CYTOKININ TREATMENT DELAYS SENESCENCE BUT NOT SUCROSE LOSS IN HARVESTED BROCCOLI

We describe details of the physiological changes that both precede and accompany visual deterioration in harvested broccoli floral tissues ( Brassica oleracea L.), and show that some of these changes are altered after treatment with the cytokinin, 6-benzylaminopurine. Cytokinin tr eatment did not prevent the rapid loss of sucrose that occurs in flore ts after harvest. During the first 6 h after harvest, sucrose concentr ation declined by approximately 50% in both controls and treated tissu es. However, after cytokinin treatment the large increases in asparagi ne and glutamine concentration were delayed by more than 48 h. Cytokin in treatment also altered the physiological changes which usually acco mpany the yellowing of broccoli florets. The decline in amino acids an d soluble proteins, and the late increase in ammonia concentration wer e all delayed after cytokinin treatment. We discuss these results in r elation to the effects of cytokinin treatment on the possible mechanis ms regulating postharvest senescence. (C) 1997 Elsevier Science B.V.