The effects of carbon dioxide on the growth and development of amphibious plants

Abstract

When grown in a stream of 5% CO2 in air on a solid substrate, the heterophyllous amphibious species Ranunculus flabellaris and Myriophyllum brasiliense developed many characteristics of the water form. Plants of the same clones grown in 0.03% CO2 exhibited the land form. Submerged plants grew rapidly when 5% CO2 in air was bubbled through the nutrient medium, and exhibited the typical water form, while plants kept in 0.03% CO2 grew poorly, and the small leaves which developed were intermediate in morphology between the land and water forms. These results are similar to those obtained previously with Marsilea. None of these species were able to utilize bicarbonate. The stream from which the Ranunculus used in the experiments was collected contained high concentrations of dissolved free CO2 during part of the growing season. Thus concentrations of free CO2 higher than those in air may be essential for the normal growth and development of submerged amphibious plants.