The chlorophyll fluorescence response of desiccation-tolerant cyanobacterial crusts from shaded and non-shaded habitats on sub-tropical inselberg rocks, Guangdong province, China to rehydration under different light intensities and temperature was studied. It was shown that chlorophyll fluorescence change showed the same trend under different light-temperature conditions. After rehydration in the dark following a term of desiccation, the potential quantum yield of PSII (Fv/Fm) and the effective quantum yield of PSII (Yield) of each sample recovered quickly, following activation after 1 minute. Moreover, the two samples could adapt to a wide range of light intensity and temperature while 250 mu mol m(-2) s(-1) light and 30 degrees C were fitted for rehydration. However, Lower light caused more inhibition in non-shaded habitats, but higher lights caused more inhibition in shaded habitats. Further, samples from non-shaded habitats suffered more damage under temperature treatments than did samples from shaded habitats. Although extreme light and temperature inhibited photosynthetic activity of the samples to some extent, cyanobacterial crusts were protected from damage under high light through photochemical fluorescence quenching (qP). In conclusion, cyanobacteria as pioneers on such bare rocks can recover photosynthesis capability after a term of desiccation, and can adapt well to different light intensities and temperatures.