Antioxidative response to abiotic and biotic stresses in mangrove plants: A review

The natural environment for mangrove plants is composed of a complex set of abiotic and biotic stress factors that include salinity, heavy metal, low oxygen, flooding, UV-B, water logging, and biotic interferences of various magnitude. Salinity stress exerts adverse effects on plants by disrupting the ionic and osmotic equilibrium of the cells leading to decrease in plant growth and development. Similarly, presence of heavy metals in environment induces a disturbance of the cellular redox balance, thereby affecting growth and productivity of mangrove plants. Anaerobic environment in mangroves manifested by anoxic or hypoxic condition exhibit various metabolic changes in plants to overcome the stress condition. Besides, the mangrove plants are also permanently exposed to various biotic stress factors that include microbial pathogens (viruses, bacteria and fungi), nematodes, insects etc. More often, these stress factors result in the production of reactive oxygen species (ROS) within different cellular compartments of the plant cell that are detrimental to the survival of the plants. However, the mangrove plants can withstand these stress conditions through morphological and physiological adaptations and development of an efficient antioxidative defence system composed of non-enzymatic and enzymatic systems. The antioxidant system works in concert to control the cascades of uncontrolled oxidation and protect plant cells from oxidative damage by scavenging of ROS produced owing to different abiotic and biotic stresses. The present review highlights various abiotic and biotic stress conditions that are prevalent in mangrove environment and the manner in which mangrove plants overcome these stress situations through metabolic changes and induction of antioxidant defence system.