Transcript Plant Evolution and Classification

Plant Structure and Function
Chapter 29
Plant Growth
• Meristems – where plant growth originates
– region where cells continuously divide.
1) Apical meristem
2) Intercalary
3) Lateral meristem
Type
Location
Growth
Function
Apical
meristems
(primary
growth)
Intercalary
meristems
(primary
growth)
Tips of stems
and roots
Increase length
at tips
Lateral
meristems
(secondary
Between the tip Increase length
and base of
between nodes
stems and
leaves
Sides of stems
and roots
Increase
diameter
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Roots
Types of Roots
• Taproot: If the first/ primary root produced by
a sprouting seed becomes the largest
Types of Roots
• Fibrous root system: The primary root does
not become large, but develops into
numerous small roots
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Types of Roots
• Adventitious roots:
specialized roots that
grow from stems or
leaves
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Root Structures
• Root cap
– Cover apical meristem
– Produces a slimy substance that acts like a
lubricant
Root Structures
• Root hairs
– Extensions of epidermal cells
– Increase surface area
– Mycorrhiza (fungus)
Apical meristem
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Root Functions
• Anchoring plant
• Absorb water and a variety of minerals
• Store carbohydrates or water
Stems
Chapter 29
Stems
• Involved in the transport and storage of
nutrients and water.
• Support leaves
• Various differences in shape and growth
represent adaptations to the environment.
Stem Structures
•
•
•
•
Grow only in length at their tips.
Each leaf is attached at a node.
Divided into segments called internodes.
At the end of the internode is a bud.
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Stem Functions
• Transportation of Nutrients
• Storage
– Stores water and nutrients
• Transport Water
– Occurs in the xylem of all plant organs
– Transpiration
Leaves
Chapter 29 Section 4
Leaves
• Extremely variable which, like stems,
represents adaptations to the environmental
conditions.
Leaf Shape
• Blade
– The broad flat, portion
of a leaf
• Petiole
– Stalklike, where blade
attaches to stem
Leaf Shape
• Simple
– Single leaf
• Coumpound
– Divided into leaflets
Leaf Structure
•
•
•
•
Cuticle
Epidermis
Mesophyll
Vascular Bundle
Epidermis
• Represents the dermal tissue
• A single layer of cells coated with a cuticle
• Epidermal hairs protect against insects and
intense light
Mesophyll
• Where photosynthesis occurs
• Ground tissue
– Made up of chloroplast-rich parenchyma cells
• Organized into 2 layers
– Palisade mesophyll: most photosynthesis
– Spongy mesophyll: gas exchange
Veins aka Vascular Bundles
• Continuous with the vascular tissue of the
stem and petiole
• Embedded in the mesophyll
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Leaf Functions
• Primary site of photosynthesis in most plants.
• Mesophyll cells use light energy, CO2, and
water to make sugars.
• MAJOR LIMITATION to photosynthesis is
insufficient water due to transpiration.
Capturing Light
• Adapt to environment to maximize light
interception
Gas Exchange
• Controlled by the stomata
• The stomata is open during the day and close
at night
• Guard cells
– Modified cells
– Regulated by the amount of water in it
Guard Cells