In vitro Regeneration and Structural and Physiological Modifications in the Foliages of Cadaba trifoliata (Roxb.) Wight & Arn.: An Endemic Tree of the Family Capparaceae

Abstract

Cadaba trifoliata (Roxb.) Wight & Arn. (Capparaceae) is an occasional and endemic tree species of the Peninsular India. In this study, an effective in vitro regeneration system is reported for the first time for this tree, and the impact of growth regulators on the micro-morphometric growth modulations was assessed. Node explants were cultivated on Murashige and Skoog (MS) medium containing 3 types of cytokinins viz., N6-benzyladenine (BA), N6-furfuryladenine (kinetin/Kin), and N6-(meta-hydroxybenzyl)adenine (meta-Topolin/mT). The MS medium with mT at 1.0 mg/L was found the most efficient cytokinin for bud break, resulting in a 90.3% organogenic response and producing 8.0 shoots/explants. Conversely, MS medium with 1.5 mg/L BA produced 4.0 shoots, and only 3.3 shoots resulted in 2.0 mg/L Kin. Additionally, a combination of mT (0.5 mg/L) and 0.25 mg/L indole-3-acetic acid (IAA) increased regeneration frequencies and a maximum of 23.0 shoots (5.4 cm length) were amplified, in contrast a combination of BA + IAA and Kin + IAA resulted in a lesser number of shoots comparatively with shoot tip necrosis. Microscopic analysis showed that the leaves developed on the optimal mT and IAA combination were structurally superior with moderately differentiated cuticle, uniform epidermal layers, and increased mesophyll density and vascular elements. The leaves from BA + IAA and Kin + IAA treatments exhibited micro-structural abnormalities. The highest rhizogenic response (95.8%) and a considerable number of roots (5.0 roots with 4.3 cm length) were regenerated from the shoots derived from mT and IAA combination on 1.25 mg/L indole-3-butyric acid (IBA). About 91.7% of the regenerated plantlets survived during ex vitro acclimatization. The study thus highlights the pivotal role of mT in stimulating the in vitro regeneration and alleviation of micro-structural and physiological disorders in cultures of C. trifoliata.