真红树和半红树植物叶片性状的比较研究

红树植物是一类生长在热带、亚热带海岸潮间带的乔木、灌木或草本植物,根据其分布特征可分为真红树植物植物和半红树植物。为了探究两者对海岸潮间带高盐、高光和缺氧等环境的生态适应策略的异同,该文选取5种真红树植物植物[卤蕨(Acrostichum aureum)、木榄(Bruguiera gymnorrhiza)、老鼠簕(Acanthus ilicifolius)、桐花树(Aegiceras corniculatum)、秋茄(Kandelia candel)]和4种半红树植物[银叶树(Heritiera littoralis)、水黄皮(Pongamia pinnata)、黄槿(Hibiscus tiliaceus)、杨叶肖槿(Thespesia populnea)]为研究对象,对叶片解剖和功能性状进行了对比研究。结果表明:(1)9种红树植物叶片的共同特征表现为均具有角质层、叶肉具有栅栏组织和海绵组织分化、气孔下陷等。(2)不同之处在于真红树植物植物叶片有蜡质层和内皮层、无表皮毛、气孔仅分布在下表皮,而半红树植物的叶片则较少有蜡质层,部分有表皮毛,无内皮层,气孔在上下表皮分布不完全一致。(3)真红树植物植物的气孔密度和比叶面积显著小于半红树植物(P<0.05),而叶片厚度、含水量、比叶重和鲜干重比则显著大于半红树植物(P<0.05)。以上结果说明真红树植物植物的叶片性状使其在维持盐度平衡及贮水保水能力方面强于半红树植物,从而能更好地适应海岸潮间带高盐环境。

Comparative study on leaf traits of true mangrove and semi-mangrove speices

Mangrove species are a group of trees, shrubs or herbs that grow in tropical and subtropical intertidal zones. They are usually divided into true mangrove and semi-mangrove speices according to their distribution; the former is confined to intertidal zones with relatively high salinity, but the latter can grow in both intertidal and upland zones. Intertidal zones are generally characterized by high salinity, high sunlight and hypoxia. In such hostile environments, how true mangrove and semi-mangrove speices differ in their ecological adaptation strategies has not been well elucidated. In order to explore the differences of ecological adaptation strategies of true mangrove and semi-mangrove speices on high salinity, high light and hypoxia in intertidal zones, we compared the leaf anatomical and functional traits of five true mangrove and four semi-mangrove speices that were widely distributed in south subtropical zones. We selected the five true mangrove species(Acrostichum aureum, Aegiceras corniculatum, Acanthus ilicifolius, Bruguiera gymnorr-hiza, Kandelia candel)and the four semi-mangrove speices(Heritiera littoralis, Hibiscus tiliaceus, Pongamia pinnata, Thespesia populnea)at Mangrove Natural Reserve of Qi''ao Island of Zhuhai City, Guangdong Province, China. We observed leaf anatomical structures including leaf epidermis and ancillary structure, hypodermis, palisade tissue, spongy tissue and stomata, and then measured stomatal density and leaf thickness under a JSM-6360LV scanning electron microscope. We measured leaf functional traits including specific leaf area, leaf mass per area, leaf water content, and leaf fresh/dry weight ratio according to a published standar-dized protocol. The results were as follows:(1)Leaves of all the nine mangrove species had common anatomical characteristics such as epidermis covered by horny layers, palisade and spongy tissues that differentiated in the mesophyll, and sunken stomata.(2)Leaves of the true mangrove species had waxy layers and hypodermis, but had no foliar trichomes, and their stomata were only distributed in the lower epidermis; however, leaves of semi-mangrove speices had less wax layers, some of them had foliar trichomes but no hypodermis, and distribution of stomata in either upper or lower epidermis was not consistent.(3)Stomatal density and specific leaf area of true mangrove species were significantly lower than those of semi-mangrove speices(P<0.05), while leaf thickness, leaf water content, specific leaf mass and leaf fresh/dry weight ratio were significantly higher than those of semi-mangrove speices(P<0.05). These results indicate that leaves of true mangrove species have more advantages in maintaining salinity balance and water conservation than semi-mangrove speices, and thus can better adapt to high salinity in intertidal environments.