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热带亚热带裸子植物苏铁与木本被子植物叶性状差异研究

Study on the differences in leaf traits between tropical-subtropical cycad gymnosperms and woody angiosperms

  • 摘要: 苏铁类(Cycads)植物是现存最古老的种子植物,主要分布在热带亚热带地区,且绝大部分处于濒危状态。本研究分析了南宁植物园苏铁分类园的28种苏铁类植物的叶(羽片)形态解剖特征和水分关系性状,同时收集79种热带亚热带森林乔木的叶性状数据进行了比较分析。结果显示:(1)与被子植物相比,苏铁类植物的叶片较厚,饱和含水量(SWC)较高,耐失水能力(Ψtlp)较强,比叶面积(SLA)及气孔密度(SD)均较低。但两个类群的叶肉组织厚度(MT)差异不显著。(2)被子植物叶性状网络的边缘密度(Edge density)显著高于苏铁类植物,而直径、平均路径长度显著低于苏铁类植物。说明热带亚热带地区被子植物性状间的关联性更强,有利于高效利用有限资源。(3)与被子植物不同,苏铁类植物的SLA、Ψtlp均与SWC解耦,表明苏铁类植物可能更依赖于根系的水分吸收或茎的存储,而不是通过叶片的物理特性进行精细调节。

     

    Abstract: Cycads, the oldest living seed plants, are primarily distributed in tropical and subtropical regions and are critically endangered. Comparative analysis of leaf traits between tropical-subtropical gymnosperm cycads and woody angiosperms offers valuable insights into the ecological strategies of cycad species. This study measured the morphological, anatomical, and hydraulic characteristics of leaves (pinnae) from 28 cycad species in the Nanning Botanical Garden. In addition, leaf traits of 79 tropical-subtropical forest tree species were compiled for comparative analysis. Results showed that: (1) Compared to angiosperms, cycads exhibited thicker leaves, higher saturated water content (SWC), stronger resistance to water loss (Ψtlp), and lower specific leaf area (SLA) and stomatal density (SD). However, the differences in leaf tissue thickness (MT) between the two taxa were not significant. (2) The network edge density (ED) of leaf traits in angiosperms was significantly higher than in cycads, while angiosperms showed lower network diameter and average path length. This indicates stronger correlations among angiosperm traits, facilitating more efficient resource utilization in tropical and subtropical environments. (3) Unlike angiosperms, SLA and Ψtlp in cycads were decoupled from SWC, suggesting that cycads rely more on water uptake through root systems or storage in stems rather than fine-tuning leaf physical properties for water regulation. This study highlights the variability and diversity of adaptive strategies across plant taxa and provides insights into the unique ecological adaptations of cycads in tropical and subtropical environments.

     

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