Physiological Mechanism Of Paclobutrazol And KCI Influence Potato Seedlings Resistance Under Drought Stress

Potato cultivated area ranks only second to rice，wheat and corn is the important food andcash crops in north China and even the world．Because of having a great demand for water，the growth and yield of potato are seriously affected by water deficit．Improving potatodrought resistance ability become the urgent problems of theoretical research and productionpractice．Therefore，it has very important theoretical and practical significance to research thepotato drought resistance．This study used the potato seedlings as experimental material todiscusse the effects of paclobutrazol(PP₃₃₃)，potassium chloride and fulvic acid on thephysiological mechanism and regulation function of potato seedling resistance’under droughtstress．Main research contents are as follows：1. Influences of PP₃₃₃on potato seedling drought resistance and tuber nutrient underdrought stress were reported in this paper．The results showed that spraying PP₃₃₃couldreduce the plant height，tuber number per plant and the acrial part biomass，increase the stembase diameter and biomass of each tuber．Spraying PP₃₃₃on the leaves of potato seedlingunder drought stress promoted the content of proline and soluble sugar and the activities ofsuperoxide dismutase（SOD）significantly，alleviated the reduction of leaf water content andchlorophyll content， alleviated the increase of MDA content and relativeconductivity．Spraying PP₃₃₃also increased potato seedlings`adaption under extreme droughtstress．Spraying PP₃₃₃under drought stress also promoted the content of starch，protein，reducing sugar，vitamin C and biomass in potato tuber．In conclusion，PP₃₃₃can enhancepotato seedlings’drought resistance and tuber nutrients under drought stress．2. The effects and its mechanism of potassium chloride on drought resistance of potatoseedlings under drought stress were elucidated in this paper．The results showed that underdrought stress potassium chloride relieved the reduction of the leaves’relative water contentand chlorophyll content significantly，inhibited the increase of MDA content and relativeconductivity，increased the contents of proline and soluble sugar，promoted the activities ofsuperoxide dismutase（SOD）and catalase（CAT）．Applying potassium chloride also reducedthe transpiration rate，improved the net photosynthetic rate，water use efficiency and thecontents of starch and vitamin C；The results also showed that applying potassium chloridecould promote plant height，base diameter，stolon number and yield per plant．In short，Potassium chloride promoted the ability of drought adaptation and enhanced the tuber quality of potato under drought stress．Thus it can be concluded that applying potassium chlorideunder drought stress could improve the drought resistance of potato seedling conspicuouslyby improving the water retaining capacity of potato seedling leaves，relieving the reductionof antioxidant enzyme activity and increasing the contents of osmoregulation substancesrelatively，thus alleviated the harmful effects caused by drought stress．3. This paper is attempt to study the protective effects of fulvic acid on membranesystem of potato seedling leaves under osmotic stress．The results showed that under osmoticstress fulvic acid significantly reduced increase of leaf cell membrane permeability，leaf waterpotential and MDA content，alleviated the reduction of the contents of leaves’chlorophyll，relative water and osmotic adjustment substance（ssoluble sugar，proline）．relatively increasedthe activity of antioxidant enzymes and increased SOD，CAT and APX activities significantlywhen osmotic stress lasted12h．When the stress lasted0h and12h，fulvic acid significantlypromoted activity of plasma membrane H⁺-ATP enzyme，and the activity of amylase wassignificantly promoted at12h and36h．Fulvic acid also significantly increase contents ofABA，Put，Spd and Spm during osmotic stress for12h and Spm content still increasedsignificantly at36h．Under osmotic stress fulvic acid alleviated the content of H2O2and thegeneration rates of ethylene，O₂^.-and the effect is obvious at12h．In short，fulvic acidincreased the activities of plasma membrane H⁺-ATP enzyme，amylase and protectiveenzyme，promoted the contents of osmotic adjustment substances，ABA and polyamine，thereby reduced contents of MDA，H2O2and generation rates of ethylene，O₂^.-，alleviated thereduction of chlorophyll content and the increase of membrane permeability．So fulvic acidplays an important role in protecting potato leaf under osmotic stress．In a word，under drought stress paclobutrazoland and potassium chloride treatment cansignificantly increase the potato seedlings’leaf osmoregulation substance contents and theactivity of antioxidant enzymes，relatively improve leaf water content and increase of leafphotosynthetic capacity，reduce the damage of drought stress to potato seedlings and thenincrease drought resistance of the potato seedlings as a whole．Studies also suggest that fulvicacid can increase contents of leaf polyamine and ABA and the plasma membrane H⁺-ATPaseactivity under osmotic stress，these may play an important role to enhance the potatoseedling leaves resistance under osmotic stress．...