Harvest characteristics of Canna × generalis L.H. Bailey leaves

The harvest characteristics of canna (Canna × generalis L.H. Bailey) ‘Butter Cup’ leaves were investigated. Leaves harvested during the daytime under fair conditions inrolled rapidly and then browned. The severities of these physiological disorders were closely related to the leaf age and harvest time. Aged leaves harvested from shoots with senescing inflorescences exhibited severe disorders, whereas young leaves harvested from shoots with tight inflorescences exhibited less physiological disorders. In addition, aged leaves harvested just before sunrise did not show any physiological disorders, but the severity of leaf inrolling and browning increased with the increase in integrated solar radiation at harvest. The transpiration rate of young leaves decreased after harvest, whereas that of aged leaves sharply increased 10 min after harvest and then gradually decreased. The leaf resistance of both young and aged leaves was inversely correlated to transpiration rates. The behavior of stomata after harvest was also consistent with these two parameters, suggesting that loss of water is responsible for inrolling of aged leaves. Three min after harvest, a rapid change in the leaf electric potential was detected in aged leaves. Several postharvest treatments indicated that suppressing transpiration rates inhibit both leaf inrolling and leaf browning, and that oxygen is needed for leaf browning. However, none of the treatments were effective in preventing the leaf inrolling and browning after the treatments were conducted and leaves were exposed to ambient air.

► Leaves of canna harvested during the fair daytime drastically inroll and brown.
► The severities are closely related to the leaf age and harvest time.
► A rapid change in the leaf electric potential occurs after harvest.
► Transpiration increase after harvest resulted in leaf inrolling.
► Oxygen is needed for leaf browning suggesting a photooxidative injury.