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This study evaluated the physiological responses, hormonal signaling, osmotic and nutrient levels, as well as the performance of essential oils, antioxidant enzymes, and secondary metabolites in Lavender plants subjected to chromium and fluoride toxicity and biochar application. The findings indicated that the administration of raw and especially multiple-chemical engineered biochars decreased fluoride (about 16-40%) and chromium (39-60%) levels in Lavender leaves, whereas raised CEC and soil pH, nitrogen (10-37%), potassium (20-47%), phosphorus (10-60%), magnesium (30-49%), calcium (20-50%), zinc (39-240%), iron (40-120%), plant biomass, and photosynthetic pigments of Lavender plant leaves under toxic fluoride and chromium conditions. The treatments with multiple-chemical engineered biochars decreased the osmotic stress and osmolyte concentration (carbohydrates, soluble proteins, and proline) in the leaves of Lavender plants. Both raw and multiple-chemical engineered biochars significantly enhanced the water content of plant leaves, reaching up to 10% under toxic circumstances. Moreover, these treatments decreased the synthesis of stress hormones such as jasmonic acid (4-17%), salicylic acid (29-49%), and abscisic acid (30-66%), while increasing the production of Indole-3-acetic acid (IAA) (15-29%) in Lavender plants subjected to chromium and fluoride stress. The use of multiple-chemical engineered biochars showed notable efficacy in enhancing antioxidant enzyme's activity against oxidative damage induced by metal toxicity and decreasing proline accumulation. Maximum concentrations of linalyl acetate, borneol, camphor, and linalool were achieved under fluoride and chromium stress conditions by metaphosphoric acid-engineered biochar. Multiple-chemical engineered biochars application can be inferred as valuable approach to enhance both the quality and quantity of lavender essential oil under conditions of fluoride and chromium-induced stress.

来源平台：JOURNAL OF CROP HEALTH