COMBINED EFFECTS OF CITRIC ACID AND 5-AMINOLEVULINIC ACID IN MITIGATING CHROMIUM TOXICITY IN SUNFLOWER (Helianthus annuus L.) GROWN IN Cr SPIKED SOIL.

Phytoremediation, assisted with different amendments, is receiving much attention around the world due to its high efficiency, low cost and ease of handling. The current study was constructed to determine the combined performance of the citric acid (CA) and 5-aminolevulinic acid (5-AA) to enhance chromium (Cr) extraction through sunflower. Healthy seeds of sunflower were grownup in Cr contaminated soil (0, 5, 10 & 20 mgkg-1) and externally provided with CA (0, 2.5 &5 mM) and 5-AA (0, 10 & 20 mg L-1) at juvenile stage. The results showed a significant reduction in sunflower agronomic traits and biomass under Cr stress. In response to Cr stress, higher production of the reactive oxygen species (ROS) significantly reduced soluble proteins, photosynthetic pigments and activities of anti-oxidant enzymes. The combined addition of CA and 5-AA considerably mitigated the Cr-induced toxic effects on sunflower. Citric acid (CA) and 5-AA application enhanced plants' agronomic and physiological attributes by lowering electrolyte leakage and ROS production. Furthermore, the introduction of 5-AA and CA significantly up-regulated the actions of antioxidants enzymes in leaves and root of sunflower. With increasing soil Cr concentration, more Cr uptake and accumulation was observed which was further boosted with mutual applications of CA and 5-AA. Results of our work summarize that, CA and 5-AA combined application can effectively mitigate Cr stress and enhance Cr extraction capability of sunflower. [ABSTRACT FROM AUTHOR]