Increasing the nitrate concentration in the nutrient media was found not to influence the carbon dioxide compensation point (Γ). However, a higher value of Γ was obtained in the presence of ammonia nitrogen in the nutrient media. Increasing the nitrate concentration in the media gave a higher activity of RuDP carboxylase, nitrate reductase, glycollate oxidase, and catalase. Similarly the plants grown in ammonia nitrogen showed higher activities of RuDP carboxylase and catalase, and a considerably higher glycollate oxidase activity.