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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.