基于功能性状评价5种植物对热带珊瑚岛环境的适应性

Abstract

植被新建是保护和改善热带珊瑚岛生态系统的关键环节，热带珊瑚岛极端干旱生境是影响植物存活和定居的主要限制因子之一，因此选取适生植物对热带珊瑚岛植被新建至关重要。通过测定在海南省文昌市苗圃和热带珊瑚岛上的草海桐（Scaevola taccada）、厚藤（Ipomoea pescaprae）、木麻黄（Casuarina equisetifolia）、花生（Arachis hypogaea）、椰子（Cocos nucifera）5种植物的光合/水力相关功能性状，探讨植物对热带珊瑚岛生境的适应性。研究发现：与对照（文昌苗圃）相比，热带珊瑚岛上的草海桐、厚藤、木麻黄最大光合速率（A_max）均显著升高；除椰子外，其余4种植物的比叶面积（SLA）降低，长期水分利用效率升高（其中木麻黄和花生升高显著）；5种植物的叶片碳含量（LC）均有不同程度降低。此外，厚藤、木麻黄、椰子的叶片导水率（K_leaf）显著升高；厚藤和花生的叶片膨压丧失点（Ψ_tlp）显著降低；厚藤和木麻黄的气孔导度（g_s）显著升高。研究结果表明草海桐、椰子、花生主要通过非气孔调节方式（提高K_leaf，降低Ψ_tlp、SLA等）适应热带珊瑚岛干旱环境；而厚藤和木麻黄同时通过气孔调节（降低g_s）及非气孔调节（提高K_leaf，降低Ψ_tlp、SLA等）两种方式促进植物碳同化和水分利用。综上所述，草海桐、厚藤、木麻黄具有更高的光合能力和水分利用效率，能有效协调碳同化和水分利用，表现出良好的适应能力，适合用于热带珊瑚岛的植被新建。;Functional traits are direct measures of plant responses and adaptations to environmental changes. In this study, we quantified the photosynthetic and hydraulic traits of five plant species (Scaevola taccada, Ipomoea pescaprae, Casuarina equisetifolia, Arachis hypogaea, and Cocos nucifera), which were either grown in a nursery in Wenchang, Hainan Province, China, or transplanted to a coral island that has harsh habitats, such as high solar radiation and low fresh water availability. The maximum photosynthetic rate (A_max) of S. taccada, I. pescaprae, and C. equisetifolia growing on the coral island increased significantly compared to the plants growing in Wenchang nursery. Except for C. nucifera, the other four species on the island had lower specific leaf areas (SLA) and higher long-term water use efficiencies. The leaf carbon content (LC) of the five species on the coral island all decreased. In addition, the leaf hydraulic conductivity (K_leaf) of I. pescaprae, C. equisetifolia, and C. nucifera increased and the leaf turgor loss point (Ψ_tlp) for I. pescaprae, and A. hypogaea decreased significantly. However, the stomatal conductance (g_s) of I. pescaprae and C. equisetifolia significantly increased. Our results demonstrated that S. taccada, A. hypogaea, and C. nucifera adapted to the island environment through non-stomatal regulation, (i.e., an increase in K_leaf, but a decrease in Ψ_tlp and SLA). In contrast, I. pescaprae and C. equisetifolia employed both stomatal regulation (i.e., an decrease in g_s) and non-stomatal regulation (an increase in K_leaf, but a decrease in Ψ_tlp, and SLA) to promote plant carbon assimilation. In conclusion, S. taccada, I. pescaprae, and C. equisetifolia had higher photosynthetic rates and water use efficiencies, which enabled them to cope better with the harsh environmental conditions. Therefore, they are recommended as suitable species for vegetation restoration on tropical coral islands.