Abstract: The research aimed to study the adaptation mechanisms of oats (Avena sativa) to exposure to soil environments with high levels of calcium salts and drought, as in karst areas. PEG-6000 was used to set up solutions with 0 (CK), -0.2, -0.4, -0.6, -0.8, -1.2 MPa osmotic potential, to simulate a range of drought environments in karst areas. Similarly, calcium chloride (CaCl₂) solutions of 0 (CK), 50, 100, 150, 200 mmol·L^-1 were prepared to provide exogenous calcium and simulate the range of soil calcium environments in karst areas. The effects of low osmotic potential and Ca²⁺ exposure singly and their interaction effect on the seed germination characteristics and seedling physiological characteristics of oats were studied. Both low and medium levels of osmotic stress and exposure to elevated Ca²⁺, singly or in combination, promoted the germination of oat seeds and enhanced the activities of superoxide dismutase, catalase, peroxidase and glutathione peroxidase in seedlings. This was especially true in seedlings subjected to 100 mmol·L^-1 CaCl₂ and -0.6 MPa PEG interactive stress,where the germination rate increased significantly by 42.17% compared with the CK treatment. Two-way ANOVA showed that the effect of salt-drought interaction stress on oats was more significant than that of either single stress (P<0.05). Through comprehensive data analysis, oat tolerance of the stressors tested was found to be as follows: interaction stress>single PEG stress>single CaCl₂ stress.The exposure levels tolerated by oats under CaCl₂, PEG and interaction stresses, were 100 mmol·L^-1, -0.6 MPa, 100 mmol·L^-1 CaCl₂+-0.6 MPa PEG, respectively. The above results show that in karst mountain areas, medium-low concentrations of Ca²⁺ and ormoderate drought typical in these areas can promote seed germination and seedling growth of oats. This study provides reference information for the introduction and cultivation of oats in karst areas and for further research into breeding for stress resistance.

Key words: oat, drought stress, exogenous calcium, seed germination, seedling physiology