Responses to Ambient CO₂ Concentrations by Sodium-Deficient C₄ Plants

Abstract

The signs of sodium deficiency in the C₄ species Amaranthus tricolor and Atriplex spongiosa were alleviated when the species were grown in conditions of high CO₂ concentration (1 500 µl CO₂ 1^-1). In experiments in which A. tricolor was grown in conditions of low CO₂ concentration (15 µl CO₂ 1^-1), the signs of sodium deficiency were accentuated. The sodium-deficient plants resembled the C₃ species Atriplex hastata and tomato in their response to the CO₂ treatments. Growth and chlorophyll concentrations increased in both the sodium-deficient C₄ plants and the C₃ plants when they were grown in conditions of increased CO₂ concentration. Sodium-sufficient C₄ plants were relatively unaffected by the CO₂ treatments.