Phenolics: A Game Changer in the Life Cycle of Plants

Abstract

Phenolics are ubiquitously present across the kingdom Plantae ranging from simple phenolic acids to very large and complex polymers. Phenolics are vital for plant growth and development as they are important in almost every process of plants including senescence, flower development, extracellular linking, pathogen and herbivore resistance, UV protection and photodamage, etc. Phenolics also act as chemical messengers or internal physiological regulators which regulate processes like transcription, trafficking of vesicles, signal transduction, and permeability of membrane. They inhibit or induce oxidative bursts and affect the respiration and photosynthesis rates. Plant phenolics also play an important role by acting as both underground signaling (mycorrhizal symbiosis, actinorhizal symbiosis, plant growth-promoting rhizobacteria (PGPR)) and as aboveground signaling molecules. Phenolics also act as potential antioxidant compounds during stressful conditions as they can donate electrons for the compound detoxification. Also, phenolics are accumulated in response to ROS under stress conditions. Phenolic compounds are also produced by plants as response to environmental stresses including wounding, salt, drought, heavy metal, temperature, etc. Phenolics provide resistance to the host plant by providing resistance against pathogen attack, herbivores, etc., and they also act as indicators of mineral deficiencies during various stages of plant growth and development. The action of resisting plants is apparently to increase either phenolic synthesizing enzyme levels or their activities, leading to increased phenolic production. Phenolics have also played a role in the plant invasion to land as the ability to synthesize phenolics has been selected throughout the course of evolution. Such compounds addressed the special needs to cope up in a constantly changing environment. It can be said that plant life without phenolics is impossible.