Somatic embryos of Daucus carota L. developed into plantlets at high frequency after addition of an extract from a marine cyanobacterium, Synechococcus sp. NKBG 042902. High molecular weight, nondialyzing fraction, separated from the extract, possessed enhanced plantlet formation promoting activity. Plantlet formation frequency was 60 % after addition of nondialysate (100 mg/l) compared to 28 % without addition. Embryos treated with the nondialysate contained five times more chlorophyll than nontreated embryos after 6 days of culture. The chlorophyll a/b ratio of 4-day old treated somatic embryos was found to be similar to that of zygotic embryos. However, the chlorophyll a/b ratio of plantlets induced from nontreated somatic embryos was variable. Nondialysate was fractionated by ultracentrifugation and an active component obtained, which gave a maximum plantlet formation frequency of 71 %, and induced rapid greening of shoots.
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