https://www.selleckchem.com/ 7-21.6% O2). Concentrations of CO2 in the burrows increased after the burrows were plugged in the evening, but did not reach physiologically problematic levels. The highest CO2 concentrations in burrows were detected in the evening during a wet period (up to 0.44%). In root-rat nest chambers, the highest (but still harmless) CO2 concentrations (up to 1.31%) were detected in the morning (measured in the late dry season only) together with an elevated concentration (up to 13.5ppm) of CH4. Regular surface activity of giant root-rats, combined with the relatively large dimensions of their nest chambers and tunnels, and the absence of heavy soils, may contribute to harmless atmospheres within their burrow systems.Allantoin as a nitrogen metabolite can improve the salt tolerance in plants, but its mechanism of action remain elusive. Herein, the effects of pretreatment with exogenous allantoin in salt tolerance were investigated in sugar beet. The seedlings were subjected to salt stress (300 mM Na+) without or with different allantoin concentrations (0.01, 0.1, and 1 mM). The effects of allantoin on plant growth, homeostasis, oxidative damage, osmoregulation, and polyamine metabolism were studied. The results showed that salt stress inhibited the net photosynthetic rate and plant growth, and caused oxidative damage. However, these adverse effects were mitigated by exogenous allantoin in a dose-dependent manner, especially at 0.1 mM. Allantoin reduced the accumulation of ROS by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and AsA content. Under salt stress, allantoin reduced the root concentrations of free putrescine (Put) but increased the free spermine (Spm) in leaves and roots. Furthermore, allantoin decreased the Na+/K+ ratio and promoted the accumulation of betaine and soluble sugars in leaves and roots. Under salinity conditions, allantoin may enhance the antioxidant