Ozone does not diminish the beneficial effects of arbuscular mycorrhizas on Medicago sativa L. in a low phosphorus soil

Enriched surface ozone (O-3) can impose harmful effects on plants. Conversely, arbuscular mycorrhizal (AM) symbiosis can enhance plant tolerance to various environmental stresses and facilitate plant growth. The interaction of AM fungi and O-3 on plant performance, however, seldom has been investigated. In this study, alfalfa (Medicago sativa L.) was used as a test plant to study the effects of O-3 and AM symbiosis on plant physiology and growth under two O-3 levels (ambient air and elevated O-3 with 60 nmol center dot mol(-1) O-3 enrichment) and three AM inoculation treatments (inoculation with exogenous or indigenous AM fungi and non-inoculation control). The results showed that elevated O-3 decreased plant net photosynthetic rate and biomass, and increased malondialdehyde concentration, while AM inoculation (with both exogenous and indigenous AM fungi) could promote plant nutrient acquisition and growth irrespective of O-3 levels. The positive effects of AM symbiosis on plant nutrient acquisition and antioxidant enzyme (superoxide dismutase and peroxidase) activities were most likely offset by increased stomatal conductance and O-3 intake. As a result, AM inoculation and O-3 generally showed no significant interactions on plant performance: although elevated O-3 did not diminish the beneficial effects of AM symbiosis on alfalfa plants, AM symbiosis also did not alleviate the harmful effects of O-3 on plants.

Automated summary

Enriched surface ozone can be harmful to plants, but arbuscular mycorrhizal symbiosis can enhance plant tolerance to environmental stresses. This study investigated the effects of ozone and mycorrhizal symbiosis on alfalfa plants and found that mycorrhizal symbiosis promoted plant nutrient acquisition and growth, while ozone decreased photosynthetic rate and biomass.