Micromorphology of Salt glands and content of marker compound Plumbagin in the leaves of Plumbago zeylanica Linn

Abstract

Background: Salt glands are highly specialized epidermal structures developed in recretohalophytic plants, intended for salt storage (reservoir) and as a means to alleviate the salt stress of the saline habitat by exo-recreto releases excess salts from the mesophyll tissues to the surrounding environment. Plumbago zeylanica Linn belongs to the family Plumbaginaceae is an important medicinal plant and espoused as a source for the drug Chitraka. Aim: The present study concerns the delineation of micromorphological characteristics of the paradermal and cross sections of the leaf epidermis, lamina, salt glands, petiole and mucilage secreting glands of the calyx of the flowers of Plumbago zeylanica Linn. Materials and Methods: Delimiting the morpho-histological profile of the leaves and to develop the chromatogram of the methanol extract of the leaves and quantification of the marker compound plumbagin in the leaves using High Performance Thin-Layer Chromatographic (HPTLC) method. Results: Distribution of uniseriate, cruciate type clothing trichomes, characteristic contour of midrib, presence of amphistomatic epidermis with anisocytic stomata, crystals in idioblast of ground tissues of petiole and mesophyll, large palisade ratio, small stomatal index, multicellular salt gland structure with 8 cells, cuticular secretory cells, crescent shaped petiole, densely distributed mucilage secreting glands on the calyx of flowers were features characteristic of the taxon. The HPTLC finger printing profile of the leaves revealed six phyto-constituents. Densitometric scanning of plumbagin had shown the absorption spectra λ max at 270 nm. Spectral matching by overlaying the absorption spectra of standard marker compound with the phyto-constituents present in the methanol extract of sample could fail to obtain any spectral matching at λ max 270 nm, suggestive that dried leaves of P. zeylanica did not contain any appreciable amount of Plumbagin. Calibration data obtained by polynomial regression had revealed that dried leaves of P. zeylanica Linn contained below 105 ng/μl of plumbagin in methanol extract of leaves.

Botanical Pharmacognosy of Bacopa monnieri (Linn.) Pennell

“…The descriptive terms of the anatomical features were used here as per Metcalfe and Chalk, 26 Conquist 27 and Sudhakaran. [28][29]…”

Secretory structures in plants: Lessons from the Plumbaginaceae on their origin, evolution and roles in stress tolerance

“…In Aegialitis, the mucilage-secreting cells are found in the axils of the leaves, on laminae, bracts, and sepals, and are very numerous, lying in an oval or circular depression, bounded by regularly-arranged cells (Wilson, 1890). Plumbago species have glandular hairs that secrete a sticky mucilage on the petiole and calyx of flowers (Singh, Naidoo, Bharuth, & Baijnath, 2019;Sudhakaran, 2019;Wilson, 1890). It has been hypothesized that sticky exudates function as an aid to pollination by acting as a barrier for insect predators like ants, so preventing predatory attacks on favoured flying insect pollinators (Panicker & Haridasan, 2016).…”

“…Amongst the halophytic species in the family it is likely that all utilize salt glands (see Table 1A), although there are some that thrive in saline habitats/environments, but where the presence of functional glands has yet to be established (e.g., Myriolimon diffusum; Table 1). There are also species with glands, whose salt tolerance has yet to be established; for example, Plumbago zeylanica (Sudhakaran, 2019) and P. europaea (Waisel, 1972) as well as nonhalophytes like Armeria caespitosa (Giménez-Benavides, Escudero, & Pérez-Garcia, 2005) and A. canescens (Scassellati et al, 2016), which have structures similar to salt glands (Table 1B). The presence of structures analogous to salt glands in species where salt tolerance has yet to be established is particularly common in the largest genus within the family, Limonium (at least 14 species; see (Thomson et al, 1988); only the glands of Limoniastrum guyonianum (with 32 cells; Tables 1 and 2) and those of Aegialitis (24 or 40 cells) have more.…”

Secretory structures in the Plumbaginaceae: origin, evolution and roles in stress tolerance

“…In Aegialitis , the mucilage-secreting cells are found in the axils of the leaves, on laminae, bracts, and sepals, and are very numerous, lying in an oval or circular depression, bounded by regularly arranged cells (Wilson, 1890). Plumbago species have glandular hairs that secrete a sticky mucilage on the petiole and calyx of flowers (Singh, Naidoo, Bharuth & Baijnath, 2019;Sudhakaran, 2019;Wilson, 1890). It has been hypothesized that the sticky exudates function as an aid to pollination by acting as a barrier for insect predators like ants, so preventing predatory attacks on favoured flying insect pollinators (Panicker & Haridasan, 2016).…”

“…Among the halophytic species in the family it is likely that all utilise salt glands (see Table 2A), although there are some that thrive in saline habitats/environments, but where the presence of functional glands has yet to be established (e,g.,Myriolimon diffusum ; Table 2). There are also species with glands, whose salt tolerance has yet to be established; for example,Plumbago zeylanica (Sudhakaran, 2019) and P. europaea (Waisel, 1972) as well as non-halophytes like Armeria caespitosa (Gimenez-Benavides, Escudero, & Perez-Garcia, 2005) and A. canescens (Scassellati, Pasqua, Valletta, & Abbate, 2016), which have structures similar to salt glands (Table 2B). The presence of structures analogous to salt glands in species where salt tolerance has yet to be established is particularly common in the largest genus within the family, Limonium (at least 14 species ; see Tables 3A and 3B; there are 34 halophytic species of Limonium with salt glands,).…”