Synseeds of in vitro roots as inoculum for storage and mass production of adventitious roots in Hemidesmus indicus (L.) R. Br.

Hemidesmus indicus (L.) R. Br. [Indian sarasaparilla] is an herbaceous climber used in traditional and modern medicines. This species is overexploited due to increased demand for its roots, resulting in population loss. Hence, there’s a necessity to explore biotechnological processes that aid in producing roots, which is crucial for conserving and sustainably utilizing this valuable plant species. In the present study, cultivation of adventitious roots of H. indicus has been achieved by utilizing leaf explants derived from in vitro grown shoots. This was accomplished by employing varying strengths of Murashige and Skoog (MS) medium, supplemented with different concentrations of auxins [indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and α-naphthalene acetic acid (NAA)]. The highest rooting (98.6%) and the number of roots (21.7 roots per leaf explant) were obtained on one-fourth MS nutrient medium containing 3.0 mg L^− 1 IBA. Synseeds were formed from the 4 wk-old in vitro-raised adventitious root pieces (⁓0.5 cm) using sodium alginate (2.0%) and calcium chloride (100 mM) solutions. These were stored at low temperatures (4 ^oC) for one year. A maximum of 89.0% synseed was germinated using one-fourth MS semi-solid medium with IBA (3.0 mg L^− 1). Further, the root inoculums were proliferated and maximum biomass production (3.0 g fresh weight and 0.134 g dry weight) was achieved on the same strength of MS liquid medium containing IBA (3.0 mg L^− 1) in the dark field within 4 wk of incubation. Interestingly, the synseeds containing differentiated in vitro roots could be cold stored and utilized as inoculums for the propagation of adventitious roots for a continuous supply of root-specific secondary metabolites, and conservation of H. indicus.