Inhibitors of photosynthesis could
not be used to study stomatal responses to light in Z. mays and C.
communis because higher concentrations than 10-r M had to be
supplied in order to reduce the net exchange of CO2 to zero within
2 h. The leaves began to evolve CO2 during the course of the
experiments and, as a consequence, the intercellular CO2 was no
longer independent of changes in stomatal conductance.