Morpho-Anatomical Investigation of selected Verbenaceae taxa from Ri-Bhoi District, Meghalaya

Nabajit Choudhury¹ and Nibedita Das^2*

^{1, 2} Department of Botany, University of Science and Technology Meghalaya, India.

*Corresponding address: nibeditadas@ustm.ac.in

Abstract

The Verbenaceae family, known for its diverse plant species, displays remarkable morphological and anatomical variations. This study explores the morphological and anatomical traits of five selected taxa belongs to Verbenaceae family i.e. Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, Lantana camara L, Clerodendrum infortunatum L. Stachytarpheta indica (L.) Vahl and Vitex negundo L., found across various locations on the University of Science and Technology Meghalaya (USTM) campus, shedding light on their taxonomy and systematics. Through detailed analysis of leaf, petiole, and stem morphology, this research enhances our understanding of the family's diversity and provides valuable data for plant identification and classification. The findings have significant implications for the taxonomy and phenology of the Verbenaceae family, underscoring the critical role of morphological and anatomical characteristics in plant systematics.

Key word: Anatomy, Morphology, Taxonomy, Verbenaceae, Meghalaya.

Introduction

The Verbenaceae family, also commonly known as the Verbena family, consists of plants mainly from tropical regions like herbs, shrubs, trees, etc. The family Verbenaceae of about 99 genera and 3151 species distributed chiefly in tropics and subtropics. About 22 genera and over 30 species have been reported from India (Roy et al., 2016). The habit of members of Verbenaceae family is widely varied from small trees to lianas to herbs and shrubs. The stems are generally 4-sided with simple leaves. The inflorescence is a raceme, panicle, cyme or head. The flowers are 4-5-merous, mostly zygomorphic with a 2-carpellate gynoecium having a terminal style, the fruit a schizocarp of 1-seeded mericarps or a drupe of pyrenes (Simpson, 2010). Most of the plants belong to this family are widely used for traditional medicinal systems in several countries. Relatively a number of the plants have been reported to comprise of bio-active phytochemicals with significant pharmacological effects. Several species belong to this family are of much economic importances viz. Vitex, Tectona, Premna, Gmelina, Callicarpa, Clerodendrum, Holmskioldia, Stachytarpheta jamaicensis (ornamental) etc. as some of these species are the source of important medicines (Srivastava & Choudhary, 2008; Sultana & Rahaman, 2020).

Ecological factors frequently cause members of the same taxon occurring in different regions to exhibit significant morphological variation. Subsequently, morpho-anatomical investigation plays a vital role in the identification and systematic revision of taxa (Metcalfe & Chalk, 1979). To accurately determine stem characteristics—such as shape, size, and the structure of primary and secondary veins—it is essential to examine anatomical features, as these traits are often difficult to assess through external morphological observation alone. Therefore, the present study aims to describe the anatomical features of petioles and stems Lippia alba (Mill.) N.E.Br. ex-Britton & P. Wilson, Lantana camara L., Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, Clerodendrum infortunatum L. Stachytarpheta indica (L.) Vahl and Vitex negundo L., as a contribution to future taxonomical studies of Verbenaceae family.

Materials and methods

The flowering twig of 5 selected species of Verbenaceae family were collected from different locations of Ri-Bhoi District, Meghalaya. The collected specimens were preserved as herbarium specimen following standard methods (Jain & Rao, 1977) and are deposited at the herbarium of USTM. The plant specimens were identified by consulting different local relevant floras and literature (Kanjilal et al., 1938; Hooker, 1982). For micromorphological analysis, thin sections of stem and petiole were prepared and stained with safranin and fast green following Johansen's (1940) method. Anatomical descriptions were studied by Metcalfe and Chalk's (1979) review.

Results

Taxonomic enumeration

1.  Clerodendrum infortunatum L. in Sp. Pl.: 637 (1753)
Terrestrial shrub, 2-4 feet in height; slightly woody; quadrangular, blackish stem and simple, opposite- decussate, petiolate, exstipulate, coriaceous, hairy leaves with a displeasing odour. Flowers are bluish- purple often white in pyramid shaped terminal panicles. Leaves opposite oblong or elliptic, serrate, flowers are blue, many in long cylindrical thyrsus and the fruits are 4-lobed, purple drupe.
Flowering & Fruiting: August-September
Local name: Dhopat-tita (Ass.), Bhant (Beng.)

2.  Lantana camara L. in Sp. Pl.: 627 (1753)
Shrubs, branch weak, recurved prickles, pubescent. Petiole 1.1-2 cm; leaf blade ovate to oblong, 3.2- 7.5 × 1.5-5 cm, rough, aromatic, base rounded to subcordate, margin crenate; lateral veins 5 pairs, prominent. Capitula terminal, 1.5-3cm. Flowers yellow or orange, deep red. Ovary glabrous. Drupes globose.
Flowering & Fruiting: throughout the year
Local name: Goubon Gu-phul (Ass.), Raimuniya (Hin.)

3.  Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson in Bot. Porto Rico 6: 141 (1925)
shrub, about 1-2 m height with thin-arched quadrangular, light brown to whitish branches. Petiole is 0.5-1.4 cm long. Leaves simple, 1.2-3.1 cm long with opposite phyllotaxy with an oblong, elliptic to ovoid leaf blade. Inflorescence is axillary with short axis. Flowers are bisexual, small, rosy-violet corolla with yellow nectar. Ovary superior, fruit globose, pear shaped with rosy-pink seeds.
Flowering & Fruiting: Throughout the year
Local name: Phukota bon (Ass.) Shada Motmotiya (Beng.)

4.  Stachytarpheta indica (L.) Vahl in Enum. Pl. Obs. 1: 206 (1804)
An erect branched woody, with slightly angled stem. stem is hairy, leaves elliptic to oblong-ovate, serrate and 2-9 cm long, decurrent base. Inflorescence, terminal spikes. Flowers deep-blue, sessile, glabrous, slender, rachis dark-green, bracteates, bracts lanceolate. The terminal spikes are rather slender, 10–30 cm long and 0.3-0.4 cm thick. The calyx is small, oblique with four teeth on margin. Corolla blue or blue-purple. Fruit enclosed with calyx and oppressed to and somewhat sunk in the smooth and oblong rachis.
Flowering & Fruiting: June to September
Local name: Nilchori/ Jarbo/ Jarbas (Assamese)

5.  Vitex negundo L. in Sp. Pl.: 638 (1753)
Deciduous shrub, woody aromatic, 2-4 m in height, branches quadrangular, bark grey. Leaves palmately compound, petiole 2.5-3.6 cm long, leaflet lanceolate or narrowly lanceolate, middle leaflet 5-10 cm long with 1-1.3 cm long petioles, remaining two sub-sessile, surface glabrous above and tomentose beneath, texture leathery. Flowers bluish-purple, small, inflorescences terminal, often compound pyramidal panicles. Fruit is rounded drupe and light brown to black in colour.
Flowering & Fruiting: July- January
Local name: Postoia (Ass.) Samalu (Beng.)

Morpho-Anatomy

Table 1: The qualitative anatomical characteristics of petiole of studied species

+= Presence of trichomes, O.S.P.C.S. - Outline shape of petiole cross section, E.C.L. - Epidermal cell layer

Table 2: The quantitative anatomical characteristics of petiole of studied species.

P.L.- Petiole length, B.O.P.-Breadth of petiole, E.C.L.- Epidermis cell layer, H.C.C.L.- Hypodermal Collenchymatous Cell Layer, C.P.C.L.- Cortex Parenchyma Cell Layer, V.B.- Vascular Bundle, N.C.P.T.- Number of Cell Present in Trichomes

Table 3- The qualitative anatomical Characteristics of Stem of Studied species

+=Trichome present, E.C.L.-Epidermal Cell Layer, C.C.S-Cortex Cell shape

Table 4- The quantitative anatomical characteristics of Stem of studied species

P.L.- Petiole length, B.O.S.- Breadth of Stem, N.O.E.C.L.- Number of Epidermis cell layer, N.O. H.C.C.L.- Number of Hypodermal Collenchymatous Cell Layer, N.O.C.P.C.L.- Number of Cortex Parenchyma Cell Layer, N.O.V.B.- Number of Vascular Bundle, N.C.P.T.- Number of Cell Present in Trichomes.

Table 5- Economic Importance of studied species

Discussion

The anatomical characters on the five species of the Verbenaceae family showed nearly similar anatomical characteristics, but some significant distinct features are observed. The resulted anatomical data offers reliable characters beneficial for the restriction of species. It is apparent that by a comparative analysis of the several petiolar characters, it will be possible to precisely characterize the taxa. Important taxonomic features for taxonomic evaluation include trichomes, petiole and stem outline shapes (in transverse section), air canals, number of main vascular bundles, thickness of chlorenchymatous and hypodermal layers and width of the middle portion and sheaths. Our observations suggest that combining morphological, qualitative and quantitative petiole and stem anatomical characters can aid in taxonomic treatment, even in the vegetative stage. More research should emphasis on integrating petiole anatomical examination with molecular data to improve taxonomic classification. Growing the study to include additional species across diverse environments could deliver deeper insights into the adaptive consequence of petiole structures (Mishra et al., 2021).

Conclusion

The comparative study of Lantana camara, Vitex negundo, Clerodendrum infortunatum, Lippia alba and Stachytarpheta indica reveals both shared patterns and distinctive adaptations within the Verbenaceae family. All five species exhibit a single, collateral vascular bundle surrounded by a well-defined bundle sheath, reflecting a conserved structural blueprint for the leaf-stem junction. However, notable differences emerge in collenchyma thickness, the development of sclerenchyma caps, and the presence of secretory cavities. Lantana camara shows a robust collenchymatous ring that likely provides mechanical support in its open, sunny habitats, while Vitex negundo possesses pronounced adaxial sclerenchyma, suggesting enhanced leaf rigidity. Clerodendrum infortunatum and Stachytarpheta indica display extensive secretory cavities, which may be linked to the production of secondary metabolites with ecological roles. Lippia alba exhibits a relatively thin collenchyma layer but a conspicuous perivascular parenchyma, possibly facilitating rapid water transport in its moist-shrub environments.

These anatomical variations correlate with the species’ ecological preferences and highlight the petiole’s role in mechanical support, vascular integration and chemical defence. The findings underscore the utility of petiolar characters for systematic and ecological inferences within Verbenaceae and suggest that further ontogenetic and phylogenetic investigations could clarify how these traits have evolved in response to environmental pressures.

Declarations

Conflict of interest: The authors declare that they have no conflict of interest.

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