Transcript growth
The Grass Plant Auricles Inflorescence Culm Leaf blade Leaf sheath Stolon daughter plant Seed Ligule Rhizome daughter plant Growth and Development Understanding turfgrass growth and development is essential to the successful culture of turf. Turf cultural programs are best when based on a knowledge of basic physiological processes, the environment, and turfgrass species and variety characteristics. Growth and Development • Growth is an irreversible increase in size. Cell division Cell expansion Growth and Development • Growth is an irreversible increase in size. Cell division Cell expansion • Development is a change in form. Vegetative vs. reproductive stage Formation of tillers, rhizomes, or stolons Process of seed germination. Root branching Caryopsis with embryo Emergence of primary root and coleoptile Components of the grass floret Caryopsis Palea Pericarp Lemma Embryo Seed coat Endosperm Grass embryo Coleoptile Scutellum First leaf Second leaf Apical dome Scutellar node Epiblast Primary root Root cap Coleorhiza Process of seed germination. Caryopsis with embryo Process of seed germination. Caryopsis with embryo Emergence of primary root and coleoptile Process of seed germination. Emergence of first leaf Root branching Caryopsis with embryo Emergence of primary root and coleoptile Shoot growth • After germination, the embryo develops into a seedling plant. Shoot growth • After germination, the embryo developes into a seedling plant. • The crown becomes more fully developed. Shoot growth • After germination, the embryo developes into a seedling plant. • The crown becomes more fully developed. • The crown gives rise to leaves, roots, tillers, and in some cases elongated lateral stems. The Crown A highly compressed stem with apical meristem, nodes, internodes, axillary buds, and roots. The crown is one of four types of stems that occur in grasses. The Crown A highly compressed stem with apical meristem, nodes, internodes, axillary buds, and roots. The crown is one of four types of stems that occur in grasses. Crowns form from the embryo of germinating seed, axillary buds and terminals of rhizomes and stolons, and from axillary buds on more mature crowns. Diagram of a grass crown. Apical meristem Primordial leaves Axillary bud Internode Node Adventitious root Primary root Tiller Tillering • Tillers arise from axillary buds on crown Tillering • Tillers arise from axillary buds on crown • Grow upward between enclosing sheath and main axis Tillering • Tillers arise from axillary buds on crown • Grow upward between enclosing sheath and main axis • Apogeotropic (upwards) growth differs from that of stolons and rhizomes Tillering • Tillers arise from axillary buds on crown • Grow upward between enclosing sheath and main axis • Apogeotropic (upwards) growth differs from that of stolons and rhizomes • Produces an identical daughter plant which becomes independent of mother plants CH2O, nutrient, and water supply. Initial Tiller Appearance Factors influencing tiller development: • Plant age • Photoperiod • Temperature • Management Nutrition Mowing Irrigation Tillering in Tall Fescue • Cool temperatures: Less than 70oF • Short days: Less than 12 hours • Conditions typical of autumn Tiller Development Cultural factors that influence tillering: Mowing • Decreasing mowing height increases tillering Tiller Development Cultural factors that influence tillering: Mowing • Decreasing mowing height increases tillering • Extremely close or frequent mowing will reduce CH2O needed for tiller development Tiller Development Cultural factors that influence tillering: Mowing • Decreasing mowing height increases tillering • Extremely close or frequent mowing will reduce CH2O needed for tiller development Nutrition Tiller Development Cultural factors that influence tillering: Mowing • Decreasing mowing height increases tillering • Extremely close or frequent mowing will reduce CH2O needed for tiller development Nutrition • N applied to C3 grasses in fall increases tillering Tiller Development Cultural factors that influence tillering: Mowing • Decreasing mowing height increases tillering • Extremely close or frequent mowing will reduce CH2O needed for tiller development Nutrition • N applied to C3 grasses in fall increases tillering • N applied to C3 grasses in spring decreases tillers Stolon Rhizome and Stolon Development • Axillary buds develop into lateral stems Rhizome and Stolon Development • Axillary buds develop into lateral stems • Stems break through enclosing leaf sheaths; a process termed extravaginal growth Rhizome and Stolon Development • Axillary buds develop into lateral stems • Stems break through enclosing leaf sheaths; a process termed extravaginal growth • Process is common to rhizomes and stolons Rhizome and Stolon Development Factors influencing rhizome and stolon growth • • • • Plant age Photoperiod Temperature Management Nutrition Mowing Irrigation Rhizome and Stolon Development Photoperiod • Favored by long days • High irradiance Temperature • Warm temperatures increase rhizome development Cultural factors that influence rhizome & stolon development: Mowing • Decreasing mowing height may increase lateral growth of stolons • Extremely close or frequent mowing will reduce CH2O needed for rhizome development Cultural factors that influence rhizome & stolon development: Nutrition • Excessive N impedes rhizome development • Frequent, moderate N applications increase stolon development Rhizome and Stolon Development Cool-season grasses Greatest production in late spring to early summer and during fall. Warm-season grasses Greatest production in summer and fall. Diagram of a grass crown. Apical meristem Primordial leaves Axillary bud Internode Node Adventitious root Primary root Leaf formation Shoot Apex Apical meristem Leaf primordia Expanding leaves Elongating leaf Immature enclosed leaf Mature leaf Senescing leaf Organization of leaves within the grass shoot showing progression of development from the crown. Upper & lower intercalary meristem. Upper intercalary meristem Collar Growing point Leaf primordia Lower intercalary meristem Crown Diagram of a grass crown. Apical meristem Primordial leaves Axillary bud Internode Node Adventitious root Primary root Rooting Root Growth and Development • Anchorage • Water absorption • Nutrient absorption • Soil stabilization/firmness/resiliency Root Growth and Development Root longevity • Primary root is short lived • Adventitious roots of most concern: Arise due to differentiation of cells at nodes Form entire root system in mature turf Exhibit seasonal growth patterns Root Anatomy Zone of differentiation Procambium Zone of cell elongation Zone of cell division Apical meristem Root cap Root Growth and Development Cool-Season Grasses • Primarily initiate roots during December to April Root Growth and Development Cool-Season Grasses • Primarily initiate roots during December to April • Minor initiation during cool periods of fall Root Growth and Development Cool-Season Grasses • Primarily initiate roots during December to April • Minor initiation during cool periods of fall • Elongation occurs during April to December Root Growth and Development Warm-season grasses • Primarily initiate roots during summer • May totally replace root system annually • Replacement usually coincides with spring greenup.