Effects Of Salicylic Acid Or Heat Acclimation On The Thermotolerance And Photosynthesis In Grape Leaves

One-year-old grape plants of Vitis vinifera L.cv.Cabernet Sauvignon were used as experiment materials. The effects of high temperature on the content of praline, soluble protein, free amino acid, soluble protein and chloregenic acid, photosynthesis and chlorophyll fluorescence parameters were studied. The measures of treatment with heat acclimation (38℃)and concentration of 100μmol·L-1 saliylic acid(SA) were taken to induce thermotolerance of young grape seedlings under high temperature stress in this experiment. The physiology and biochemical mechanism of heat stress on grape were discussed. All results provided the base theory for cultivation and breeding of grape plants.the main results are as follows.(1) Results from the experiment showed that salicylic acid and heat acclimation could significantly increase the content of soluble sugar. The content of soluble suger in grape leaves with salicylic acid treatment was 0.41﹪, that with heat acclimation treatment and the control treatment were 0.31﹪and 0.26﹪, respectively.(2)The content of free proline with salicylic acid treatment, heat acclimation treatment and the control tratment increased at the beginning, then decreased and went up again. Salicylic treatment and heat acclimation both significantly decreased the content of proline, which may be related to the degration of soluble protein under heat stress. The free amino acid with salicylic acid,heat acclimation and the control treatment decreased at the begaining, then went up again. The content of free amino acid with heat acclimation firstly decreased to the lowest point, from which we could conclude that salicylic acid may have more thermotolerance than heat acclimation.(3)The changes of the content of soluble protein of grape plants with salicylic acid, heat acclimation and control treatment were almost the same, which increased at first, then decreased.Most of the molecular weight of the protein through SDS-PAGE was between 16KD and 67KD.(4)The content of chlorogenic acid in grape plants with salicylic acid treatment and the control treatment during the course of different high temperature stress time which were 0, 1, 3, 6, 12h at 42℃decreased at the beginning, then went up and decreased again.(5)Salicylic acid reduced the decreasing of chlorophyll fluorescence parameters which are Fv/Fm, Fv/Fo, Fm/Fo, yield, etr and decreased the increasing of non-photochemical quenching parameters. Salicylic acid have increased maximum quantum yield of PSⅡ, the potent activities of PSⅡ, the electron transport, photochemical quantum yield of PSⅡand apparent photosynthesis electrom transport rate, decreased the increasing of non-photochemical quenching, so as to decrease photoinhibition at noon. The changes of non-photochemical quenching in the day increased at first, then decreased.The SAS treatment and HA treatment significantly reduced the increasing of non-photochemical quenching, which disclosed that the two treatments could relieve the photoinhabition.(6)The shape of diural changes of photosynthesis(Pn)of grape leave with salicylic acid, heat acclimation and the control treatment was that the net photosynthesis increased to the maximum at 13 o'clock, then decreased to the minimum in the following two hours. After 15 o'clock, the net photosynthesis increased again and got to the second maximum at 17 o'clock, then began to go down again. the changes of transpiration rate increased at first, then went down. The grape leaves with salicylic acid treatment at 15 o'clock had more net photosynthesis than the control treatment. At 15 o'clock, the stomatal conductance and the transpiration rate with salicylic acid treatment were higher than that with the other two treatments.