Oxygen deficiency is environmental challenge which affects plant growth, development and distribution in land and aquatic ecosystems as well as crop yield losses worldwide. The capacity to exist in the conditions of deficiency or complete lack of oxygen depends on a number of anatomic, developmental and molecular adaptations. The lack of molecular oxygen leads to an inhibition of aerobic respiration, which causes energy starvation and acceleration of glycolysis passing into fermentations. We focus on systemic metabolic alterations revealed with different approaches of metabolomics. Oxygen deprivation stimulates accumulation of glucose, pyruvate and lactate indicating acceleration of sugar metabolism, glycolysis and lactic fermentation respectively. Among Krebs cycle metabolites only succinate level increases. Amino acids related to glycolysis, including phosphoglycerate family (Ser, Gly), shikimate family (Phe, Tyr, Trp) and pyruvate family (Ala, Leu, Val) are greatly elevated. Members of Asp family (Asn, Lys, Met, The, Ile) as well as Glu family (Glu, Pro, Arg, GABA) accumulates too. These metabolites are important members of metabolic signature of oxygen deficiency in plants linking glycolysis with altered Krebs cycle and allowing alternative pathways of NAD(P)H reoxidation to avoid excessive accumulation of toxic fermentation products (lactate, acetaldehyde, ethanol). Reoxygenation induces down regulation of levels of major anaerobically-induced metabolites including lactate, succinate and amino acids, especially members of pyruvate family (Ala, Leu, Val), Tyr, Glu family (GABA and Glu), and Asp family (Asn, Met, Thr, Ile). The metabolic profiles during native and environmental hypoxia are rather similar consisting in accumulation of fermentation products, succinate, fumarate and amino acids, particularly Ala, Gly and GABA. The most intriguing fact is that metabolic alterations during oxidative stress are very much similar with plant response to oxygen deprivation, but not to reoxygenation.