Biomass and nitrogen fixation dataset of L. and L. cultivated under elevated CO and nitrogen addition.

It is expected that CO concentration will increase in the air, thereby stimulating the photosynthesis process and, hence, plant biomass production. In the case of legumes, increased biomass due to higher CO concentration can stimulate atmospheric nitrogen (N) fixation in the nodules. However, N fixation is inhibited by external N supply. Thus, biomass production and N fixation were analysed in two legumes ( L. and L.) grown at two levels of CO and three N levels. reduces fixation with high soil N (facultative), while maintains high fixation regardless of soil N levels (obligate). The N fixation and plant and nodule biomass of the two species were evaluated in a pot experiment under controlled conditions using growth chambers with artificial CO supply and N addition. The proportion of N derived from the air (%Ndfa) present in the plants' biomass was calculated from the natural abundance of N and the N concentration of plant tissues using nonlegumes reference plants. Additionally, N content data are presented for both species growing at two levels of air CO. The data may be useful for plant physiologists, especially those working on biological N fixation with non-model legumes at elevated CO.