Oats are one of the most useful and widespread cereal crops in the world. In permafrost conditions (Central Yakutia), based on metabolic changes in late summer-sown oat plants (Avena sativa L.), the key processes involved in the cold acclimation of a valuable cereal species were identified. During the onset of low ambient temperatures, metabolites from leaf samples were profiled using gas chromatography with mass spectrometry (GC-MS) and were analyzed using principal component analysis (PCA). A total of 41 metabolites were identified in oat leaves. It was found that acclimation to suboptimal temperatures during the fall period leads to biochemical (accumulation of mono- and disaccharides and decrease in fatty acids and polyols) as well as physiological and biophysical changes (decrease in leaf PRI reflectance indices and chlorophyll a fluorescence). Therefore, the study contributes to a more holistic understanding of oat metabolism under low-temperature cryolithozone stress. It is believed that the analysis of changes in leaf reflection properties and JIP-test parameters of chlorophyll a fluorescence using leaf metabolomic profiling can be used in the selection of valuable varieties of cereal crops to obtain plant fodders with high nutrient contents under conditions of a sharply continental climate.

Plant sterols (STs) are essential for the regulation of fluidity and permeability of cell membranes, which have a wide structural diversity. The dynamics of changes in sterol molecular species in leaves of a valuable cereal crop, spring oat (Avena sativa L.), as a function of different sowing dates were studied. In particular, 11 molecular species of sterols (STs) and triterpenoids in A. sativa leaves were identified by GC-MS. Triterpenoids Ψ-taraxasterol, cyclolaudenol, and betulin were identified in A. sativa leaves for the first time, which may be related to adaptation to extreme climatic conditions of the cryolithozone. The dynamics of STs and triterpenoids changes were revealed during growth and development of the standard term and late summer sowing term during A. sativa hardening to low ambient temperatures. The ratio of β-sitosterol to campesterol was found to increase in response to low positive air temperatures, while the ratio of stigmasterol to β-sitosterol remained constant from mid-September to the end of October. Overall, leaves of standard-seeded A. sativa plants maintained higher levels of absolute STs and triterpenoids by 1.9-fold than leaves of late-seeded A. sativa plants. It is suggested that the ability of A. sativa plants to synthesize β-sitosterol and stigmasterol may be part of an evolutionary adaptation process to cope with wide temperature fluctuations and to maintain important membrane-bound metabolic processes.