Photosynthetical gas exchange and chlorophyll fluorescence are important measures of plant adaptation to environments.However,their temporal variation during plant growth is still not clear.Our objective is to elucidate how they change as the plant grows.A local lucerne (Medicago sativa L.cv.Longdong) was chosen and gas exchange,chlorophyll fluorescence,chlorophyll content,sucrose content and related synthase activities,and biomass were measured at different growth stages of each cut in a glass house experiment.(1)Dry matter of the aboveground part and leaf increased as lucerne grew in each cut,while the average dry matter increment per day increased in the anterior two cuts and first increased and then decreased in the third cut,appearing some “S” type of growth.(2)Net photosynthetic rate (P_n),stomatal conductance and carboxylation efficiency decreased as lucerne grew in each cut,while intercellular CO₂ concentration did oppositely,and water use efficiency and stomata limitation to P_n decreased in the first cut but increased in the latter two cuts.(3)Sucrose content increased,while the activities of sucrose synthase and sucrose phosphate synthase did not change significantly.(4)Chlorophyll contents,including chlorophyll a,b and both,increased as lucerne grew in each cut.Chlorophyll fluorescence changed obviously only at the beginning in the first cut,and maintained stable in the rest cuts.Conclusively,lucerne showed obvious but different temporal variations in gas exchange and chlorophyll fluorescence in response to the environmental factors during stand growth.