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    香樟幼苗对NaCl 胁迫的生理响应

    Physiological response of Cinnamomum camphora seedlings to NaCl stress

    • 摘要: 为研究香樟(Cinnamomum camphora)的耐盐性,为南方沿海盐碱地的引种栽培提供参考。本文以实生香樟苗为材料,采用盆栽法,设置0(CK)、2‰、4‰、6‰、8‰ 5 种盐处理,对不同NaCl 盐处理下香樟生长指标,水分生理指标,叶片光合色素质量分数、光合作用参数、叶绿素荧光参数、抗氧化酶活性、渗透调节物质、膜稳定性等进行分析。结果表明:1)香樟苗高、基径相对生长量随着盐处理浓度的增加依次降低,且超过4‰的盐处理对其生长量的抑制作用显著(P <0.05)。2)随着盐处理浓度的增加,香樟叶片水分饱和亏损、丙二醛含量逐渐增加,膜稳定性指数、光合能力逐渐降低。3)2‰盐处理下香樟叶片相对含水率、光合色素质量分数、Fv/ Fm、NPQ、抗氧化酶活性、脯氨酸含量、可溶性蛋白含量高于CK,而膜稳定性指数、Yield、ETR 虽然有所下降但降幅较小。4)盐处理达4‰后,香樟叶片光合色素质量分数、净光合速率、光化学效率、水分利用效率、膜稳定性指数显著减小(P < 0.05),丙二醛含量、脯氨酸含量显著上升(P <0.05),水分状况显著变差,与此同时抗氧化酶活性、可溶性糖含量,可溶性蛋白含量降低。综上所述,香樟的耐盐性处理在2‰~4‰,超过4‰的盐处理能显著抑制香樟的生长, 2‰盐胁迫下,香樟可通过提高相对含水率、光合色素质量分数、NPQ 的耗散,关闭部分气孔,提高抗氧化酶活性,增大脯氨酸、可溶性蛋白含量来应对盐胁迫。盐处理达4‰后,香樟抗氧化酶活性逐渐下降,酶系统损伤越来越严重;可溶性糖和可溶性蛋白含量所起的调节作用逐渐变小;脯氨酸含量大量增加,所起的渗透调节作用逐渐变大,但远不足以应对盐胁迫,因此叶片严重失水;膜脂过氧化,膜稳定性遭破坏,光合机构损伤严重,危及其生命。

       

      Abstract: Background Cinnamomum camphora is a precious economic tree species, it has important application value in the southern coastal areas of soil and water conservation. There are varied degrees of salinity in the southern coastal regions, the research on C. camphora 's salt tolerance had been little reported, nor systematically. The purpose of this work is to study the salt tolerance of C. camphora, and to provide the reference for the cultivation in saline alkali soil in southern coastal regions. Methods We chose C. camphora seedlings as test materials and used potted method, the seedlings were treated with NaCl treatment at 2‰, 4‰, 6‰and 8‰, and fresh water as the control (CK). With different NaCl salt treatment, the C. camphora growth indexes, moisture physiological indexes, photosynthetic pigment content, antioxidant enzymes activity, osmotic regulation substances and membrane stability of leaves were measured; the photosynthesis parameters and chlorophyll fluorescence parameters were measured by CIRAS-2 and CFI, respectively. Results 1) With the increasing of salt concentration, C. camphora seedling height and relative growth rate of base diameter decreased, and more than 4‰ of the salt treatment had significant inhibitory effect on the growth(P < 0.05). 2) With the increasing of salt treatment concentration, the water saturation deficit (WSD) and malondiadehyde (MDA) content of seedling leaf rose gradually, while the membrane stability index (MSI) and photosynthetic capacity decreased gradually. 3) The leaf relative water content (RWC), the photosynthetic pigment content, Fv/ Fm, NPQ, antioxidant enzyme activity, proline (Pro) content, and soluble protein (SP) content of seedling leaves at the salt concentration of 2‰ were higher than CK, while the MSI, Yield, and ETR reduced in a little magnitude. 4 ) The photosynthetic pigment content, net photosynthetic rate, photochemical efficiency, WUE, and MSI reduced significantly when the salt concentration was 4‰ (P< 0.05), while MDA content, and Pro content increased significantly ( P < 0.05), moisture conditions became worse; at the same time, the antioxidant enzyme activity, soluble sugar (SS) content,and SP content decreased. Conclusions The salt tolerance of camphor seedlings is 2‰ to 4‰, and when the salt concentration over 4‰, the growth of seedlings could be inhibited significantly. C.camphora seedlings could endure low salt stress (2‰) via increasing RWC, photosynthetic pigment content, the dissipation of NPQ, the activity of antioxidant enzymes, the content of Pro and SP, and shutting down part of the stomas. But when the salt concentration reached 4‰, with the increase of salt concentration, the antioxidant enzyme activity of seedling leaves gradually declined, the damage of enzyme system was more and more serious; the regulating effect of SS and SP became smaller; Pro was producing massively, and the regulating effect of osmotic regulation increased gradually, but far enough to resist the salt stress. Thus, the water in leaves lost severely, membrane lipid peroxided, membrane stability deteriorated, photosynthetic agencies seriously damaged, which resulted in their lives in danger.

       

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