Medicinal plants are valuable sources of botanical drugs, extracts and pure compounds. Although several species can be propagated or collected, the access to herbal material is limited in certain cases. The protection of natural habitats and biodiversity demands new sources to provide plant secondary metabolites of medical importance. Adventitious root culture is used to harvest the secondary metabolites from the medicinally important plants, thereby offering an alternative to collection and propagation of medicinal plants. In this review, we comprehensively summarize the previously published data on the use of adventitious root cultures for numerous therapeutic plants. Adventitious roots showed elevated growth rates and production of pharmaceutically important metabolites under sterilized condition with optimized plant-growth regulators in culture media. In the present study, major influencing factors, such as the stages involved in the process of adventitious root formation, medium composition and type of growth regulators, specifically the effect of different auxins on the initiation and formation of roots, are discussed. Elicitation strategies using biotic (yeast extracts, chitosan and pectin) and abiotic factors (MJ, SA, CuSO₄, AgNO₃, NaCl) that affect the in vitro growth of adventitious roots and the role of bioreactors, which are new advancements in the scale-up process, are also highlighted. The development of adventitious root cultures for the production of secondary metabolites of medicinal importance is a perspective that is advantageous from ecological and economical aspects as well.

Synthetic seed technology is an innovative in vitro technique that provides improved storage capabilities for vegetative propagules. Its success mostly depends on the encapsulation matrix’s composition and the encapsulation procedure. The present study focuses on optimizing an encapsulation protocol for short-term storage and germplasm exchange using micro-cuttings of Salix tetrasperma. Among the different synthetic seed types evaluated, double-layered synthetic seeds (DLSs) exhibited the highest re-growth (93.6%) on MS medium supplemented with meta-Topolin (mT) (5.0 µM) and α-naphthalene acetic acid (NAA) (0.5 µM) after 8 weeks of culture. Viability assessment of non-embryogenic synthetic seeds during low-temperature storage (4 °C) demonstrated the enhanced resilience of double-layered synthetic seeds (DLSs) compared to their single-layered (SLS) counterparts. Following acclimatization in Soilrite^®-filled cups, 82% of the plantlets were successfully established in a greenhouse after four weeks. The increased activity and concentration of antioxidants in DLS-derived plantlets suggest the potential role of the extra layer of alginate in mitigating the effects of low-temperature stress during storage. SCoT molecular analysis confirmed the genetic integrity of the synthetic seed-derived plants.