EDTA and IAA Ameliorates Phytoextraction Potential and Growth of Sunflower by Mitigating Cu-Induced Morphological and Biochemical Injuries

As an essential micronutrient, copper is vital for normal growth and development of plants, however, its accumulation in soil exerts a severe negative impact on the agronomic characteristics and yield of the crop plants. Phytoextraction is a low-cost method for restoring soil fertility and avoiding losses due to heavy metal contamination. We found that using EDTA and IAA together improved sunflower hyperaccumulation capacity. Sunflowers were cultivated under various levels of Cu (0 (control), 25, 50, and 75 mg/kg of soil) and treated with EDTA alone or combined with IAA. The results revealed that the amended treatment significantly enhanced the absorption and accumulation of Cu in the sunflowers. Furthermore, the various doses of Cu significantly reduced the root and shoot growth of sunflowers in a concentration-dependent manner by impairing the chlorophyll content, hormones (indole 3-acetic acid, salicylic acid, and gibberellic acid), flavonoids, phenolics, and antioxidant response. The injurious effect of Cu was reduced by the addition of EDTA alone, and the supplementation of IAA led to a significant restoration of shoot growth (similar to 70%) and root growth (similar to 13%) as compared to the plant treated with Cu alone. Moreover, significantly higher levels of chlorophyll content, GA(3), endogenous IAA, and flavonoids were recorded, indicating the effectiveness of the treatment in ameliorating plant health. The results also showed considerable restoration of the catalase and ascorbate peroxidase activities in plants treated with EDTA and IAA. These results are suggestive that application of EDTA and IAA enhances the Cu absorption potential of sunflower and increases its tolerance to copper, which may not only serve as a better technique for phytoextraction of Cu, but also to bring Cu contaminated soil under cultivation.

Automated summary

Copper is a vital micronutrient for plant growth and development, but its accumulation in soil negatively affects crop agronomic characteristics and yield. The combination of EDTA and IAA improved sunflower's ability to hyperaccumulate copper. Sunflowers treated with different levels of copper (0 (control), 25, 50, and 75 mg/kg of soil) and EDTA alone or with IAA showed significantly enhanced copper absorption and accumulation. Copper reduced root and shoot growth, impaired chlorophyll content, hormones, flavonoids, phenolics, and antioxidant response. EDTA alone reduced the harmful effects of copper, and the addition of IAA restored shoot and root growth. Higher levels of chlorophyll content, GA(3), endogenous IAA, and flavonoids were also observed, indicating improved plant health. The catalase and ascorbate peroxidase activities were restored in plants treated with EDTA and IAA. These findings suggest that EDTA and IAA can enhance sunflower's copper absorption potential and tolerance, making it a potential phytoextraction technique for copper-contaminated soil.