Auxin induced morphogenetic responses in long-term in vitro subcultured Mammillaria san-angelensis Sánchez-Mejorada (Cactaceae)

Observations were made as to the influence of auxins, as the sole exogenous growth regulator, on the morphogenesis of long-term in vitro subcultured plantlets of the severely endangered cacti Mammillaria san-angelensis. Sections of long-term subcultured shoots were exposed to different auxins at various concentrations, and plant regeneration was recorded as a direct effect of auxin concentration. It was found that morphogenetic potentiality was retained in long-term subcultures, and that the best regeneration was seen in the resence of IAA (34.25 mM). Histological analysis revealed two processes leading to regeneration: de novo production of shoots and axillary meristem activation. Of the two, de novo shoot production was found to occur both in controls and in explants growing in the presence of IAA, while axillary meristem activation was observed only in the presence of IAA.