Chlorophyllase (Chlase) actívity measured as the in vitro degradation of chlorophyll (Chl) was variably enhanced by various heavy metals (Cd2+, Pb2+, Mn2+, Co^"*", Ni2+ and their mixture). The en2yme actívity on Chl a was higher than that on Chl b. Chlase isolated from Chlorella fusca oř Kirchneriella lunaris responded differently to the heavy metals. The inclusion of Ca2+ in the assay media affected the enzyme actívity. While some concentrations were stimulatory, others were inhibitory depending on partícular heavy metal, the algal species, and the Chl a oř b.
The 77 K fluorescence emission was measured on Chlorella cells at regular intervals during adaptatíon of high CO2 (1.8 % CO2 v/v) grown cells to air level of CO2. The ratíos of the peaks at 686 and 697 nm (photosystem 2, PS 2, fluorescence) to the peak at 720 nm (PS 1 fluorescence) decreased and approached a constant level in about 1.5 h. The extemal concentration of dissolved inorganic carbon (DlC) required for the half-maximum rates of C02-dependent O2 evolutíon, 5, also decreased and reached a constant level aíter the same period of adaptatíon. Hence the íncreased demand for ATP/NADPH during the CO2 assimilatíon by the ''C02-concentrating mechanism" induces the redistribution of excitation energy from PS 2 to PS 1 and increases formation of ATP by the cyclic photophosphorylatíon.