Effects of N6-benzyladenine on shoots of five willow clones (Salix spp.) cultured in vitro

Growth and differentiation in shoot cultures of five willow clones on media of different BA concentrations were compared. The tendency of axillary shoots to develop on shoot cultures depended on the genotype, the type of shoot and the number of previous subcultures. The optimum concentration for shoot multiplication was either 5×10^-7 M or 10^-6 M. On BA concentrations of 10^-5 M or higher, browning and death of shoots occurred. Depending on the genotype, shoot elongation was best on media containing 0–5×10^-7 M BA. Rooting ability was also genotype dependent. Prolonged culture in vitro improved the rooting ability of the two most reluctant clones. BA concentrations of 5×10^-7 M or higher inhibited rooting almost completely, but this was not a permanent effect. All clones could be rooted on medium containing 10^-6 M NAA. Shoots were transferred to greenhouse conditions and rooted with varying degrees of success depending on shoot size and genotype.