**Abstract**

The green algae *Chlorella* sp. DT (DT) and *Chlorella pyrenoidosa* 211-8b (8b) had similar cell growth rates and photochemical efficiency (Fv/Fm) when they were cultivated under a moderate irradiance of 120 μmol photons m<sup>−</sup><sup>2</sup> s<sup>−</sup><sup>1</sup> in combination with a series of temperatures that decreased from 32 to 7°C. Upon shifting the cultures to the relatively high irradiance of 240 μmol photons m<sup>−</sup><sup>2</sup> s<sup>−</sup><sup>1</sup> , DT exhibited higher cell growth rates than 8b under the chilling temperatures of 20°C and 15°C and differences in the Fv/Fm and Chl *a*/*b* ratios from 8b. In particular, DT possessed more new differentially induced SOD isoforms than 8b.

**Keywords:** *chlorella*, chilling temperature, relatively high irradiance, chlorophyll content, Fv/Fm, Chl *a*/*b*, superoxide dismutase
