We used Buchloe dactyloides.ramets as materials to research physiological metabolic response of B.dactyloides.leaves active oxygen scavenging system to differences photoperiod response.Clonal ramets were labeled as O (old sister ramet) and Y (young sister ramet),then we set connective group and disconnected group.O ramet and Y ramet were connected through the internode in connective group,whereas the internodes were cut off in disconnected group;the light cycle of O ramet was set for light 12 h/dark 12 h in both two groups,instead,light cycle of Y ramet was set for 12 h darkness/12 h light (just opposite to O ramet).And the activities of superoxide dismutase (SOD),peroxidase (POD),catalase (CAT),ascorbate peroxidase (APX),and malondialdehyde (MDA) content of ramet leaves were continuous measured 48 h illumination after cultivation of 7 d differences photoperiod treatment and 72 h stable illumination conditions.The results showed that after one weeks of different photoperiod treatments,under continuous light conditions,SOD,POD,CAT,APX activities and MDA content in disconnected ramets of B.dactyloides.leaves basically showed the opposite variation trend within 24 h.However,SOD,POD,CAT,APX activities and MDA content in connected ramets of B.dactyloides.leaves presented convergence of variation trend within 24 h.It indicated that reactive oxygen species scavenging system of B.dactyloides.showed rhythmic expression patterns,and B.dactyloides.connected ramets reactive oxygen species scavenging system tends to be synchronized under different photoperiod treatments.