The effect of growth regulators and apex removal on branching and flower bud production of jojoba

Abstract

The effects of three concentrations of 6-benzyladenine (BA), gibberellic acid 4 and 7 (GA 4 + 7) and Promalin (a mixture of BA and GA 4 + 7) on branching and flower production of three jojoba ( Simmondsia chinensis (Link) C. Schneid.) clones were studied in greenhouse and field conditions. Treatments involving pinching were also included. Time of treatment application significantly influenced the plant's quantitative response, although the same qualitative changes were obtained. For plants treated in August, the growth regulators had a significant effect on both branching and flower bud production, and clones differed in their response. For the most responsive clone, the most effective treatments were 100 ppm GA 4 + 7 and 100 ppm Promalin and these resulted in a 133% and 110% increase in flower buds after 17 months, respectively, relative to non-treated control plants. For this same clone, the best BA treatment (100 ppm) resulted in a 74% increase in flower buds, while pinching resulted in a 47% increase. The increase in flower buds was associated with an increase in the number of growing tips and node production. The ratio of flower buds per node was not changed. Similar responses were observed in a field experiment. The results of these studies indicate that growth regulators can be used to significantly increase branching and flower bud production on jojoba in the early years of growth.