Cell Viability, Mitotic Index and Callus Morphology of Byrsonima verbascifolia (Malpighiaceae)

The combined analysis of cell viability, mitotic index and callus morphology of species of commercial interest may favor the identification of cell masses with embryogenic characteristics at early stages of cultivation, allowing the development or improvement of protocols for in vitro plant regeneration through indirect embryogenesis. Byrsonima verbascifolia L. (DC.) (Malpighiaceae) is a Brazilian medicinal species native to the Cerrado, which has a low seed germination rate due to tegument dormancy. This study aimed to identify cells with embryogenic characteristics during growth of callus of B. verbascifolia , by assessing cell viability, mitotic index and cell morphology. Callus was induced from leaf explants and inoculated on MS medium with 4.52 μM 2,4-D and 4.44 μM benzylaminopurine (BAP). Friable calli were obtained at four distinct growth phases: lag (until the 30th), exponential (from 31st to the 70th day), linear (from 71st to the 100th day) and decline (from 101st to the 120th day). Calli with 20 and 30 days showed cells with embryogenic characteristics, that is, isodiametric shape, juxtaposed, with small vacuoles, thin cell wall and presence of amyloplasts. After 120 days, calli were mostly elongated cells with lower cell viability and mitotic index.