IB Biology Review Chapter 35: Plant Structure What are the

1
IB Biology Review

• Chapter 35 Plant Structure

2
What are the two types of plants IB focuses on?

• Angiosperms
• Monocots / Monocotyledonous
• Eudicots / Dicots / Dicotyledonous
• What do the names mean?
• Monocot One cotyledon
• Dicot Two cotyledons
• What is a cotyledon?
• Seed leaf

3
What are the main structures in a plant?

• Leaves
• Stem
• Roots
• Flowers

4
How does leaf structure differ in monocots and
eudicots?

• Monocots
• Parallel leaf veins
• Eudicots
• Netlike leaf veins

5
How does the arrangement of vascular tissue
differ in monocots and eudicots?

• Monocots
• Scattered throughoutstem
• Eudicots
• In a ring on the edge of the stem

6
How does the root structure differ in monocots
and eudicots?

• Monocots
• Fibrous root
• No main root
• Eudicots
• Taproot
• Primary root

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How does the number of flower parts differ in
monocots and eudicots?

• Monocots
• Petals etc. in multiples of 3
• Eudicots
• Petals etc. in multiples of 4 or 5

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Function of Leaf Tissues

• Palisade Mesophyll
• main photosynthetic cells (have many
  chloroplasts) in leaf
• located near top of leaf (sun) to maximize rate
  of photosynthesis
• Spongy Mesophyll
• near bottom of leaf where CO2 enters stomata and
  oxygen and water leaves
• air spaces between cells allow gas movement
• Xylem
• centrally located next to palisade mesophyll
• provides easy water and nutrient supply to
  palisade cells for photosynthesis

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Function of Leaf Tissues cont.

• Phloem
• centrally located next to palisade mesophyll
• takes away sugars produced by photosynthesis
• Guard cells and stomata
• located on the bottom of the leaf because that is
  where gas and water vapor exchange occur
• this way, no interference with photosynthesis
• Upper epidermis
• Top layer of cells where sun hits the leaf,
  covered with cuticle
• Cuticle
• waxy coating to prevent water loss

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Leaf and Leaf Tissue Structure

• Cuticle
• Upper / lower epidermis
• Palisade mesophyll
• Xylem
• Phloem
• Spongy mesophyll
• Guard Cell
• Stoma

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Stem Structure in Eudicots

• Consists of
• Epidermis
• Vascular Bundle
• Xylem
• Phloem
• Cortex
• Endodermis
• Pith
• BE ABLE TO DRAW THIS

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Function of Roots

• What do roots do for the plant?
• Absorb nutrients
• Absorb water
• Keep the plant in the ground
• For some, roots store excess energy
• What are root hairs?
• Small root-like projections off the root
• Increase surface area of root

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What are two modifications of leaves?

• Spines (as on a cactus)
• protect the plant from herbivory
• Tendrils (as on pea plant)
• help the plant cling to objects for support and
  growth

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What are two modifications of stems?

• Stolons (as on raspberry plant)
• horizontal stems that grow along the ground
  surface and allow the plant to extend itself
  into adjacent areas fast
• a form of asexual reproduction
• Bulbs (like onion)
• Vertical underground shoots consisting of
  enlarged leaves that store food

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What are two modifications of roots?

• Storage roots (like sweet potato)
• purpose is storage of starch and water
• Pneumatophores/ air roots (as in mangroves and
  bald cypress trees)
• these roots extend above the surface of the water
  in waterlogged soils to allow oxygen to get to
  the roots

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Two Types of Plant Growth

• Apical
• Vertical growth / height
• Lateral
• Sideways growth / width
• Which group of plants (monocots/eudicots) usually
  has both apical and lateral growth?
• Eudicots

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Apical and Lateral Growth

• Where does growth occur?
• Apical meristems
• Extend the length of root or stem
• Cell division occurs in meristematic region (zone
  of elongation) at the end of root or stem
• Lateral Meristems
• Increase girth of stem
• Cell division occurs in vascular cambium around
  stem

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Function of Auxin

• plant hormone that stimulates cell elongation
• one of the processes that auxin controls is
  phototropism
• directional growth toward the source of light
• shoot tips respond to light intensity by
  producing more auxin on the side with less light,
  making that side grow longer, thus bending the
  shoot tip toward the light

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Function of Auxin
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1. Outline three differences between the
structures of dicotyledonous (eudicot) and
monocotyledonous plants.
(6 marks)
IB Exam Question

• Monocots
• One cotyledon
• Parallel leaf veins
• Scattered vascular tissues
• Fibrous root system
• Flower parts in multiples of 3

• Eudicots
• Two cotyledons
• Net-like leaf veins
• Vascular tissue arranged in rings
• Taproot or primary root
• Flower parts in multiples of 4 or 5

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2. The leaves of plants are adapted to absorb
light and use it in photosynthesis. Draw a
labelled diagram to show the arrangement of
tissues in a leaf. (6 marks)
IB Exam Question

• Award 1 for each of the following structures,
  shown in the correct relative position and
  labelled. Individual cells are not needed but do
  not penalize if they are shown.
• upper epidermis
• palisade layer / mesophyll
• spongy layer / mesophyll
• lower epidermis
• xylem (in a major or minor vein)
• phloem (in a major or minor vein)
• guard cells (do not accept stoma/stomata only)

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3. Draw and label the tissues within a leaf and
explain the relationship between the distribution
of those tissues and their function.
(12 marks)
IB Exam Question

• palisade mesophyll Main photosynthetic cells in
  leaf, located near top of leaf to maximize rate
  of photosynthesis
• spongy mesophyll Near bottom of leaf where Co2
  enters stomata and oxygen and water leaves air
  spaces between cells allow gas movement.
• xylem Centrally located next to palisade
  mesophyll to provide easy water and nutrient
  supply to palisade cells for photosynthesis
• phloem Centrally located next to palisade
  mesophyll to take away sugars produced by
  photosynthesis
• guard cells Located on the bottom of the leaf
  because that is where gases enter. This way, no
  interference with photosynthesis
• upper epidermis On top of leaf they have a
  waxy coating to prevent water loss (sun is
  hitting top)

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4. Identify and describe modifications of roots,
stems, and leaves for different functions ( 10
marks)
IB Exam Question

• Storage roots (like sweet potato) purpose is
  storage of starch and water
• Pneumatophores / air roots (as in mangroves and
  bald cypress trees) these roots extend above the
  surface of the water in waterlogged soils to
  allow oxygen to get to the roots
• Stolons horizontal stems that grow along the
  ground surface and allow the plant to extend
  itself into adjacent areas fast. Is a form of
  asexual reproduction
• Bulbs (like onion) vertical underground shoots
  consisting of enlarged leaves that store food
• Spines (as on a cactus) protect the plant from
  herbivory
• Tendrils (as on pea plant) help the plant cling
  to objects for support and growth

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5. Compare growth due to apical and lateral
meristems in dicotyledonous plants. (3
marks)
IB Exam Question

• Apical meristems
• Extend the length of root or stem
• Cell division occurs in meristematic region (zone
  of elongation) at the end of root or stem
• Lateral Meristems
• Increase girth of stem
• Cell division occurs in vascular cambium around
  stem

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6. Explain the role of auxin in phototropism.

(6 marks)
IB Exam Question

• shoots of plants grow towards light / positively
  phototropic
• roots grow away from light / regularly
  phototropic
• shoot tips produce auxin
• acts as a growth promoter
• allows cell expansion
• is distributed in the tip from the lighter to the
  darker side
• plant bends towards the light