)in the two varietis was increased first and then decreased,and the peak of the activity was basically at the third sampling.On August 18 th,compared with normal watering the activity of AGPase in Kexin 22 and Kexin 19 unde water stress were decreased by 5.32% and 5.51%,respectively,and acitivity of SSS was decreased by 17.88% and 20.12%,respectively.The amount of GBSS of Kexin 22 and Kexin 19 was decreased 14.39% and 15.61%,respectively,and the activity of SBE of Kexin 22 and Kexin 19 was decreased by 14.55% and 12.98%,respectively.6.The amylose accumulation rate of the two varieties was significantly or highly significantly positively correlated with the changes in AGPase and GBSS activities.The rate of amylopectin accumulation was significantly or highly significantly positively correlated with the activity of AGPase,SSS and SBE.The rate of accumulation of crude starch was significantly or highly significantly positively correlated with the activity of AGPase,GBSS,SSS and SBE.