Epidermal and Cytological Studies on Cultivars of Xanthosoma (L.) Schott. and Colocasia (L.) Schott. (Araceae)

Abstract

Epidermal and cytological studies were carried out on the cultivars of Colocasia and Xanthosoma species to determine their taxonomic value within and between the accessions. Upper and lower epidermal membranes of the leaves were peeled and stained with 0.1% safranin solution. Young healthy roots (about 15mm long) were obtained and fixed in 3:1 ethanol: acetic acid for about 18-24 hours and stored in 70% ethanol. The root tips were squashed in FLP Orcein and observed under the microscope. Stomata were found on both upper and lower epidermis of both Colocasia and Xanthosoma spp. but were more abundant on the lower epidermis of both species. Papillae were present on the lower epidermal cells of Xanthosoma but absent on the lower epidermal cells of Colocasia. Details of the ultra structure of the papillae showed that intraspecific variations occurred in the epidermis of these species. The epidermal variations in stomatal index within the Xanthosoma and Colocasia cultivars reflect their ecological adaptation to variation in the degree of wetness of the environment. All accessions of Xanthosoma gave the somatic chromosome count 2n = 2x = 24 while all Colocasia cultivars gave the somatic chromosome count 2n=2x=42. The chromosomes varied mostly from metacentric to subacrocentric in both species. These observations form part of the baseline data needed in planning their improvement and germplasm conservation.