Root anatomy of Venezuelan species of Geonoma (Arecaceae: Arecoideae: Geonomateae)

Abstract In this research we studied root anatomy of eight species and two morphotypes from the genus Geonoma in Venezuela, in order to explore their structural and taxonomic implications. Fresh material sampled wild population was fixed in FAA and hand-sectioned or with a rotary microtome, following standardized protocols. Histochemical tests were carried out in some components. Obtained preparations were studied under a calibrated optical microscope; some variables were quantified by means of an eyepiece micrometer. The obtained results allowed the anatomical differentiation of the studied species and the two morphotypes. Most informative diagnostic variables identified include the thickening shape of the cells in the exodermis walls (transverse section), parenchyma cells with circular contours in the cortex, length of air spaces, the differentiation of passage cells in the endodermis, shared “V” and “Y” shaped xylem arches, the shape of phloem strands and scattered metaxylem vessels in the pith. Our results are also discussed in the context of other structural studies published on roots of different members of Arecaceae.

摘要：本研究以委内瑞拉境内格诺莫棕榈属（Geonoma）的8个物种与2个形态型为研究材料，旨在探究其根部解剖结构的分类学价值与结构特征。研究人员从野生种群中采集新鲜样品，采用福尔马林-乙酸-酒精固定液（FAA）进行固定，随后依照标准化实验流程，通过徒手切片或旋转式切片机制备组织切片。部分组织组分被用于组织化学检测。将制备完成的切片置于校准后的光学显微镜下观察，并借助目镜测微尺对部分观测变量进行定量统计。研究结果可实现对所涉物种及2个形态型的解剖学区分。本研究鉴定出的最具诊断指导意义的特征包括：横切面视角下外皮层细胞壁的加厚形态、皮层内具圆形轮廓的薄壁细胞、气腔长度、内皮层通道细胞的分化模式、呈“V”形与“Y”形的共现木质部弧、韧皮部束的形态，以及髓部中散生的后生木质部导管。本研究结果还结合已发表的不同棕榈科（Arecaceae）类群根部结构相关研究展开了讨论。