Objective: To investigate the relationship between the photosynthetic response characteristics

daily variation of photosynthetic parameters and environmental factors in leaves of Fagopyrum dibotrys. Method: The daily variation of photosynthetic parameters and light response curves of leaves of F. dibotrys were measured by portable photosynthesis apparatus. Result: Both diurnal variation of net photosynthetic rate(Pn) and the diurnal variation of stomatal conductance(Gs) in leaves of F.dibotrys showed a double peak curve

with an obvious midday depression phenomenon. Their net photosynthetic rate was 19.13 and 16.54 μmol·m-2·s-1 respectively

and bottom was at 14:00 with a net photosynthetic rate of 15.04 μmol·m-2·s-1

about 78.62% of the maximum peak value

showing a phenomenon of midday depression of photosynthesis. The net photosynthetic rate was positively correlated with the main influencing factors including photosynthetically active radiation (PAR)

transpiration rate(Tr)

stomatal conductance

and negatively correlated with atmospheric CO2 concentration (Ca) and intercellular CO2 concentration(Ci). Conclusion: F. dibotrys is a stomatal limiting plant

and Pn has obvious midday depression of photosynthesis phenomenon. Photosynthetic active radiation

transpiration rate

stomatal conductance and atmospheric temperature are the main influencing factors for Pn in leaves of F. dibotrys.