Abstract:

This experiment investigated whether application of nitrogen fertilizer could promote the improvement of drought resistance for Cynodon dactylon. Nitrogen fertilizer at various rates including zero nitrogen （0 mmol·L^-1）， low nitrogen （1.5 mmol·L^-1）， medium nitrogen （7.5 mmol·L^-1） and high nitrogen （15.0 mmol·L^-1） was applied to pot of C. dactylon cv.‘Xinnong No.1’with a slowly developing moisture deficit. The turf quality， relative water content， relative electrolyte leakage， malondialdehyde content， antioxidant enzyme activities ［superoxide dismutase （SOD）， peroxidase （POD）， catalase （CAT）］， hydrogen peroxide content， electrical conductivity and levels of substances linked to osmotic adjustment （soluble protein， proline， soluble sugar） were determined at 0， 7 and 14 d after water deficit commencement and 7 d after-watering. Heat map cluster and principal component analysis of drought resistance indexes at 7 and 14 days after water deficit commencement were carried out. The results showed that the effect of nitrogen application rates on turf quality differed depending on the degree of water deficit stress. Turf quality of C. dactylon was better under the high nitrogen treatment （15.0 mmol·L^-1） under normal irrigation and moderate drought stress， and medium nitrogen treatment （7.5 mmol·L^-1） significantly improved turf quality under severe drought stress. Compared with drought control plants， the relative water content， CAT activity， SOD activity， soluble protein， proline and soluble sugar contents of C. dactylon leaves were increased by 60.98%， 154.40%， 163.73%， 61.75%， 144.71% and 31.53%， respectively， with medium nitrogen application under drought stress， and thus maintained higher lawn quality. After re-watering， turf quality of C. dactylon recovered more quickly under medium and high nitrogen treatments， than in low nitrogen treatments. This may be due to reduced damage under drought stress. In conclusion， medium nitrogen application prior to drought stress partially alleviated water deficit damage to C. dactylon seedlings under drought stress.

Key words: Cynodon dactylon cv. ‘Xinnong No.1’, ammonium nitrate, drought stress, antioxidant enzyme, osmotic adjustment