Morphogenetic Investigations in Callus Cultures of Tylophora indica

Callus cultures derived from stem explants of Tylophora indica (Fam. Asclepiadaceae) show a broad spectrum of tissue differentiation and regenerative potentialities over a wide range of nutrient conditions resulting in the production of roots, shoots, bipolar embryos and plantlets. This has been investigated and interpreted on a histological basis. Studies on the morphogenesis of embryos have shown that only such embryonal cells which were deeply embedded with in the callus parenchyma showed an ontogenic development reminiscent of ovular embryogeny whereas in those organized in the superficial layer of the callus the sequence of embryogeny was entirely different. Free cells growing in agitated liquid media first developed into filamentous structures and eventually, by repeated intercalary divisions, organized into bipolar embryos. Development of accessory embryos through cleavage and budding in the callus, differentiation of amphicribral vascular nodules, and meristematic colonies organized into spheres of parenchyma were also observed. These alternative morphogenetic events probably reflect the biochemical subtleties occurring within the callus as a result of an inadequacy or an imbalance of the various constituents in the culture medium.