Roots, Stems, and Leaves

1
Roots, Stems, and Leaves

• Plant Organs

2

• Roots Absorb water and nutrients
• Anchor plants in ground
• Stems support plant body
• transport nutrients among plant parts
• Leaves carry out photosynthesis
• funnel water to roots exchange sites for
  oxygen and carbon dioxide

3
Root, Stem, and Leaf Tissues
Section 23-1
Leaf
Stem
Root
Dermal tissue Vascular tissue Ground tissue
4
Tissue Systems

• Dermal outer covering of plants
• single layer of epidermal cells
• covered with waxy cuticle that protects
  against water loss
• Vascular xylem and phloem carry water and
  nutrients through the plant
• Ground parenchyma, collenchyma,
  schlerenchyma, support the plant and site
  of photosynthesis
• Meristematic only in tips of shoots and roots,
  responsible for plant growth

Page 581
Page 582
Page 583
Page 580
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Fibrous Roots vs. Taproots

• Fibrous roots are shallow and wide-reaching
• Taproots are DEEP and concentrated downwards

See pages 584-585 in text
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Figure 35.14 Primary growth of a root
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Water Transport in a Root
Section 23-2
Epidermis
Endodermis
Cortex
Casparian strip
Cell wall
Root hairs
Cell membrane
Cortex
Phloem
Active transportof minerals
Xylem
Movement of water by osmosis
VascularCylinder
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Figure 35.3 Radish root hairs
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Figure 35.18 Organization of primary tissues in
young stems
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Layers of a Tree Trunk
Section 23-3
Wood
Bark
Cork
XylemHeartwood
Cork Cambium
Phloem
Vascular Cambium
Xylem Sapwood
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Stem adaptations

• See page 594
• Tuber stem growing underground (potato)
• Bulb central stem surrounded by leaves
• (amaryllis)
• Corm thickened stem that stores food
  (gladiolus)
• Rhizome horizontal, underground stem
• (ginger)

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Figure 35.5 Simple versus compound leaves
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The Internal Structure of a Leaf
Section 23-4
Cuticle
Veins
Epidermis
Palisademesophyll
Xylem
Vein
Phloem
Spongymesophyll
Epidermis
Stoma
Guardcells
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Transpiration
Section 23-5
A
B
Evaporation of water molecules out of leaves.
Pull of water molecules upward from the roots.
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Function of Guard Cells gas exchange (CO2 in,
O2 out)
Section 23-4
Guard cells
Guard cells
Inner cell wall
Inner cell wall
Stoma
Stoma Open
Stoma Closed
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Figure 35.6 Modified leaves Tendrils, pea plant
(top left) spines, cacti (top right) succulent
(bottom left) brightly-colored leaves,
poinsettia (bottom right)
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Water tranport

• Capillary action water moves upward through
  narrow tubes against the force of gravity
  (adhesion and cohesion)

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Food Transport

• Movement from source (where sugars are produced
  by photosynthesis) in leaves to
• where sugars are used or stored