Studies on the Induction of Embryogenic Globular Structures in Opuntia ficus-indica

In studies on the induction of somatic embryogenesis in Opuntia ficus-indica, globular structures were obtained from isolated, in vitro-germinating zygotic embryos in the presence of 0.45×10-6 mol·l-1 2,4-D and 0.91×10-6 or 9.1×10-6 mol·l-1 kinetin. The globuli displayed typical morphological characteristics of embryogenic globuli, i.e., a well-defined globular shape without vascular connection to the original tissue, demonstrating yellowish-white colour. Serial histological analysis during the first 4 weeks of culture revealed that these structures were directly induced after about 2 weeks of primary culture at the periphery, beneath the first cell layers, preferably emerging at subepidermal regions of young cotyledons. Also, a suspensor-like tissue embedding the globuli in the originating material was observed. However, in comparison to young embryonic structures from other species, the globuli from O. ficus-indica displayed atypical cytological characteristics that are related to water management in plants.