Peanut, (Arachis hypogaea L.) cvar. C76-16, was grown either in the field, or in open gas exchange chambers under elevated or ambient CO2 concentrations. Stomatal density and other selected epidermal parameters associated with leaf development and gas exchange were measured on recently fully expanded canopy leaves. It was hypothesized that exclusion of solar UV by chambers would affect stomatal density, but no clear statistically significant chamber effect on stomatal density was found. However, elevated [CO2] did lead to a reduction in both adaxial and abaxial stomatal developmental initiation and in stomatal density. Since each stomate was bounded by companion cells resulting from developmental events, non-random stomatal spacing as the “one cell spacing rule” appears to result from ontogeny rather than a long hypothesized chemical signal inhibiting adjacent meristemoid differentiation into guard cells. A method of visualizing epidermal patterns is also described.
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