|
In plant morphology, thorns, spines, prickles, and in general spinose structures (as ''spinose teeth'', ''spinose apical process'') are all hard structures with sharp, stiff ends, generally with the same function of physically deterring animals from eating the plant material. In common language the terms are used more or less interchangeably, but in botanical terms, thorns are derived from shoots (so they can be branched or not, they can have leaves or not, and they arise from a bud),〔Simpson, M. G. 2010. "Plant Morphology". In: ''Plant Systematics, 2nd. edition''. Elsevier Academic Press. Chapter 9.〕〔Judd, Campbell, Kellogg, Stevens, Donoghue. 2007. "Structural and Biochemical Characters". In: ''Plant Systematics, a phylogenetic approach, third edition''. Chapter 4.〕〔(Turner et al. 2005, ''Sonoran Desert Plants, an Ecological Atlas.'' University of Arizona Press. )〕〔(Van Wyk, Van Wyk. 2007. ''How to identify trees in South Africa.'' Struik. )〕 spines are derived from leaves (the entire leaf or some part of the leaf that has vascular bundles inside, like the petiole or a stipule),〔〔〔〔 and prickles are derived from the epidermis (so they can be found anywhere on the plant, and do not have vascular bundles inside so they can be removed more easily and cleanly than thorns and spines〔).〔〔〔 Leaf margins also may have teeth, and if those teeth are sharp, they are called spinose teeth on a spinose leaf margin〔〔 (some authors consider them a kind of spine〔). On a leaf apex, if there is an apical process (generally an extension of the midvein), and if it is specially sharp, stiff, and spinelike, it can be called spinose or pungent apical process〔 (again, some authors call them a kind of spine〔). When epidermis is covered with very long, stiff trichomes (more correctly called bristles in this case,〔 for some authors a kind of prickle〔) is called ''hispid vestiture'',〔〔〔 if is covered with stinging trichomes it can be called ''urent vestiture''.〔 ==Function== The predominant function of thorns, spines and prickles is deterring herbivory in a mechanical form. Not all functions of spines or glochids are limited to defence from physical attacks by herbivores and other animals. In some cases, spines have been shown to shade or insulate the plants that grow them: for example, the saguaro cactus spines shade the apical meristem in summer and in members of the Opuntioideae glochids insulating the apical meristem in winter. Agrawal ''et al.'' (2000) found that spines seem to have little effect on pollinators, which the plants need in order to reproduce.〔Agrawal, A, A., Rudgers, A, J., Botsford, W, L., Cutler, S., Gorin, B, J., Lundquist, C, J., Spitzer, W, B., & Swann, L, A. (2000). Benefits and Constraints on Plant Defense against Herbivores: Spines Influence the Legitimate and Illegitimate Flower Visitors of Yellow Star Thistle, ''Centaurea solstitialis'' L. (Asteraceae). JSTOR, 45(1), 1-5. http://www.jstor.org/stable/3672545. retrieved 2012-03-20〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thorns, spines, and prickles」の詳細全文を読む スポンサード リンク
|