Assessing the impacts of intra-and interspecific competition between Triticum aestivum and Trifolium repens on the species’ responses to ozone

Abstract

Tropospheric ozone is considered to be the most phytotoxic air pollutant because of its oxidizing power. The main objective of this study was to analyze the effect of intra-and interspecific competition between Triticum aestivum L. and Trifolium repens L. on the responses to high concentrations of ozone of both species, and the role of the symbiotic relationship Rhizobium – T. repens on the abovementioned responses. Monocultures and mixtures of both species in different densities were sown. Pots were transferred to open top chambers either with 90–120 ppb ozone or without ozone. Ozone had an overall negative impact on leaf area and biomass production per individual plant. These responses were dependent on species and sowing density in monocultures, but were not changed by species proportion in the mixtures. There was a positive relationship between Rhizobium nodules and plant biomass, with a tendency for smaller plants to present lower number of nodules under ozone. These results suggest that competitive and mutualistic interactions could have a greater role in determining responses to novel air pollutants than species sensitivity to the xenobiotic, per se.