Application of petiole and pedicel anatomy in plant taxonomy of five Solanaceae species from West Bengal, India

Received: 25-Aug-2025, Manuscript No. mp-25-170439; Accepted: 15-Sep-2025, Pre QC No. mp-25-170439 (PQ); Editor assigned: 27-Aug-2025, Pre QC No. mp-25-170439 (PQ); Reviewed: 10-Sep-2025, QC No. mp-25-170439; Revised: 14-Sep-2025, Manuscript No. mp-25-170439 (R); Published: 18-Sep-2025

Introduction

The family Solanaceae Juss., commonly known as the nightshade family, comprises 103 genera (POWO, 2025). Among the 103 genera, the type genus Solanum L. comprises 1,237 species, and is the largest genus within this family (POWO, 2025). Datura L. comprises 14 species, and Physalis L. comprises 94 species (POWO, 2025). Initially, Clarke, 1883 mentioned 27 Solanum, three Datura, and two Physalis species in the Flora of British India. In the more recent study, Kumari, 2004 reported 48 Solanum, four Datura, and eight Physalis species from India. Prain, 1903 in Bengal plants reported 11 Solanum, two Datura, and two Physalis species. Kalidass and Panda, 2019 reported 23 wild Solanum species with three cultivated Solanum species from the Eastern Ghat of India. Aubriot and Knapp, 2022 reported 51 spiny Solanum species from the major part of Asia. Gulaguli, et al. 2025 reported five Datura species from Karnataka, India. Among the five species, Datura metel includes three morphotypes.

Gómez-Nucamendi, et al. 2016 reported that leaf anatomical characters are helpful to distinguish four Datura species and a variety. Tovar and Giacomin, 2022 described a new species, Solanum boshii J.D. Tovar and reported that it differs from its morphologically similar species, Solanum chlamydogynum Bitter based on trichome morphology. Santos, et al. 2025 concluded that leaf anatomical studies are useful to separate taxa in the Athenaea sp. of Solanaceae.

Mbagwu, et al. 2024 studied the petiole anatomy of five species of the genus Solanum in Nigeria. Akinsulire, et al. 2018 found that petiole anatomy is taxonomically significant in Terminalia. Ekeke and Ogazie, 2020 found that petiole anatomy was taxonomically significant at both the genus and species levels in Asteraceae. Akhtar, et al. 2021 found that petiole anatomical characters were helpful in identifying asteraceous taxa from the Western Himalaya of Pakistan. Simon, et al. 2022 found that the anatomy of the tomato pedicel varies in relation to genotype. Nurit-Silva and Agra, 2011 concluded that leaf trichome morphology played an important role in distinguishing Solanum species.

For the present investigation, three species of Solanum- Solanum nigrum L., Solanum sisymbriifolium Lam., and Solanum torvum Sw.; one species of Physalis (Physalis angulata L.); and one species of Datura (Datura metel L.) were selected. In the past, a few research studies have explained the petiole anatomy of Solanaceae. Most experiments on the petiole anatomy are based on a single species of this family, and very few experiments are used in comparative studies on petiole anatomy among different species. Pedicel anatomy is very rarely considered in the field of taxonomy in Solanaceae. The present investigation aims to evaluate the taxonomic significance of petiole, flower pedicel, and fruit pedicel anatomy in the Solanaceae.

Materials and Methods

Plant samples were collected from various locations in Bankura and Burdwan districts of West Bengal (Tab. 1). For each species, three to five plant samples were collected from a single spot. Petioles from mature leaves, pedicels from mature flowers, and pedicels from mature, unripe fruits were selected for this investigation. Multiple samples of each species were preserved in FAA (formaldehyde, acetic acid, and alcohol). For anatomical study, freehand sections were prepared from the middle portion of the petiole and pedicel using a razor blade. For each species, at least five petioles, five flower pedicels and fruit pedicels were examined to assess the range of variation. Samples were stained using the safranin single-staining procedure. Each section was stained with 1 % safranin in 70% ethanol, then the excess stain was removed, and dehydration of the sample was done with the help of 70%, 90% and 95% ethanol. The samples were then mounted in glycerol to prepare semipermanent slides. Anatomical slides were studied and photographed under a Hoverlabs trilocular microscope attached with a 16 megapixel microscope camera.

For identification and authentication, various references, such as Bengal Plants and Flora of British India were consulted. Relevant protologues associated with the species names were also examined. Type materials available in various digital herbaria were examined (Tab. 1). Also, checked the present status of these species in POWO, 2025, Tropicos, 2025, and IPNI, 2025.

Results

The petiole connects the leaf blade to the plant, while the pedicel serves as a connective structure between the flower or fruit and the plant. In the present investigation, a total of 28 characters were examined in detail (Tab. 2). Petiole outlines are generally circular or oval with a flat to convex adaxial surface, and vascular bundles or vascular system shape are generally open, lunar-shaped except S. torvum and D. metel showing C or U shaped (Fig. 1. B, J, S, AG, AQ). Petiole thickness and breadth sometimes vary and may overlap, but the breadth of S. torvum is clearly distinct from the other species. Vascular bundles or vascular system contain three central bundles in S. nigrum, five to six in D. metel, and the other three species contain three to four bundles. The vascular bundle of the petiole in S. nigrum is comparatively thinner than in the other species. The epidermal cells are generally oval to rectangular. In addition to the main vascular bundles, two subsidiary vascular bundles are present in all studied species, and S. torvum subsidiary vascular bundles are relatively larger among the five species (Fig. 1. B, E, J, M, S, T, AG, AH, AQ, AR). Winged petioles are characteristic of S. nigrum and P. angulata (Fig. 1. B, J). Spines are consistently present in the leaf petioles of S. sisymbriifolium, whereas in S. torvum they are variable, being present only occasionally (Fig. 1. U, AK). In leaf petiole, stellate trichomes occur only in S. torvum, whereas long glandular hairs (Stalk multicellular, head unicellular), partly gland-tipped branched hairs, and branchlet hairs occur only in S. sisymbriifolium (Fig. 1. T, AI). S. nigrum has finger hairs and short glandular hairs on the leaf petiole, with the adaxial surface bearing more hairs compared to the abaxial region (Fig. 1. B, D). Few hairs are present in P. angulata (Fig. 1. J, L). Only finger hair present in D. metel petiole (Fig. 1. AS). The smallest floral pedicel diameter is present in S. nigrum, and the largest in D. metel compared to others (Fig. 1. F, N, V, AL, AT). The floral pedicel cuticle of S. nigrum and P. angulata is thinner than that of D. metel. The vascular bundles of the floral pedicel are thicker in D. metel than in the other species (Fig. 1. F, N, O, V, W, AL, AM, AT, AU). The fruit pedicel diameter is comparatively larger in D. metel and S. torvum than in the other species (Fig. 1. G, P, AA, AN, AV). The vascular bundle thickness in D. metel is greater than in the other species (Fig. 1. G, H, P, Q, AA, AB, AN, AO, AV, AW). In the flower pedicel, stellate hairs with a gland tip are present only in S. sisymbriifolium (Fig. 1. V). A similar pattern was observed in the flower pedicel. Spines are present only in the flower and fruit pedicels of S. sisymbriifolium (Fig. 1. Z, AE).

Figure 1: Habit, petiole anatomy and pedicel anatomy. A. Habit of S. nigrum, B-E. Petiole anatomy of S. nigrum, F. Pedicel anatomy of S. nigrum flower, G-H. Pedicel anatomy of S. nigrum fruit. I. Habit of P. angulata, J-M. Petiole anatomy of P. angulata, N-O. Pedicel anatomy of P. angulata flower, P-Q. Pedicel anatomy of P. angulata fruit. R. Habit of S. sisymbriifolium, S-T. Petiole anatomy of S. sisymbriifolium, U. Petiole anatomy of S. sisymbriifolium spine region, V-Y pedicel anatomy of S. sisymbriifolium flower, Z. Pedicel anatomy of S. sisymbriifolium flower spine region, AA-AD. Pedicel anatomy of S. sisymbriifolium fruit, AE. Pedicel anatomy of S. sisymbriifolium fruit spine region. AF. Habit of S. torvum, AG-AJ. Petiole anatomy of S. torvum, AK. Petiole anatomy of S. torvum spine region, AL-AM. Pedicel anatomy of S. torvum flower, AN-AO. Pedicel anatomy of S. torvum fruit, AP. Habit of D. metel, AQ-AS. Petiole anatomy of D. metel, AT-AU. Pedicel anatomy of D. metel flower, AV-AX. Pedicel anatomy of D. metel fruit. Note: WI: Wing; VB: Vascular Bundle; SVB: Subsidiary Vascular Bundle; SGH: Short Glandular Hair; FH: Finger Hair; LGH: Long Glandular Hair; GSH: Stellate hair with a gland tip; BH: Branchlet Hair; GBH: Gland-tipped Branched Hair; PGBH: Partly Gland-tipped Branched Hair; SH: Stellate Hair.

Table 2: Comparative data of petiole and pedicel anatomy of five species under Solanaceae. (values are represented as “Average ± Standard Deviation (n values) (Minimum value-Maximum value)”.)

Discussion

A very primitive-level taxonomic review was required for the identification of selected material. The most popular and confusing synonym of P. angulata is P. minima. Linnaeus, 1753 published the names P. minima L. and P. angulata L. in Species Plantarum, but POWO, 2025 treated P. minima as a synonym of P. angulata and P. angulata as an accepted name. Another popular name, Datura fastuosa L., is the synonym of D. metel (POWO, 2025). Ekeke and Ogazie, 2020 reported that the number of accessory vascular bundles in Asteraceae petioles varied. The present study showed that the number of accessory vascular bundles or subsidiary vascular bundles is constant (i.e., two), but their size is highly variable. They also mentioned that the sizes of the vascular bundles were quite different. The present study shows that vascular bundle size differs not only in the petiole but also in the pedicel, which is also helpful for identification. Mbagwu, et al. 2024 reported that petiole shape could be Semicircle, oval or triangular-semicircle, and petiole vascular bundle shape could vary as arc, U, or V shape. The present investigation shows that the petiole shape is circular or oval with a flat to convex adaxial surface, and vascular bundles arc or lunar, or sometimes C or U shaped. Akinsulire, et al. 2018 mentioned that the shape and arrangement of vascular bundles play a good role in classifying five taxa under Terminalia. The present work shows that the vascular system of D. metel is different to the other four taxa, which helps in identification. Akhtar, et al. 2021 used wing character in their study on Asteraceae and found wings present in some species others without wings. The Present study shows that among the five species, only S. nigrum and P. angulata have wings. Wahua and Nkomadu, 2017 reported that bicollateral vascular bundles are present in the D. metel petiole. The present investigation supports this, as D. metel petiole vascular bundles are of the bicollateral type with two subsidiary vascular bundles. Bhat, et al. 2018 found U-shaped bicollateral type vascular bundle and two additional traces in the lateral wings of the petiole of P. angulata. Present research shows lunar-shaped vascular bundle with two subsidiary vascular bundles in the wings. They also mentioned trichomes are absent. But the present investigation shows finger hairs present, but very rare. Al-Hadeethi, et al. 2021 found an ovate-shaped petiole with two lateral sides, average cuticle thickness 1.5 μm, unicellular and uniseriate trichome, and average epidermis thickness 16.5 μm in S. nigrum. The present work shows a circular petiole and a convex-shaped adaxial surface with two lateral wings, cuticle thickness varies from 1.52 μm to 3.40 μm, with an average of 2.50 μm, adaxial epidermal cell thickness varies from 14.85 μm to 22.88 μm, with an average of 20.26 μm, and abaxial epidermal cell thickness varies from 18.29 μm to 35.99 μm, with an average of 27.02 μm. Nurit-Silva, et al. 2011 reported that the petiole anatomy of S. torvum is a circular outline, bicollateral vascularization, three to four central bundles, U shape, and two accessory bundles. The present study supports this previous investigation. Rančić, et al. 2010 studied the anatomy of Lycopersicon esculentum (Tomato) of the Solanaceae fruit petiole, and repoted presence of cuticule on epidermal cells with long multicellular nonglandular hair and glandular trichome. Present research shows the presence of cuticle on pedicel epidermis and different types of hair.

Ahmad, 1964 reported short glandular hair with a 1-celled stalk with a multicelled head, long two to four cells stalk glandular hair with 1 to multi-celled head and nonglandular hair three to five celled, uniseriate and simple in the leaf of D. metel. The present study shows the presence of short glandular hair with nonglandular hair in the pedicel and only nonglandular hair in the petiole of D. metel. Non-glandular hair cell numbers vary from one to four. Ahmad, 1964 also reports short glandular hair, and nonglandular hair one to multi-celled, uniseriate and simple in the leaf of S. nigrum. Present studies show 2 to 5 celled finger hair in the petiole, whereas one to four celled finger hair in the pedicel, and short glandular hair present in both the petiole and pedicel. Seithe and Anderson, 1982, Seithe and Sullivan, 1990 reported different types of hairs in a single species; our studies also support this. Seithe and Sullivan, 1990 found only a few hairs in P. angulata, the present study shows the same character in the petiole and pedicel. Sumitha and Thankappan, 2018 found stellate hair in S. nigrum and S. torvum in foliar epidermis. The Present study shows that in the case of petiole stellate hair only present in S. torvum. Huang, et al. 2023 found phylogenetic analysis shows Solanum is closer to Physalis not Datura. Anatomical data of pedicel and petiole from the present analysis show that S. nigrum shares some characteristics with P. angulata.

Conclusion

Among the five species of Solanaceae, the number of bundles in the vascular system of the petiole, petiole shape, petiole size, vascular bundles shape, size, wing character, subsidiary vascular bundle size, presence of spine and trichome types are helpful to distinguish. However, the present study shows that these characters are not always genus-specific but are useful at the species level. For example, wing characters are not genus-specific when comparing S. nigrum and P. angulata, but they show significant differences between D. metel and P. angulata. Furthermore, wing characters are not present in all species of Solanum. The number of hairs is less in P. angulata and Datura metel, with only two types of hair, i.e. finger hair and short glandular hair. Some trichome characters are highly species-specific, such as stellate trichomes in S. torvum, and partly gland-tipped branched hairs and branchlet hairs found only in S. sisymbriifolium. Floral and fruit pedicel diameter, vascular bundle thickness, trichome types, and spine characters also help distinguish different species. Rather than relying on a single character, the combination of multiple characters is taxonomically stronger and more significant for distinguishing species. To fulfill the detailed study on the global Solanaceae, a phylogenetic relationship with a detailed morphoanatomical study including pedicel and petiole anatomy, trichome diversity will be required in future.

Acknowledgement

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