. 2009 Oct 8;61(1):121–130. doi: 10.1093/jxb/erp287

Table 3.

N₂ fixation of alfalfa plants (‘Saranac’) before and during application of different levels of CO₂ concentration to the root/nodule compartment

Parameter	Treatments
	+CO₂	–CO₂
Total N₂ fixation activity before introduction of treatments (mg N plant⁻¹ d⁻¹)	192±42	171±31
Total N₂ fixation activity 2 d after introduction of treatments (mg N plant⁻¹ d⁻¹)	283±134	126* 50
Total N₂ fixation activity 21 d after introduction of treatments (mg N plant⁻¹ d⁻¹)	965±279	415*±241
EAC 21 d after introduction of treatments	0.59±0.01	0.61±0.11
Specific N₂ fixation 21 d after introduction of treatments (mg N g⁻¹nodule dry matter d⁻¹)	43±15	39±14
N₂ fixation activity of an individual nodule 21 d after introduction of treatments (μg N nodule⁻¹ d⁻¹)	61±40	11*±7

Plants were grown for 3 weeks with different levels of CO₂ concentration in the root/nodule compartment. N₂-fixation was calculated from nodule H₂ evolution according to Schulze et al. (2006). Data are means of four replicates ±sd. An asterisk indicates a statistically significant difference from the +CO₂ treatment (t test, P ≤0.05).