A laboratory experiment was conducted to study the effects of 24-epibrassinolide (EBR) on the polyamines
(PAs), inorganic ion content, and ATPase activity in roots of cucumber seedlings under hypoxia stress. Hypoxia stress induced the significant increase of PAs, the decrease of (Spd+Spm)/Put ratio, and the significant decrease of K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ contents and of ATPase activity. EBR could increase the Spm and Spd contents and the (Spd + Spm)/Put ratio under hypoxia stress, and in addition, significantly increase the Ca²⁺, Mg²⁺, Fe³⁺, and Mn²⁺ contents and the ATPase activity. It was suggested that EBR could regulate the PAs content, increase the ATPase activity, enhance the inorganic ion content, and thereby, alleviate the damage of hypoxia stress.