Chemically degraded soil rehabilitation process using medicinal and aromatic plants: review

In recent decades, the increasing number of degraded lands worldwide makes their rehabilitation essential and crucial. Various techniques have emerged to fulfill these needs but most of them are expensive and difficult to be applied. Revegetation is a cost effective, environmental friendly, and aesthetically pleasing approach suitable for degraded areas. However, the use of edible crops, especially for areas with heavy metals (HM) contamination, is not ecologically suitable because the HM may enter the food chain. Alternatively, non-edible, fast-growing, deep-rooting, and metal-stabilizing plants with high biomass, which can produce high-value products hold a great potential and have been regarded as potential candidates of edible crops. This current review presents the benefits of using aromatic and medicinal plants (AMPs) and their associated microorganisms for revegetation of degraded sites as they are high-value economic crops. We discussed the effect of various stress on productivity of secondary metabolites in AMPs in addition to the potential health risk with human consumption of these plants and their products. A focus was also given to the effect of HM stress on the essential oil (EO) content of certain AMPs. Reported data showed that AMPs growing on HM-contaminated soils are safe products to use as they are not significantly contaminated themselves by HM.