Die anatomie en histochemie van Grewia lasiocarpa E. Mey. ex Harv. (Malvaceae)

Abstract

Grewia lasiocarpa E. Mey. ex Harv is commonly known as the forest raisin(s) due to its edible red-brown 4-lobed fruit(s), which turn black as they age. The genus is easily recognised by its distinctive morphology (edible fruits, crystals, trichomes) and abundant medicinal properties (antimicrobial, anti-inflammatory, antioxidant). In order to distinguish this species from other Grewia species, this study aimed to describe the morphology, ultrastructure of the leaves, stem bark and secretory structures of G. lasiocarpa using microscopic techniques and histochemical tests. The morphological and anatomical studies revealed the presence of glandular trichomes. One type of peltate, three types of capitate and non-glandular (simple, stellate, multangulate-stellate) trichomes were found on the leaves and stem bark of G. lasiocarpa. The histochemical investigation revealed that certain primary and secondary metabolites such as starch, protein, mucilage, lignin (polyphenols) and alkaloids are present in the leaves, stem bark and indumentum. This is the first report on the morphological, ultrastructure and histochemical studies of leaves and stem bark of Grewia lasiocarpa. This structural characterisation of the leaves and stem bark would help to distinguish this species from others in this genus, its ascertain authenticity, contribute to the pharmacognostic usage and general knowledge.

Development and Biomechanics of Grewia lasiocarpa E. Mey. Ex Harv. Trichomes Exudate

“…This adaptation is responsible for the variety of trichome morphologies observed in plants. This correlates with our findings in [19] as there are different trichomes morphology in Grewia lasiocarpa which contain different phytometabolites. Although their distribution within a plant differs considerably [22,27], phytometabolites such as alkaloids, flavonoids, essential oils, and phenols are present in glandular trichomes [28,29].…”

“…The glandular trichomes of species of this genus are composed of a multicellular head having either sessile or a short multicellular stalk, while four types of non-glandular trichomes with nine subdivisions are commonly found in plants of this genus. The presence of glandular and non-glandular trichomes on the leaves and stem bark of Grewia lasiocarpa has been previously reported [19]. Glandular trichomes contain substances of metabolic importance, that are released upon maturity [58,59].…”

“…There are two types of trichomes viz., glandular and non-glandular [16], the development of these trichomes could be genetically [17] or epigenetically controlled [18]. They occur in a wide range of sizes (length, breadth), colours, and numbers [19,20]. They constitute 1-3% of plant fresh weight and sometimes have high toxicity [21,22].…”

“…Different morphological variations occur in plant trichomes although certain degree of similarity may be observed in species of the same genus and families [24,25]. The trichomes of the genus Grewia are not exempted from this either, as they occur in diverse shapes and sizes such as stellate, multangulate-stellate, T-shaped, simple [19,23]. According to [26] plants have adapted varied storage techniques which depend on the type of secretion.…”

“…This variation in trichome morphology and phytometabolites that are present in the glandular trichomes as a result of multiple evolutionary events [30]. The presence of non-glandular and glandular trichomes has been reported on the leaves and stem bark of Grewia lasiocarpa [19]. Particularly in the leaf trichomes of the model plant Arabidopsis thaliana, the molecular mechanism of unicellular trichome development has been intensively studied [31,32].…”