Plant Structure and Growth

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Plant Structure and Growth

• Chapter 35

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Monocots vs. dicots
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Monocot or Dicot?
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Monocot or Dicot?
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Monocot or Dicot?
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Monocot or Dicot?
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Roots

• Fibrous Root systems
• Monocots
• Anchor plants tenaciously
• Prevent erosion
• Increases surface area for absorption of water
  and nutrients

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Taproot Systems

• Dicots
• Anchor plants firmly
• Stores food
• Carrots, turnips, sugar beets
• Can go far below ground
• Desert plants

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Root Hairs

• Epidermal extensions
• Increase surface area

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Symbiosis with fungi

• Most plants have mutualistic partnership with
  fungi forming a root/fungus structure called
  mycorrhizae
• Fungi absorb water and select minerals for host
  plant (HUGE surface area)
• Host plant nourishes fungus

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Stems

• Axillary Bud usually dormant bud, can form
  branch
• Terminal bud bud at shoot tip that has
  developmental leaves

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What is apical domiance?

• Concentration of growth at the tip of a plant
  shoot, where a terminal bud inhibits axillary bud
  growth
• Hormonally regulated (auxin produced from
  terminal bud)
• Adaptation allows for plant to get taller in
  shaded woods

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Why do owners of houseplants pinch them back?

• To remove the terminal bud, thereby removing
  inhibition of the axillary buds, causing branching

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Modified stems

• Stolons

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Modified Stems

• Rhizomes

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Modified Stems

• Bulbs

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Leaves

• Flattened blades
• Petioles join leaf to the stem node
• Not present in many monocots
• Monocots have parallel leaf veins
• Dicots have net-like leaf veins

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Cell Types

• Parenchyma
• Most abundant type
• typical plant cell
• Relatively unspecialized
• Thin primary cell walls
• Most ground tissue, sieve tube members, fruit
  tissue

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Cell types

• Collenchyma
• Thick primary cell walls
• Lack secondary walls
• Provides support for young shoot, petioloes
• Living, flexible, capable of elongating

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Cell types

• Sclerenchyma
• Supports
• Thick secondary cell walls
• Not capable of elongating (cant grow)
• May be dead at maturity (tracheids of xylem)
• Hemp, flax

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Tissue Systems

• Dermal tissue
• Protects
• Secretes waxy cuticle
• Root hairs
• Guard Cells, stomata

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• Vascular Tissue

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Xylem

• Transports water and nutrients up from the roots
• Tracheids and vessel elements (functional cells)
• All vascular have tracheids
• Angiosperms and few others have vessel elements
• Dead at maturity
• Pits connect tracheids
• Has thick secondary walls (often hardened with
  lignin), supports the plant

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Phloem

• Transports food from leaves to other parts of the
  plant
• Sieve tube members and companion cells
  (functional cells)
• Sieve tube members lack nuclei, ribosomes
• Alive at maturity
• Sieve plates connect sieve tube members

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Ground Tissue

• Photosynthetic
• Storage

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Vascular tissue organization

• Dicot root xylem forms a cross in the center

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Vascular tissue organization

• Monocot Root xylem and phloem alternate in a
  ring

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Vascular tissue organization

• Monocot Stem vascular bundles (combo of xylem
  and phloem) scattered
• Dicot stem vascular bundles arranged in a ring
  around the periphery

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Plant Growth

• Meristems
• def perpetually embryonic tissues
• Indeterminate growth
• Primary growth lengthens roots and shoots
• Secondary growth thickens roots and shoots

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Primary Growth

• Tip covered by root cap
• Protection
• Polysaccharide slime secretion
• Zone of cell division
• Zone of cell elongation
• Zone of cell maturation
• Quiescent center

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Secondary Growth

• Growth in girth
• Two lateral meristems (dicots)
• Vascular cambium
• Forms secondary xylem and phloem
• Secondary xylem accumulates (wood) while
  secondary phloem is sloughed off
• Cork cambium
• Forms cork
• Barkcork, cork cambium, and secondary phloem

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Leaves

• What is the ground tissue of the leaf?
• Mesophyll
• How is the mesophyll arranged?
• Spongy and palisade regions
• Spongy region has spaces for gas circulation

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