Plant Structure, Growth, and Development

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Plant Structure, Growth, and Development
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• Plant hierarchy
• Cells
• Tissue group of similar cells with similar
  function Dermal, Ground, Vascular
• Organs multiple kinds of tissue, very diverse
  function
• Organ systems
• Organism

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Roots
35.1

• Roots
• an organ that anchors a vascular plant.
• Absorbs water inorganic nutrients
• Storage of nutrients
• Types of roots
• Taproot Systems
• Consist of one main vertical root
• Gives rise to lateral roots (like branches)
• Taproots store organic nutrients used in
  flowering and fruit production.
• Fibrous Root System a mat of roots that spread
  out below the soil
• Root Hair an extension of a root that gathers
  nutrients
• Root cap covers root tip (apical meristem)
  primary growth site
• epidermis, ground and vascular tissue.
• Mycorrhizae mutualistic fungi and plant roots.

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Roots Cont.
http//belizebreeze.com/images/lamanai_tree_roots_
rev_lowres.jpg
http//quorumsensing.ifas.ufl.edu/HCS200/images/st
emsroots/korni.jpg
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Stems

• an organ consisting of an altering system of
• nodes point where leaves are attached
• internodes stem segments between nodes
• Axillary bud a structure that potentially forms
  a lateral shoot otherwise known as a branch
• At the end of this branch is a terminal end which
  develops leaves.
• Apical Dominance
• A phenomenon where the proximity of the terminal
  bud inhibits the growth of an axillary bud
• This is an evolutionary adaption where resources
  are concentrated toward elongation it also
  increases the plants exposure to light.
• If one is removed then the bud stimulates the
  growth of an axillary bud which produces more
  shoots.
• That is why pinching back a plant makes it
  bushier.

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Apical Dominance
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Stems Cont.
http//www.infovisual.info/01/015_en.html
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Xylem and phloem
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Sieve cells
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Leaves

• the main photosynthetic organ of vascular plants
• Leaves usually consist of
• blade
• petiole Joins the leave to a node on the stem
• veins vascular tissues of the leaves
• Veins are how monocots and dicots differ
• Monocots have parallel veins
• Endicots are multi branched
• There are many different types of modified leaves
  
• Spines, tendrils, storage, bracts (poinsettias),
  reproductive (succulents)

http//photos.somd.com/data/500/LEAF.jpg
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http//academic.kellogg.cc.mi.us/herbrandsonc/bio1
11/images/stems/stems.4.jpg
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Three Types of Tissue Dermal, Vascular, and
Ground

• Tissue system one or more tissues organized
  into a functional unit
• Dermal Tissue System
• Outer protective covering (like skin)
• Non woody plants single layer of epidermis
• Cuticle A waxy coating on the leaves and the
  stems that helps prevent water loss.
• Woody plants periderm replaces epidermis
• Vascular Tissue System
• Carries out long distance transport between root
  and shoot.
• Two vascular tissues
• Xylem conveys water and dissolved mineral up to
  shoots
• Phloem transports organic nutrients to where
  they are needed.
• Vascular tissue of a root stele
• Ground Tissue System
• Tissues that are neither dermal nor vascular

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Tissue System
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
leafstru.gif
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Plant Cells

• Type of cells found in plants
• Parenchyma Cells a relatively unspecialized
  plant cell type that carries out most of the
  metabolism, synthesizes and stores organic
  products, and develops into a more differentiated
  cell type.
• Guard cells
• Sieve tube cells
• Tracheoid cells
• Palisade mesophyll Photosynthesis
• Spongy mesophyll spaces allow the exchange of
  gases

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Meristems generate cells for new organs
35.2 - 35.4

• Apical meristems elongate shoots and roots
  through primary growth
• With the process of primary growth it also allows
  roots to extend throughout the soil and for
  shoots to increase there exposure to light and
  CO2
• Lateral meristems add girth to woody plants
  through secondary growth.
• Root cap secretes a mucus that allows tip growth
  through soil

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Primary Growth Roots

• Primary growth produces the primary plant body.
• ROOTS the root tip is covered by a thimble-like
  cap which protects the vulnerable apical meristem
  as the root pushed through the soil.
• GROWTH occurs just behind the root tip, zone of
  cell division, elongation, and maturation.
• The zone of cell division produced in the
  apical meristem
• The zone of elongation, root cells elongate and
  new cell are added allowing the root to dive
  further into the soil.
• The zone of Maturation, cells complete their
  differentiation and become functionally mature.

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Primary Growth of Shoots

• The apical meristem of a shoot is a dome shaped
  mass which is located in the terminal bud, where
  it gives rise to a repetiton of internodes and
  leaf bearing nodes.

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The Vascular Cambium and secondary Vascular tissue

• The vascular cambium develops from parenchyma
  cells into a meristematic cylinder that produces
  secondary xylem to the inside and secondary
  phloem to the outside.
• Older layers of secondary xylem (heartwood)
  eventually become inactive.
• Younger layers (sapwood) still conduct water.
• Only the youngest secondary phloem is active.

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Cork Cambia and the Production of Periderm

• The cork cambia is a lateral meristem
• Makes dermal tissue or periderm.
• The bark on the other hand consists of all the
  tissues external to the vascular cambium which
  include secondary phloem and periderm.

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Growth, Morphogenesis, and the Differentiation
Produce the Plant Body



35.5

• Morphogenesis The development of body form and
  organization Each cell in the plant body contains
  the same set of genes, exact copies of the genome
  present in the fertilized egg.
• Different patterns of gene expression among cells
  cause the cellular differentiation that creates a
  diversity of cell types.
• The three developmental processes of growth,
  morphogenesis, and cellular differentiation act
  in concert to transform the fertilized egg into a
  plant.

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Growth Cell Division and Expansion

• Cell division and self-expansion are primary
  factors for growth
• Plant cells rarely expand in all directions,
  their greatest expansion occurs in the plants
  main axis.
• Growing plant cells expand mainly through water
  uptake. In a growing cell, enzymes weaken
  crosslinks in the cell wall, allowing it to
  expand as water diffuses into the vacuole by
  osmosis.
• Orientation of the cytoskeleton also affects
  direction of cell elongation by controlling the
  orientation of cellulose micro fibrils.

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Preprophase Band
http//www.nature.com/nrm/journal/v2/n1/images/nrm
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Differentiation and Pattern Formation

• Development of tissues and organs in specific
  locations (pattern formation) depends on cells
  ability to detect and respond to positional info.
  
• Polarity-is the idea that a cell (egg) has diff.
  concentration of contents
• Homeotic genes often control morphogenesis and
  also mediate many of the other events in an
  individuals development, such an initiation of
  an organ.
• Gene Expression and control of Cellular
  Differentiation
• Cellular differentiation selective gene
  expression
• Cellular differentiation depends on a large
  extend on positional information, where a
  particular cell is located relative to other
  cells.

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Gene Expression
http//www.biosci.ohio-state.edu/bdinglab/Researc
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Shifts in Development Phase Change

• Internal or environmental cues may cause a plant
  to switch from one developmental phase to
  another.
• From the development of juvenile leaves to the
  development of mature leaves, these are called
  phase changes.

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Juvenile vs. Adult Leaves
http//upload.wikimedia.org/wikipedia/en/c/ce/Pinu
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Genetic Control of Flowering

• Research on organ identity genes in developing
  flowers provides an important model of pattern
  formation.
• The ABC model of flower formation identifies how
  3 classes of organ identity genes control the
  formation of sepals, petals stamens, and
  carpels.
• The floral organs develop in four circles, or
  whorls Sepals form the fourth (outermost) whorl
  petals form the third stamens form the second
  and carpels form the first (innermost) whorl.
  Plant biologists have identified several organ
  identity genes that regulate the development of
  this characteristic floral pattern. Organ
  identity genes, also called plant homeotic genes,
  code for transcription factors. Positional
  information determines which organ identity genes
  are expressed in a particular floral organ. The
  result is development of an emerging leaf into a
  specific floral organ, such as a petal or a
  stamen.