of CO2 of 80 Pa or 120 Pa. Ainsworth and Long (2004) showed that,
although it depends on the plant species, the rate of photosynthesis
of C3 plants is increased by a factor of 1.2–1.4 in an elevated CO2
environment; the concentration of CO2 is increased from 475 ppm
to 600 ppm. It is found that the increase in the rate of photosynthesis
is the same level as that in this study. In this study, the rate of
photosynthesis increased about 1.4-fold when the elevated partial
pressure of CO2 was 80 Pa. On the other hand, under an elevated
pressure higher than 0.3 MPa, there was no difference between the
results under the high and low absolute humidities (Fig. 8).
From the results of this study, it is suggested that that plants can
be grown more efficiently under elevated total pressure. Moreover,
the cost of plant growth could be lower