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.