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PLANT PARTS
The four main plant parts are roots, stems, leaves, and flowers.
Each part has a unique structure and function.
The plant’s vascular system is found in roots, stems and leaves.
These tube-like structures carry water and dissolved nutrients
through the plant.
XYLEM - carries water and minerals from the roots up
PHLOEM - carries nutrients down through the plant from the
leaves
Why do water and nutrients move in these particular directions?
The vascular bundles in a stem contain the xylem and phloem.
Where would xylem and phloem be found in a leaf?
Let’s start with roots.
What jobs do roots do?
They: 1.) support and anchor the plant
2.) absorb water
3.) store food ( in the form of starch)
Can you name some roots that we eat?
Parts of a root
Root cap - provides protection for growing root
Epidermis - protective layer covering entire root
Root hairs - help to absorb water and minerals
Cambium cells - in center of root; divide to produce more xylem
and phloem
Roots can be taproots (one main root) or fibrous (many
small roots.)
STEMS
What jobs do stems do?
They: 1.) support the plant.
2.) hold leaves up to the light.
3.) contain xylem and phloem.
4.) may store water and starch.
Herbaceous stems are green, soft and flexible, like a flower stem.
Woody stems are brown and rigid, like a tree trunk.
LEAVES
What jobs do leaves do?
They: 1.) capture light.
2.) carry out photosynthesis
3.) carry out gas exchange.
The size and shape of leaves may change with their
needs and environment.
This is a cross-section of a leaf.
Cuticle - waxy, protective layer
Epidermis - protective skin
Mesophyll - spongy layer where photosynthesis occurs
Veins - contain xylem and phloem
Stomates - openings on leaf bottom; gas exchange
These are stomata as seen under a microscope.
The opening is protected and controlled by guard cells.
When the guard cells are full of water, they open the stomate.
When they have less water, they are smaller and the stomate is closed.
Transpiration - loss of water vapor through stomata
Stomata are usually open during the day and closed at night.
Can you explain why?
FLOWERS
What jobs do flowers do?
They carry out reproduction.
Petals - colorful to attract pollinators
Sepals - protective covering of flower bud
Stamen - male reproductive part; produces pollen; consists of:
a.) filament (stalk)
b.) anther (top)
Pistil - female reproductive part; contains ovules; becomes seed
bearing fruit; consists of: a.) stigma (sticky top)
b.) style (tube pollen travels down)
c.) ovary ( where fertilization occurs)
Pollination - pollen is transferred from anther to stigma
How might pollination occur?
Fertilization - pollen travels down style (pollen tube) to ovary
Where pollen and egg meet; becomes a seed and ovary becomes
fruit
Perfect flowers have both
pistils and stamens.
Imperfect flowers
have pistils OR
stamens.