Objective  Studying the physiological response and drought resistance mechanism of Cyperus esculentus var. sativus under different drought degrees can provide reference for the introduction and cultivation of C. esculentus var. sativus in northern sandy area.

  Method  C. esculentus var. sativus, a burgeoning oil crop in arid and semi-arid sandy area, was studied in a pot water control experiment with 4 different drought treatments of control check, light stressed group, moderate stressed group, and severe stressed group (the soil moisture contents were over 12%, 8% to 11%, 5% to 8% and less than 5%, respectively). The morphological structures, physiological and biochemical characteristics of C. esculentus var. sativus were tested, and then the drought resistant ability of C. esculentus var. sativus was evaluated by gray related degree analysis method and membership function method.

  Result  (1) With drought degree increasing, the crown breadth, tuber number descended significantly. The physiological and biochemical indexes such as net photosynthetic rate and stomatal conductance increased under the light drought and then decreased with drought degree increasing, indicating that light stress could enhance physiological activity. (2) Bio-chemistry mechanisms of C. esculentus var. sativus such as osmotic adjustment, antioxidant enzyme system and hormone secretion got activated to resist drought, and they played different roles in the drought stress. The responses of roots and leaves to drought stress were varied. (3) The activities of APX antioxidant enzymes reached peak values under the light in leaves, while under the severe drought stress in roots, the GB content of roots increased with the aggravation of drought stress, while it reached peak value under the light drought in leaves. (4) Comprehensive drought resistance value of C. esculentus var. sativus was 0.468, indicating moderate drought resistant ability.

  Conclusion  The study suggests that the optimum soil mass moisture content for C. esculentus var. sativus is 8% − 12%, C. esculentus var. sativus can be introduced into semi-arid sandy areas with the support of irrigation facility.