Dark CO 2 fixation by roots of willow and barley in media with a high level of inorganic carbon

Abstract

Summary Willow ( Salix cv. Aquatica gigantea) and barley ( Hordeum vulgare L.) plants were grown in a nutrient solution (pH 7) enriched with HCO 3 − or gaseous CO 2 . The initial and potential in vivo rates of dark CO 2 fixation in the roots were measured using 0.015 mmol/L and 0.74 mmol/L H 14 CO 3 − as substrates of phosphoenolpyruvate carboxylase (PEPC). Enrichment of the nutrient solution with HCO 3 − or CO 2 increased the initial rate of dark CO 2 fixation in roots of both willow and barley compared with the corresponding control roots. In plants grown with NO 3 − the initial activity of PEPC was 38 and 89% higher than in control willow and barley, respectively, after the addition of HCO 3 − . When the nutrient solutions were enriched with CO 2 the initial activity of PEPC increased 52 % in willows and 58% in barley, compared with the controls. The supply of HCO 3 − into NH 4 + media increased the initial activity of PEPC in the roots of willows and barley by 50% and 17%, respectively. The amount of soluble protein in the roots was also higher in plants grown with inorganic carbon than in the control plants.