Taxonomic implications of leaf anatomy in Thai Smilax (Smilacaceae).

Kladwong, Pornchai; Chantaranothai, Pranom; Simpson, David A.

Taxonomic implications of leaf anatomy in Thai Smilax (Smilacaceae).

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Kladwong, Pornchai

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Chantaranothai, Pranom

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Simpson, David A.

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Date published

February 24, 2025

Abstract

Observations and phenetic analyses of the leaf anatomy of 23 species from Thailand were carried out to assess the utility of anatomical characters in elucidating the taxonomy of the genus. The outline of the petiole in transverse section is circular or elliptic. The abaxial outline of the midrib is rounded, acute or attenuate. Parenchymatous, sclerenchymatous and sclereid cells are observed in ground tissues. The number of vascular bundles ranged from 8 – 27 in the petioles and 2 – 11 in the midribs. The vascular bundles are surrounded by sclerenchymatous or parenchymatous cells. The mesophyll consists of 1 – 4 cell layers in the palisade part and 3 – 10 cell layers in the spongy part. Papillae are observed on the abaxial leaf surfaces of some species. Idioblast cells containing raphides are usually found in the ground tissue of the petioles, midribs and mesophylls. Epidermal cells are jigsaw-like or irregular in shape. Prismatic crystals are observed in the leaf epidermis. Stomata are anomocytic. The phenetic study was based on 11 anatomical characters using Principal Components Analysis and Discriminant Analysis to demonstrate the suitability of the classification of the studied species. Significant characteristics are the marginal outlines and the numbers of vascular bundles of the petioles, the abaxial outlines of the petioles and midribs, the numbers of cell layers of the spongy mesophyll, epidermal cell shapes and lamina types (amphistomatic or hypostomatic). The species are classified into three groups. Group I comprises three species, , and . Group II comprises 10 species, , , , , , , , , and . Group III comprises 10 species, , , , , , , , , and . Descriptions of the groups and keys to the species within each group, based on the anatomical characters, are provided. Our analyses suggest that further investigation of the anatomical groups, using taxa from a broader distributional range, will be needed to clarify the relationships between the groups and the currently recognised sections.