Abstract: A hydroponic experiment was carried out to explore the effects of exogenous calcium and H+ on ion content and ATPase activity of cucumber under hypoxic stress. The results showed that K+，Ca2+，Mg2+ contents were significantly lower and plasma membrane，tonoplast，endoplasmic reticulum ATPase activities were significantly decreased under hypoxic stress. Application of 4 mmol · L-1 CaCl2 in nutrient solution significantly alleviated the hypoxic stress，and the K+，Ca2+，Mg2+ contents were significantly higher than those in the hypoxic treatment，while the plasma membrane，tonoplast，endoplasmic reticulum H+-ATPase and Ca2+-ATPase activities were significantly higher than hypoxic treatment and closed to the control level. Application of 50 μmol · L-1 H+ in nutrient solution significantly reduced the contents of K+，Ca2+，while the content of Mg2+ was not significantly differed from the hypoxic treatment. H+-ATPaseand Ca2+-ATPase activities of plasma membrane were significantly lower than the hypoxic treatment，but the H+-ATPase and Ca2+-ATPase activities of vacuole membrane and endoplasmic reticulum were not significantly differed from the hypoxic treatment. It is suggested that application of exogenous calcium ions can increase the mineral absorption and transport，enhanced the activities of ATPase，and alleviated the hypoxic injury of cucumber and enhanced cucumber tolerance hypoxia.

Key words: hypoxic stress, calcium, cucumber, K+, Ca2+, Mg2+, ATPase