Tissue culture in Pinus caribaea mor. var. hondurensis barr & golf. 1. effects of two auxins and two cytokinins on callus growth and greening

Growth of callus explants was studied by manipulating the hormonal composition of Von Arnold and Eriksson's (AE) 1977 medium. Various auxin – cytokinin combinations were tested. Growth of callus on fresh weight basis, was best promoted by 2mgl-1 Naphthalene Acetic Acid (NAA) and also by the interaction between Indole Butyric Acid (IBA) at 2mgl-1 and 6- Benzyl Amino Purine (BAP) at 0.5mgl-1. Although there were no significant differences among the various combinations of NAA levels with kinetin levels and NAA levels with BAP levels with respect to fresh weight production, per cent increments over the controls were determined. Maximum increments were obtained from 1mgl-1 NAA x 0.5mgl-1 kinetin (406.5%) and 1mgl-1 NAA x 0.5mgl-1 BAP (198.06%). There were strong indications that high fresh weights were not always synonymous with dry matter production. Among the levels of NAA, 0mgl-1 and 0.5mgl-1 produced the highest percentages. In NAA x kinetin cultures, 0mgl-1 produced a value of 0.467% while 0.5mgl-1 in NAA x BAP cultures produced a value of 0.485%. For kinetin levels, 5mgl-1 produced the maximum percentage of 0.451% while for BAP levels, 0mgl-1 (0.471%) and 5mgl-1 (0.462%) produced the optimum percentages. With respect to the hormonal interactions, optimal percentages were obtained in 0mgl-1 NAA x 5mgl-1 kinetin (0.643%) and 0.5mgl-1 NAA x 0mgl-1 BAP (0.625%) cultures. Spectrophotometric studies revealed the existence of an association between the chlorophyll content of calluses and the grade of greening. Callus greening was best promoted by the main effects of kinetin (5mgl-1), BAP (5mgl-1) and NAA (2mgl-1). An unusual sign of physiological specialization (reddish pigmentation) was observed in some of the callus clumps. The implications of the results have been discussed.. Keywords: Totipotency, Explants, Auxins, Cytokinins, Callus Agro-Science Vol. 4(1) 2006: pp. 14-23