Turnover of Dl protein as influenced by actual irradiance and growth irradiance was analyzed in the photoautotrophic suspension cultured cells of Chenopodium rubrum. Proteins were labelled by adding 35S-methionine to the ceU suspension. Following electrophoresis the labelled proteins were detected by autoradiography. Relative label incorporation into the Dl protein containing band was calculated from scans of the autoradiographs and ušed as an estimate of Dl protein synthesis (pulse experiments) and Dl protein degradation (chase experiments). Total label incorporation was not affected by the irradiance during labelling but Dl protein synthesis and degradation were boťh increased at 900 pmol m-2 s*i as compared to 120 pmol m'2 s*^ The effect of growth irradiance was analysed by comparing cells which had been pre-cultured at 120 pmol m'2 s"^ (HL cells) and 900 pmol s‘i (PIL cells) for at least 6 d. The inhibition of chloroplastic protein synthesis by cUoramphenicol exacerbated the effect of photoinhibitory irradiance on the chlorophyll fluorescence parameters in these cells. The inhibitor effect was more pronoímced in PIL cells than in HL ones. This points to a higher chloroplastic protein synthesis capacity of the former cell type. Due to a considerable difference in total label incorporation pulse experiments could not be ušed to check this hypothesis. The chase experiments indicated that the Dl-protein degradation rate was higher in PIL cells tiian in HL cells. Probably a generál increase in the Dl protein tumover occiu^ if the cells are exposed to photoinhibitory irradiances for a prolonged period.
The σ-finiteness of a variational measure, generated by a real valued function, is proved whenever it is σ-finite on all Borel sets that are negligible with respect to a σ-finite variational measure generated by a continuous function.