不同光环境对海南龙血树幼苗表型可塑性及生存策略的影响

Effects of Light Intensity on Phenotypic Plasticity and Survival Strategy of Dracaena cambodiana Seedlings

摘要:

为了解光照对海南龙血树（Dracaena cambodiana）幼苗生长的影响，研究了不同光照环境下海南龙血树幼苗形态、生理特性和生物量分配的变化，并分析了其生态适应性。结果表明，海南龙血树幼苗的形态、生理和生物量分配指标在不同光照强度间存在显著差异，各指标的可塑性指数为0.08~0.86，其中根茎叶及总生物量的可塑性指数普遍较高（0.67~0.86），表明海南龙血树幼苗有较好的光照适应性，其策略主要是通过调整根茎叶生物量的分配来适应光照的变化。随着光照强度的降低，海南龙血树幼苗的比叶面积、叶根比呈现显著增大趋势，表明幼苗可通过增加单株叶面积比例，扩大光合作用面积，有效调节自身生物量配置。37.3%自然光照（L2）是海南龙血树幼苗生长的最佳光照强度。现存海南龙血树生境改变，生境缺少林荫以致光照强度过大，不利于幼苗根系生长，难以度过干旱季节，可能是海南龙血树自然更新失败的重要原因之一。

Abstract:

In order to understand the effect of light intensity on seedling growth of Dracaena cambodian, the changes in morphological, physiological and biomass allocation characteristics were studied under four kinds of light intensity, including 100%, 37.3%, 15.5%, and 4.2% nature sunlight. The results showed that there were significant differences in morphological, physiological and biomass allocation indexes among different light intensities. The PI (plasticity indices) of all indexes ranged from 0.08 to 0.86, in which PI of biomass was generally higher (0.67-0.86) than that of the others, indicating that the seedlings had better adaptability to illumination conditions by adjusting the allocation of biomass. With the decrease of light intensity, the specific leaf area (SLA) and leaf area to root mass ratio (LARM) significantly increased, which indicated that the seedling could increase the leaf area and the area of photosynthesis to effectively adjust biomass allocation. In conclusion, the seedling growth of D. cambodiana would be the best under 37.3% NS (L2). Because the existing habitat of D. cambodiana was damaged, and the seedlings lacked shading, it was unfavorable to the growth of seedling root system during the dry season. So, this may be one of important reasons for the failure of the natural regeneration of D. cambodiana.