Application of Cytokinin under Modified Atmosphere (MA) Delays Yellowing and Prolongs the Vase Life of Davallia solida (G. Forst.) Sw. Leaves

Cut leaves of Davallia solida are widely used in bouquet greenery. However, the leaves wilt and yellow after seven days. Postharvest applications of exogenous cytokinins (CKs), a plant growth regulator (PGR), preventing senescence in many green leafy plants, were studied by pulsing cut D. solida leaves with 6-benzylamiopurine (BA) at a concentration of 100 ppm, or thidiazuron (TDZ) at a concentration of 10 μM for 24 h, compared with distilled water as a control, and then placing the ferns in a controlled room (21 + 2 °C, 70–80% relative humidity (RH), under cool-white fluorescent lights for 12 h/d). Pulsing with BA and TDZ delayed leaf yellowing while preserving chlorophyll (Chl) content. This was due to reduced Chl-degrading enzyme activities on day 8 of the vase life of the leaves, resulting in longer display life of 11.1 and 11.5 days, respectively. TDZ delayed Chl breakdown on day 8 of the vase life of leaves more than was the case for BA. Subsequently, leaves were pulsed in 10 μM TDZ, or distilled water for 24 h, and then 10 leaves from each treatment were packaged in a 25 × 30 cm, 25-μm thickness BOPP bag. All the packages were stored at 10 °C in 10 h/d light for one, two and three weeks, then unpacked and placed in distilled water. Pulsing with TDZ before one-week storage delayed leaf yellowing, maintained Chl content and extended their vase life to 9.6 days compared with one-, two-, and three-week control leaves, which had a vase life of 6.2, 5.8, and 3.6 days, respectively. After one week, the relative fresh weight of the leaves and water uptake did not alter between the control and TDZ groups. The activities of Chl degradation enzymes in the leaves of D. solida pulsed with TDZ prior to storage were significantly suppressed, related to higher Chl content and a lower percentage of leaf yellowing than the control, resulting in a longer vase life of 9.0 days, while the control lasted 7.0 days. A 10 µM TDZ pulsing treatment significantly prevented the yellowing of D. solida fronds during the vase period or storage period, and one-week storage under MA with light conditions is recommended for retaining postharvest quality after storage.