Lead Toxicity and Tolerance in Plants

Lead (Pb) is the most common heavy metal contaminant in the environment. Plants absorb Pb from their environment, but it is not an essential element. Pb is quite common especially in the soil of roadside fields as a result of emission from the automotive exhaust. It is also found in fields with a long history of fertilization with fertilizers containing Pb as impurity. In fact, there are numerous sources of Pb including soil, water, air, batteries, toys, cans and fertilizers among others. Here in this review, we focus on the effects of Pb on plant growth and development and also discuss the mechanisms plants adopt to tolerate lead toxicity. Pb is among the most commonly present heavy metals in terrestrial and aquatic ecosystems. It enters these ecosystems through various natural and anthropogenic sources. Pb gets accumulated in a dose-dependent manner and causes toxicity to the plant. Due to uptake of Pb, the concentration of Mn is increased, while the total concentrations of most other minerals including K, Ca, Na, P, Mg, Zn, Fe, and Cu is reduced by Pb. The sprouting of young seedling and its development is limited by the plant exposure to Pb. Plants protect themselves against Pb toxicity through various mechanisms. There are at least three basic mechanism plants use to protect against Pb toxicity and they are passive mechanisms, inducible mechanisms and via antioxidant enzymes. Overall, we can conclude that Pb is harmful, but plants employ mechanisms to resist it. Thus further research should be to select and develop cultivars that have superior tolerance to Pb.