Effect Of Drought On Drought Resistant Physiology And Yield Of Sweet Potato With Different Starch Content During Expansion Period

This paper mainly studied the effect of different natural drought duration on the yield and drought resistance mechanism of sweet potato with different starch content during the expansion period.Drought during root bulking can lead to serious reduction on sweet potato yield.Many studies have investigated the effects of drought in stable soil relative water content on sweet potato.In fact,the amount of rain has a marked effect on soil relative water content and can vary greatly from month to month that lead drought happened in specific time.Sweet potato is usually planted in May in Chongqing.The critical period after planting 60-90 days for sweet potato stem and leaf to grow up and root tuber to expand was high temperature and drought at mid-july to mid-august,which greatly affeced the yield of sweet potato.The adaptability of different sweet potato varieties to drought was different.Therefore,it is important to study the effect of natural drought duration on yield and drought-resistant mechanism of sweet potato varieties with different starch content.A split plot design with natural drought duration(A0:normal watering;A1:natural drought 10d;A2:natural drought 20d;A3:natural drought 30d)as the main plot factor,and sweet potato varieties(B1:medium starch content variety with starch content about 25%;B2:medium starch content variety with starch content about18%;B3:low starch content variety with starch content about 12%)as the subplot factor.Sweet potato suffered drought after planting for 60 days and re-watered after treatment to identify drought tolerant amount clones and investigate the drought resistance mechanism under different natural drought duration and sweet potato varieties with different starch content.The results are as follows:1.Effects of natural drought duration on the growth of sweet potato varieties with different starch content.The above-ground dry weight,under-ground root fresh weight,agronomic traits and LAI were significantly affected by different natural drought duration,and the LAI decreased with the extension of drought duration,both were minimized by A3 treatment.The decrease rate of aboveground dry weight of B1(25.70%)was the largest,and that of B2(19.55%)was the second,and that of B3(15.11%)was the smallest.Fresh weight of roots was not significantly different among sweet potato varieties,which were 26.32%,23.68%and 23.21%,respectively.Among the agronomic traits,the maximum values of vine length,stem diameter and branch number were obtained under A0 treatment,and the differences among varieties were significant.2.Effects of natural drought duration on photosynthetic characteristics of sweet potato varieties with different starch contents.The effects of natural drought time on CHLA,Chlb,TCHL,Carotenoid,PN,CI,TR and GS were significantly different,except for CHLB and Carotenoid.The other indexes showed a decreasing trend with the extension of natural drought time,and the Carotenoid increased first and then decreased with the extension of natural drought time.Among the three varieties,B1 had the largest decrease in TCHL,PN,PN and CI.3.Effects of natural drought duration on osmotic adjustment substances and membrane lipid peroxidation in sweet potato cultivars with different starch contents.LSS,LSP,Pro and MDA were significantly affected by different natural drought duration.LSS,Pro and MDA all increased with the extension of natural drought time,but LSP decreased all the time.The contents of Pro,LSS and LSP of B3 were significantly higher than those of the other two cultivars in all stages,which indicated that the low starch cultivars could accumulate more osmotic adjustment substances under drought condition.l SS,Pro and MDA were all maximized under A3 except that LSP was maximized under A0.4.Effects of natural drought duration on antioxidant enzyme activities and ABA in sweet potato varieties with different starch contents.SOD,CAT,POD,APX and ABA were significantly affected by the duration of natural drought,and increased with the duration of natural drought.Sod and CAT showed B3>B2>B1 in all-natural drought duration,and the difference was significant,which indicated that B3 had stronger antioxidant enzyme activity.under adversity Pod of B1was significantly larger than that of other cultivars during 70d and 80d transplanting,but B1 was significantly smaller than that of other cultivars during 90d transplanting,which indicated that POD of B1 was the main antioxidant enzyme during the early stage of drought.There were significant differences among varieties,and the trend of increase with the extension of drought time.The results showed that B1>B2>B3,B2>B1>B3,B3>B2>B1,B3>B2>B1.A factor,B factor and the interaction of the two factors had a significant effect on ABA,and the content of ABA increased with the extension of drought time.The content of ABA of B1 variety decreased with the extension of time,but the content of ABA of B2 and B3 varieties increased with time.5.Effect of natural drought duration on yield and quality of sweet potato varieties with different starch content.The results showed that the yield of three varieties decreased by 40.57%,35.45%and 30.29%respectively under A3 treatment,and the yield of B3 was the highest under all-natural drought duration,the highest yield was 1916.56 kg/667m~2 under A1B3treatment,which indicated that proper drought was helpful to increase yield.Natural drought treatment had significant effect on starch content and soluble protein content,but had no significant effect on soluble sugar content.Among them,starch content and soluble protein content showed as B1>B2>B3,while soluble sugar content showed as B3>B2>B1.Under the condition of water shortage and drought,sweet potato adapts to the soil water environment by regulating the contents of osmotic substances,the activities of antioxidant enzymes and the changes of endogenous hormones in leaves,but the adaptability of different sweet potato varieties to the outside environment is different.The drought-resistant sweet potato varieties in this experiment have higher contents of osmotic substances and higher antioxidant enzyme activities,there was a significant negative correlation between starch content of sweet potato root tuber and starch content.