入侵植物南美蟛蜞菊营养器官的形态解剖研究

Anatomical study on vegetative organs of invasive plant Wedelia trilobata

南美蟛蜞菊(Wedelia trilobata(L.)Hitchc.)是华南地区常见的入侵植物之一,其环境适应性强,繁殖速度快,对入侵地生态环境的破坏而导致生物多样性丧失的危害现象已经引起关注。结构与功能的相适应是生物学的基本观点之一,对入侵植物营养器官的内部形态解剖结构的研究,是理解入侵能力与其生物特性之间关系的直接路径,同时也是其他生理机理研究的结构基础。为研究入侵植物南美蟛蜞菊营养器官内部形态结构与其入侵能力的适应性,采用常规徒手切片技术对其根、茎及成熟叶片3大营养器官进行解剖及显微观察。结果表明:南美蟛蜞菊根、茎均具有次生结构。根韧皮部外方薄壁细胞具有分泌道,次生结构横切面中央为发达的次生木质部所填充,周皮代替表皮起保护作用,根的初生生长时期长,具有次生生长可视为其入侵定居时与本地物种形成地下资源和空间竞争的结构基础;茎的初生结构分化不久即产生次生结构,次生结构中央有明显的髓,次生维管束组织产生于初生结构的维管束之间并形成一管状结构明显将皮层和髓分开,茎内部组织高度木质化可视为是其茎直立生长及竞争地上资源和空间的结构基础;叶片为异面叶,上下表皮均具有气孔器和表皮毛,叶片内部具有分泌道,维管束发达且具有束鞘延伸,能与叶片表皮细胞共同构成辅助输导系统,叶片的结构特征是构成其喜阳植物的基础。此外叶片及根分泌道的存在可能与其化感物质的分泌有关。研究结果丰富了南美蟛蜞菊入侵适应性研究的背景基础,同时也弥补其在形态结构研究中的空缺。

Wedelia trilobata was one of the common invasive plants in south China area. Because of its strong environmental adaptability and fast propagation speed, the phenomenon that the destruction of the ecological environment of invasion area led to the loss of biodiversity had aroused wide concern. What’s more, the adaptation between structure and function was one of the basic concepts of biology. Studies on anatomical structure of vegetative organs of invasive plants was the direct way to understand the relationship between the invasion ability and its biological characteristics and was also the basis for researching other physiological mechanism. Morphological and anatomical characteristics of vegetative organs（root, stem, leaf） of Wedelia trilobata was studied by freehand slice technique. The results were as follows：The structures of root and stem had secondary growth. There was a quantity of secretory canals distributed in root and leaf. The developed secondary xylem filled in center of the transverse section of root and the periderm replaced epidermis in protect function. The results that Wedlia triloata’s roots had the long period of the primary growth and secondary growth may be the basics for their successful competition with other native species for resources and space.The stem had structural characters of high ability to transport and support. The primary structure of stem was soon producing secondary structure that formed tubular structure and clearly separated the cortex from the pith. The internal organization of stem becoming lignified may be a key for their successful invasions. The leaf was bifacial leaf and had long epiderm hairs on its upper and lower epidermis. There were well-developed vascular bundles and bundle sheath extension distributing in the structure of the leaf. In addition, the secretory canal that distributed extensively in the leaves and roots may have something to do with the secretion of allelochemicals. The conclusions in this study not only enriched the background for the studies on the intrusion adaptability of Wedelia trilobata, but also made up for the vacancy in the study of morphological structure.