The Requirement of Aquatic Bryophytes for Free Co2 as an Inorganic Carbon Source: Some Experimental Evidence

Summary Twenty bryophyte species were tested for photosynthetic uptake of bicarbonate by immersing plants in 2.0 mM and 0.2 mM NaHCO3 and monitoring rise in pH. Equilibrium values were clustered around pH 9.0 and pH 8.0 in the two solutions, indicating limitation by free CO2 and inability to use bicarbonate. Anthoceros husnotii reached a maximum pH value of 9.5 in 2.0 mM NaHCO3, suggesting possible, although inefficient, bicarbonate uptake. Four species of bicarbonate‐using plants tested for comparison gave final pH values in the range of 10.1 to 10.9. Field measurements gave results consistent with the laboratory experiments. Availability of CO2 to bryophytes growing in different aquatic habitats is discussed and their ecology is considered in light of the results.