Revealing the effects of drought stress on the photosynthetic characteristics and yield of naked oats (Avena nuda L.) is significant for enhancing the productivity of oats. In this study, a potted experiment consisting of four water levels was conducted in the Bashang area of Hebei Province, China. The drought stress period was established as the continual 8 days during the jointing-heading stage. The aims were to reveal the impacts of drought stress on the photosynthetic characteristics and yield of naked oats during the critical stage. The results showed that the photosynthetic rate (P_n), transpiration rate (T_r), and stomatal conductance (G_s) decreased under all conditions of drought stress. The intercellular CO₂ concentration (C_i) decreased under light drought stress, while it increased under moderate and severe drought stress. The initial chlorophyll fluorescence rate (F_o) increased by 9.03-50.92% under drought stress, and the maximum fluorescence rate (F_m) decreased by 8.49-19.73% under drought stress. The photochemical efficiency (F_v/F_m) increased by 10.37-24.12% under drought stress. The yields decreased by 9.5-12.7%, 16.8-27.0% and 44.1-47.7% under light, moderate and severe drought stress during the critical stage, respectively. The grains per panicle decreased by 1.7-12.5%, 8.3-24.3% and 32.7-34.2% under light, moderate and severe drought stress conditions, respectively. The 1000-grain weight decreased by 5.7-8.6%, 12.7-14.5% and 16.8-19.1% under light, moderate and severe drought stress conditions, respectively. The panicle numbers did not vary significantly among the different drought stress treatments. The photosynthetic rate, stomatal conductance and transpiration all had significant positive relationships with the yield of naked oat (P < 0.01). Parameters of PS II except for F_o all had significant positive relationships with the yield of naked oats (P < 0.05). This study is significant for enhancing the production efficiency of naked oat under drought stress.

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