Grass Seedling Morphology When Planted at Different Depths

Abstract

Depth of planting has been acknowledged in the literature as a factor which modifies grass seedling morphology. However, the type and extent of this modification has not been clearly documented. A growth chamber study was conducted to evaluate the mesocotyl, coleoptile, and leaf internode development of smooth bromegrass 'Lincoln' (Bromus inermis Leyss.), sideoats grama 'Pierre' [Bouteloua curtipendula (Michx.) Torr.], and western wheatgrass 'Rodan' [Agropyron smitilii Rydb.; syn. = Pascopyron smithii Rydb. (Love)] seedlings when planted at 6, 25, 51, 76, and 102-mm soil depths. Environmental conditions within the growth chamber were held constant for all treatments. Mesocotyl, coleptile, and/or leaf internodes did not elongate equally for all planting depths. Shallow-planting lessened elongation while deep planting maximized elongation within the genetic limits possible for each species and individual genotype. When evaluating grass seedling morphology, regardless of species or seed size, planting depth must be great enough to allow inherent genetic expression in the development and elongation of the mesocotyl, coleoptile, and leaf internodes. When planting for a grass stand, the sower should keep in mind that percent emergence for smooth bromegrass, sideoats grama, and western wheatgrass decreased significantly when planted deeper than 26, 8, and 52 mm, respectively. Adventitious root numbers at the coleoptilar node decreased significantly when planting depths exceeded 25, 51, and 51 mm for smooth bromegrass, sideoats grama, and western wheatgrass, respectively.