Melatonin modified root architecture system and accelerated mineral nutrient concentration of different pepper species under vanadium toxicity

Heavy metal contamination has adversely affected crop productivity around the world. Vanadium (V) toxicity is a significant environmental factor that lowers agricultural productivity by inhibiting plant development, diminishing nutrient uptake, and damaging root morphology. Melatonin (ME) is a well-known powerful antioxidant and multifunctional molecule that improves the resilience of plants against environmental stressors. In this work, we investigated the response of different pepper species [Capsicum annuum L. (CA), C. baccatum L. (CB), C. pubescens Ruiz & Pav. (CP)] to V toxicity as well as the possible roles of ME in enhancing V stress tolerance. Pepper roots were pretreated with ME (5 mmol · L^-1) for three days, then V (30 mg · L^-1) was applied for 2 weeks as a stress treatment. The findings showed that plants pretreated with ME exposed to V stress had improved root activity and biomass production. The root morphology and mineral nutrient accumulation of the pepper species were greatly improved by ME application. In addition, ME treatments lowered leaf V concentrations by lowering V translocation from root to shoot. In a nutshell, ME treatment modified root architecture system, increased concentration of mineral nutrient, and reduced V accumulation of pepper species under V stress.