CELLULAR ARCHITECTURE IN SELECTED SPECIES OF GENUS DIOSCOREA, KERALA, INDIA.

The cellular architecture is a clue to the species and variety differences in this group. A special, spiral, blend ending, corner located ‘Dioscoreal raphides’ present in the pith cells of D. pentaphylla (5-3leaves) and D. bulbifera (Red stem). Needle shaped bundles of raphides present in pith cells of D. bulbifera (Green stem) and D. kalkapershadii. Large amount of chloroplast present in pith cells of D. tomentosa, which also bearing sclerids around the phloem tissue and in D. kalkapershadii, sclerids are present around the vascular bundle. Large and small starch grains along with different amounts of chloroplast are common in this group. A ring of cells in the inner most hypodermis contains a mass of starch grains present in D. bulbifera (Red stem) and D. kalkapershadii. Large phloem cavities formed after disintegration of phloem cells. Evolutionary changes from Eustele to Atactostele of vascular bundles have seen in this group of plants. Vascular bundles are monocot mesarch and broken ring arrangement in D. kalkapershadii, D. pentaphylla and D. tomentosa. Unpaired metaxylem present in D. bulbifera and distantly paired metaxylem in D. hispida.