Effects of Light Quality on Growth and Quality of in Vitro Plantlets during Low-temperature Storage

Abstract

Broccoli `Green Duke' plantlets, which were ready for transplanting after 2 weeks of photoautotrophic (sugar-free) culture under the conditions of 1100 μmol·mol–1 CO2 (outside the vessel), 22±4C air temperature, and 140 μmol·m–2·s–1 photosynthetic photon flux (PPF), were stored for 6 weeks at 5C in darkness or in white, red, or blue light at 2 μmol·m–2·s–1 PPF. Photoperiod was set at 24 h/day during storage. Spectral quality significantly affected plantlet quality: stem length was longer and chlorophyll concentration of leaves was lower in red or in blue light than in white light or in darkness after 6 weeks in storage. Regardless of the spectral quality, light in storage maintained plantlet dry weight at a level comparable to that before storage, while dry weight was reduced significantly in dark-stored plantlets. Spectral quality did not significantly affect the photosynthetic and regrowth potential of plantlets. All plantlets stored in light, regardless of light spectra, showed comparably high photosynthetic ability after storage and had similar dry weight, number of leaves, and stem length after 9 weeks of transplanting to the greenhouse under natural light.