Leaf Anatomy and Stomatal Characteristics of Four Tall Fescue Selections Differing in Forage Yield1

Leaf anatomy and stomatal characteristics of four tall fescue ( Festuca arundinacea Schreb.) selections differing in forage yield were examined to determine if selection differences in these characteristics existed that might be important to yield differences. Selections were grown in a greenhouse. Transverse sections of leaf blades that were within 4 days of full expansion and for which CO 2 ‐exchange rate (CER) measurements had been made in a concurrent study were used in the anatomical study. Leaf impressions of fullyexpanded leaves of comparable tiller position of the same genotypes were used to study stomatal characteristics. In all selections, mesophyll cell area was the major fraction and comprised 40 to 44% of total cross‐sectlonal area, while large air spaces comprised 20 to 27 % of the area. Bulliform cells contributed more than 50% of the adaxial epidermal tissue area. The presence of prominent adaxial leaf ridges, lignified vascular bundle fibers, and lignified fiber caps was also noted. While adaxial stomatal frequency was more than 3.5 times greater than abaxial stomatal frequency, adaxial stomatal size (guard cell length) was only about 10% smaller than abaxial stomatal size. The lowest yielding selection in field trials, TFM 16, had approximately 22, 16, and 25% greater fractions of cross‐sectional area consisting of fiber cap tissue, epidermal cell layers, and bulliform cell area within the adaxial epidermis, respectively, compared with other selections. Selection TFM 16 also had 9% smaller abaxial stomata, 44% lower abaxial stomatal frequency, but 10% greater adaxial stomatal frequency, on average. No difference among selections was found for percent cross‐sectional areas of vascular bundle, phloem, metaxylem, and mesophyll tissues or in number of ridges, ridge height, leaf thickness, or metaxylem and mesophyll cell diameters. Mesophyll cell diameter did not appear to be related to CER. while significant differences among selections of CER were found, diameters of mesophyll cells of the same leaves were similar.