摘要： 研究了浓度为100mmol⁄L,pH值分别为7.0,8.0,9.0,10.0碱性盐胁迫下桑树幼苗叶片的叶绿素含量、相对含水率、细胞膜透性变化以及叶绿素荧光特性对光强的响应特点。结果表明,在盐溶液浓度为100mmol⁄L时,pH值7.0~9.0的碱性盐胁迫下,随pH值的升高桑树幼苗叶片的叶绿素含量和叶片含水率降低幅度较小,丙二醛含量未明显增加,细胞膜未发生明显的过氧化。桑树幼苗叶片的PSⅡ生理功能也未受到明显的抑制,桑树幼苗叶片可以通过增加以叶黄素循环为主的非辐射能量耗散机制来保护PSⅡ反应中心的正常生理功能,叶片PSⅡ可以保证正常的电子传递能力及光能的利用能力,即桑树幼苗叶片的PSⅡ功能具有一定的耐碱性盐能力。但当pH值达10.0时,浓度为100mmol⁄L的碱性盐胁迫下桑树幼苗叶片的膜系统受到破坏、叶片大量失水、单位面积叶绿素含量特别是叶绿素a含量明显降低。另外,桑树幼苗叶片的光合电子传递受阻,吸收的光能不能完全用于光合电子传递,同时依赖于叶黄素循环的非辐射能量耗散机制也受到了抑制,从而导致叶片中过剩光能(1-q_P)⁄NPQ大量积累,迫使PSⅡ反应中心的关闭程度和失活比例增加,桑树幼苗叶片可能通过反应中心失活的方式来减轻PSⅡ反应中心的压力,但这同时使桑树幼苗叶片对光能的利用能力特别是对高光强的利用能力降低。

关键词: 桑树, 碱性盐胁迫, pH值, 叶绿素荧光

Abstract: In this paper, taking mulberry seedlings as test material, the effects of diffierent concentration alkaline salt (Na₂C0₃)stress(Density of concentration was 100 mmol/L and value of pH were 7.0,8.0,9.Oand10.0) on chlorophyll content relative water content, cell membrane permeability changes and Chlorophyll fluorescence haracteristics in mulberry seedlings were investigated. The results shoved that under the alkaline salt stress with pH values in 7. 0一9. 0,chlorophyll content and relative water content were reduced smaller malondialdehyde contents were no apparent increased and peroxidation of membrane were no occurred significantly. Meanwhile,the inhibitions of PS, physiological function were also not being obvious in leaves of mulberry seedlings. However the leaves of mulberry seedlings could protect normal physiological function of PS, reaction centers by non}adiative energy dissipation mechanism which was xanthophyll}egulated thermal energy dissipation as the main,thus leaves of PS could guarantee the normal capacity of electronic transport and utilization of solar energy. Namely,the PS in Leaves of Mulberry seedlings had an alkaline salt-tolerance ability in some degree. But when the pH up to 10. 0,membrane systems in leaves of Mulberry seedlings were damaged, leaves water loss were seriously, and Per unit area of chlorophyll content were appreciably reduced which reducing of chlorophyll a content particularly clear. Furthermore,photosynthetic electron transports were hindered in leaves of Mulberry seedlings, and the absolute energy could used in photosynthetic electron transports imcompletely. The non-radiative energy dissipation mechanisms by xanthophyll cycle were inhibited simultaneously, which resulted in an accumulated excess light energy(1-q_P)/NPQ in the leaves. Then closure and deactivation of PS II reaction centers accelerated rapidly,which might be a way to alleviate the pressure on PS reaction centers, but at the same time decreased the capacity of solar energy utilization in particular to high light intensity utilization in the leaves of Mulberry seedlings.

Key words: Mulberry, Alkali salt stress, pH value, ChlorophyⅡ fluorescence

中图分类号: 

• Q945.1