Salicylic acid alleviates decreases in photosynthesis under heat stress and accelerates recovery in grapevine leaves.
BACKGROUND
Although the effect of salicylic acid (SA) on photosynthesis of plants including grapevines has been investigated, very little is yet known about the effects of SA on carbon assimilation and several components of PSII electron transport (donor side, reaction center and acceptor side). In this study, the impact of SA pretreatment on photosynthesis was evaluated in the leaves of young grapevines before heat stress (25 degrees C), during heat stress (43 degrees C for 5 h), and through the following recovery period (25 degrees C). Photosynthetic measures included gas exchange parameters, PSII electron transport, energy dissipation, and Rubisco activation state. The levels of heat shock proteins (HSPs) in the chloroplast were also investigated.


RESULTS
SA did not significantly (P < 0.05) influence the net photosynthesis rate (Pn) of leaves before heat stress. But, SA did alleviate declines in Pn and Rubisco activation state, and did not alter negative changes in PSII parameters (donor side, acceptor side and reaction center QA) under heat stress. Following heat treatment, the recovery of Pn in SA-treated leaves was accelerated compared with the control (H2O-treated) leaves, and, donor and acceptor parameters of PSII in SA-treated leaves recovered to normal levels more rapidly than in the controls. Rubisco, however, was not significantly (P < 0.05) influenced by SA. Before heat stress, SA did not affect level of HSP 21, but the HSP21 immune signal increased in both SA-treated and control leaves during heat stress. During the recovery period, HSP21 levels remained high through the end of the experiment in the SA-treated leaves, but decreased in controls.


CONCLUSIONS
SA pretreatment alleviated the heat stress induced decrease in Pn mainly through maintaining higher Rubisco activation state, and it accelerated the recovery of Pn mainly through effects on PSII function. These effects of SA may be related in part to enhanced levels of HSP21.
Wang
Li-Jun
LJ
Key Laboratory of Pant Germplasm Enhancement and Speciality Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, PR China.
Fan
Ling
L
Loescher
Wayne
W
Duan
Wei
W
Liu
Guo-Jie
GJ
Cheng
Jian-Shan
JS
Luo
Hai-Bo
HB
Li
Shao-Hua
SH
D002245:Carbon Dioxide / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D004579:Electron Transport; D006360:Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism*; D018526:Plant Transpiration; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D020156:Salicylic Acid / Q000494:pharmacology*; D013312:Stress, Physiological; D027843:Vitis / Q000187:drug effects* / Q000378:metabolism
D006360:Heat-Shock Proteins; D045332:Photosystem II Protein Complex; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D020156:Salicylic Acid