低温胁迫下24-表油菜素内酯对高山离子芥幼苗叶片荧光特性和抗氧化系统的影响

Effect of 24-epibrassinolide on Chlorophyll Fluorescence and Antioxidant Defense System of Chorispora bungeana under Chilling Stress

油菜素内酯(Brassinosteroids,BRs)参与植物的许多生理过程,并能减轻多种生物和非生物胁迫对植物体造成的伤害。为了进一步研究BRs在植物冷胁迫中的作用,对高山离子芥幼苗叶片用不同浓度(0、0.02、0.1、0.5μmol/L)的24-表油菜素内酯(24-epibrassinolide,EBR)喷洒处理后,移至低温(4°C)下生长5d后发现,EBR(0.1μmol/L和0.5μmol/L)能显著改善高山离子芥幼苗的生长状况,并能有效地减轻高山离子芥幼苗在低温胁迫下的氧化损伤。在冷胁迫条件下,EBR显著提高了叶绿素含量、叶绿素荧光参数Fv/Fm和电子传递速率,而脂质过氧化(MDA)水平和膜离子渗漏(MEL)被显著抑制。抗氧化酶(SOD、CAT、APX和GR)活性在冷胁迫条件下上升,经EBR处理的叶片中酶活性显著增加。另外,EBR明显提高了冷胁迫下高山离子芥幼苗叶片中抗坏血酸(AsA)和谷胱甘肽(GSH)的含量。可见,外源EBR处理增强了冷胁迫下高山离子芥幼苗的抗氧化防御能力,减轻了冷胁迫对高山离子芥幼苗的伤害。

Brassinosteroids (BRs) elict diverse physiological processes and ameliorate various biotic and abiotic stresses.In order to further explore and elaborate their roles in plants subjected to chilling stress,the seedlings of Chorispora bungeana were sprayed with different concentrations of 24-epibrassinolide (EBR)(0,0.02,0.1,0.5 μM) at low temperature (4°C) for 5 days.We found that 0.1 μM and 0.5 μM EBR treatments improved seedling growth and alleviated oxidative damage more effectively under chilling conditions.Under chilling stress,the reductions of chlorophyll (Chl) content,Fv/Fm ratio and electron transport rate (ETR) of Chl fluorescences significantly increased with EBR application.The increased lipid peroxidation level and membrane electrolyte leakage (MEL) were significantly inhibited by EBR treatment.Activities of antioxidative enzymes such as superoxide dismutase (SOD),catalase (CAT),ascorbate peroxidase (APX) and glutathione reductase (GR) greatly increased during the period of chilling treatment,and these increases were remarkably enhanced by EBR treatment.In addition,EBR treatment also greatly enhanced the contents of ascorbate (AsA) and reduced glutathione (GSH) under chilling conditions.These data suggested that the elevated level of antioxidant defense system contributed to the amelioration of chilling stress in C.bungeana seedlings.