[Differences in the temperature-dependence of the respiratory gas uptake of a chlorophyll-free Chlorella mutant in darkness and in blue light]

Abstract

In the temperature range of 20-50°C the O2-uptake of resting cells of a chlorophyll-free, carotenoid-containing mutant of Chlorella vulgaris Beijerinck (211-11h/20) in the dark is greatest at 47°; in blue light, however, it is highest at 32° (Fig. 1).A preceding one-hour exposure to temperatures of 15-45° in the dark affects neither the O2-uptake at subsequent 30° in darkness nor its enhancement by blue light. Pre-exposure to 50°, however, results in a slightly decreased dark rate and in the absence of any blue light effect, while pre-incubation in 55-70° leads to almost complete suppression of the O2-uptake in darkness as well as under blue light (Fig. 2). The temperature dependence of the O2-consumption of cells supplied with 1% of exogenous glucose in the dark shows an optimum around 36° (Fig. 3a), which correlates with that of the temperature dependence of an active uptake of 3-O-methylglucose (Fig. 3b).The resemblance of these latter temperature dependencies to that of enhanced O2-uptake in blue light leads-together with Georgi's (Dr. thesis, Cologne, 1974) results of pulse chase experiments with [(14)C]glucose-to the discussion of an effect of blue light on intracellular membrane transport systems, which might result in a greater supply of sugar to the respiratory machinery.