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Plants
Structure, Growth, & Development
Plant Structure Introduction
https://www.youtube.com/watch?v=DGpPHrLF-5M
Parts of a Seed
Seed


Each seed contains a plant embryo
Each seed also contains food for the embryo
 A tough outer case protects the embryo,
known as a seed coat
Parts of a Seed

External seed coat
 Developing plant embryo
 Stored food called endosperm
Seed Dispersal
 The
main function of the fruit is to disperse
the seeds
 Four Types:
• Self dispersal
• Wind dispersal
• Water dispersal
• Animal dispersal
Seed Dormancy

Ensures that the seed will germinate only when
there are optimal conditions

Plants stay dormant until the right
environmental conditions
Seed Germination

Seeds do not always germinate right away;
can wait for long periods of time to grow

Seed need water, nutrients and the right
temperature to grow
Order of Growth
embryonic root, embryonic shoot, leaves
Seed Labeling

You have 5 minutes to complete the diagram
Lima Bean Dissection
https://www.youtube.com/watch?v=pQYJ2PSDu3A
Plant Growth & Tissue
Meristems

Plant cells that contain stem cells

Apical meristems
• Elongate shoots and roots through primary growth
• Located at the tips of roots and in the buds of
shoots

Lateral meristems
• Add thickness of stems and roots through
secondary growth
Tissue Systems

Dermal tissue system
 Consists of the epidermis

Ground tissue
 Various cells specialized for:
 Storage
 Photosynthesis
 Support
Three Tissue Systems:
Dermal, Vascular, & Ground

Each plant organ has…
 Dermal, vascular, and ground tissues
Dermal
tissue
Ground
tissue
Vascular
tissue
Vascular Tissue

Vascular tissue system
 Transport of materials between roots and shoots

Xylem
 Transports water upward from roots into the shoots

Phloem
 Transports nutrients from where they are made to
where they are needed
Vascular Tissue
Roots
Roots

Root Structure
 Apical meristem
 New cells along roots & stem; differentiate into other tissue
 Root Cap
 Protects root as it grows

Key role in water & mineral transport
Roots

Anchor plants firmly in the ground
 Absorb
water and minerals
from the soil
 Some
roots can be used
to grow a new plant
Types Roots

Fibrous roots
• Multiple smaller roots

Tap roots
• Large main central root
Roots

Absorption of water & minerals near root tips
• Large numbers of tiny root hairs increase the
surface area of the root
 Minerals use active transport
Roots Labeling

You have 5 minutes to complete your
roots diagram
Stems
Stems

Structure
 Produce leaves, branches, and flowers
 Hold leaves up
 Transport substance between roots and leaves

Transport system
Stems
 Xylem and phloem
 Major tubule systems
 Transport water & nutrients
 Nodes
 Attachment for leaves
 Internodes = stem between nodes
 Petiole
 “Stem” of the leaf
Types of Stems

Woody
 Thick cell walls
 Trees, shrubs, and vines

Herbaceous
 Supported by hydrostatic pressure (turgor)
 Dandelions, zinnias, petunias
Underground Stems

Tubors
 Used to store food for the plant

Bulbs
 Allows the plant to be dormant
with cold temperature

Rhizome
 Horizontal underground stem = produces
shoot and root systems of a new plant
Stems

Lenticles
• Pore in the stem providing
direct gas exchange

Buds
• Undeveloped shoot from which
embryonic leaves or flower parts arise
Transport in Plants
 Capillary
action
• Tendency of water to rise in a thin tube
• Adhesion & cohesion
Leaves
Leaves

Sight of photosynthesis

Anatomy
 Cuticle – covers and protects leaf
 Blade – thin flattened section
 Petiole – stalk that attaches stem to blade

Covered by epidermis and cuticle
 Create water proof barrier
Mesophyll & Stomata

Mesophyll – site of photosynthesis
 Palisade mesophyll – absorb light
 Spongy mesophyll – air space for gas diffusion

Stomata – pores on the underside of the leaf
 CO2 enters  O2 + H2O exit
 Most active during the day

Guard Cells – open and close stomata
Leaf Adaptations

Excess of Sunlight
• Thick cuticle
• Small/narrow leaves

Limited Sunlight
• Thin cuticle
• Large/broad leaves
Transport & Tropisms
Transport in Plants

Transpiration
 Osmotic pressure moves water
out of vascular tissue
 This pulls water up from the stem
to the leaves
 Affected by heat, humidity, wind
Gravity

Response to gravity is gravitropism
 Roots show positive gravitropism
 Stems show negative gravitropism
Hydrotropism
 Roots
grow toward water (positive)
Thigmotropism

Growth in response to touch
 Plant grows toward (+) or away from (-) pressure
•
Vines and other climbing plants
Thermotropism

Plant response to temperature
Phototropism
 Plants grow toward a
source of light
Tropisms
https://www.youtube.com/watch?v=pCFstSMvAMI
Plant Hormones
Plant Hormones & Tropisms

Hormones
• Chemical signals that coordinate growth,
development, and responses to stimuli
• Tropisms are often caused by hormones
Auxin

Any chemical substance that promotes cell
elongation (growth) in different target tissues

Formation & branching of roots
Gibberellins

Stem elongation (growth)
 Fruit growth
 Seed germination
Cytokinins

Stimulate cell division
 Found in actively growing tissues
Ethylene
“Aging” hormone
 Causes fruits to ripen
