水杨酸和油菜素内酯对低温胁迫下黄瓜幼苗光合作用的影响

Effects of exogenous salicylic acid and brassinolide on photosynthesis of cucumber seedlings under low temperature stress

为了探明外源水杨酸(SA)和2,4-表油菜素内酯(EBR)对低温胁迫下黄瓜幼苗光合作用的调控机理,以‘优博1-5’黄瓜为试材,用1 mmol·L^(-1)SA和0.1μmol·L^(-1)EBR喷施预处理幼苗,每天喷1次,连喷2 d后置于低温下[10℃/5℃,光强(PFD)80μmol·m^(-2)·s^(-1)]处理.结果表明:低温胁迫下黄瓜幼苗生长量及净光合速率(P_n)下降;喷施SA和BER显著提高了P_n、光系统Ⅱ最大光化学效率(F_v/F_m)、光系统Ⅱ实际光化学效率(Φ_(PSⅡ))和光化学猝灭系数(q_P),减缓了非光化学猝灭系数(NPQ)增加的幅度,同时核酮糖-1,5-二磷酸羧化/加氧酶(Rubisco)、景天庚酮糖-1,7-二磷酸酯酶(SBPase)、转酮醇酶(TK)和果糖-1,6-二磷酸醛缩酶(FBA)活性明显升高.说明SA和EBR可以通过调节光合关键酶的活性,缓解低温对黄瓜幼苗光合作用的影响,增强其对低温的适应性.

An experiment was conducted to investigate the mechanism of the regulation of salicylic acid （SA） and 2,4-epibrassionolide （EBR） on photosynthesis in cucumber （ Cucumis sativa） seed- lings under low temperature stress. Taking cucumber cuhivar ＇ Youbol-5＇ as material, the seedlings were pre-treated with 1 mmol · L-1 SA or 0.1 ixmol · L-IEBR （sprayed once a day）, and then were exposed to chilling temperature （ 10 ℃/5 ℃, PFD 80 μ mol · m-2 · s-1 ） after being pre-treated 2 days. The results showed that the growth and net photosynthetic rate （P,） of cucumber seedlings were decreased under low temperature stress. However, the Pn, maximal photochemical efficiency of PS Ⅱ （ Fv/Fm） , actual photochemical efficiency of PS 11 （ 45ps u ） and photochemical quenching coefficient （qe） were significantly improved in SA- and EBR-pretreated seedlings, and the increase range of non-photochemical quenching coefficient （NPQ） was decreased. Moreover, the activities of ribulose 1,5-biphosphate carboxylase/oxygenase （ Rubisco ）, sedoheptulose-1,7-bisphosphatase （ SBPase）, fructose- 1,6-bisphosphate aldolase （FBA） and transketolase （TK） were signi-ficantly increased. These findings suggested that SA and EBR improved photosynthesis of cucumber seed- lings by promoting the activities of key enzymes and increased low temperature tolerance.