[PPT]11. Transport in Plants - IGCSE Coordinated Sciences - … · Web viewTitle 11. Transport in Plants Subject GCSE Additional Science - Biology (Spring 2007) Author Boardworks

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How do plants get what they need?

Like all organisms, plants have to get materials for growth from their environment. Plants must then get these nutrients to the part of the plant that needs them.

What do plants need for healthy growth?

minerals

carbon dioxide for photosynthesis

water

oxygen for respiration

sunlight

Where do plants get these nutrients?


Moving materials

How do plants transport materials to where they are needed?


How are plants adapted for transport?

The structures of cells and tissue in different parts of the plant are adapted to allow transportation of essential materials.

Leaves are entry and exit points for the gases needed by plants.

Roots absorb water and minerals from the soil.

Stems connect the roots to the leaves, flowers and fruits. They contain cells specially adapted for transportation of water, minerals and sugars.


What are the functions of plant parts?



Which cells transport nutrients?

The cells are arranged in plants as vascular bundles.

Plants contain two types of cell adapted for transportation.

Phloem cells transport sugars produced in the leaves up and down the stem to growing and storage tissues.

Xylem cells transport water and minerals up the stem from the roots to the shoots and leaves. This transport occurs in one direction only.

Both phloem and xylem form continuous systems connecting roots, stems and leaves.


Inside a plant stem


What are vascular bundles?


How is xylem adapted for transportation?

Xylem vessels have thick cellulose cell walls, strengthened by lignin. The inside of the cell is hollow. Xylem vessels are dead cells.

The thick walls of xylem cells also help support plants.

Water and minerals travel in xylem vessels.

Xylem vessels transport water and minerals from the roots to the shoot and leaves. This transport only occurs in one direction.


Sugars are carried from the leaves to the growing and storage parts of the plants. This movement takes place in both directions.

How is phloem adapted to transportation?

Phloem is made of columns of living cells. They transport food, in the form of sugars.

Phloem cells are also called sieve tubes. Cells are joined by small holes in the cell wall at the end of each cell, forming a continuous system. The end cell walls are called sieve plates.


Cells in the vascular bundles



Do plants produce waste?

All animals eat food to survive.

Does this mean they do not produce any waste?

Not all of the food can be used by the body, so eventually some will exit the body as waste.

Oxygen is made during photosynthesis but not all of it is used by the plant. It is a waste product.

Plants are different from animals because they produce their own food through the process of photosynthesis.

How is it removed from the plant?


How do gases move in and out of plants?

When the concentration of carbon dioxide inside the plant is low, it will diffuse in from the air, through pores in the leaves into the plant cells.

Plants use carbon dioxide during photosynthesis and produce oxygen. These gases move in and out of the plant through the leaves by diffusion.

If the concentration of oxygen is high inside the plant, it will diffuse from the plant cells through the pores and into the air.


How are leaves adapted for diffusion?

The diffusion of gases occurs in the leaves. They are adapted for this function in the following ways:

Leaves are thin. This decreases the distance gases have to travel between the air and cells.

There are air spaces between cells. This increases the speed of diffusion from the air to the cells inside the leaf.

There are lots of stomata (pores) on the undersides of leaves. These let gases in and out.


What are stomata?

On the underside of leaves are small holes, or pores, called stomata. A single hole is called a stoma.

Each stoma is surrounded by two guard cells, which control the opening and closing of the stoma.

When carbon dioxide levels are low inside the plant, the guard cells gain water and become turgid. They curve out, opening the stoma and allowing gases in and out. Water also evaporates through stomata.

High carbon dioxide levels cause the guard cells to lose water, closing the stoma.

What would happen if the stomata were permanently open?


Opening and closing of stoma


Diffusion of gases



How do tall trees get enough water?

Redwoods are the tallest species of tree in the world.

How does a plant this size get water from its roots to the branches at the top?

What experiment could show that water travels up stems?

The tallest redwood ever measured was 120 metres tall. That is six times the height of the Angel of the North!

The water will travel up the stem, or trunk, of the tree.


Movement of water up a stem


What is transpiration?

Although it may seem bad for plants, transpiration actually moves water from the roots to the top of the plant, without using energy. How does this work?

Water always moves from an area of high concentration to an area of low concentration. This movement of water is a type of diffusion called osmosis.

Transpiration is the loss of water by evaporation from plants.

Plants lose water when they open the stomata in the leaves to let in carbon dioxide.

Air around the plant usually contains less water than the cells of the plant, so water evaporates into the air.


Transpiration


humidity (amount of moisture in the air)

Is the rate of transpiration constant?

The speed at which a plant loses water is called the rate of transpiration. This varies depending on the plant’s environment.

Transpiration is a bit like a straw, pulling water up the plant. Sometimes the pulling force will be stronger and the plant will lose more water.

What environmental factors will affect the rate of transpiration?

light intensity

temperature

air movement (wind).


Why does transpiration vary?


How is the rate of transpiration measured?

Transpiration can be measured using a potometer.

A cut plant stem is sealed into the potometer using a rubber bung.

This gives an indirect measurement of the rate of transpiration.

An air bubble is introduced to the capillary tube.

The distance the bubble travels shows how much water the stem has taken up.


Transpiration – true or false?



How are roots adapted to their function?

Roots contain thousands of tiny root hair cells, which project out into the soil.

The roots of this hyacinth bulb are long and thin. They have formed a fine network, filling the available space.

How do these features make roots suitable for absorbing water and minerals?

high surface area to volume ratio maximum contact with the soil

firm anchorage.


How do minerals enter plants?

Like water, minerals enter plants through the roots. However, they do this by different methods.

Water passively diffuses with a concentration gradient from the soil into the roots and up the stem.

Diffusion cannot take place against a concentration gradient.

Minerals are usually found in the soil in lower concentrations than they occur in the plant. Why can they not be transported by diffusion?

Instead, minerals enter the roots by active transport.


Active transport uses energy from respiration to move substances against a concentration gradient.

What is active transport?

Specific minerals from the soil enter through channels in the cell walls of the root hair cells.

The minerals then travel around the plant in the xylem vessels.

soil

mineral

root hair cell

Plants may take up some minerals in the soil but not others. Why is it important that plants select which minerals to transport?


Active transport


Transporting minerals – activity



Glossary (1/2)active transport – The movement of a substance from

an area of low concentration to high concentration. concentration gradient – A change in the

concentration of a substance from one area to another. cellulose – The main component of cell walls. diffusion – The movement of a substance from an area

of high concentration to low concentration. guard cells – A pair of cells that control the opening and

closing of a stoma (single hole). humidity – The amount of water vapour in the air. lignin – A substance found in some xylem cells, which

strengthens the cell wall. osmosis – The movement of water from an area of high

concentration to low concentration.


Glossary (1/2)phloem – Plant tissue that transports food. potometer – A piece of equipment that can be used to

indirectly measure the rate of transpiration. root hair cell – A thin, hair-like outgrowth on roots. transpiration – The evaporation and diffusion of water

from leaves into the air. sieve tube – A series of joined phloem cells. stoma (singular) – A single hole on the lower surface of

the leaf that allows gases in and out. stomata (plural) – Small holes in the lower surface of a

leaf that allow gases in and out.vascular bundle – A grouping of transport tissues. xylem – Plant tissue that transports water and minerals.


Anagrams


Multiple-choice quiz

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[PPT]11. Transport in Plants - IGCSE Coordinated Sciences - … · Web viewTitle 11. Transport in Plants Subject GCSE Additional Science - Biology (Spring 2007) Author Boardworks