Leaf epidermal features in relation to taxonomy of some species of Bulbophyllum (Orchidaceae) from Northeast India

Madhavi Singh, Vimala Y., Lavania S.* & D. Verma

Published on : 31-Dec-2020

DOI : https://dx.doi.org/10.22244/rheedea.2020.30.4.02

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Abstract

Twelve epiphytic species of the genus Bulbophyllum Thouars, including one endemic (B. sunipia J.J.Verm., Schuit. & de Vogel), collected from Northeast India (Meghalaya) were investigated for their leaf epidermal features using bright field and scanning electron microscopy (SEM) and hand sectioning. Features such as epidermal cell size, stomata type, stomatal complex size and index, trichome type and density, cuticular thickening pattern, number of subsidiary cells, number of stomatal rims and stomatal ledge aperture (SLA) shape were considered to generate data for their qualitative and quantitative assessment. The stomata in B. striatum (Griff.) Rchb.f. were found to be of the tetracyclocytic type, with 4–6 subsidiary cells, and a high density (80.52/mm2) and highest number of stomatal groups (14–16). Bulbophyllum cherrapunjeense Barbhuiya & D.Verma exhibited some distinguishing features viz. lowest stomatal density (17.61/mm2), range of subsidiary cell number (3–5), area occupied by stomata (0.017 mm2), and maximum glandular trichome density (235.27/mm2) on the adaxial surface per mm2 of lamina, and smooth cuticular thickening. Characters like occurrence of stomatal rim, group arrangement of stomata (except in B. affine Wall. ex Lindl., B. cherrapunjeense and B. cauliflorum Hook.f.), epicuticular wax deposition on the surface and presence of scales (multicellular sessile glandular trichome) are reported for the first time for this genus. The study is important for species identification and provides some baseline data for future empirical studies on the taxonomic value of the studied leaf characters.