CHANGES IN HORMONAL PATTERN OF THE NEW GROWTH OF SCLEROCARYA-BIRREA AFTER REJUVENATION TREATMENT WITH GA(3) AND HEADING BACK

Gibberellic acid (GA(3)) was injected into the stems of adult trees of the African fruit tree species Sclerocarya birrea ssp. caffra to caus e rejuvenation. Invigorated growth after such treatment in comparison to control trees was visible after 14 days. Another tree, rejuvenated by 'heading back', also showed growth invigoration. Histological analy sis of shoots showed less xylem vessels in the shoots of the GA treate d and the 'headed back' tree in comparison to control trees. Levels of gibberellins, indoleacetic acid (IAA), abscisic acid (ABA), zeatin/ze atin riboside (Z/ZR), and isopentenyladenosine (IPA) were determined i n leaves and 'shoots' of the newly emerged tissues. In addition to the expected large increase of GA(3) in the new flush, the concentrations of IAA and ABA were also found to be greater in the 'shoots' of treat ed trees. No significant difference could be detected in the cytokinin pattern. Changes in hormonal pattern of GA(3) treated and the 'headed back' tree were similar. There was a better rooting of cuttings from treated rejuvenated trees.