Stomatal Frequency and Size in Vicia faba L.1

Variation in stomatal frequency and size and the relationship of those characters with other plant features were studied in Vicia faba L. to provide information about possibilities of modifying water use by breeding. A field trial comprised I0 cultivars belonging to major, equina, and minor types grown at 20 and 40 plants/m2. The main effects studied were cultivars, leaf position on main stem, and plant density. A substantial independence among stomata, trichome, and other plant characteristics was observed. Cultivars differed mainly in stomatal and trichome frequency. Frequency and number of stomata and trichomes per leaflet were affected by plant density. Leaflets on the seventh node had a greater number of stomata and trichomes than leaflets on the first node. The stomatal frequency, number, and dimensions were higher on the lower (abaxial) leaf surface than the upper (adaxial) leaf surface, whereas the frequency and number of trichomes were higher on the upper surface. Cultivar and leaf position had significant effects on almost all characters meao sured. First‐ and second‐order interactions also were significant, but the latter for only a few characters. In general, stomatal size was less affected by the factors tested than stomatal and trichome frequency. The implications of the results for breeding new cultivars based on physiological selection criteria are that stomatal frequency can be altered by breeding to improve water use.