Abstract: Bracts of dove tree (Davidia involucrate Baill.) are adaptive to the driving forces of pollinators and abiotic factors, which are sensitive to environmental factors. To reveal the changes of functional traits and their relationships across different altitudes, the independentsample t test and standardized major axis estimation were used to examine the functional traits and relationships of bracts in dove trees at 1400 m and 1800 m in Longcanggou, Sichuan. The results showed that: (1) Length, width and area of large and small bracts, as well as the total area of single flower bract in the population from low altitude (1400 m) were significantly larger than that from high altitude (1800 m) (P<0.05), while area and mass of large and small bracts in high and low altitude populations grew in proportion. (2) The mass of the large and small bracts and the total mass of the single flower bract in the population from low altitude (1400 m) were significantly higher than those from high altitude (1800 m) (P<0.05). (3) There was no significant difference in the length and the mass of inflorescence axis between high and low altitude populations (P=0.446;P=0.791). There was an allometric relationship between the mass of the inflorescence axis and the length at high altitude, but an isometric relationship at low altitude. (4) The relationships between length, width, area and mass of bracts showed isometric relationships at high and low altitudes. The total area and the total mass of single flower bract showed an isometric growth relationship with the mass of inflorescence axis at high and low altitudes, but showed an allometric growth with the length of inflorescence axis. In all, our results highlighted differences in the functional traits and the relationships between traits of bracts in dove tree at different altitudes, which may be an adaptive strategy to resist environmental interference, protect reproductive organs, and improve pollination rate.

Key words: Medlyn model, leaf net photosynthetic rate, Jarvis model, Ball-Berry model, Li-6400 portable photosynthesis system., Leuning model