Mechanisms of the Prevention of Cold Storage-induced Postharvest Leaf Chlorosis by Supplemental Light and Gibberellins in `Stargazer' Hybrid Lilies

Abstract

Leaf chlorosis induced by short-term, postproduction cold storage is a common postharvest disorder in potted lilies. In `Stargazer' hybrid lilies, 2 weeks of storage at 4 °C results in chlorosis in more than 30% of leaves by 6 days after transferring to 22 °C. Because we observed that foliar sprays of GA4+7 or supplemental light during cold-storage could prevent this leaf chlorosis in Lilium sp. `Stargazer' hybrid lilies, this study was conducted to investigate the mechanisms underlying these preventive effects. Hybrid lilies at “puffy bud” stage were stored for 2 weeks at 4 °C either in darkness (control), provided with 40 μmol·m–2·s–1 light by cool-white fluorescent lamps, or sprayed with 100 mg·L–1 GA4+7 prior to storage. Leaves from lower half of the plant were sampled during cold storage and upto 6 days after transferring to 22 °C. Leaf chlorophyll, total nitrogen, and soluble protein concentrations decreased slightly during cold-storage in all treatments, but decreased rapidly after transferring to 22 °C only in control plants. Total soluble sugar concentration (TSS) in leaves decreased in control and GA4+7-treated plants during cold storage, whereas TSS increased in plants provided with light. After transferring to 22 °C, TSS decreased in all treatments, but the decrease was more rapid in control plants. SDS-PAGE protein profiles revealed that degradation of larger polypeptides that occurred in control plants did not occur in GA4+7-treated plants or plants provided with light. Catalase and superoxide dismutase activities in leaves decreased in control plants after transferring to 22 °C, whereas these activities were maintained in other treatments.