Glandular trichome diversity on leaves ofLippia origanoidesandLippia stachyoides(Verbenaceae): morphology, histochemistry, and ultrastructure

Abstract

Despite the ecological and medicinal importance of glandular trichomes in Verbenaceae, information on their structure, mainly at the subcellular level, is sparse. We analyzed the morphology and histochemistry of glandular trichomes in Lippia origanoides Kunth and Lippia stachyoides Cham., using conventional methods in anatomy, histochemistry, scanning and transmission electron microscopy, and ultracytochemical techniques. Five morphotypes (I–V) of glandular trichomes were identified in L. origanoides, and four morphotypes (I, III–V) in L. stachyoides. Morphotype I is the most abundant in both species. Lipids were detected in all morphotypes except IV; terpenes in I, II, and V; phenolic compounds in all morphotypes except V; neutral polysaccharides and protein in all morphotypes; mucilage exclusively in IV; alkaloids only in III. Each glandular morphotype showed ultrastructural peculiarities compatible with the chemical compounds produced. An association between glandular morphotype, secretion composition, and ultrastructural features in Lippia species was revealed, suggesting functions specific to each glandular morphotype.

Morphology and histochemistry of glandular trichomes in Hyptis villosa Pohl ex Benth. (Lamiaceae) and differential labeling of cytoskeletal elements

“…This suggests some type of evolution of the transfer cells molded by physiological selection pressures, facilitating the short distance transport (Gunning & Pate 1969). The widespread occurrence of plastids devoid of thylakoids in the stalk cells of morphotype II indicate that these organelles are the main sites of production of the total lipids and terpenes detected in these cells (Evert 2006;Tozin et al 2015a). Similarly, the abundance of plastids and oil drops in the basal cells are indicatives of oil production in this portion of the trichome (Evert 2006;Tozin et al 2015a).…”

“…Polysaccharides are important in the maintenance of the hydric potential of the cells protecting the organs against desiccation (Ascensão et al 1999;Werker 2000), important role in environment with low humidity as in the Brazilian Cerrado. Phenolic compounds are also important in the defense against herbivores and pathogens and in the protection of the plants against high irradiance, like that in the Cerrado, that could cause photoinhibition and damage to the cell machinery (Liakoura et al 1997;Tozin et al 2015a;Silva et al 2016). Total lipids and terpenes were abundantly stained by the histochemical tests in the morphotype I, mainly in the head cells.…”

“…Glandular trichomes are epidermal appendices with highly variable morphology and responsible for the production of secretion with economic, medicinal and ecologic values (Ascensão et al 1999;Argyropoulou et al 2010;Tozin et al 2015a). Substances of diff erent chemical categories can be produced by glandular trichomes, and their subcellular features vary according to the substances produced and the form of release of the secretion (Ascensão et al 1995;Ascensão & Pais 1998;Appezzato-da-Glória et al 2012;Naidoo et al 2012;Tozin et al 2015a;Silva et al 2016).…”

“…Substances of diff erent chemical categories can be produced by glandular trichomes, and their subcellular features vary according to the substances produced and the form of release of the secretion (Ascensão et al 1995;Ascensão & Pais 1998;Appezzato-da-Glória et al 2012;Naidoo et al 2012;Tozin et al 2015a;Silva et al 2016).…”

“…Th e subcellular features of glandular trichomes have been exhaustively described to several species from diff erent families (Ascensão & Pais 1998;Sacchetti et al 1999;Argyropoulou et al 2010;Papini et al 2010;Paiva & Martins 2011;Appezzato-da-Glória et al 2012;Naidoo et al 2012;Amrehn et al 2014;Tozin et al 2015a;Silva et al 2016 and references therein); however, some important aspects, such as the involvement of the cytoskeletal elements in such secretory process remains poorly studied. It has been demonstrated that movement of oil droplets in the Morphology and histochemistry of glandular trichomes in Hyptis villosa Pohl ex Benth.…”