EFFECT OF CARBON DIOXIDE ON ABSORPTION OF WATER AND NUTRIENTS BY ROOTS

Open Access
Publisher Website
Google Scholar
Abstract
Absorption of water by the roots of wheat, maize and rice growing in water cultures was reduced 14-50% by bubbling CO2 through the solns. for 10 min. out of each hr. Bubbling air through cultures at the same intervals increased water absorption by 9%, and, in one expt., bubbling with N2 increased absorption by 13%. Adding H2SO4 to bring the solns. to the pH reached with CO2 had no effect upon water absorption. None of the plants were visibly injured by treatments lasting 36 hrs. CO2 treatments reduced the absorption of 5 nutrient elements in the order K>N>P>Ca> Mg. Ca and Mg absorption was reduced about as much as water absorption. K was excreted from the roots of many of the plants treated with CO2. N and P absorption were intermediately affected. It is suggested that the toxic effect of CO2 on plant protoplasm is associated with its specific ability to change the internal pH of cells and to form hydrogen-bond com- pounds with proteins. Reported CO2 concs. in field soils are above toxic levels, and CO2 toxieity should be included with O2 deficiency as a factor affecting plant development in poorly aerated soils. Because of the importance of roots in raising soil CO2, this gas may be a factor in root competition, particularly in the deeper layers of heavy soils.