Extensive worldwide use of oxytetracycline (OTC),a member of the tetracyclines,has resulted in its accumulation in soils,posing a potential risk to food production and safety.A pair of OTC-sensitive (Heyou 1) and OTC-tolerant (Yannong 21) wheat (Triticum aestivum L.) cultivars was compared hydroponically at 0.01,0.02,0.04,and 0.08 mmol L-1 OTC in terms of wheat growth and photosynthesis.Biomass and shoot length decreased significantly with the addition of OTC,with the decreases in dry biomass and shoot length being 5.61%-13.75% and 3.33%-8.57% larger,respectively,for Heyou 1 than Yannong 21.Photosynthesis of Heyou 1 was suppressed by OTC as indicated by the significant decreases in photosynthetic rate (PN),transpiration rate (TR),and stomatal conductance (GS) and the significant increase in intercellular CO 2 concentrations (CI),at all OTC levels.Stomatal limitation (LS) and water use efficiencies (WUE) of Heyou 1 also increased significantly,but not at 0.08 mmol L-1 OTC.However,photosynthesis of Yannong 21 was suppressed by OTC only at high OTC levels from 0.02 to 0.08 mmol L-1 as indicated by the decreases in PN,GS,TR,and LS;at 0.01 mmol L-1 OTC,PN,CI,GS,and TR significantly increased.It was noted that WUE of Yannong 21 was not affected by OTC addition.The results from this hydroponic test suggested that OTC had a potential risk to crop growth through inhibition of photosynthesis,requiring further confirmation with soil tests. Extensive worldwide use of oxytetracycline (OTC), a member of the tetracyclines, has resulted in its accumulation in soils, posing a potential risk to food production and safety. A pair of OTC-sensitive (Heyou 1) and OTC-tolerant (Yannong 21 ) Triticum aestivum L. cultivars was compared hydroponically at 0.01, 0.02, 0.04, and 0.08 mmol L- 1 OTC in terms of wheat growth and photosynthesis. Biomass and shoot length decreased significantly with the addition of OTC, with the decrease in dry biomass and shoot length being 5.61% -13.75% and 3.33% -8.57% larger, respectively, for Heyou 1 than Yannong 21. Photosynthesis of Heyou 1 was suppressed by OTC as indicated by significant loss in photosynthetic rate (PN), transpiration rate (TR), and stomatal conductance (GS) and the significant increase in intercellular CO 2 concentrations (CI), at all OTC levels. Tomatal limitation (LS) and water use efficiencies (WUE) of Heyou 1 also increased significantly, but not at 0.08 mmol L -1 OTC.However, photos ynthesis of Yannong 21 was suppressed by OTC only at high OTC levels from 0.02 to 0.08 mmol L-1 as indicated by the decrease in PN, GS, TR, and LS; at 0.01 mmol L -1 OTC, PN, CI, GS, and TR significantly increased. It was noted that WUE of Yannong 21 was not affected by OTC addition. The results from this hydroponic test suggested that OTC had a potential risk to crop growth through inhibition of photosynthesis, requiring further confirmation with soil tests.