Inhibition of chloroplast development in Euglena by streptomycin: Differential inhibition of the appearance of photosynthesis in the presence of the continued synthesis of chlorophyll

Summary Streptomycin effectively inhibits chloroplast development in dark-grown non-dividing Euglena gracilis when added at the onset of greening but apparently exerts a diminished effect on chlorophyll synthesis when added at later stages. We have further investigated this phenomenon and show that streptomycin added to a Euglena culture at 24 h of development has a differential inhibitory action on the extent of synthesis of several chloroplast-associated parameters. Chlorophyll, carotenoids, cytochrome 552 and photosystem I Hill activity are all slightly, if at all, inhibited and to approximately the same extent between 24 and 72 h of development. We find a very strong inhibition of both ribulose diphosphate carboxylase synthesis and photosystem II Hill activity.Abbreviations A absorbance - chl chlorophyll - Cyt cytochrome - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DPIP 2,6-dichlorophenolindophenol - DPC diphenylcarbazide - PS photosystem - Rib-5-P ribose-5-phosphate - RuDP ribulose-1,5-diphosphate - Sm Streptomycin Present Adress: Laboratoire de Photosynthèse C.N.R.S. 91190 Gif-sur-Yvette, France. After 1 June 1976: 50 rue Pasteur. 78460 Chevreuse, France