Phytomanagement of heavy metals in contaminated soils using sunflower: A review

Contamination of soils with heavy metals (HMs) is an important issue due to the contamination of agricultural crops, which are further transferred into the food chain. Phytoremediation is an emerging method of remediating metal-contaminated soils. Sunflower has been widely adopted for phytomanagement of HM-contaminated soils owing to its high biomass production and capacity for metal accumulation. Sunflowers can tolerate the toxic effects of certain HMs through different mechanisms, such as enhancements in antioxidant enzyme activities, deposition in nonactive parts of the plant, and stimulation of osmolytes. Stress caused by HMs affected negatively the seed germination, nutritional status, photosynthesis, and growth of sunflower. However, the responses of sunflowers to this stress vary with cultivar/variety, soil type, metal type, dose, and duration of metal exposure. This review critically summarizes the effects of HMs in sunflowers and examines field-relevant approaches to improve the phytoextraction capability of sunflowers. Proper selection of tolerant cultivars along with agronomic practices may be an effective strategy for the phytomanagement of soils contaminated with HMs.