Agronomic Crop Responses and Tolerance to Polycyclic Aromatic Hydrocarbon Toxicity

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are made up of only carbon and hydrogen and composed of two or more fused benzene cycles. It includes a large and heterogeneous group of organic contaminants that are mainly formed and emitted because of the incomplete combustion of organic materials. Polycyclic aromatic hydrocarbons are toxic for all living organisms, and their mutagenic and carcinogenic effects are well known. Hence, their fate and transport in the environment are of worldwide attention. Over 90% of PAHs in the environment reside in surface soils; therefore, plants grown in PAH-contaminated soils can uptake them, and that can make problems in terms of agronomic crop yield and contamination of food chains. Polycyclic aromatic hydrocarbons can enter the plant via stomata as well as the root system and can lead to a range of disorders in plants. Decrease in photosynthesis and respiration, changes in enzyme activities and photosynthetic pigment content, and injury to membranes by lipid oxidation are some known effects of PAHs in plants. The increasing load of PAHs to the environment can be a crucial factor for the future diversity of plant species in the habitat, and it may determine the level of possible economic yields. Thus, it is important to exactly understand how PAHs influence the overall plant growth and development. This chapter revises some concepts about PAH importance in the environment, those effects on plants, and plant responses to PAHs.