Stomatal Movements, Frequencies, and Resistances in Two Maize Varieties Differing in Photosynthetic Capacity

The Stomatal characteristics of two maize varieties previously found to differ in rates of net photosynthesis were examined in a controlled environment. Measurements with a ventilated diffusion porometer showed that one variety exhibited a pronounced and the other a weak periodicity in stomatal resistance of the adaxial epidermis. At equal illumination the stomatal resistance of the adaxial epidermis decreased from upper to lower leaves, while the resistance of the abaxial epidermis changed in the opposite manner. Stomata on the adaxial and abaxial surfaces of maize leaves exhibited random not compensatory, movements in a constant environment. The variety with the lesser stomatal frequency and higher total leaf resistance to water loss had nevertheless faster net photosynthesis than the variety with the greater stomatal frequency, demonstrating the importance of the so-called mesophyll resistance.