Low-temperature Storage for Quality Preservation and Growth Suppression of Broccoli Plantlets Cultured in Vitro

Abstract

Broccoli (Brassica oleracea L. Botrytis Group `Ryokurei') plantlets, cultured photoautotrophically (without sugar in the medium) in vitro for 3 weeks at 23C and 160 μmol·m–2·s–1 photosynthetic photon flux (PPF), were stored for 6 weeks at 5, 10, or 15C under 0 (darkness) or 2 μmol·m–2·s–1 PPF (continuous lighting) supplied by fluorescent lamps (white light). Dry weight of the plantlets stored for 6 weeks at 5 or 10C in light was not significantly different from that of the plantlets before storage. Dry weight of the plantlets decreased as temperature increased and was maintained at higher levels in light than in darkness. Chlorophyll concentrations of the plantlets were higher at the lower temperatures. Chlorophyll fluorescence kinetics indicated higher activities of chlorophyll of the plantlets stored in light than in darkness. Lighting at as low as 2 μmol·m–2·s–1 PPF was important to preserve photosynthetic and regrowth abilities and dry weight of the plantlets during low-temperature storage.