贵州野生柑橘的抗寒性测定和综合评价

目的研究低温胁迫前喷施外源表油菜素内酯(EBR)和过氧化氢(H₂O₂)对烤烟幼苗生理和生长的保护效应。方法以烤烟品种K326和湘烟7号为试验材料，在七叶一心期进行叶面喷施0.01 mg/L EBR和340 mg/L H₂O₂处理，连续喷施4 d后进行低温胁迫处理，对低温胁迫下烟草叶片幼苗抗氧化酶活性、渗透调节物质和丙二醛(MDA)含量以及生物量进行测定。结果(1) 2种烤烟在经历低温胁迫后均出现叶面积变小、生物量减少和根冠比减小的现象，但MDA含量均上升；K326的抗氧化酶活性和渗透调节物质含量降低，而湘烟7号仅POD和CAT活性以及可溶性蛋白含量降低。(2)与仅低温胁迫的处理相比，喷施外源物质+低温处理后K326的生物量、抗氧化酶活性和渗透调节物质含量均显著升高(P<0.05)，MDA含量显著降低(P<0.05)。(3)与仅低温胁迫的处理相比，喷施外源物质+低温处理后湘烟7号的MDA含量变化不显著(P>0.05)，仅有部分渗透调节物质含量和抗氧化酶活性增加，且整体变化幅度小于K326。结论喷施外源EBR和H₂O₂可作为保护剂提高2个烤烟品种对于低温胁迫的耐受性，且对K326的保护效果更好。

Positive charges of polyamines protect PSII in isolated thylakoid membranes during photoinhibitory conditions

PurposeTo study the protective effects of exogenous epibrassinolide (EBR) and hydrogen peroxide (H₂O₂) sprayed before low temperature stress on the physiology and growth of tobacco seedlings. MethodsThe test materials were tobacco varieties K326 and Xiangyan No.7. Foliar sprays of 0.01 mg/L EBR and 340 mg/L H₂O₂ were applied at the seven-leaf-one-center stage, and then treated with low temperature stress for four days. The antioxidant enzyme activities, osmoregulatory substances contents, malondialdehyde (MDA) content, and biomass of tobacco leaf seedlings were measured. Results1) After low temperature stress, the leaf area, biomass and root-shoot ratio of two varieties of tobacco decreased, but MDA content increased. The antioxidant enzyme activities and osmoregulatory substance contents of K326 were reduced; while only POD and CAT activities and soluble protein content were reduced in Xiangyan No.7. 2) Compared with the only low temperature stress treatment, biomass, antioxidant enzyme activities and osmoregulatory substance contents of K326 were significantly higher (P<0.05) and MDA content was significantly lower (P<0.05) in the sprayed exogenous substance+low temperature treatment. 3) Compared with the only low temperature stress treatment, the change of MDA content of Xiangyan No.7 was not significant (P>0.05), and only some osmoregulatory substances contents and antioxidant enzyme activities were higher in the sprayed exogenous substance+low temperature treatment, but the overall changes were smaller than that of K326. ConclusionExogenous EBR and H₂O₂ were applied as protectants to improve the tolerance of both tobacco varieties to low temperature stress, and the protection effect was better for K326.