Key Words And Concepts From Lecture 11 Bio106

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Plant Development

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The sum of all changes that progressively elaborate an organism's body.

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Plant growth adn development is broken into three groups:

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Growth
Morphogenesis
Differentiation

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Plant growth is Indeterminate

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carries on through the life of a plant.
Can be: Annuals-complete life cycle in 1 yr.
Biennials- complete life cycle in 2 yrs.
Perennials- live many years

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Indeterminate growth is made possible by:

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Meristems

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Growth

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is irreversible increase in size resulting from cell division and cell enlargement.
Starts at fertilization

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Morphogenesis

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the processes giving rise to body shape and organization. Begins in early divisions of embryo.

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Cellular Differentiation

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divergence in structure adn function as cells become specialized.

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Cell division and expansion is guided by the cytoskeleton

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Plant shape depends upon spatial orientations of cell divisions and cell expansions.
Orienting cell division
Orienting the plane of cell expansion: cells expand when cell wall yields to turgor pressure.

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Expansins

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A protein that causes cell walls to stretch.

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Microtubules

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dictate the direction of expansion. Also dictate orientation of cellulose microfibrils

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Seeds

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From seed to seedling: Initial phase: Imbibition- the absorption of water occurs readily due to the low water potential of a dry seed.

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Primary Growth

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Apical meristems extend roots and shoots by giving rise to the primary plant body.

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Meristems

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on division one cell remains called the intital meristem, and the other a derivative.
Apical Meristems: at the tip of roots and shoots, source of primary growth.
Lateral Meristems: cylinders of dividing cells extending through tissues, adds new layers to vascular tissue and thickens epidermis.

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3 primary meristems

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Protoderm
Procambium
Ground Meristem

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Zone of cell division related to the zone of elongation.
Zone of maturation

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Zone of cell division blends into the zone of elongation.
Elongation is responsible for pushing the root tip ahead. Sustains growth by adding cells to the youngest end of the zone.
Zone of maturation: bells begin to specialize in structure and function.

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Protoderm

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The outermost primary meristem, produces the single cell layer of the epidermis

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Procambium

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Produes the Stele.
It's a central cylinder of vascular tissure wher xylem and phloem develop.

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Lateral Roots

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Established roots may sprout Lateral Roots from outermost layer of stele or Pericycle.

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Shoot apical meristem

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a dome of dividing cells at the tip of the terminal bud.

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Primordia

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At the edges of leafs, grow to form leaves.

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Axillary buds

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may form branches later in development.

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Secondary growth of shoots

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later meristems add girth by producing 2" vascular tissue and periderm.

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Vascular Cambium

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produces xylem and phloem.
Also is the vascular meristem in woody stems

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Cork Cambium

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Produces a tough external covering for roots and stems that replaces epidermis.
Cylinder of meristematic tissue that produces protective layers that cover plant body.

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Vascular Cambium exists in two forms

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1. Fusiform intitals: form the Axial System
2. Ray intitals: form the Radial System.

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Periderm

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Phelloderm plus cork cambium plus cork cells

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Bark

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all tissues external to the vascular cambium. (phloem plus periderm)

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Lenticels

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spongy regions in cork which permit gas exchange

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Hearwood

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no longer conducts water but its fosrm a central column that supports the tree.

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Sapwood

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Functions in the upward transport of water and minerals, called the xylem sap

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wood

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Secondary xylem

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Conifer wood

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only tracheids, has resin ducts

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Angiosperm wood

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typically has vessels more parenchyma in rays

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Dendrochronology

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Tree rings tell us more than age, width of rings is related to environmental conditions v. consistent conditions, can give insight to climatic patterns

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Reaction Wood
2 forms

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1. In conifers: Comprssion wood
2. In angiosperms: Tension wood