Role of H2O2 in Seed Germination

Abstract

Hydrogen peroxide (H₂O₂) is increasingly recognized as a significant molecule in seed germination, functioning as both a signaling molecule and a modulator of physiological processes. Its dual role as an oxidative agent and signaling molecule allows it to influence various stages of seed germination. During seed germination, the production and accumulation of H₂O₂ are tightly regulated. Low to moderate levels of H₂O₂ promote seed germination by breaking seed dormancy, enhancing water uptake, and facilitating the mobilization of storage reserves. H₂O₂ acts by modulating the expression of genes associated with growth and stress responses, thereby aiding in the transition from dormancy to active growth. H₂O₂ influences the balance between abscisic acid (ABA) and gibberellic acid (GA), two critical hormones in seed germination. It has been observed that H₂O₂ can reduce ABA levels while promoting GA biosynthesis, thus favoring germination. Additionally, H₂O₂ interacts with other reactive oxygen species (ROS) and antioxidant systems to maintain cellular redox homeostasis, which is crucial for cellular metabolism and signal transduction during germination. Exogenous application of H₂O₂ has also been shown to improve germination rates, especially under stress conditions such as salinity, drought, and heavy metal exposure. It can enhance the seed’s tolerance to adverse environmental conditions by activating stress-responsive pathways and antioxidant defense system. However, excessive levels of H₂O₂ can be detrimental, causing oxidative damage to cellular components, thereby inhibiting germination and reducing seed viability. Therefore, the role of H₂O₂ in seed germination is concentration-dependent, with a critical balance required to ensure optimal germination and early seedling development. Various studies have illustrated the performance of H₂O₂ in seed aging also. Seed aging results in a loss of germination capacity, due to accumulation of H₂O₂ highlighting its detrimental effect. This chapter represents the mechanisms of H₂O₂ action and its interactions with other signaling pathways during seed germination and aging, plant development, and stress adaptation.