Abstract
Varieties of in vitro-grown yam plantlets belonging to four species, Dioscorea rotundata, D. cayenensis, D. alata, and D. trifida were acclimatized over a 4-week period using a simple, cost-effective, and efficient procedure which gave 99% survival. lnvertase activity in the leaves and stems of these plantlets was found to decrease significantly within the first two weeks of hardening, indicating a switch from heterotrophic to autotrophic growth. Peroxidase activity also decreased during the first two weeks, then increased again until the fourth week. The initial decrease indicates the physiological stress imposed on the plantlets during their transfer from in vitro conditions to the hardening operation. A survival rate of 86% was observed when the hardened plantlets were transferred to the open field, and tubers harvested after seven months of growth weighed between 0.2-1.0 kg.
