The role of Aspergillus flavus in modulating the physiological adjustments of sunflower to elevated CO2 and temperature

Abstract

Exploring the interactions between plants and foliar endophytic fungi under varying climatic conditions is crucial for harnessing endophytes that enhance plant resilience to environmental stressors. This study examines the role of a specific strain of Aspergillus flavus as an endophyte in sunflowers under standard and altered CO₂ and temperature regimes. We assessed the impact of this fungus on physiological traits such as chlorophyll and flavonoid content, gas exchange, and Chlorophyll a fluorescence using open-top chambers simulating ambient (∼420 µmol mol⁻¹) and elevated (∼880 µmol mol⁻¹) CO₂ levels, along with a temperature increase of 3°C. The findings indicate that A. flavus promotes nitrogen assimilation and chlorophyll production under ambient conditions, potentially enhancing sunflower growth and photosynthetic performance. However, under elevated temperatures (eT), inoculation with A. flavus resulted in decreased biomass and reduced Photosystem II efficiency. Elevated CO₂ (eCO₂) conditions also led to unexpected negative effects, with reductions in foliar nitrogen, leaf area, and light capture efficiency, culminating in diminished biomass. When both elevated CO₂ and temperature conditions were combined (eCO₂eT), the interaction further impaired Photosystem II efficiency, suggesting exacerbated physiological stress. These results demonstrate that environmental modifications can transform A. flavus from a beneficial endophyte to a potential pathogen, highlighting the dual nature of plant-fungal interactions. This study underscores the complexity of these relationships under changing climatic conditions and suggests a cautious approach to the agricultural use of endophytes to ensure plant health and productivity.