Impacts of seeding depth on emergence and seedling structure in eight perennial grasses

Abstract

The effects of seeding depth (1.5, 3, or 6 cm) on seedling emergence, morphology, and anatomy were examined in cool-season (Agropyron dasystachyum, Agropyron desertorwn, Agropyron smithii, Elymus angustus, and Elymus junceus) and warm-season (Andropogon scoparius, Bouteloua curtipendula, and Bouteloua gracilis) perennial grasses. Caryopsis weights ranged from 0.5 mg in Bouteloua spp. to 4.7 mg in E. angustus. Prominent 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 relatively 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. dasystachyum and Agr. smithii and poorest in the type A species and in E. junceus. Diameters of xylem vessels in the subcoleoptile and intracoleoptile internodes remained relatively constant, but numbers of vesels 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 subcoleoptile internodes and smaller effective vessel radii in the former. Key words: grass seedling emergence, hydraulic conductance, morphology, seeding depth, seed weight, xylem dimensions.