Responses of the lichen Cladonia convoluta to high CO2 level and heavy metal treatment

Despite of the downward acclimation of photosynthesis in C. convoluta, incr eased net photosynthesis and carbon balance can be anticipated in response to elevated atmospheric CO2 level. CO2 exchange measurement seems to be mor e indicative when detecting heavy metal stress than fluorescence parameters . Among these, the relative fluorescence decrease ratio (RFd690) shows dama ge first, suggesting that the primary attack site for heavy metal ions is C O2 fixation and reaction centres are harmed last. Long-term elevated CO2 am eliorates partly this damage by improving C-balance to a greater extent in the heavy-metal stressed lichens.