When a pea is germinating, it means that it is still growing, so as it continues growing, the need for O2 consumption grows as well, so the rate is higher the more germinating it becomes. If that was the case, then CO2, oxygen and water levels would all remain the same in the environment that its in. This is because for every CO2, Oxygen, Water molecule that is used or produced in photosynthesis, the opposite happens in respiration