Comparative Growth Analysis and Acclimatization of Tissue Culture Derived Cocoyam (Xanthosoma sagittifolium L. Schott) Plantlets

The current study was carried out to compare the external leaf structure of tissue culture-derived and conventionally-propagated Cocoyam [Xanthosoma sagittifolium (L) Schott] plantlets and to develop an efficient acclimatization protocol for these plantlets. Acclimatization studies were carried out during winter and summer to ascertain seasonal influence relative to plant survival upon transfer from in vitro to natural conditions. Results indicated that, cocoyam leaves have few stomates on both abaxial and adaxial surfaces with fewer on the adaxial surface. High levels of epicuticular wax (EW) found in vitro may have contributed to reduced transpiration rates. The reduced amounts of EW on acclimatized plants could be attributed to the rapid cell enlargement in expanding leaves, more rapid than the rate of wax formation. Acclimatization using humidity tent decreased leaf wilting and damage compared with the control treatment or with the mist treatment. Mist-acclimatized plantlets produced about 50% fewer leaves than those acclimatized in a humidity tent. Similar results were obtained during winter acclimatization with a lower rate of leaf formation compared to summer acclimatization. A relatively high humidity (60-80%) for approximately two weeks reduced leaf injury from wilting and desiccation.