Lemos Renata Cristina Cassimiro de, da Costa Silva Delmira, Flavia de Albuquerque Melo-de-Pinna Gladys
Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Bahia, Brazil.
PLoS One. 2017 Nov 14;12(11):e0187905. doi: 10.1371/journal.pone.0187905. eCollection 2017.
Extrafloral glands in Passifloraceae species have aroused the interest of many researchers because of their wide morphological diversity. The present work analyzed the foliar glands on 34 species of Passiflora from samples containing glands in the petiole and foliar blade fixed in 50% solution of formaldehyde-ethanol-acetic acid and stored in a 70% ethanol solution. For anatomical analyses, part of the material was embedded in Paraplast, longitudinally sectioned and double stained with safranin and astra blue. Scanning electron microscopy analysis was also carried out. To analyze the presence of sugars in the secretion of foliar glands, a glucose strip test was used. Based on the results of morphological, anatomical and glucose strip tests, the foliar secretory glands in Passiflora can be grouped into two categories: Type I glands, defined as nectaries, can be elevated or flattened, and can have a sugar content high enough to be detected by the glucose strip test analysis. Type II glands are elevated and did not show a positive reaction to the glucose strip test. From an anatomical viewpoint, glands characterized as extrafloral nectaries show a multistratified secretory epidermis, typically followed by two flat layers of nectariferous parenchyma with dense content. Internal to these layers, vascular bundles are immersed in the subsecretory parenchyma and terminate in phloem cells. On the other hand, type II glands show a single layer of elongated secretory epidermal cells. Internal to this single layer, parenchyma and vascular tissue with both phloem and xylem elements can be observed. The analyzed species show a wide diversity of gland shape and distribution, and the combined analysis of morphology, anatomy and preliminary tests for the presence of glucose in the exudate in different Passiflora subgenera suggests the occurrence of two categories of glands: nectaries and resin glands.
西番莲科植物的花外腺体因其广泛的形态多样性引起了许多研究人员的兴趣。本研究分析了34种西番莲属植物的叶腺体，样本包括叶柄和叶片上带有腺体的部分，这些样本用50%的甲醛-乙醇-乙酸溶液固定，并保存在70%的乙醇溶液中。为了进行解剖分析，部分材料被包埋在石蜡中，纵向切片，并用番红和阿斯特拉蓝进行双重染色。还进行了扫描电子显微镜分析。为了分析叶腺体分泌物中糖的存在情况，使用了葡萄糖试纸测试。基于形态学、解剖学和葡萄糖试纸测试的结果，西番莲属植物的叶分泌腺体可分为两类：I型腺体，定义为蜜腺，可隆起或扁平，其糖含量高到足以通过葡萄糖试纸测试分析检测到。II型腺体隆起，对葡萄糖试纸测试未显示阳性反应。从解剖学角度来看，被鉴定为花外蜜腺的腺体有多层分泌表皮，通常后面跟着两层扁平的产蜜薄壁细胞，内含物密集。在这些层的内部，维管束浸没在分泌下层薄壁组织中，并在韧皮部细胞中终止。另一方面，II型腺体有单层细长的分泌表皮细胞。在这单层细胞的内部，可以观察到同时含有韧皮部和木质部成分的薄壁组织和维管组织。所分析的物种显示出腺体形状和分布的广泛多样性，对不同西番莲亚属的形态学、解剖学以及渗出物中葡萄糖存在情况的初步测试的综合分析表明存在两类腺体：蜜腺和树脂腺。
