Source of nitrogen nutrition affects pea growth involving changes in stomatal conductance and photorespiration

Abstract

The effect of the source of nitrogen (N) nutrition [N₂ fixation and nitrate (NO₃) assimilation] on plant productivity, gas exchange, N assimilation, water relations, and glycollate oxidase activity were studied in pea plants. Nitrogen‐fixing plants showed a higher RGR over the study period. This higher RGR was correlated with higher stomatal conductance and, consequently, a higher transpiration rate. Photosynthetic N‐use efficiency was also higher when plants were nodulated. We found glycollate oxidase activity, a key enzyme of the photorespiratory pathway, much lower in N₂ fixing plants, what strongly suggests that energy losses due to photorespiration are lower in these plants, and therefore, photosynthetic efficiency was higher.