2,4-表油菜素内酯对亚适温弱光下黄瓜幼苗光合特性和抗氧化系统的影响

为了探讨外源2,4-表油菜素内酯(EBR)对亚适温弱光(18/12℃,光照80μmol·m~(-2)·s~(-1))下黄瓜幼苗生长的调节作用,以优博1-5为试材,以常温喷施清水为对照,采用叶面喷施EBR的方法,研究其对叶绿素含量、光合气体交换参数、叶绿素荧光参数、碳同化关键酶活性和抗氧化酶活性的影响。结果表明,亚适温弱光下黄瓜幼苗的净光合速率(Pn)和叶绿素相对含量(SPAD值)分别比对照显著降低53.61%和21.73%,丙二醛(MDA)含量增加78.90%,进而导致干物质积累减少。亚适温弱光下喷施0.1μmol·L~(-1)EBR后,比叶重、Pn、SPAD值、光系统Ⅱ最大光化学效率(Fv/Fm)、光系统Ⅱ实际光化学效率(ΦPSⅡ)和光化学猝灭系数(q P)显著增加,非光化学猝灭系数(NPQ)减小,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,抗氧化酶(SOD、POD、CAT)活性显著增加,膜脂过氧化程度减轻。由此可见,外源EBR可以通过提高叶绿素含量、光化学效率和碳同化关键酶活性改善亚适温弱光下黄瓜幼苗的光合性能,并通过提高抗氧化酶活性以降低膜脂过氧化伤害,从而有效缓解亚适温弱光对黄瓜幼苗的伤害。本研究结果为阐明EBR缓解黄瓜幼苗亚适温弱光胁迫的调控机制提供了一定理论依据。

Effects of 2, 4-epibrassinolide on Photosynthesis Characteristics and Antioxidant System of Cucumber Seedlings Under Suboptimal Temperature and Low Light

To explore the regulation mechanism of 2,4-epibrassionolide (EBR) on the growth of cucumber (Cucumis sativa L.) seedlings under suboptimal temperature and low light intensity (18/12 ℃,PFD 80 μ mol · m-2 · s-1),cucumber Youbol-5 was used as experimental material and seedlings sprayed with distilled water as the control.The method of spraying the seedling leaves with EBR was employed and the effects of EBR on chlorophyll content,gas exchange parameters,chlorophyll fluorescence parameters,the activities of key enzymes involved in calvin cycle and antioxidant enzymes were measured in cucumber seedlings under suboptimal temperature and low light.The results showed that compared with the control,the photosynthetic rate (Pn) and the relative chlorophyll content (SPAD) of seedlings in suboptimal temperature and low light treatment significantly decreased by 53.61％ and 21.73％,respectively.The malondialdehyde content of cucumber seedlings increased by 78.90％ and thus eventually led to the reduction of dry matter accumulation.However,the stressed cucumber seedlings pretreated with 0.1 μ mol· L-1 EBR maintained a higher value of specific leaf weight,Pn,SPAD,maximal photochemical efficiency of PS Ⅱ (Fv/Fm),actual photochemical efficiency of PS Ⅱ (ΦPS Ⅱ) and photochemical quenching coefficient (qP),but a decreased nonphotochemical quenching coefficient (NPQ).Moreover,EBR treatment significantly increased the activities of ribulose 1,5-biphosphate carboxylase/oxygenase (Rubisco),sedoheptulose-1,7-bisphosphatase (SBPase),fructose-1,6-bisphosphate aldolase (FBA) and transketolase (TK),and also promoted the activities of superoxide dismutase (SOD),peroxidase(POD),catalase(CAT),decreased the membrane lipid peroxidation.The results suggested that EBR could improve photosynthesis by increasing chlorophyll content,photochemistry efficiency and the activities of enzymes involved in Calvin cycle,enhance the antioxidant enzyme activities to decrease membrane lipid peroxidation,and thereby,effectively promote the growth of cucumber seedlings under suboptimal temperature and low light.Therefore,the findings provided a theoretical basis to clarify the regulation mechanism of the alleviation role of EBR on growth of cucumber seedlings under suboptimal temperature and low light.