Low-temperature storage of micropropagated plantlets under selected light environments

Broccoli (Brassicaoleracea L. Botrytis Group 'Green Duke') and Hosta tokudama F. Maekawa 'Newberry Gold' plantlets, which were ready for transplanting after photo-autotrophic (sugar-free) culture, were stored 4 to 6 weeks at 5C under various light qualities and photosynthetic photon fluxes (PPF). Illumination during storage maintained quality, photosynthetic ability, and regrowth potential of plantlets stored at low temperature. PPF affected quality of broccoli and Hosta plantlets. Broccoli plantlets responded to storage light quality, while Hosta did not. White light maintained the quality of broccoli plantlets better during 6 weeks of storage than did red or blue light. Red and blue light caused an increase in internode length and reduction in chlorophyll concentrations compared to white light. Photosynthetic and regrowth potentials of plantlets were not affected by spectral quality during storage. Considering changes in dry weight, stem length, and leaf yellowing, the quality of broccoli plantlets was best maintained under white light at 2 μmol.m^-2.s^-1 PPF. PPF and light quality were shown to be important factors in the preservation of transplant quality and suppression of growth of the plantlets during low- temperature storage.