Effects Of High Temperature Stress On Physiological And Gene Expression Characteristics Of Grapevine (Vitis Vinifera L. Hongti) During Seedling Stage

The global temperature has been rising continually due to massive emissions of greenhouse gases,and extreme high temperature occurred frequently in these years.Grape is one of the most important fruits in the world,and its cultivation area and range are increasing year by year,while the high temperature significantly affected the growth and development of grape.Although some researches have been conducted in the effects of high temperature stress(HTS)on grape,mostly concentrated in the Kyoho,Summer Black,and Cabernet Sauvignon,and the study in response of Hongti to HTS was reported rarely.Thus,two-year old grape seedlings(Vitis vinifera L.Hongti)were studied in growing chambers,which subjected constant high temperature stress(CHTS)and variable high temperature stress(VHTS).The temperature for CHTS was 41?,43?,45?,and 47?,and all plants were treated continously for 1h,3h,5h,and 7h,respectively.The temperature for VHTS was set as 34?,36?,38?,and 40?,all plants were treated for 2d,4d,6d,and 8d,taken 28? as control.The aim was to study the effects of HTS on photosynthetic and fluorescence characteristics of Hongti;the effects of HTS on anti-aging characteristics;the effects of HTS on endogenous hormones;the effects of HTS on heat shock genes expression;and the determination of high temperature stress level.The main results indicated that:1.The semi-lethal temperature was obtained by Logistic equation,and the value was 44.6?.For CHTS,the net photosynthetic rate(Pn)and the max net photosynthetic rate(Pmax)were 16.21%and 11.22%to CK after 7h of stress under 47?.For VHTS,the chlorophyll a,chlorophyll b,carotenoids,and chlorophyll(a+b)increased at first,and then decreased with an increase of temperature at 2,4,and 6d,while all of them decreased with an increase of temperature at 8d;the Pn and Pmax peaked at 28?,but the minimum appeared at 40?.With an increase of temperature and stress time,the original fluorescence(Fo)increased;the maximum fluorescence(Fm),maximum photochemical efficiency(Fv/Fm),potential reactivity(Fv/Fo)and ETo/RC decreased;while ABS/RC,TRo/RC,and DIo/RC presented an increase trend at first,and then decreased,the significant change appeared at 3h under 47?.2.The superoxide free radical(O2-),hydrogen peroxide(H2O2),malondialdehyde(MDA),relative electrical conductivity(REC),proline(Pro),superoxide dismutase(SOD),and catalase(CAT)increased with the rise of temperature and stress time under CHTS;peroxide(POD)increased under 41 ? and 43?,increased at first and then decreased under 45? and 47?;while the soluble protein increased at first and then decreased under 41? and 43?,and presented a decreasing trend under 45? and 47?.The changing trend for O2-.H2O2,MDA,REC,and Pro under VHTS was the same with that of CHTS,the SOD,POD,CAT increased at first and then decreased,while the soluble protein decreased with an increase of stress time.3.Auxins(IAA),gibberenllins(GA3),and trans-zeatin(ZT)of grape terminal buds decresed,while abscisic acid(ABA)increased with an extension of stress time under both CHTS and VHTS.The IAA,GA3,and ZT content increased significantly after 7h of stress time under CHTS,while the ABA decreased obviously at this time(P<0.05);The decreasing trend of IAA,GA3,and ZT was distinct after 8d of stress time under VHTS.4.Five heat shock genes were analyzed by fluorescence quantitative method,the relative expression level of heat shock proteins genes(VvHsp70 and VvHsp1OO),and heat shock transcription factors genes(VvHsfAl,VvHsfA2,and VvHsfBl)increased significantly under 41?,43?,45?,and 47? compared to that of Oh.The maximums of VvHsp70,VvHsp10O,VvHsfAl,VvHsfA2,and VvHsfBl all appeared at 47?,but the time was different.The VvHsp70 and VvHsfAl peaked at 3h of stress time,while VvHsp10O,VvHsfA2,and VvHsfBl peaked at 5h of stress time under 47?.5.The correlation among MDA,REC,and other physiological and gene expression characteristics was analyzed for CHTS and VHTS,respectively,and signicantly correlated indexes were selected for principal component analysis.According to the results of principal component analysis,the indexes which had high scores were chose for calculating the stress index.Based on the new stress index in this study,the stress level for CHTS and VHTS was devided into four grades,that is,mild,moderate,severe,and extreme,respectivey.At the same time,the temperature range and duration for CHTS and VHTS were developed.