9D Plants for food

© Tony P. Thould

September 2000

PLANTS FOR FOOD - AN OVERVIEW

•Every animal, including Man, needs plants to survive.

•Plants supply animals directly ( Herbivores ) or indirectly ( Carnivores ) with food / energy.

•Plants are able to make their own food by Photosynthesis from Carbon Dioxide and Water using sunlight energy absorbed by Chlorophyll.

•The leaves are the main food producing organs of a plant.

•Man must know how to take care of plants so that their food supply is maintained.

One of the eight characteristics of living things is that every living thing needs to feed.

From the food they get the fuel to change into the sort of energy they need.

The energy can be then used by the plant or animal for movement, growth etc.

WHERE DOES THE ENERGY COME FROM?

PHOTOSYNTHESIS

This is the way by which green plants make their own food.

They use Carbon Dioxide and Water as these two raw materials contain the elements Carbon, Hydrogen and Oxygen which are all needed to make Glucose sugar - their food.

Energy from the sun is absorbed by Chlorophyll and used to make the Glucose. This stores the sun’s energy as chemical energy

PHOTOSYNTHESIS

CarbonDioxide

Water

Chlorophyll absorbs the light energy from the sun and uses it to make Glucose sugar from carbon dioxide and water

Sun’s Energy

This is how green plants make food:-

The Glucose make by Photosynthesis can be added to in order to form other essential substances for the plant to grow well.

For example by taking in Nitrogen, the plant has the right materials ( along with the Carbon, Hydrogen and Oxygen in Glucose ), to form proteins. Proteins are essential to grow new cells and repair damaged ones.

A SPECIALISED PLANT CELL

NUCLEUS

CYTOPLASM

CELL MEMBRANE

CELLULOSE CELL WALL

CHLOROPLASTS

VACUOLE

A Palisade Leaf Cell specialised to be the main food making centre in a plant. Each cell has a great many Chloroplasts containing Chlorophyll. This absorbs the sun’s energy, essential for Photosynthesis.

PHOTOSYNTHESIS

Carbon Dioxide + Water

Using Sunlight Energy

Absorbed by Chlorophyll

Glucose + Oxygen

!!!YOU MUST LEARN THIS EQUATION!!!!

Energy from the sun reaches the plant in the form of light and heat.

The plant uses the suns’ energy to make food by

Photosynthesis

PRODUCER

The Palisade cells in the leaves make the food by Photosynthesis

FOOD CHAINS AND FOOD WEBS

At the start of every food chain is a green plant. This is because plants produce their own food and in turn become food for animals.

The animals that eat the plants are called Primary Consumers. They are Herbivores - plant eaters.

Secondary Consumers are Carnivores as they eat the Primary Consumers.

This is the basis of of Food Chain I.e.

PRODUCERPRIMARY

CONSUMERSECONDARY CONSUMER

The arrows shows the energy passing from one link to the next.

How may Food Chains make up this Food Web?

Why is it important for Man to look

after his crops and wild plants?

WATER ( Hydrogen and

Oxygen )

From the AIR

Carbon Dioxide

SUN’S ENERGY

Plants make their own food - Glucose - which is a Carbohydrate ( made up from Carbon, hydrogen and

Oxygen ) and stores it as Starch.

CHLOROPHYLL in the Leaves

6CO2 + 6H2O C6H12O6 + 6O2

WATER ( ____________ and

__________ )

From the AIR ___________

___________

SUN’S ________

Plants make their own food - ___________- which is a Carbohydrate ( made up from ________, __________

and ___________) and stores it as Starch.

_______________ in the Leaves

6CO2 + 6H2O C6H12O6 + 6O2

Plants need a Balanced Diet too!

We must eat a good variety of foods to keep us healthy - all the right

nutrients - we cannot just eat chips.

Plants cannot just live on the Glucose made by Photosynthesis but need a variety of nutrients to keep them

healthy.

FERTILIZERS

The soil has many more nutrients which the plant needs to grow healthily. These include

Nitrogen ( N ), Phosphorus ( P ) , Potassium ( K ) and Magnesium (Mg ).

N, P, K and Mg may be added to the soil by using Fertilizers in the form of granules,

manure or compost.

FERTILIZERS

Bags of fertilizers have labels on them to show what the fertilizer contains. This is usually in the form of numbers e. g. 20 :10 :10, 5 : 15 : 25

These numbers stand for the amounts of N, P and K contained in the bag of fertilizer.

Nitrogen gives the plant good leaves and stems

Phosphorus makes good roots

Potassium makes good flowers, seeds and fruits

FERTILIZERS

Bags of fertilizers have labels on them to show what the fertilizer contains. This is usually in the form of numbers e. g. 20 :10 :10, 5 : 15 : 25

These numbers stand for the amounts of __ __ _____ ___ contained in the bag of fertilizer.

Nitrogen gives the plant good ___________________

Phosphorus makes good _________

Potassium makes good _________________________

20 : 5 : 15

SUPER

GROW

NP

K

N

P

K

FEEDING THE PARTS OF THE PLANT

Nitrogen for good stem and leaves

Potassium for good flowers,

fruits and seeds

Phosphorus for good roots

N

P

K

20 : 15 : 15

SUPER

GROW

The parts get bigger and better

MAGNESIUM ( Mg )

Plants need this to make Chlorophyll

No Mg Has Mg

No Chlorophyll

Plenty of Chlorophyll

Which leaf would not make food by Photosynthesis - why?

Pesticides Pests and diseases

Commercial crop growing

Need to feed population

Weeds

Plants in our diet directly and indirectly.

Plants in our diet directly and indirectly.

A pupil once said that he did not care about plants as all he ever ate for any meal was meat and all he ever drank was milk.

What would you say to him about the importance of plants in his diet?

PLANTS IN OUR DIET

Which of the following foods came from plants either directly or indirectly?

Chips Toast Butter Eggs

Bacon Cheese Cornflakes Lamb

Cake Spaghetti Baked Beans

Yoghurt Beefburgers

Chocolate Biscuits Rice

Pests, Diseases and Weeds

•Name some pests, diseases and weeds found in crops grown in this country.

•How do the above have an affect upon the food supply of our country?

•What can Man do to try and stop these three from affecting our crops?

•Are there any side effects upon the environment e.g. on food chains, in using these methods?

Pests, Diseases and Weeds

•Pests such as greenflly feed on the sap in the plants and drain them of vital nutrients. The plants become weak and produce fewer fruits.

•Diseases such as mildew makes the plant leaves and fruit bad so that the crop is unfit to pick and eat.

•Weed compete with the crop for food, light, water and space. Weeds are often hardier and more successful at surviving than the crop and therefore the crop becomes weak and less productive.

Pesticides and Herbicides - the knock on effect.

By spraying crops with chemical pesticides and herbicides, a grower may kill not only the pests but also other beneficial creatures.

By killing various animal and plant pests, the grower is saving the crop but affecting the food supply of a number of links in the food chain and food web.

Some of the chemicals sprayed onto crops stay in the soil for years and so affect the environment for a long time.

Need to feed population and Commercial crop growing

Growers have developed several methods of growing crops in conditions that will produce larger, better quality and a higher yield than

would normally be found.

What are some of these Methods?

Need to feed population and Commercial crop growing

Many growers grow their plants in green houses.

Growers can and fertilisers to the crops.

New breeds of plants can improve the yields of the crops and also help them to tolerate extreme weather conditions.