Biochar alleviates fluoride toxicity and oxidative stress in safflower (Carthamus tinctorius L.) seedlings.

An original research was laid out as factorial to evaluate the possible effects of biochar (0, 25 and 50 g kg-1 soil) on mitigating fluoride toxicity (non-contamination, 100, 200, 400 and 800 mg NaF kg-1 soil) in safflower seedlings. Increasing fluoride toxicity up to 200 mg NaF kg-1 soil did not decrease the safflower growth. However, the growth of plants under 400 and 800 mg NaF kg-1 was reduced by enhancing soluble fluoride concentration in the soil. This growth reduction was the consequence of an increase in fluoride content of plant tissues, generation of super oxide radicals and hydrogen peroxide, lipid peroxidation, misbalancing potassium and calcium ions, and a decrease in synthesis of photosynthetic pigments including chlorophylls, carotenoids, anthocyanin, flavonoids and xanthophyll's and photochemical efficiency of photosystem II. Application of biochar decreased the fluoride solubility, fluoride content of plant tissues, oxidative stress and antioxidant enzymes activities, leading to an increase in cation exchange capacity of soil and the pH, calcium and potassium uptakes, maximum efficiency of photosystem II, synthesis of photosynthetic pigments, and plant growth. In general, addition of 50 g biochar to 1 kg soil was the best treatment for alleviation of the fluoride toxicity in safflower plants.