Physiological screening of ruderal weed biomonitors of atmospheric nitrogen deposition

Background: Plants take up various species of reactive nitrogen and their different physiological responses to the increase of nitrogen availability can be useful in biomonitoring. Questions: Does atmospheric nitrogen deposition affect the physiology of ruderal weeds? Which species are most responsive to the nitrogen deposition? Studied species: Eleven ruderal weeds. Study site and dates: Morelia, Michoacán, Mexico. 2019. Methods: Under scenarios of 10, 20, 40 and 80 kg N ha-1year-1, we quantified plant responses of biomass production, nitrate reductase activity, chlorophyll content, photosynthetic efficiency, δ15N, nitrogen and carbon content. Results: Total biomass production increased with the rate of nitrogen deposition for Bidens pilosa, Chloris gayana,Lepidium virginicum, and Pennisetum setaceum, as chlorophyll content in B. pilosa, C. gayana, and L. virginicum. In turn, the below- to above-ground biomass ratio decreased for B. pilosa and C. gayana, as photosynthetic efficiency in C. gayana, L. virginicum, and Chloris pycnothrix. Nitrate reductase activity was only affected in L. virginicumm, C. gayana, and T. officinale.    With the exception of C. pycnothrix, the nitrogen content increased, while the carbon augmented in C. gayana, C. pycnothrix, and P. setaceum. The C/N ratio was reduced in B. pilosa, C. gayana, Chloris virgata, P. setaceum, and T. officinale. The δ15N was increased in B. pilosa, C. gayana, C. virgata and P. setaceum. Conclusions: Bidens pilosa, C. gayana, L. virginicum, and P. setaceum were the species with more affected variables to nitrogen deposition, which could be useful in the biomonitoring.