Effect of ethephon and 6-benzylaminopurine on chlorophyll degrading enzymes and a peroxidase-linked chlorophyll bleaching during post-harvest senescence of broccoli (Brassica oleracea L.) at 20°C

Effects of ethephon and 6-benzylaminopurine (BAP) treatments on enzyme degrading enzymes and a peroxidase-linked chlorophyll bleaching were investigated in broccoli (Brassica oleracea L.) florets. The florets were dipped in solutions containing either BAP or ethephon and then incubated in darkness at 20 degreesC. The hue angle values and chlorophyll contents of ethephon-treated florets declined the most of the five-day experiment. In contrast, hue angle and chlorophyll content declined the least in BAP-treated florets. Pheophytin levels increased the most in ethephon-treated florets and the least in BAP-treated florets. Chlorophyllase, Mg-dechelatase, and peroxidase-linked chlorophyll bleaching increased over the five days in control (untreated) florets. Ethephon treatment enhanced chlorophyllase, Mg-dechelatase, and peroxidase-linked chlorophyll bleaching levels as compared with control. BAP treatment reduced chlorophyllase, Mg-dechelatase, and peroxidase-linked chlorophyll bleaching levels. It was concluded that the activities of chlorophyllase, Mg-dechelatase, and peroxidase-linked chlorophyll bleaching could be regulated by external application of either ethylene (applied as ethephon) or a cytokinin (applied as BAP). In the case of ethephon treatment, accelerated rates of chlorophyll degradation were found and in the case of BAP-treatment, reduced rates of chlorophyll degradation were found. (C) 2004 Published by Elsevier B.V.