Abstract
The objectives of this research were: 1) to determine if leaf age significantly affects leaf resistance to gaseous diffusion in Phaseolus vulgaris at constant light and external CO₂ level, leaf temperature, ambient humidity and leaf water potential; 2) to test the possibility that three parameters inherently related to leaf age, shading of lower leaves, stage of plant development, and stomatal density, also affect leaf resistance; 3) to determine the extent to which the leaf age effect on leaf resistance alters the rate of CO₂ assimilation in the light; 4) to test the hypothesis that the controlling mechanism of the leaf age effect on leaf resistance (if any) is an increase in the CO₂ concentration in the substomatal cavity. Bean plants were grown and tested in environmental chambers under constant conditions of high light (900-1150 microeinsteins s⁻¹m⁻², 400-700 nm), 12 hour photoperiod, 30°C air temperature, 25°C dew point, 320 ppm CO₂ and 1 ms ⁻¹ air speed. Measurements of leaf resistance, leaf water potential, stomatal density and light level at the leaf were made throughout all stages of plant growth (60 days from emergence). In one experiment leaf resistances were simultaneously measured with a diffusion porometer cup and a CO₂ assimilation cup. The values obtained by both methods were in close agreement.
Davis, Stephen Darrel (1974). Effect of leaf age on stomatal resistance and its significance for carbon dioxide assimilation in bush bean (Phaseolus vulgaris L.). Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -172399.