中国生态农业学报Issue(3)：345-355,11.DOI:10.13930/j.cnki.cjea.151028
外源 EBR 对 NaCl 胁迫下紫花苜蓿幼苗微量元素吸收及叶绿素荧光动力学参数的影响
Effect of exogenous 2,4-epibrassinolide on trace element absorption and chlorophyll fluorescence of Medicago sativa L. seedlings under NaCl stress
摘要
Abstract
Due to the serious secondary soil salinization, salt injury has become a limiting factor of the development of high quality alfalfa industry in Northwest and North China. Brassinosteroid (BR) has been globally recognized as a new plant growth hormone with high and broad spectrum activity, which could regulate plant growth and development and mitigate a series of abiotic stresses due to high salinity, heavy metal contamination, high temperatures, low temperatures, drought and hypoxia. It also plays an important role in regulating the photosynthesis and absorption of trace element of plants. Given the importance of the study of the effects of BR on trace element absorption and fluorescence kinetics parameters in Medicago sativa L. seedlings under salt stress, we investigated salt resistance and possible physiological regulation mechanism of M. sativa seedlings induced by exogenous 2,4-Epibrassinolide (EBR). The effects of EBR on the absorption, transportation and allocation of trace elements, leaf PSⅡ function, electron transport rate and light allocation in seedlings of M. sativa cv. Zhongmu No.3 and M. sativa cv. Longzhong under NaCl stress were determined using the hydroponics method. Four treatments were conducted in the experiment ― CK (distilled water), 150 mmol·L-1 NaCl, 0.1 μmol·L-1 EBR and 150 mmol·L-1 NaCl +0.1 μmol·L-1 EBR. The results showed that Cu2+ content increased significantly in different organs (leave, stem and root) of the seedlings, also Fe2+, Mn2+ and Zn2+ contents significantly decreased and then Fe2+/Na+, Mn2+/Na+, Cu2+/Na+ and Zn2+/Na+declined markedly under 150 mmol·L-1 NaCl stress. The metabolic process of the uptake, transportation and distribution of inorganic ions was disordered and PSⅡ reaction center damaged. Concurrently, there was a drop in the transportation ratio of photosynthetic electrons (ETR) and photochemical reaction energy. NaCl stress facilitated antenna dissipated energy and reaction center dissipated energy, which resulted in a drop in photosynthetic capacity. This condition was reversed by the addition of 0.1 μmol·L-1 EBR under NaCl stress. Addition of EBR significantly decreased Cu2+ content in different plant organs (leave, stem and root), while significantly increased contents of Fe2+, Mn2+ and Zn2+, and ratios of Fe2+/Na+, Mn2+/Na+, Cu2+/Na+ and Zn2+/Na+. The uptake and transportation of inorganic ions were effectively regulated, accompanied by a decrease in antagonism among positive ions like Na+, Fe2+, Mn2+, Cu2+, Zn2+, etc. Leaf F0 and NPQ significantly decreased and Fm, Fv/F0, Fv/Fm, ФPSⅡ, Fv′/Fm′, qP and ETR significantly increased. Absorbed light energy was allocated more to photochemical reaction energy, less light was allocated to antenna pigment dissipation and excess light energy to reaction center. This illustrated that EBR improved the selective absorption, transportation and distribution of inorganic ions and maintained ion metabolic balance under NaCl stress. Furthermore, EBR effectively alleviated any harm to M. sativa seedlings caused by NaCl stress by raising ETR, reducing antenna heat dissipation and excess light energy of reaction center and maintaining a higher level PSⅡ photochemistry activity. This further stimulated even energy allocation between PSⅠ and PSⅡ and decreased damage to PSⅡ reaction center.关键词
紫花苜蓿/NaCl 胁迫/2,4-表油菜素内酯/离子代谢/叶绿素荧光动力学/光系统Ⅱ(PSⅡ)Key words
Medicago sativa/NaCl stress/2,4-Epibrassinolide/Ion metabolism/Chlorophyll fluorescence kinetics/PhotosystemⅡ complex (PSⅡ)分类
农业科技引用本文复制引用
寇江涛,康文娟,苗阳阳,师尚礼..外源 EBR 对 NaCl 胁迫下紫花苜蓿幼苗微量元素吸收及叶绿素荧光动力学参数的影响[J].中国生态农业学报,2016,(3):345-355,11.基金项目
国家现代牧草产业技术体系建设专项(CARA-35)和全国种质资源保护项目(NB2130135)资助* The study was supported by the National Modern Forage Industry System Construction Project (No. CARA-35) and the National Germplasm Resources Conservation Project (No. NB2130135) （CARA-35）
