CHLOROPLAST CULTURE X: THYLAKOID ASSEMBLY IN VITRO

The conversion of prothylakoids into macrograna has been demonstrated in vitro. Etiochloroplasts were preloaded with prothylakoid components by pretreatment of etiolated cucumber cotyledons with kinetin + gibberellic acid. The plastids were then isolated and incubated under continuous illumination with exogenous δ-aminolevulinic acid and cofactors. Massive amounts of chlorophyll a were formed, which together with the prothylakoid material were assembled into giant grana. The chlorophyll a pool was formed via short wavelength and long wavelength protochlorophyll(ide) holochrome species. The major chromophore of the latter consisted mainly of divinyl protochlorophyllide.