CARBOHYDRATE STATUS AND TRANSPLANT QUALITY OF MICROPROPAGATED BROCCOLI PLANTLETS STORED UNDER DIFFERENT LIGHT ENVIRONMENTS

Broccoli (Brassica oleracea L. Botrytis Group 'Green Duke') plantlets, which were ready for transplanting after photoautotrophic (sugar-free ) culture, were stored for 6 weeks at 5 degrees C under white, red or blue light or under darkness. Storage light intensity was 2 mu mol m(- 2) s(-1) photosynthetic photon flux (PPF). Regardless of light quality , shoot dry weight remained unchanged when light was present during st orage. Light quality affected transplant quality of the plantlets but did not affect CO2 exchange rate during storage. Stem elongation was o bserved for plantlets stored in red or blue light. Chlorophyll degrada tion was more pronounced in red or blue light than in white light or i n darkness. The levels of soluble sugars (sucrose, glucose, and fructo se) and starch were reduced significantly in dark-stored plantlets, wh ile they were maintained at high levels in light-stored plantlets. Red and blue light enhanced hexose (glucose and fructose) accumulation in stems during storage, which may have caused stem elongation. All plan tlets stored in darkness died early during the following acclimatizati on stage. The plantlets stored in light, however, were acclimatized su ccessfully. Regardless of light quality, illumination during storage m aintained dry weight, carbohydrate levels, and therefore, regrowth pot ential of micropropagated plantlets during storage. (C) 1997 Elsevier Science B.V.