Abstract: By the method of controlling dissolved oxygen concentration in nutrient solution, this paper studied the effects of applying calcium to the nutrient solution on the functions and nitrogen metabolism of cherry root system under hypoxia stress. As compared to the control, applying calcium significantly increased the root activity, mitigated the inhibition effect of hypoxia on root respiration rate, and improved the activities of enzymes involved in nitrogen metabolism, such as nitrate reductase (NR), glutamine synthethase (GS), and glutamate dehydrogenase (NADH-GDH). All these effects could supply enough energy for root respiration, supply NAD⁺ to glycolytic pathway, promote the electron transfer, and consequently, alleviate the harm of hypoxia stress to cherry plant. Applying 10 mmol·L^-1of Ca²⁺ had better effects than applying 5 mmol·L^-1of Ca²⁺. Calcium deficiency under hypoxia stress significantly decreased the root activity and NR, GS, and NADH-GDH activities, and aggravated the root respiration inhibition. It was suggested that applying calcium in growth medium could mitigate the damage of hypoxia stress on cherry root system.

Key words: Karst forest, Human disturbance, Degradation evaluation, Guizhou