Study on the Diurnal Variation of Photosynthetic Characteristics of Scrophularia ningpocnsis Hemsl.

[Objective] The purpose was to study the diurnal variation characteristics of the net photosynthetic rate of Scrophularia ningpoensis Hemsl.and provide reference for the cultivation of S.ningpoensis.[Method] By using Li-6400 portable photosynthesis system,the net photosynthetic rate under different photosynthetically active radiation at different periods and the effects of environmental factors on the diurnal variation of photosynthetic rate were determined.[Result] The light response curve of S.ningpoensis was a single peak curve,the light saturation point and light compensation point of S.ningpoensis were 1 624 and 21.16 μmol/(m2·s) respectively.The diurnal variation of net photosynthetic rate showed a double peak curve and had the typical 'midday depression' phenomenon.The correlation analysis showed that net photosynthetic rate of S.ningpoensis had positive correlations with photosynthetically active radiation,transpiration rate, stomatal conductance and temperature,and it had a negative correlation with intercellular CO2 concentration.Its correlation with the relative humidity was not significant.[Conclusion] S.ningpoensis is a kind of heliophyte.The stomatal conductance,photosynthetically active radiation and transpiration rate are main environmental factors that affect the net photosynthetic rate of S.ningpoensis leaves.