Metabolic responses of pesticides in plants and their ameliorative processes

Abstract

The major challenge faced by modern agriculture today is to overcome the impending serious food shortage considering the rising population even while battling to maintain crop yields under unfavourable environmental conditions. Pesticides are important chemicals recurrently applied for enhancing crop yields in agriculture and also for amelioration of vector-borne diseases. Rampant use of these chemicals has led to serious health implications to man and his environment. In developing nations (like India), 76 % of the total pesticide used is harmful insecticide as against just 44 % in the developed countries. This difference in the pesticide usage pattern evidently affects the total cost-benefit ratio between these nations. It is commonly believed by the general public that ‘if little is good, a lot more will be better’. This unchecked and unwise use of pesticides leads to deposition of 95 % of pesticides in soil, water and atmosphere as well as in nontarget organisms. Consequently, pesticide residues have been found in raw as well as processed fruits and vegetables. Pesticides not only kill insects and weeds but also are toxic to a variety of other nontarget organisms like birds, fish, beneficial insects and plants. Soil microflora has also been adversely affected by treatment of soil with pesticides. Xenobiotics, such as pesticides, trigger a defence response in plants. The mechanism by which pesticide is perceived and the signalling is transmitted within plant cells still remains elusive. Various xenobiotics induce oxidative stress and often activate cell signalling pathways, leading to production of stress proteins and upregulation of antioxidants. These changes include the evolution of new metabolic pathways, generation/accumulation of low molecular weight metabolites, synthesis of special proteins, detoxification mechanisms and reduction/elevation in phytohormone levels. Comparison of metabolic pathways, detoxification mechanisms and variance in tolerance level of different plants to pesticides can aid us in designing efficient and cheap vegetative treatment systems for decontaminating soil and water containing pesticide residues. Thus, understanding metabolism of pesticides in plants is necessary for developing strategies for amelioration of their harmful effects in nontarget organisms and also for remediation of contaminated soil, water and atmosphere.