The effects of salicylic acid on distribution of 14C-assimilation and photosynthesis in young grape plants under heat stress

摘要

The effects of salicylic acid (SA) on assimilation of grape leaves under heat stress were studied with 14CO2 labeling. All leaves of young grape plants were cut off except the 4th, 5th, 6th, 7th and 8th leaves (counted from top to base). The following treatments were examined: the fourth leaves of treatment plants were sprayed with 100 micro mol L-1 SA solution, the fourth leaves of control plants were sprayed with water. After spraying, the sixth leaves of all plants were fed with 14CO2 for 30 min, then the fourth leaves were subjected to an elevated temperature of 38 degrees C for 1, 3, 6 or 12 h respectively while the other parts of plants were kept at 27 degrees C. The results showed that more 14C-assimilate of the sixth leaves in SA-treated plants was exported than in the control plants. Moreover, more 14C-assimilate was transported into the SA-treated fourth leaves than the control fourth leaves. Photosynthesis parameters were also investigated at 1, 3, 6 or 12 h after the fourth leaves were exposed to 38 degrees C. Net photosynthetic rate and Fv/Fm (chlorophyll a fluorescence parameter) in the treated plants were much higher than in the control plants except at 1 h under heat stress, while stomatal conductance, intercellular CO2 concentration and transpiration rate of the fourth leaves in the treated plants were not different from those of the control plants although all these physiology indices declined. This indicated that SA may improve photosynthesis mainly through alleviating PSII damage under heat stress. SA sprayed on grape leaves may improve thermotolerance through increasing photosynthetic capability and adjusting distribution of assimilates..