Desiccation-tolerant plants under elevated air CO2: A review

This article summarises present knowledge of the ecophysiological responses to elevated atmospheric CO2 of desiccation tolerant (DT) plants. It deals primarily with lichens and bryophytes, as the most prominent groups of DT p hotosynthetic organisms, but includes some comment on algae and vascular DT plants. Results of research on DT plants are compared with those on desicc ation sensitive vascular Cg plants, the most widely investigated group in t he field of global change. Both DT and non-DT plants show an immediate posi tive response of photosynthesis to elevated CO2, but in both groups the lon ger term effect is generally reduced (or even reversed) by down-regulation or feedback inhibition of photosynthesis, or other limitations on productio n and growth. In bryophytes and lichens, enhanced short-term photosynthesis may or may not be reflected in increased production; bryophytes have limit ed source-sink differentiation, and lichens invest excess photosynthate in secondary metabolites. DT plants may gain some advantage from elevated CO2 at both low and excessive water contents. Neither theoretical consideration s nor experimental results suggest that elevated atmospheric CO2 will lead to any substantial shift in the balance of advantage between DT and non-DT plants.