A Study on Stomatal Complex and Phenology of Certain Epiphytic Orchids of Western Ghatts of Karnataka

Abstract

The study indicated genotypic differences with respect to habitat, inflorescence, floral position, phenology, orientation, texture, leaf surface and stomatal complex of eleven species of epiphytic orchids belonging to three genera Viz., Aeridis, Bulbophyllus and Dendrobium of Western ghats of Karnataka. A ringens, A.maculosum, B.neilgeriensis and D.ovalifolium have shown receme type of inflorescence. B.fischerii D.nutantifolium D.cripidatum D.macrostychum and D.heterocarpum cyme type inflorescence whereas B. fimbriatum has shown umbellate and D. herbaceum have shown umbellate terminal raceme type of inflorescence. The floral position varied from base of leaf sheath, base of the bulb, from the nodes and node of the pseudo stem. Flower phenology indicated different climatic periods like pre monsoon, monsoon and even summer indicating influence of climatic factors. The leaf surface was hypostomatic in all the species except B.Neilgeriensis where it was Amphistomatic. The type of stomata was Anomocytic in A.ringens, A.maculosum, B.fischerii, D.ovalifolium and D.heterocarpum. Anisocytic in B.neilgeriensis D.cripidatum and paracytic in B.fimbriatum D.herbaceum, D.Nutantifolium and D.macrostychum. The Species Dendrobium macrostychum has shown least stomatal index and frequency followed by B.neilgeriensis. This could be due to strong drought tolerant mechanism by which these species are capable of curtailing transpiration water loss as these species generally found in harsh climatic conditions like rocks and dry bark of trees and also open conditions.