Impact of Nitrogen Oxides on Tropical Plants

Abstract

In many parts of the world, notably in Asia, the release of nitrogen oxides (NOX) into the atmosphere has been a developing trend in recent decades. The level of nitrogenous pollution will continue to surpass permissible levels due to increased industries and rising auto exhaust emissions. Numerous secondary air pollutants—including ozone, smog, and particulate matter—are preceded by NOX. At present, scholars have differing opinions on the impact of NOX on plants. According to one theory, NOX can produce organic nitrogenous compounds in plants when it is digested and absorbed into the nitrate absorption pathway. This process does not harm the plants. Another theory claims that most plants are resistant to NOX and incorporate little NO2-N. When plants are exposed to significant amounts of NOX, especially NO2, they possibly go through a range of physiological responses, including alterations in the distribution of nitrogenous metabolic products, N-metabolic enzyme activity and the activity of antioxidant enzymes in various plant tissues. These changes can have negative effects, such as the inhibition of N assimilation, production of reactive oxygen species (ROS), stunted plant growth, acute leaf damage, whole-plant chlorosis, or even death of the plant. Although various plant species respond to NOX in different ways, there is currently no agreement over how NOX affects plants, which is still a topic of intense debate. In order to comprehend the current situation, this chapter explores the status of NOX and its impacts on plants in tropical parts of the world using the available research.