# What Do Plants Need? 3

In this worksheet, students will be challenged to consider a variety of investigations where plants are placed in different conditions and the probable outcome is predicted.

Key stage:  KS 2

Curriculum topic:   Plants

Curriculum subtopic:   Requirements for Life and Growth

Difficulty level:

### QUESTION 1 of 10

In the following questions you will be presented with a series of imaginary experiments in which plants are placed in certain conditions.

Using your knowledge of what plants need to grow well, you should consider the possible outcomes listed and decide on which is the most likely result under the given conditions.

You have two identical tomato plants. They are placed in the following conditions:

• Plant A has sunlight, is given 50cm3 of water per day and grows in a temperature of 20oC.
• Plant B has sunlight, is given 50cm3 of water per day and grows in a temperature of 0oC.

Predict which of the following is likely to happen.

Plant A will grow faster than Plant B

Plant B will grow faster than Plant A

Both plants will grow at the same rate

You have two further tomato plants.  You place them in the following conditions:

• Plant A has sunlight, 0cm3 of water per day and a temperature of 20oC.
• Plant B has sunlight, 50cm3 of water per day, and a temperature of 20oC.

Predict the likely outcome of this experiment.

Plant A will grow faster than Plant B

Plant B will grow faster than Plant A

Both plants will grow at the same rate

This time you are growing bean plants.  You place two plants in pots as follows:

• Plant A has sunlight, 50cm3 of water per day and a temperature of 15oC.
• Plant B has sunlight, 50cm3 of water per day and a temperature of 15oC.

Predict the likely outcome of this experiment.

Plant B will grow faster than Plant A

Plant A will grow faster than Plant B

Both plants will grow at the same rate

You have two lovely potted Busy Lizzie plants. You place them in different conditions as follows:

• Plant A has 50cm3 of water per day, a temperature of 20oC and is kept in a dark cupboard.
• Plant B has 50cm3 of water per day, a temperature of 20oC and is kept on the windowsill.

Predict the likely outcome of this experiment.

Plant A will grow yellow leaves

Plant B will grow yellow leaves

Both plants will grow green leaves

You open a packet of cress seeds and sow them on pieces of damp kitchen towel in two dishes. You place the dishes in the following conditions:

• Dish A is in a dark cupboard and given 50cm3 of water per day.
• Dish B is placed on the windowsill and given 50cm3 of water per day.

Predict what you think is likely to happen over the next few days.

The seeds in Dish A will not change

The seedlings in Dish A will grow taller than the ones in Dish B

The seedlings in Dish B will grow taller than the ones in Dish A

You so enjoyed experimenting with the cress seeds (which grow really easily) that you set up a further experiment. You decide to try three dishes of seeds sown on damp kitchen towel and given 50cm3 of water per day. You place them as follows:

• Dish A is kept in a dark cupboard for a week.
• Dish B is kept in a dark cupboard for 4 days and then put on the windowsill for 3 days.
• Dish C is kept on a windowsill for a week.

At the end of the week which dish do you predict will contain the cress plants with the darkest green leaves?

Dish A

Dish B

Dish C

Back to the Busy Lizzie plants you met in Q4. This time you take the two potted plants and place them as follows:

• Plant A is left on the windowsill and given 50cm3 of water per day.
• Plant B is well-watered and then sealed inside an airtight transparent plastic bag and left on the windowsill.

Both the Busy Lizzies are left on the windowsill for a week. Predict what you think you are likely to observe at the end of the investigation.

Plant A has grown normally

Plant B has withered and died

Both plants have grown normally

Apart from the questions about cress seeds, each of the previous experiments have involved two plants: one placed in one set of conditions and the second in another.

If you were actually carrying out these investigations, which do you think is a sensible number of plants to place under each set of conditions?

2

10

100

1000

You know that plants make their own food (by a process called PHOTOSYNTHESIS), which they use to grow and which all animals rely on down the food chain. To do this they need the green pigment (chlorophyll) in their leaves and which of the following?

sunlight, water, oxygen

sunlight, carbon dioxide, water

water, warmth, oxygen

The process of making food from simple raw materials also produces a gas which plants release as a waste product. What is the gas called?

carbon dioxide

air

oxygen

• Question 1

You have two identical tomato plants. They are placed in the following conditions:

• Plant A has sunlight, is given 50cm3 of water per day and grows in a temperature of 20oC.
• Plant B has sunlight, is given 50cm3 of water per day and grows in a temperature of 0oC.

Predict which of the following is likely to happen.

Plant A will grow faster than Plant B
EDDIE SAYS
Both tomato plants have the conditions they need to make food (sunlight, water and air) but the chemical reactions that convert those simple chemicals into sugar (food) happen much faster in warmer conditions, so Plant A (at 20°C) will grow faster.
• Question 2

You have two further tomato plants.  You place them in the following conditions:

• Plant A has sunlight, 0cm3 of water per day and a temperature of 20oC.
• Plant B has sunlight, 50cm3 of water per day, and a temperature of 20oC.

Predict the likely outcome of this experiment.

Plant B will grow faster than Plant A
EDDIE SAYS
This time Plant A has been given no water. Once it has used up any water left in the pot its growth will more-or-less cease until it is given more.
• Question 3

This time you are growing bean plants.  You place two plants in pots as follows:

• Plant A has sunlight, 50cm3 of water per day and a temperature of 15oC.
• Plant B has sunlight, 50cm3 of water per day and a temperature of 15oC.

Predict the likely outcome of this experiment.

Both plants will grow at the same rate
EDDIE SAYS
Under the same conditions both plants should grow at about the same rate; however you know that in practice this rarely happens! Both plants are different (like people) and so are likely to differ a little bit in how they react to identical conditions. Still, in theory, they should be the same.
• Question 4

You have two lovely potted Busy Lizzie plants. You place them in different conditions as follows:

• Plant A has 50cm3 of water per day, a temperature of 20oC and is kept in a dark cupboard.
• Plant B has 50cm3 of water per day, a temperature of 20oC and is kept on the windowsill.

Predict the likely outcome of this experiment.

Plant A will grow yellow leaves
EDDIE SAYS
Plants need light in order to make their green pigment (CHLOROPHYLL). Without light it is slowly lost and the leaves turn yellow, so Plant A in the dark will develop yellow leaves.
• Question 5

You open a packet of cress seeds and sow them on pieces of damp kitchen towel in two dishes. You place the dishes in the following conditions:

• Dish A is in a dark cupboard and given 50cm3 of water per day.
• Dish B is placed on the windowsill and given 50cm3 of water per day.

Predict what you think is likely to happen over the next few days.

The seedlings in Dish A will grow taller than the ones in Dish B
EDDIE SAYS
When seeds GERMINATE (start to grow) they grow upwards searching for the light. If you keep them in the dark they grow tall quickly, as they 'know' the light's up there somewhere! So the seedlings in Dish A in the dark will grow taller than those in Dish B.
• Question 6

You so enjoyed experimenting with the cress seeds (which grow really easily) that you set up a further experiment. You decide to try three dishes of seeds sown on damp kitchen towel and given 50cm3 of water per day. You place them as follows:

• Dish A is kept in a dark cupboard for a week.
• Dish B is kept in a dark cupboard for 4 days and then put on the windowsill for 3 days.
• Dish C is kept on a windowsill for a week.

At the end of the week which dish do you predict will contain the cress plants with the darkest green leaves?

Dish C
EDDIE SAYS
Dish C has been in the light for the whole week and so will have the most green chlorophyll in its leaves. Dish A's seedlings will have entirely yellow leaves whilst those in Dish B will be light green.
• Question 7

Back to the Busy Lizzie plants you met in Q4. This time you take the two potted plants and place them as follows:

• Plant A is left on the windowsill and given 50cm3 of water per day.
• Plant B is well-watered and then sealed inside an airtight transparent plastic bag and left on the windowsill.

Both the Busy Lizzies are left on the windowsill for a week. Predict what you think you are likely to observe at the end of the investigation.

Both plants have grown normally
EDDIE SAYS
Although you would be very unhappy about being sealed inside a transparent plastic bag, a plant has no problem with it! As long as it has light, water and air it will make its food and grow normally. The water you gave it is still all inside the bag (some will have condensed on the inside of the bag and dripped down to be re-used). Many people have 'indoor gardens' in their living rooms which are colonies of plants growing inside a big round glass jar.
• Question 8

Apart from the questions about cress seeds, each of the previous experiments have involved two plants: one placed in one set of conditions and the second in another.

If you were actually carrying out these investigations, which do you think is a sensible number of plants to place under each set of conditions?

10
EDDIE SAYS
A tray of 10 plants in each set of conditions is a sensible number. Like human beings, plants are individuals and will vary in how they behave, so to iron out any natural differences you should always have more than one example to experiment on. In research laboratories they do have hundreds, or even thousands, of plants on test, but for experiments at home or at school that's not really practical (besides, you might get into trouble if your bedroom's covered in trays of plants!).
• Question 9

You know that plants make their own food (by a process called PHOTOSYNTHESIS), which they use to grow and which all animals rely on down the food chain. To do this they need the green pigment (chlorophyll) in their leaves and which of the following?

sunlight, carbon dioxide, water
EDDIE SAYS
When plants make their own food they use the energy in the sunlight to change water (from the soil) and carbon dioxide (from the air) into sugar. It's an amazing process and all of life on the planet depends upon it.
• Question 10

The process of making food from simple raw materials also produces a gas which plants release as a waste product. What is the gas called?

oxygen
EDDIE SAYS
The process by which plants make food (photosynthesis) not only produces all the food that feeds the world but it also produces the oxygen that all animals rely on to breathe. Plants are AMAZING!
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