Postharvest transient water deficit limits longevity of cut Dendrobium ‘Khao Sanan’ orchid

Abstract

A negative water imbalance due to a temporary water deficit (WD) after harvest can stimulate early flower senescence and reduce flower quality and vase life of orchids. To clarify the physiological responses of cut Dendrobium ‘Khao Sanan’ inflorescences under WD stress and early responses during water recovery, relative water content (RWC), water potential, reactive oxygen species (ROS), ethylene production, lipid peroxidation, antioxidant enzymes, and osmolyte were determined. The inflorescences were exposed to WD for 0, 24, 48, and 72 h after harvest, then placed in water for recovery and vase life determination. The results showed that WD significantly reduced RWC in petals, and over 24 h of WD adversely affected postharvest quality including vase life of cut inflorescences by increasing flower abscission, flower bud opening, and decreasing flower quality score. Moreover, ethylene production was induced early by 72 h of WD. Exposure of cut flowers to WD also increased hydrogen peroxide (H2O2) content, malondialdehyde (MDA) content, proline content, and lipoxygenase (LOX) activity. Additionally, ascorbate peroxidase (APX) and catalase (CAT) activities fluctuated with durations of dry and recovery periods. After rewatering, RWC, water potential, MDA content, and LOX activity of all WD periods recovered at non-WD control levels while H2O2 and proline content remained higher than control. On the other hand, ethylene production of the inflorescences exposed to WD over 24 h remarkably increased after rewatering. Our findings suggested that Dendrobium ‘Khao Sanan’ could tolerate transient WD up to 24 h with negligible reduction in longevity, probably corresponding to the lowest ethylene production during the WD period and the accumulation of antioxidant enzymes and osmolytes.