Tissue culture in Pinus caribaea Mor. var. Hondurensis barr. and golf.: II:: Effects of two auxins and two cytokinins on callus growth habits and subsequent organogenesis

The growth habits of calluses of Pinus caribaea Mor. were investigated to determine their correlation with organogenesis for micropropagation purposes. Two forms of callus growth habits were observed; friable and compact calluses. Their development occurred over a range of auxin-cytokinin combinations. In naphthalene acetic acid (NAA) x 6-furfuryl amino purine (kinetin) cultures, 100% friable calluses were obtained while in NAA x 6-benzyl aminopurine (BAP) cultures, 100% friable callus was formed only with 1: 2 NAA/BAP ratio. Many compact calluses were also formed by the various combinations of NAA and BAP. Friability of calluses was further promoted by the interaction of indole butyric acid (IBA) and BAP, but organogenesis was not achieved. However, different degrees of greening were observed in some of the cultures (both compact and friable type). Thus, greening was not associated with a particular type of callus growth habit. Anatomical studies indicated that the differences between the compact and friable calluses were in the distribution of the meristematic cells. The histological studies also revealed some important and unexpected features. These were the presence of embryo-like structures, tracheary elements, lignification and starch-grain like structures. These results have further demonstrated the potential totipotency of callus cells of P. caribaea.