Distribution of Peltate Glandular Trichomes on Developing Leaves of Peppermint

The pattern of peltate glandular trichome initiation and ontogeny on expanding peppermint (Mentha × piperita) leaves was defined by surveying the populations of peltate glands in each of seven developmental stages within sampling areas of leaf apical, mid-, and basal zones for both abaxial and adaxial surfaces. It was shown that new peltate glands continue to form until leaf expansion ceases and that regions of active gland initiation are unevenly distributed. The distribution of gland initiation reflects the basipetal pattern of leaf maturation, with relatively immature regions at the leaf base continuing to produce oil glands long after gland production has stopped at the leaf apex. The proportion of glands in the secretory stage as a function of leaf development and the direct observations of living glands over a period of 33 h indicate that a period of only 20 to 30 h of secretory activity is required for filling of the gland storage compartment with essential oil. These findings are discussed in relation to earlier literature describing age-related changes in glandular essential oil content.

本研究通过对展开期胡椒薄荷（Mentha × piperita）叶片顶端区、中区与基区的远轴面（abaxial surface）及近轴面（adaxial surface）三个采样区域内7个发育阶段的盾状腺毛（peltate glandular trichome）种群进行调查，明确了该物种叶片上盾状腺毛的起始模式与个体发育过程。研究证实，新的盾状腺毛会持续形成直至叶片展开终止，且活跃腺毛起始的区域分布并不均匀。腺毛起始的分布模式反映了叶片成熟的向基式（basipetal）规律：当叶尖的腺毛产生过程早已停止时，叶基部相对未成熟的区域仍会持续产出油腺。结合按叶片发育阶段统计的分泌期腺毛占比，以及对活体腺毛长达33小时的直接观测结果可知，将腺存储腔（gland storage compartment）充盈精油（essential oil）仅需20至30小时的分泌活动。本研究的相关发现将结合此前关于腺毛精油含量随年龄变化的相关文献展开讨论。