Effects of Elevated CO 2 Concentration on the Biomasses and Nitrogen Concentrations in the Organs of Sainfoin ( Onobrychis viciaefolia Scop.)

Abstract

In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO 2 concentration probably affects the biomass, nitrogen (N) concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin ( Onobrychis viciaefolia Scop.) seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO 2 concentrations (ambient or ambient + 350 μmol mol −1 CO 2) without adding nutrients to them. After 90 days exposure to CO 2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO 2 concentration, the elevated CO 2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO 2 concentration. However, the elevated CO 2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO 2concentration. The elevated CO 2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO 2 concentration had no effect on the N content in the plants compared to the ambient CO 2concentration. The elevated CO 2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO 2concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.