Dragon’s blood is the name given to a red exudate produced by some plant species belonging to the genera Daemonorops, Dracaena, Croton and Pterocarpus. These are endemic to various parts of the globe. It is classified as a resin or latex depending on its mode of secretion and its chemical composition, which is species specific. This red substance functions in defence and is produced (a) constitutively and stored in preformed anatomical structures, or (b) by induction in response to traumatic events, such as mechanical injury, pathogen attack or invasion by insects. Apart from its defensive role in plants, dragon’s blood is also a valuable natural resource renowned since antiquity for its diverse medicinal properties and uses in art. Despite the great importance of dragon’s blood, our knowledge of the biological basis for its secretion is still incomplete. This review summarizes recent advances in the study of the anatomical basis for its secretion, and discusses its classification and ecological function. Bringing some clarity to these issues may also help in the commercial sourcing of dragon’s blood.

中文翻译：

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龙血的分泌物及其生态意义。

龙血是龙血树属、龙血树属、巴豆属和紫檀属的一些植物产生的红色分泌物的名称。这些是全球各地特有的。根据其分泌方式及其化学成分（物种特异性），它被分类为树脂或乳胶。这种红色物质具有防御功能，并且是（a）组成性产生并储存在预先形成的解剖结构中，或（b）通过响应创伤事件（例如机械损伤、病原体攻击或昆虫入侵）而诱导产生。除了在植物中的防御作用外，龙血还是一种宝贵的自然资源，自古以来就因其多种药用特性和艺术用途而闻名。尽管龙血非常重要，但我们对其分泌的生物学基础的了解仍然不完整。本文综述了其分泌的解剖学基础的研究进展，并讨论了其分类和生态功能。澄清这些问题也可能有助于龙血的商业采购。