The effects of age and size of seed on seedling vigor, rate of respiration, and 2,3,5‐triphenyl‐2H‐tetrazolium chloride (TTC) reduction by germinating seeds were studied in the laboratory. Wheat seed (Triticum aestivum ssp. compactum (Host) MacKey ‘Elmar’) was used. Stratification was necessary to eliminate the effect of dormancy in the youngest seed class. Significant positive correlations were found between rate of emergence and vigor (ability to emerge from deep seeding), emergence and rate of respiration, and between vigor and both tetrazolium reduction and rate of respiration for seed of different ages. With different seed size classes, significant positive correlations were found between seed weight and tetrazolium reduction, and between shoot weight per plot and tetrazolium reduction. In a preliminary test, varietal differences in seedling vigor, which were largely due to relative coleoptile elongation, were not correlated with TTC reduction. The possible place of TTC reduction as an empirical seedling vigor test and respiration of germinating seeds as a component of vigor are discussed.

Yield losses occur in cereals as a result of lodging. Ethephon [(2‐chloroethyl)phosphonic acid] has been reported to reduce lodging; however, studies of its effect on grain yield have produced conflicting results. In this study. selected cultivars of semidwarf wheat (Triticum aestivum L.), normal height barley (Hordeum vulgare L.) and triticale (Triticale hexaploid L.) were treated with ethephon to determine (1) if this growth regulator had an effect on yield other than via a reduction in lodging and (2) the optimum growth stage and rate (kg/ha) of application. Foliar‐applications to field grown plants (the soil was a fine‐silty, mixed, mesic Cumulic Haplaxeroll) were made at two plant growth stages, late boot and early heading. Ethephon was applied at 0, 0.28, and 0.55 kg&ha in 1976 and at 0, 0.28, 0.55, and 0.85 kg/ha in 1977. Main plots were fertilized with 45 or 90 kg N/ha in 1976 and 90 or 180 kg N/ha in 1977. Ethephon applications at the late boot stage reduced the elongation of plants more effectively than applications at early heading. Ethephon treatments reduced elongation of tall cereal species, i.e., barley and triticale were significantly shorter following treatment of 0.28 kg/ha in 1977. Ethephon treatments increased harvestable yields when they reduced lodging. For instance, untreated ‘Unitan’ barley lodged heavily, but ethephon treatment of 0.55 kg/ha reduced lodging which resulted in increased harvestable yields. Ethephon treatment of 0.84 kg/ha significantly inhibited stem elongation in semidwarf wheats, but semidwarf wheats did not lodge and treatment did not increase yields. The results of this study indicate that further field testing should be conducted in regard to ethephon's potential to benefit yields of tall, ‘weak‐stemmed’ cereals such as barley, since no benefit was derived from ethephon treatment to semidwarf wheats.

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Lines of Triticum, representing diverse sources of germplasm, were characterized for stomatal frequency. Wheat leaf variation between the first, second, third, and fourth leaves on a tiller, sampling position at the base, center, and tip of each leaf, and sampling position in relation to adaxial or abaxial surface of the leaf were measured.Stomatal frequency was always greater on the adaxial than on the abaxial surface. Mean ratios (abaxial/adaxial) were .748 for the first leaf and .728 for the second leaf on a culm. Frequencies ranged from 9,219 to 6,372 stomata cm‐2 for the adaxial and 8,024 to 3,487 for the abaxial surface of the first leaf. For the second leaf frequencies ranged from 8,875 to 4,597 for the adaxial and 8,172 to 3,487 for the abaxial surface. Stomatal frequency decreased in relation to position of leaf insertion on the culm. The first leaf had the greatest stomatal frequency, the second had the next greatest, and the fourth had the least. The leaf base contained the most, and the tip, the fewest stomata per unit of leaf area.Plants grown on Cercosporella‐inoculated plots had more stomata per unit of leaf area than did those grown on the control plots.No general relation was found between grain yield and number of stomata cm‐2 of leaf surface nor between grain yield and bn (the product of stomata length and stomata per unit of adaxial leaf area).