IMPACTS OF SEEDING DEPTH ON EMERGENCE AND SEEDLING STRUCTURE IN 8 PERENNIAL GRASSES

The effects of seeding depth (1.5, 3, or 6 cm) on seedling emergence, morphology, and anatomy were examined in cool-season Agropyron dasysta chyum, Agropyron desertorum, Agropyron smithii, Elymus angustus, and E lymus junceus) and warm-season (Andropogon scoparius, Bouteloua curtip endula, and Bouteloua gracilis) perennial grasses. Caryopsis weights r anged from 0.5 mg in Bouteloua spp. to 4.7 mg in E. angustus. Prominen t elongation of the subcoleoptile internode at greater seeding depths and short coleoptiles were observed in And. scoparius, B. curtipendula , and B. gracilis (type A seedlings). The remaining species had relati vely long coleoptiles and no subcoleoptile internode elongation (type B seedlings). Up to 40% of the seedlings in the Agropyron species had intracoleoptile internode elongation when seeded at 3- and 6-cm depths . Relative emergence from 6 cm compared with 1.5 cm was best in Agr. d asystachyum and Agr. smithii and poorest in the type A species and in E. junceus. Diameters of xylem vessels in the subcoleoptile and intrac oleoptile internodes remained relatively constant, but numbers of vess els decreased with depth of seeding, especially in the type A species. Decreases in hydraulic conductance with depth of seeding were greater in type A than in type B seedlings, mainly because of longer subcoleo ptile internodes and smaller effective vessel radii in the former.