The Effect of Cadmium on Net Photosynthesis, Transpiration, and Dark Respiration of Excised Silver Maple Leaves

Excised leaves of silver maple (Acer saccharinum L.) exposed to 0, 0.045, 0.090, or 0.180 mM Cd²⁴ exhibited reduced net photosynthesis and transpiration, and increased dark respiration. Rates of net photosynthesis and transpiration diminished with time and were strongly correlated with solution concentration and tissue content of Cd²⁴, Net photosynthesis and transpiration were reduced to 18 and 21%, respectively, of the untreated controls after 64 h. Dark respiration increased as much as 193% of the untreated controls but was poorly correlated with solution concentration or tissue content of Cd²⁴, Diffusive resistances of leaves to carbon dioxide and water vapor transfer increased with both increasing Cd²⁴ concentration and time. These findings are discussed in relation to stomatal function.