Involvement of ascorbate-glutathione cycle in senescence of stored broccoli (Brassica oleracea L.)

Abstract

Changes in reducing substances and enzymes involved in the ascorbate- glutathione cycle were determined in senescing broccoli (Brassica oleracea L.). Levels of L-ascorbic acid and reduced glutathione decreased greatly in senescing of broccoli during storage at 15°C, whereas the NADPH content increased gradually. Glutathione reductase activity changed little following a slight decrease during storage at 15°C. Dehydroascorbate reductase activity decreased gradually with yellowing of the floral tissues, whereas ascorbate peroxidase activity decreased following an increase 2 days after storage. Thus, the decrease in reducing substances and enzyme activities involved in the cycle seems partly responsible for the acceleration of senescence.