Enhanced multiplication and improved ex vitro acclimatization of Decalepis arayalpathra

Abstract

The proposed work describes a protocol for high-frequency in vitro regeneration through nodal segments and shoot tips in Decalepsis arayalpathra, a critically endangered medicinal liana of the Western Ghats. Nodal segments were more responsive than shoot tips in terms of shoot proliferation. Murashige and Skoog’s (MS) basal medium supplemented with 5.0 μM 6-benzyladenine (BA) was optimum for shoot initiation through both the explants. Among different combinations of plant growth regulators and growth additive screened, MS medium added with 5.0 μM BA + 0.5 μM indole-3-acetic acid + 20.0 μM adenine sulphate effectuated the highest response: 11.8 shoots per nodal segment and 5.5 shoots per shoot tip with mean shoot length of 9.2 and 4.8 cm, respectively. Half-strength MS medium with 2.5 μM α-naphthalene acetic acid was optimum for in vitro root induction. The plantlets with the well developed shoot and root were acclimatized in Soilrite™ with 92 % survival rate in the field conditions. During acclimatization, chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate were gradually changed in dependence of formation of new leaves. Further, the changes in activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) as well as activity of carbonic anhydrase were also observed: a continuous rise in SOD activity, but a rise and fall in the activities of CAT, APX, and GR were also noticed. Maximum fresh mass (3.1 g plant-1), dry mass (0.35 g plant-1) of roots and 2-hydroxy-4-methoxybenzaldehyde content of 9.22 μg cm-3(root extract) were recorded after 8 weeks of acclimatization.