In Vitro Regenerative Competence of Cleisostoma racimeferum (Orchidaceae) Aerial Roots

Regeneration competence of aerial roots of Cleisostoma racimeferum (Orchidaceae) from in vivo and in vitro sources was tested. The protocorm-like bodies and shoot buds were obtained from 2 w old in vivo grown aerial roots and 20 w old in vitro grown roots on Murashige and Skoog medium containing sucrose (3%) (w/v), casein-hydrolysate (2 g l⁻¹), coconut water (15%) (v/v), citric acid (200 mg l⁻¹) and different plant growth regulators. The morphogenetic response from in vivo grown roots was poor and only 20% of the cultures yielded protocorm-like bodies and shoot buds on medium containing IAA (2 mM) and kinetin (2 mM) in combination after 75 d of culture. While 100% morphogenetic response was exhibited by in vitro grown roots on MS medium enriched with IAA (1 mM) and kinetin (1 mM) in combination only after 25 d of culture initiation. The response initiated at the cut ends of the roots and subsequently the entire root length was taken over. Both IAA and kinetin singly stimulated mostly callusing of the explants. The rooted plantlets and multiple shoot buds were obtained after 30 d of culture from protocorm-like bodies and shoot buds on basal medium enriched with IAA (2 mM) and kinetin (6 mM) in combination. The well developed rooted plants could be obtained for transferring to potting mix after ~24 w of culture initiation.