Micro-morpho-anatomical mechanisms involve in epiphytic adaptation of micropropagated plants of Vanda tessellata (Roxb.) Hook. ex G. Don.

Vanda tessellata (Roxb.) Hook. ex G. Don. (grey orchid, family Orchidaceae) is an epiphytic orchid of horticultural importance and currently under threat due to overharvesting and habitat destruction. Micropropagation protocols were developed for the production of grey orchid but the survival success of in vitro regenerated plantlets is uncertain due to lack of understanding about the adaptation mechanism during hardening. The present study describes the structural adaptation mechanism of V. tessellata when the in vitro regenerated plantlets were acclimatized under the greenhouse conditions. Light microscopy has been implicated to identify the adaptational alterations during in vitro to ex vitro transition of micropropagated plantlets. The in vitro induced morpho-anatomical anomalies were more prominently observed in the density of stomata, veins (architecture) and raphides, leaf, and root structural parameters such as water cells and velamen tissues. The results indicated that remarkable reconciliation occurred in structural developments of mechanical and vascular tissues upon epiphytic adaptations of V. tessellata. The study could help in understanding the adaptation mechanism of in vitro regenerated plantlets (especially velamen tissues of epiphytic roots) when transferred to the greenhouse for acclimatization. RESEARCH HIGHLIGHTS: Vanda tessellata is an epiphytic orchid of horticultural importance. Comparative micro-morpho-anatomical analysis at subsequent stages of in vitro regeneration was conducted. Foliar structural and developmental mechanisms towards epiphytic adaptation were studied. In vitro induced structural abnormalities were repaired and epiphytic adaptation was visualized. Stomata, leaf, and root architectures and velamen tissues were well developed in acclimatized plantlets. The report could be useful in the conservation and sustainable utilization of Vanda tessellata.