where D0 is 0.138, T is the temperature, T0 is 273 K, P0 is 0.1 MPa
and P is the total pressure. This equation indicates that the diffusion
coefficient of CO2 (D) increases in proportion to the square of
temperature (T) and decreases with increasing total pressure (P).
As a result, the left-hand side of Eq. (1) decreases under elevated
total pressure, and the rate of respiration also decreases. However,
the rate of respiration increased with increasing pressure from
0.3 to 0.5 MPa under the low-absolute-humidity condition reported that, at a higher partial pressure of CO2, the rate
of respiration was increased in some experiments. Therefore, the
rate of respiration under a high partial pressure of CO2 could be
increased. In addition, the stomatal opening speed is higher at a
high absolute humidity than at a low absolute humidity Since stomatal opening
may have a proportional effect on the rate of respiration, it
could be considered that the rate of respiration was increased under
elevated total pressure and low-absolute-humidity conditions.