We can see through the three curves in Figure A, at P point, no matter what the temperature is, the rate of photosynthesis is the same, so it is proved that the temperature is not the limiting factor of the rate of photosynthesis, the limiting factor from the graphic judgment is the intensity of light, because the intensity of light is too weak, so no matter what the temperature is high or low, the photosynthesis is very difficult to carry out.

After point P, the temperature is different and the rate of photosynthesis is different, which means that temperature is already the limiting factor.