A Solid State pH Control System for Algal Culturing and Uptake Studies

A bstract. An inexpensive solid state pH control circuit was built for external use with existing pH meters that can use either a gas or a liquid solution for pH control of culture media. Mastigocladus laminosus showed a 49% reduction in the rate of radiophosphate (P-32) uptake between gas-controlled (30% C02 in air) pH intervals of 8.7 (optimal uptake) and 5.7. Isotope uptake rates at higher pH values (achieved by manual additions of 0.1 N NaOH) decreased slightly between pH 8.7 and 9.7 and declined 36% between 9.7 and 10.7, where trichome motility and the ability to colonize new substratum were inhibited. Suppression of growth based on short-term (96 hr) dry weights, of which only 24 hr were at the selected pH values, was not evident throughout the experimental pH range.