Low-temperature Storage of Micropropagated Plantlets under Selected Light Environments

Abstract

<jats:p>Broccoli (<jats:italic>Brassica oleracea</jats:italic> L. Botrytis Group `Green Duke') and <jats:italic>Hosta tokudama</jats:italic> F. Maekawa `Newberry Gold' plantlets, which were ready for transplanting after photoautotrophic (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 <jats:italic>Hosta</jats:italic> plantlets. Broccoli plantlets responded to storage light quality, while <jats:italic>Hosta</jats:italic> 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<jats:sup>–2</jats:sup>·s<jats:sup>–1</jats:sup> 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.</jats:p>

Media Composition and Light Affect Storability and Poststorage Recovery of Micropropagated Hosta Plantlets

“…Regardless of medium composition, light quality did not affect plant growth during or after storage at 5 and 10 °C. This supports previous research by Kubota et al (1996), who showed that micropropagated hosta plantlets stored at 5 °C for 6 weeks did not respond to red or blue fluorescent lights. Therefore, blue and red data are not presented for the 5 and 10 °C experiments, and white light was used as the only light source during the 22 °C storage experiment.…”

“…However, few reports exist on low temperature storage of in vitro plantlets. Broccoli seedlings can survive illuminated storage in vitro at 5 °C for up to 6 weeks (Kubota et al, 1996), but not more than 8 weeks (Wilson et al, 1998a). Storage at 1 °C improved plantlet quality and regrowth potential, with red light being particularly effective in increasing dry weight and photosynthetic capacity of stored seedlings (Wilson et al, 1999).…”

Photoautotrophic (sugar-free medium) Micropropagation as a New Micropropagation and Transplant Production System

“…However, physiology of plants under different light qualities at low temperature has not been well investigated. Along with findings on optimum environmental conditions for storing transplants, effects of light quality on transplants stored at low temperature have been examined (Fujiwara et al, 1999a;Kubota et al, 1996 andWilson et al, 1998a and b). Broccoli plantlets grown in tissue culture vessels exhibited greater stem elongation and decrease in chlorophyll concentration under red and blue light than those under white light after 6 weeks in storage at 5 C .…”

“…Fujiwara et al (1999b) also reported that the quality of harvested culinary herbs was better maintained under red light than white light. The red light source employed in Wilson et al (1998a and1998b) and 209 Fujiwara et al (1999b) was light emitting diodes, while that in Kubota et al (1996 and was fluorescent lamps covered with a spectral filter. Therefore conflicts of the findings with regard to the plant responses to red light during storage may include potential effects of different spectra employed in these experiments.…”

Photoperiod Improves Long-term Survival of In Vitro-stored Strawberry Plantlets

“…Light levels higher than the light compensation point (2-3 µmol·m -2 ·s -1 ) stimulate shoot elongation during storage. Low temperatures (5 °C) and a photoperiod (16-h at 2 µmol·m -2 ·s -1 ) of white light are essential for maintaining dry weight and maintaining short internodes in broccoli during low-temperature storage (Kubota et al, 1996). Prunus shoots stored for 10 months have better survival with a 16-h photoperiod at 4 or 8 °C, than in darkness, but store better in darkness at -3 °C (Marino et al, 1985).…”