Mucilaginous Secretions in the Xylem and Leaf Apoplast of the Swamp Palm Mauritia flexuosa L.f. (Arecaceae)

Abstract

Mauritia flexuosa palms inhabit wetland environments in the dry, seasonal Brazilian savanna (Cerrado) and produce mucilaginous secretions in the stem and petiole that have a medicinal value. The present study sought to characterize the chemical natures of those secretions and to describe the anatomical structures involved in their synthesis. Chemical analyzes of the secretions, anatomical, histochemical analyses, and electron microscopy studies were performed on the roots, stipes, petioles, and leaf blades. Stipe and petiole secretions are similar, and rich in cell wall polysaccharides and pectic compounds such as rhamnose, arabinose, xylose, mannose, galactose, and glucose, which are hydrophilic largely due to their hydroxyl and carboxylate groups. Mucilaginous secretions accumulate in the lumens of vessel elements and sclerenchyma fibers of the root, stipe, petiole, and foliar veins; their synthesis involves cell wall loosening and the activities of dictyosomes. The outer faces of the cell walls of the parenchyma tissue in the mesophyll expand to form pockets that rupture and release pectocellulose substances into the intercellular spaces. The presence of mucilage in the xylem, extending from the roots to the leaf veins and continuous with the leaf apoplast, and sub-stomatal chambers suggest a strategy for plant water economy.

Ontogenesis of Resin Ducts and Secretory Process in Protium spruceanum (Burseraceae) Stems

“…Alkaloids produced by Protium species are considered responsible for deterrent actions against herbivores (Souza et al, 2016), and the phenolic compounds found in P. serratum have antioxidant activities (Tanamatayarat, 2016). The mucilage present in the secretions of species growing in dry environments, such as the Cerrado, also appear to aid in water retention (Silveira et al, 2020; Souza et al, 2020; Costa et al, 2021) and the proteolytic action of the proteins aids in controlling infections (Ramos et al, 2019). Plant secretions such as resins have important protective ecological roles.…”

Complementary water and nutrient utilization of perianth structural units help maintain long floral lifespan inDendrobium

“…Polysaccharides, including extracellular polysaccharides, have been shown to increase the ability of plant organs (e.g. stems, leaves, roots, and flowers) to store water and to buffer water deficits ( Nobel et al , 1992 ; Clifford et al , 2002 ; Chapotin et al , 2003 ; Silveira et al , 2020 ). Previous studies have shown that Dendrobium stems accumulate high levels of polysaccharides when they experience environmental and biotic stresses ( Huang et al , 2015 ; Wu et al , 2016 ; Abdullakasim et al , 2018 ).…”