Morphogenesis in Punica granatum (pomegranate)
Explants of root, hypocotyl, cotyledon, stem, shoot tip, and leaf of seedlings obtained by in vitro germination of seeds, as well as embryos excised from seeds, were utilized for the induction of callus. Murashige and Skoog basal medium supplemented with naphthaleneacetic acid (4 ppm), kinetin (2 ppm), and coconut water (15%) was found to be optimal for induction and growth of callus from all explants. Growth rate experiments were performed with callus to study the effect of different growth regulators at various concentrations. The calluses were heterogeneous in nature and consisted predominately of diploid cells, although a few polyploid cells were also observed after two and four subcultures. Plantlets, isolated roots, leaves, and shoots were differentiated in various callus cultures. The root tips and shoot tips of such plantlets revealed only diploid constitution. Embryolike structures were formed in callus on transfer to media containing naphthaleneacetic acid and 6-benzylaminopurine. Embryoid development was traced to a single cell which was invariably isolated from the rest of the callus tissue. This initial divided to form a multicelled structure which later gave rise to a globular, ovoid, or heart-shaped embryoid, or one with irregular form. The embryoids germinated into complete plantlets with root and shoot. The embryoidal initials were mostly diploid but occasional aneuploids or polyploids were observed.