Preliminary Study on Photosynthetic Diurnal Variation of Michelia figo Leaves in Spring

An experiment was conducted to study the diurnal variation of photosynthetic characteristcs of Michelia figo Leaves.and its light response by Li-6400 portable photosynthesis system.The results showed that: the net photosynthetic rate of Michelia figo presented a double-peak curve.The highest peak in the morning appeared at about 10:00.The second peak appeared at about 13:00 with an obvious photosynthesis 'midday depression'.The maximum of net photosynthetic rate was 4.783 μmol·m-2·s-1.While the net photosynthetic rate,stomatal conductance and transpiration rate change bimodal curve,while the intercellular CO2 concentration showed a gradual reduction in the first 12:00 to the second peak,then decreased,and finally slowly increased to reach peak 17:00.Net photosynthetic rate and stomatal conductance,transpiration rate,leaf temperature was positively correlated with net photosynthetic rate and intercellular CO2 concentration was negatively correlated with stomatal conductance and transpiration rate were positively correlated.