Vol. 9, Special Issue 12, Part I (2025)

Oxygen accessibility is a pre-requisite for the lives of many living beings. In plants, when the oxygen supply is insufficient, most cellular capacities are compromised, which can lead to death. Hypoxia is a condition where oxygen level limits aerobic respiration (usually between 1% and 5%). Oxygen is a major factor of seed germination since it allows resumption of respiration and subsequent metabolism reactivation during seed imbibition, thus leading to the production of reducing power and ATP. It is also demonstrated that the covering structures of seed mainly inhibit germination by limiting oxygen supply to the embryo during imbibition. The pivotal function of oxygen in the molecular networks that govern the processes of seed germination and dormancy via the hormonal balance (ethylene, ABA, and GA), the hormone-signaling pathway, specifically the ABA sensitivity, the growing significance of mitochondria in the generation of reactive oxygen species during hypoxia, and the participation of the N-degron pathway in the turnover of proteins linked to seed tolerance to hypoxia. Due to the slow diffusion of O₂ in water, submerged plant tissues become O₂ deficient. Ethylene response factors (ERFs) are transcription factors that allow rice plants to survive submergence paved the way for the discovery of the ability to sense oxygen in plants (Loreti and Perata, 2020). Therefore, molecular and metabolic reactions are rapid and profound reprogrammed to withstand the stress of O₂ deficiency. The upregulation of the key enzyme Amy 3 is effective in mobilizing starch to produce energy and shifts ATP production from aerobic to anaerobic respiration through signaling cascades and metabolic regulation under low O₂ stress. O₂ deficiency induces the termination of the Krebs cycle and oxidative phosphorylation, diverts ATP production from mitochondrial electron transport chain (mETC) to ethanol fermentation (Taiz et al., 2015) ^[22]. The ability to use "omic" technologies, genetics and micro-measurements using microsensors has made significant progress in understanding the mechanisms behind the development of hypoxia tolerance possible over the years.