Plant Growth and Development II

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Plant Growth and Development II

• "It is at the edge of a petal that love awaits.
• ...William Carlos Williams

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Primary Root Morphologycont.
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Root Morphology
The Zone of Elongation Cells Grow in
Size Vacuole Appears and Grows Mature
Organelles are Produced
The Zone of Mitosis Makes new cells by
Mitosis Meristematic Cells Divide by Mitosis
The Root Cap To reduce friction from growth in
soil The root cap secretes mucilage The root
cap sloughs cells
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RAMRoot Apical Meristem
Fig. 35.14
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RAMRoot Apical Meristem
produces new cells proximally and distally.
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Roots Radial View
Fig. 35.15
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More Root Morphologyimportant
Endodermis ...innermost layer of the cortex.
Casparian Strip suberin (fatty) band around
the endodermis.
Stele central cylinder within roots and stems
of dicots.
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Primary Root Morphology
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Pericycle

• outermost layer of the stele in roots, the
  source of nascent meristematic cells that gives
  rise to lateral roots,

root primordia form, protoderm, ground
meristem and procambium form, root cap forms,
pushes through the cortex, vasculature forms
between stele and differentiating derivatives of
the root primordium.
Fig. 35.16
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Today

• How do plant organs, tissues and cells develop?
• Examine Plant Growth,
• primary growth,
• secondary growth,
• cell elongation.

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Cell Growth new map?
Patterns of Development
Zygote
Embryo
Cotyledons Hypocotyl
SAM
Cell Differentiation
1o Growth
RAM
Root Tissues
1o Growth
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Lateral Meristems...

• provide for secondary growth by producing
  secondary vascular tissue and periderm (secondary
  dermal tissue).

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Secondary Growth of Stems

• Two Lateral Meristems,
• Vascular cambium produces secondary vascular
  tissue,
• Cork cambium produces tissue (periderm) that
  replaces the epidermis,
• secondary phloem and periderm comprise bark.

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Vascular Cambium
Fig. 35.20
see Fig. 35.22
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Secondary Growth Year 1
Fig. 35.21
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Lateral Meristem Cells
Fusiform initials meristematic cells that give
rise to xylem and phloem.
Ray initials meristematic cells that give rise
to (primarily) parenchyma cells that serve as
radial connections.
Tangential Section
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Secondary Growth Year 2
Fig. 35.21
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Secondary Growth
Fig. 35.21
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Secondary Growth
Fig. 35.22
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Assignment
same w/ root, w/o periderm.
Be able to construct a tree from a seedling using
these meristems, - at the tissue level.
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Growth / Differentiation

• Growth,
• the irreversible increase in size that (in
  plants) almost always results from both cell
  division and cell enlargement,
• Differentiation,
• the process by which a cell acquires metabolic,
  structural and functional properties distinct
  from those of its progenitor.

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Cell Division / Cell Walls / Cell Growth
Fig. 35.10c
Fig. 12.8
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Plane of Division
Fig 35.28
Fig 35.27
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Plant Cell Walls
Cell Morphology
Water Relations
Biochemistry
Plant Morphology
Pathogen Defense
Mechanical and Structural
Bulk Flow
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Cellulose / Cell Walls
Fig. 5.8
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Cell Wall Synthesis
Fig 35.29
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Cell Expansion
Biased Microfibril Distribution allows for
directional growth. Turgor water potential is
lowered in the cell, allowing water uptake. The
force of the water pressure drives cell
expansion.
Secondary Walls More ordered, restricts general
enlargement, often lignified (wood).
Primary Walls Less ordered, allows general
enlargement.
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Acid-Growth Hypothesis
1. Plasma Membrane H-ATPases acidify the
apoplast (cell wall).
2. Cell wall loosening enzymes are activated.
3. Electrochemical gradient drives solutes into
the cell, - lowers osmotic potential, H2O?
4. Vacuolar ATPase provides membrane potential
for transport of solutes into the vacuole, etc.
etc.
ATP hydrolases (ATPases)
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Transport

• Wednesday

Through Chapter 36, 748 - 754