Ethylenediurea as a potential tool in evaluating ozone phytotoxicity: a review study on physiological, biochemical and morphological responses of plants

Present-day climate change scenario has intensified the problem of continuously increasing ground-level ozone (O-3), which is responsible for causing deleterious effects on growth and development of plants. Studies involving use of ethylenediurea (EDU), a chemical with antiozonant properties, have given some promising results in evaluating O-3 injury in plants. The use of EDU is especially advantageous in developing countries which face a more severe problem of ground-level O-3, and technical O-3-induced yield loss assessment techniques like open-top chambers cannot be used. Recent studies have detected a hormetic response of EDU on plants; i.e. treatment with higher EDU concentrations may or may not show any adverse effect on plants depending upon the experimental conditions. Although the mode of action of EDU is still debated, it is confirmed that EDU remains confined in the apoplastic regions. Certain studies indicate that EDU significantly affects the electron transport chain and has positive impact on the antioxidant defence machinery of the plants. However, the mechanism of protecting the yield of plants without significantly affecting photosynthesis is still questionable. This review discusses in details the probable mode of action of EDU on the basis of available data along with the impact of EDU on physiological, biochemical, growth and yield response of plants under O-3 stress. Data regarding the effect of EDU on plant 'omics' is highly insufficient and can form an important aspect of future EDU research.