Improved micropropagation and foliar micromorphological studies in Turnera ulmifolia L. – An important medicinal plant

The present study reports an efficient in vitro propagation system for Turnera ulmifolia using nodal segments as explants. Turnera ulmifolia (Passifloraceae) is an important garden plant with multipotent medicinal values. Effective shoot proliferation was achieved on agar gelled MS medium (Murashige and Skoog, 1962). The maximum number of shoots (8.3 ± 0.57) per initial explant was obtained on MS medium supplemented with 8.88 mM of 6-benzylaminopurine (BAP) and 0.54 mM of α-naphthalene acetic acid (NAA). The highest number of shoots (59.5 ± 2.10) proliferated on semi-solid MS medium (with agar) augmented with 2.22 mM of BAP and 2.32 mM of kinetin (Kin) along with 0.54 mM of NAA. Longer (4-5 cm) and healthy shoots were rooted (12.0 ± 0.10 roots per shoot) on half-strength MS medium fortified with 9.84 mM of indole-3 butyric acid (IBA). The in vitro regenerated plantlets were hardened in the greenhouse and transferred to the field. Significant developmental changes were observed in the foliar micromorphology of in vitro raised plantlets when these were transferred to the field. The stomatal index was gradually reduced (26.72 to 21.25) in the leaves from in vitro to field environments. But, vein-islets and veinlet terminations (13.4 and 7.6) were increased (39.7 and 18.4) respectively from in vitro to in vivo grown plants. Simple, unicellular, less frequent and underdeveloped trichomes were observed with the leaves of in vitro plants but fully developed trichomes recorded in the field transferred plants. The study could help in understanding the response and adaptation of tissue culture raised plantlets towards changed environmental conditions.