Density and Behavior of Stomata of Pelargonium hortorum Ait. Grown Under Three Soil Moisture Regimes.1,2

Abstract

Two cultivars of Pelargonium hortorum Ait. were exposed to 3 soil moisture regimes for 10 weeks at which time rubber silicone impressions were made of the abaxial leaf surface of young and old leaves. ‘Dark Red Irene’ leaves had fewer stomata per unit area and greater diffusion resistance than did ‘Princess Irene’ exposed to the same regime. Increase in soil water content promoted the differentiation of stomata in early stages of leaf development. As the leaves increased in size and matured the number of stomata per unit area became inversely related to soil moisture content as a result of increased leaf area with high soil moisture. The stomatal resistance, determined by diffusion porometer, in young leaves of both cultivars was highest for plants grown in soils with high moisture and lowest with medium moisture.