元宝山南方红豆杉的解剖结构及其环境适应性

以分布于广西北部元宝山自然保护区的南方红豆杉为研究对象,利用石蜡切片方法和光学显微技术,对其茎和叶的解剖结构及其对环境的适应性进行了研究和探讨。结果表明:(1)茎和叶的表皮细胞均较小,外壁角质层发达,胞内富含单宁类物质;(2)1～2年生茎无周皮,皮层基本薄壁组织分成5瓣,茎横切面呈"梅花"形,3年生茎具周皮,次生韧皮部薄壁组织发达、细胞内含物丰富;(3)叶片下表皮气孔带和中脉带均有角质层乳状突起分布,乳突大而密集,气孔仅分布于下表皮,气孔器为双环型,叶肉海绵组织发达,约占叶肉厚度的3/4。进一步分析显示,元宝山南方红豆杉茎和叶的解剖结构与元宝山的中亚热带山地气候和阴生环境相适应;与前人研究结果不同,本研究发现叶片角质层乳状突起遍布下表皮,这可能与元宝山南方红豆杉的分布区海拔高且环境温度低有关。

Anatomical structure and environmental adaptability of Taxus wallichiana var.mairei in Yuanbaoshan

The anatomy structures of stems and leaves of Taxus wallichiana var.mairei from Yuanbaoshan Nature Reserve,northern Guangxi were studied by paraffin-sectioning and optical microtechnique to explore the adaptability. The results showed that epidermal cells of the stems and leaves were small,and the well-developed horny layers of the cells with abundant tanning were found. Periderms of stems were absent in 1-2 year-old individuals. Ordinany parenchyma of cortex was composed of 5 lamellas. The cross section of stem seemed to be quincuncial. Periderms in stems of 3-year-old individuals were found,followed by the finding of developed parenchymatous tissue with abundant cellular contents in the secondary phloem. Midvein had the same corneous layer emulsion swelled of stomatal band in the lower epidermis of leaf ,and the papillate was dense and large. Stomas with bicyclic stomatal apparatus of the leaves were only detected in the lower epidermis. The spongy tissue constituted a three-quarter proportion in the thickness of the mesophyll. Further analysis indicated that the anatomy structures of stems and leaves were considered as adaption to the mid-subtropica mountain climatic and shade environment. Opposite to previous studies,it was found that the corneous layer emulsion swelled is spread all over the lower epidermis of leaf ,which were correlated with the higher elevation and lower temperature of the habitat.