热带海滨植物水芫花(Pemphis acidula)的生理生态学特性

The Ecophysiological Characteristics of Pemphis acidula, A Tropical Beach Plant

热带珊瑚岛生态系统处于高温、强光、台风频发、季节性干旱等恶劣环境气候条件下,极易退化,有必要进行植被恢复。水芫花(Pemphis acidula)为千屈菜科小灌木,自然分布于热带海滨和石灰质岩岸,在海岸固沙和海岛植被恢复中具有潜在的应用价值。以中国西沙群岛自然生长的水芫花为研究对象,对其叶片和茎秆形态解剖结构、生理学特征、叶片营养元素及适生土壤理化性质进行了分析研究,以期全面了解水芫花的生理生态特性及其对海滨环境的适应机理。研究结果表明,水芫花叶片厚度达到703.798μm,栅栏组织与海绵组织的厚度比值仅为0.563,叶片高度肉质化,有利于叶片保水。叶片气孔密度低,仅为44.44 mm-2,有利于减小蒸腾。水芫花导管直径偏低(35.639μm),导管密度为49.528 mm-2,有利于提升水分利用效率并有效避免栓塞。水芫花叶片超氧化物歧化酶活性较高(340.827 U?g^(-1)),总抗氧化能力高达834.016 U?g^(-1),总酚含量较高(16.482 mg?g^(-1)),丙二醛含量仅为10.490 nmol?g^(-1),说明其通过提高抗氧化能力降低膜脂过氧化伤害程度。水芫花生长环境的土壤养分含量低,但钙含量高达38.570 g?kg^(-1),含水量仅为9.5%,土壤环境较差;而水芫花叶片的氮磷含量属于正常水平,说明其能够高效利用贫瘠土壤中的养分。综上,水芫花具有较强的抗干旱能力和抗胁迫能力,适宜生长于土壤较为贫瘠的热带滨海生境中,是热带珊瑚岛植被恢复的重要备选物种。

The tropical coral island ecosystem is easy to degenerate under the harsh environment such as high temperature, strong sunlight, frequent typhoon, seasonal drought, so the vegetation restoration is necessary. Pemphis acidula （lythraceae） is a small shrub, mainly distributes in tropical coastal beach and calcareous rocky shores, with potential application value in costal sand fixation and island revegetation. In this study, leaf and branch morphological and anatomical structures, physiological characteristics, leaf nutrient elements and the suitable soil characteristics of P. acidula habitated in Xisha islands were analyzed. The results showed that the leaf thickness of P. acidula was up to 703.798 μm, and the palisade tissue/spongy tissue ratio was only 0.563. The leaf was highly succulent, which was beneficial to water retention. The leaf stomatal density was as low as 44.44 mm-2, which was beneficial to reduce transpiration. The vessel diameter was low （35.639 μm） and the vessel density was 49.528 mm-2, which were beneficial to improve water use efficiency and effectively avoid embolism. The leaf superoxide dismutase activity was high （340.827 U·g-1）, the total antioxidant capacity was up to 834.016 U·g-1, the total phenolic content was high （16.482 mg·g-1）, and the malondialdehyde content was as low as 10.490 nmol·g-1, which indicated that P. acidula decreased the degree of oxidative damage by improving its antioxidant capacity. The suitable soil nutrient contents were low, soil calcium content was high, soil water content was as low as 9.5%, showing poor soil environment. But the leaf nitrogen and phrophros contents were high, showing high efficiencies in absorbing and utilizing nutrients. Based on the above results, P. acidula has strong ability in resisting drought and stress, suitable for growing in tropical coastal beach habitats with relatively poor soil, and is a potential species for rehabilitation in tropical coral islands.