THE INFLUENCE OF 6-BENZYLAMINOPURINE ON POSTHARVEST SENESCENCE OF FLORAL TISSUES OF BROCCOLI (BRASSICA-OLERACEA VAR ITALICA)

The pattern of post-harvest senescence of broccoli (Brassica oleracea) and the effect of the cytokinin 6-benzylaminopurine (6-BAP) were investigated. Chlorophyll degraded before ammonia production increased and this was earlier in florets at the edge of the head than those at the centre. Application of 6-BAP delayed the onset of both chlorophyll degradation and ammonia production. Pedicels contained low levels of chlorophyll which changed little over the duration of the experiment. Pedicels were unresponsive to 6-BAP treatment with no differences between chlorophyll degradation or ammonia accumulation between the treated and non-treated tissues. Application of 6-BAP to the carpel delayed chlorophyll degradation in the sepals, stimulated growth of the carpel and, when over-mature heads of broccoli were used, stimulated petal emergence. Treatment of florets with 1-aminocyclopropane carboxylic acid (ACC) and silver ions indicated that ethylene may be involved in the control of chlorophyll degradation. Cytokinin application negated the ACC-stimulated senescence.