生物多样性 ›› 2005, Vol. 13 ›› Issue (5): 387-397.doi: 10.1360/biodiv.050142

所属专题: 探索长江流域物种的濒危机制

• 论文 • 上一篇    下一篇

濒危植物银杉幼树对生长光强的季节性光合响应

张旺锋1, 樊大勇1, 谢宗强1*, 蒋晓晖2   

  1. 1 (中国科学院植物研究所植被数量生态学重点实验室, 北京 100093)
    2 (湖南省郴州市林业局, 湖南郴州 423000)
  • 收稿日期:2005-06-27 修回日期:2005-08-23 出版日期:2005-09-20
  • 通讯作者: 谢宗强

The seasonal photosynthetic responses of seedlings of the endangered plant Cathaya argyrophylla to different growth light environments

Wangfeng Zhang 1, Dayong Fan 1, Zongqiang Xie 1*, Xiaohui Jiang 2   

  1. 1 Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093
    2 Chenzhou Forestry Bureau, Chenzhou, Hunan 423000
  • Received:2005-06-27 Revised:2005-08-23 Online:2005-09-20
  • Contact: Zongqiang Xie

银杉(Cathaya argyrophylla)是我国松科中特有的单种属植物, 被认为处于濒危状态。在对银杉群落多年调查研究的基础上, 针对银杉幼树生长过程对光强的需求特性, 我们开展了银杉幼树对光的适应性研究。试验在人工培育的银杉苗圃地, 采用遮荫的方法设置不同的光环境处理(100%、45%和3%自然光强), 利用气体交换技术和叶绿素荧光技术测定了3种光强下银杉叶片光合生理指标的变化, 探讨了不同光环境下银杉幼树光合能力在夏季和冬季的变化及其对生长光强的响应等。结果表明: 在夏季银杉生长旺盛时期, 遮荫导致叶片最大光合速率(Pnmax)、羧化效率(CE)下降, 但不同叶龄叶片的下降幅度不同。随生长光强的下降, 银杉幼树的光补偿点(LCP)和光饱和点(LSP)有所降低, 但全晴天时, 低光强(3%自然光强)条件下实际的光辐射量高于当年生叶片光补偿点的累积时间约6 h, 而且与光饱和的区域相差极大, 造成全天碳同化量低, 同化物累积少, 严重影响了银杉幼树的正常生长。在不同处理中全光强条件下银杉幼树长势最好, 45%光强条件下幼树生长减慢。冬季银杉最大光合速率(Pnmax)、羧化效率(CE)值均低于夏季, 光补偿点(LCP)和光饱和点(LSP)也较夏季降低。全光照条件下无论是当年生叶片和一年生叶片, 在冬季均出现了轻微光抑制现象, 适度遮荫有利于银杉抵御冬季光抑制。无论在遮荫或不遮荫条件下, 冬季银杉叶片将所吸收的相对过剩光能通过非辐射途径耗散出去, 表现出一种光保护策略。

Cathaya argyrophylla, an endangered species endemic to China, belongs to a single species genus of the pine family. Previous ecological studies indicated that the specific light requirement was one of the key limiting factors for its survival. Here we investigated the adaptation of its seedlings to different light availabilities created by different layers of black nylon net over the nursery site. The treatment of light avail-abilities included three levels, 100%, 45% and 3% of full daylight. The photosynthesis-related parameters under these three light environments were measured in summer and winter by the technique of gas exchange and chlorophyll fluorescence. Results showed that the low light environment decreased the maximal rate of photosynthesis(Pnmax)and carboxylation efficiency(CE)in the summer growing season, but the degree of depression depended on leaf age. Shading also caused a decrease of light compensation point(LCP)and light saturation point(LSP)to some degree. The accumulation of time that light intensity was higher than the light compensation point(LCP)in low light(3% daylight)on sunny days was not longer than six hours in an entire day. These results indicate that the growth of C. argyrophylla was greatly depressed under low light condi-tions. Its growth was the best under full daylight conditions and declined when light was lower than 45% daylight. The Pnmax, CE, LCP, and LSP in winter were lower than in summer, which may be attributed todown-regulation of the photosynthetic apparatus by the combined effect of low light and low temperature. Both current-year leaves and one-year-old leaves showed slight photoinhibition in winter under illumination, and moderate shade favored the adaptation to photoinhibition in winter. Compared with summer, the leaf of C. argyrophylla in winter dissipated a higher proportion of absorbed light energy in the form of heat, which could be indicated from the higher coefficients of non-photochemical fluorescence quenching (NPQ).

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