Plant Structure

Plant Structure

6 Volunteers please!

What we need to know!

The structure and function of the leaves, stem and roots.

Discuss with the person next to you.. Functions of each part of the plant

Leaf

Stem

Roots

Tissue system and its functions

Component tissues

Location of tissue systems

Dermal Tissue System• protection• prevention of water loss

EpidermisPeriderm (in older stems and roots)

Ground Tissue System• photosynthesis• food storage• regeneration • support• protection

Parenchyma tissueCollenchyma tissueSclerenchyma tissue

Vascular Tissue System• transport of water and minerals• transport of food

Xylem tissuePhloem tissue

The Stem

3 Main Functions!

• Provides support for the plant

• Transports water from the roots to the leaves and rest of plant

• Transports glucose from the leaves to the parts of the plant that need it. Ok… so how????

So…Xylem and Phloem make up the transportation system of the plant.

They are like the circulatory system of the plant

The xylem of a plant is the system of tubes and transport cells that circulates water and dissolved minerals.

As a plant, you have roots to help you absorb water. If your leaves need water and they are 100 feet above the ground, it is time to put the xylem into action!

A one way system - root to leaves

XYLEM

Xylem is made of vessels that are connected end to end for the maximum speed to move water around. They also have a secondary function of support.

When someone cuts an old tree down, they reveal a set of rings. Those rings are the remains of old xylem tissue, one ring for every year the tree was alive

Enter phloem.The phloem cells are laid out end-to-end throughout the entire plant, transporting the sugars and other molecules created by the plant. Phloem is always alive.

PHLOEM FUN!!

What is the best way to think about phloem? Think about sap coming out of a tree. That dripping sap usually comes from the phloem.

Phloem

2 way process!

Roots to shoots to leaves and back again

So how does the stem have a role in photosynthesis??

2 Minutes to discuss with person next to you

The Roots

• Hold plant in position

• Absorb water and minerals from the soil

• Have specialised cells to increase surface area for water intake

Function

Carrots are one giant root!!

Radish Plant

Root hairs

Fragile parts of cells that grow from the main root

They massively increase the surface area for absorption

1. Root Hairs: increase surface area for water & mineral absorption

2. Meristem: region where new cells are produced

3. Root Cap: protects tip of growing root

The Structure of a RootRoot Hairs

Meristem

Root Cap

XylemPhloem

Root Types

2. Tap Roots –larger central root reaches deep water sources undergroundEx. Trees, Carrots, & Dandelions

1. Fibrous Roots: Branching roots hold soil in place to prevent soil erosionEg. Grasses

So what role to roots play in photosynthesis??

2 mins to discuss!

Leaves!

1. Main photosynthetic organ

2. Broad, flat surface increases surface area for light absorption

Leaf Functions!

3.Have systems to prevent water loss

• Stomata open in day but close at night or when hot to conserve water

• waxy cuticle on surface

4. System of gas exchange

• Allow CO2 in and O2 out of leaf

Leaf Functions!

Greener on top

CO2 gets in here

Leaf Structure

Most of the chlorophyll

CO2

Leaf cell - palisade

Position?Upper

surface of leaf

Features?Box shape

ChloroplastsFunction?

Photosynthesis

Most of the chlorophyll

CO2

Gas exchange Leaves are designed to allow

carbon dioxide to get to the main chlorophyll layer at the top of the leaf

They have small holes called stomata on the under surface

Each hole is open & closed by 2 guard cells

Stoma position

Stoma is a small holeIts size is controlled by 2 guard cells

closed open

Stoma function is for gas exchange in the leaf

Carbon dioxide

oxygenGuard cell

Provided plant is photosynthesising

Stomata open and close at different times of the day

When it is light the plant needs CO2 for photosynthesis so the stoma open

At night (darkness) they close

So we’ve said the stoma allows for gas exhange i.e. CO2 in and O2 out..

How does this happen??

What is diffusion???

So thinking about photosynthesis.. How does CO2 enter the leaf by diffusion and how does O2 leave by diffusion??

HOMEWORK

Construct a poster of a NZ native plant. Label with plant parts and the functions of them relating to photosynthesis – make them pretty!!