Abstract: 【Objective】To investigate the drought tolerance of oat in morphology and structure.【Methods】Three water treatments of soil water content is 75%, 45% and 30% of the water holding capacity in the field were set up,and the effects of drought stress on oat Mengyan 1 yield,the dry matter quality at different growth stages,and the ultrastructure of epidermal cells and mesophyll cells in leaves at different filling stages were observed. 【Results】With the increase of the drought stress and the prolongation of time,the yield decreased significantly;the effect on the dry matter quality of the leaves was greater than that of the stems and ears;the structure of the leaf was more sensitive to the drought stress. With the increase of the drought stress time and degree,the number and area of leaf stomata decreased,and the density of epidermal hair decreased. The number of short cells of epidermis increased,while the fullness of epidermal cells decreased. With the increase of the drought stress time and degree,the area of mesophyll cells decreased,the number and area of chloroplast decreased,and the chromatin of nucleus gradually aggregated;the thylakoid gradually disintegrated and the mitochondria gradually expanded. Long-term severe drought stress leads to changes in the shape of the chloroplast and agglomeration between the chloroplasts. 【Conclusion】The above research indicated that the drought resistance of oat was strong.

Key words: Oats, Drought stress, Yield, Ultrastructure of leaves