Comparative anatomy and DNA fingerprinting of two species of the genus Ceratostylis Bl. (Orchidaceae) from North-East India with their adaptive significance

Abstract

Taxonomic classification of the family Orchidaceae are generally based on morphological features and the floral attributes. At this juncture, a general query arises when species with morphological variations are placed under the same genera at times. This has triggered investigations towards comparative study on anatomy and genetic polymorphism. Anatomical studies of stem and leaf was carried out for the first time in two species of Ceratostylis Bl. viz., C. himalaica Bl. and C. subulata Hk. f. which are distributed in North-East India. Anatomical features like cuticle, epidermal layer, stomata, water storage cells, mesophyll, shape and arrangement of vascular bundles of both the species were comparatively studied. Cellulose wall of water storage cells with banded thickenings were observed in C. himalaica, whereas banded and mesh like thickenings were found in C. subulata. The water storage cells were larger in C. subulata. Anisocytic and paracytic stomata were observed in C. subulata but C. himalaica possess only paracytic type. Inter- simple sequence repeats (ISSR) analysis using 17 different primers showed differential banding patterns in the DNA fingerprint of the two orchid species with commendable polymorphism which helped in differentiating the two species at genomic level. This study shows that the significant differences between the two species in relation to their morphological appearance, internal structures and genetic polymorphism throws an insight towards a better understanding of their divergent adaptation and genetic diversity which is beneficial for the conservation of these two species.