Laboratory of Plant Anatomy, Department of Botany, Institute of Biosciences, Federal University of Rio Grande do Sul, Bento Gonçalves Avenue, 9500, Porto Alegre, Rio Grande do Sul, Brazil.
Electrochemical Processes and Corrosion Laboratory, Department of Metallurgy, School of Engineering, Federal University of Rio Grande do Sul, Bento Gonçalves Avenue, 9500, Porto Alegre, Rio Grande do Sul, Brazil.
Am J Bot. 2023 Nov;110(11):e16248. doi: 10.1002/ajb2.16248. Epub 2023 Nov 14.
Leaf subepidermal secretory cavities are a notable trait in Myrtaceae, but their formation is still controversial because of the lack of consensus on their ontogeny among authors. Knowledge about the compounds present in these cavities has grown over the last few years, demonstrating that terpenoid-rich oils are not their unique content. These two points are the focus of this study on the ontogeny, structure, and contents of secretory cavities in neotropical Myrtaceae.
We used histochemical tests and Raman analysis to verify the basic chemical composition of the cavity contents of nine species. We studied the ontogeny of glands in one species, comparing aldehyde-fixed tissues and fresh sections mounted in an inert medium.
We observed schizogenous development and appearance of the secretory cavities and found that sample processing may induce cell breakdown, which can be misinterpreted as lysigeny. The content of these cavities contains putative terpenes, resins, carbonyl groups, and flavonoids.
Our findings support the hypothesis that the lysigenous appearance of the oil glands is a technical artifact. These tissue distortions must be considered when interpreting the development of this type of secretory structure. Moreover, the basic analyses of chemical constituents show for the first time that the glands of neotropical Myrtaceae are potential reservoirs of some compounds such as flavonoids previously reported as novelties for a few other myrtaceous species. Because some of them are non-lipid compounds, the idea that the glands are just oil repositories is no longer applicable.
叶表皮下分泌腔是桃金娘科的一个显著特征，但由于作者对其个体发生缺乏共识，因此其形成仍存在争议。近年来，关于这些腔室内存在的化合物的知识不断增加，证明富含萜类的油类并非其唯一成分。这两点是本研究的重点，研究对象是新热带桃金娘科植物分泌腔的个体发生、结构和内容。
我们使用组织化学测试和拉曼分析来验证九种物种腔室内内容物的基本化学成分。我们研究了一个物种的腺体个体发生，比较了醛固定组织和用惰性介质安装的新鲜切片。
我们观察到了裂生性发育和分泌腔的出现，并发现样本处理可能会诱导细胞破裂，这可能被错误地解释为溶生性。这些腔室内容物含有萜类、树脂、羰基和类黄酮等潜在的萜类化合物。
我们的发现支持这样一种假设，即油腺的溶生性外观是一种技术假象。在解释这种分泌结构的发育时，必须考虑到这些组织扭曲。此外，对化学成分的基本分析首次表明，新热带桃金娘科的腺体是一些化合物的潜在储存库，如先前报道的一些其他桃金娘科物种的新型黄酮类化合物。由于其中一些是非脂类化合物，因此腺体只是油类储存库的观点不再适用。
