Influence of form of activated charcoal on embryogenic callus formation in coconut (Cocos nucifera)

Development of micropropagation protocols for Cocos nucifera has progressed slowly. Activated charcoal is included in the culture medium of each protocol, mainly to prevent tissue browning. Charcoal production procedures can affect the properties of different brands. In this study, eight types of activated charcoal were evaluated for their effects on free 2,4-dichlorophenoxyacetic acid level, pH, conductivity, and osmolarity of the culture medium and on the frequency of embryogenic callus induction. Moreover, the effect of particle size of the optimum charcoal type on embryogenic callus development was also studied. Charcoal type had a significant effect on (Y3) culture medium properties. Free 2,4-D was highest in Reactivos y Productos Químicos Finos-containing medium and pH was lowest in MERCK-containing medium. Charcoal type also influenced embryogenic callus induction, with acid washed for plant cell and tissue culture-, DARCO- and United States Pharmacopeia-containing media promoting ~60% embryogenic callus, but with different optimal 2,4-D concentrations. Particle size profiles varied among all charcoal types, although small particle fraction (