Sucrose Supply Can Increase Longevity of Broccoli (Brassica-Oleracea) Branchlets Kept At 22-Degrees-C

Sucrose was supplied several hours after harvest to broccoli branchlets via the transpiration stream in order to increase the amount of sucrose available for respiration and to determine its influence on longevity at 22 degrees C. Calculations based on solution uptake indicated that an 8% (w/v) sucrose solution supplied sufficient substrate for respiration, but the pattern of respiratory decline after harvest was not altered by supply of exogenous sucrose, and yellowing of floret sepals began after 2 days. However, when sucrose was supplied immediately after harvest, yellowing was delayed. Treatment with cytokinin (50 ppm 6-benzylaminopurine), to delay yellowing, had no effect on levels of sucrose in branchlets after 4.5 days, but retarded loss of chlorophyll. Floret tissues appear to sense the decline in sucrose after harvest, the result being induction of senescence as judged by yellowing. 6-benzylaminopurine may block the sensing mechanism