Rubisco Activase and Its Regulation on Diurnal Changes of Photosynthetic Rate and the Activity of Ribulose 1,5 Bisphosphate Carboxyase/Oxygenase(Rubisco)

To clarify the factors determining the diurnal courses of photosynthesis in a day, photosynthetic rate(P n), photosynthetic photon flux(PPF), stomatal conductance(S c), intercellular CO 2 concentration(C i), relative humidity(RH), temperature(T), transpiration(Trans), initial Rubisco activity(RI), total Rubisco activity(RT),Rubisco activase activity(RCA) were measured. The maximal photosynthetic rate occurred at about 8:30 a.m. when initial Rubisco activity reached the maximum. Then both of them gradually decreased down. After 13:00 p.m., they rose up positively correlated with P n and the regression coefficient between them was 0.9368. By the correlation analysis and path analysis, stomatal conductance and initial Rubisco activity were found to be major factors limiting photosynthetic rate. The interaction of Rubisco activase activity and other factors on photosynthetic rate were studied by using response surface, and the response surface of every mathematical model was drawn to express their intrinsic relationship. The study showed that Rubisco activase activity had an effect on photosynthetic rate by its regulating initial Rubisco activity.