Postharvest studies on leaf yellowing of cut chrysanthemum.

Leaf yellowing may compromise the commercial value of several cut flowers. The aim of this study was to investigate the effect of cytokinins on delaying leaf yellowing in two cultivars of cut chrysanthemum, one sensitive (cv. Regan bianco) and one insensitive (cv. Regan giallo) to leaf yellowing. Cytokinins such as benzyladenine (BA) 50 or 100 µM and thidiazuron (TDZ) 5 or 10 µM were applied as pulse treatment for 24 hr to cut flowers. Insensitive cut chrysanthemum flowers were also treated with 50 or 100 µM TDZ. Results showed that both cytokinins were able to delay leaf yellowing in the sensitive cultivars. However, the effect of TDZ was stronger and significantly increased total leaf chlorophyll content by 35% measured at the end of the experimental period (40 days) compared to the initial value. Treatments with TDZ in the insensitive cultivars prevented the weight losses and improved the hydraulic conductance along the stem.