增强UV-B辐射对柚树苗生长和生理特性效应研究

Effects of Enhanced UV-B Irridiation on Growth and Physiological Characteristics in Pomelo Seedlings

增强的ＵＶ－Ｂ辐射明显降低柚树苗的株高，叶面积，比叶面积，增加叶片厚度和叶肉密度。柚树苗叶片叶绿素，可溶性蛋白含量和硝酸还原酶活性降低，可溶性糖含量上升。不同品种柚苗对ＵＶ－Ｂ辐射反应存在差异，酸柚抗性较强。经ＵＶ－Ｂ增强处理后，叶片Ｐｎ值下降，Ｒｄ先上升后恢复原有水平。Ｆｖ／Ｆｍ，ФＰＳⅡ，ｑｐ均有不同程度的降低，而ｑＮ和Ｋｐ升高，表明增强ＵＶ-Ｂ导致那ＰＳⅡ失活，ＰＳⅡ原初光化学效率、开放ＰＳⅡ中心数目和非环式电子传递效率下降。部分激发能通过非光化学荧光碎灭形式耗散。ＵＶ-Ｂ辐射使叶片膜脂过氧化产物ＭＤＡ含量大幅度上升。ＳＯＤ和ＡＰＸ活性在处理初期提高，随后下降，初步推测：增强ＵＶ-Ｂ辐射诱导膜脂过氧化作用，攻击光合作用中心靶点并导致ＰＳⅡ失活，进而降低植物光合能力和物质代谢强度，最终导致袖树苗生长受到抑制。

Enhanced UV -B radiation significantly decreased plant weight, leaf area, and specific leaf area of pomelo seedlings, increased leaf thickness and mesophyll density. The contents of chloro- phyll, soluble proteins and the activity of NR were reduced, soluble sugar content was increased. Dif- ferent responses to UV -B were existed among different pomelo cultivars. Under enhanced UV - Btreatment, leaf Pn was declined, Rd increased at first, then returned original standard. Fv/Fm, ■qpⅡ，qp were decreased at different level, qN and KD were raised, these demonstrated that enhanced UV -B radiation led to PS Ⅱ inactivaton, the primary photochemical efficiency, the number of PS Ⅱ opening centre, and noncyclic electron transport of PSⅡ were reduced. Partial excitation energy might dissipate the useful nonphotochemical fluorecence quenching. Enhanced UV -B radiation led to a re- markble increase of MDA. The activities of SOD, APX were promoted at initial stage of treatment, then dropped. The results suggested that enhanced UV-B radiation induced membrane lipid peroxida- tion, attacked photosytnem center and led to PS Ⅱ inactivation, thus reduced plant photosynthesis and metabolism strength, finally led to the inhibition on the growth of pomelo seedlings.