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Investigating Plant Growth

In this worksheet, students will investigate what affects how plants grow, looking at several factors and how they might be changed.

'Investigating Plant Growth' worksheet

Key stage:  KS 2

Curriculum topic:  Plants

Curriculum subtopic:  Requirements for Life and Growth

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

 Mrs. Bates's science class are working on plants.

 

"Today we're going to begin an investigation on what plants need to grow well," she tells them.

"Each of you will be given a plant and we're going to change certain things called factors to see what effect it has upon the growth of the plant."

 

Class measuring plants

 

Let's see what they're up to.

Here is a list if different things (called factors or variables) that might affect how well a plant grows.

 

What do you think is most important for a plant to grow?

Tick three answers.

 

Seedling

light

warmth

noise

water

type of pot

silence

smell in the air

Why do you think Mrs. Bates is giving each student in her class a plant to test? Wouldn't it be just as good to have just one plant to investigate?

Yes, it's a waste of plants for everyone to have one.

No, it's fairer if everyone has a go.

No, you need several plants to get results that mean anything.

First Mrs. Bates shows her class how to measure the growth of a plant by measuring its height each day.

 

Which of these pictures do you think represents the best way of measuring the plant so that the students can discover whether it's growing?

 

Measuring plants

A

B

C

Mrs. Bates divides her students up into groups who will be investigating whether leaves, water and warmth are important to growth.

 

In the group investigating whether leaves are important to a plant's growth, half the students cut all the leaves off their plant while the other half are instructed to leave their plant as it is.

 

Scissors

 

Why do you think that Mrs. Bates made half of the group cut their plant's leaves off?

She likes being cruel to plants.

So the growth of the plants with and without leaves could be compared.

Plants grow better with some of their un-necessary leaves removed.

The group studying the effect of water on the growth of plants were also divided into two groups. The first group added 100 cm3 of water to their plant each day and the other group added no extra water.

 

Watering can

 

What do you predict will happen to the two groups of plants?

The watered ones will grow better.

The ones left alone will grow better.

There won't be any difference between them.

The group studying the effect of warmth on the growth of plants were divided into two groups – one was to keep their plants in a cold, bright room (at 10°C) and the other group were to put their plants in the classroom near the heater (at 20°C). The classroom was also very bright.

 

Lottie wanted to know why their plants couldn't go in the fridge to make them even colder.

 

Fridge

 

What do you think?

In a fair test only one factor should be changed, but if they put the plants in the fridge both warmth and light will be changed.

The plants can't fit into a fridge.

The plants need to be where everyone can see them easily.

How long do you think Mrs. Bates should allow her students to carry on their investigation for in order to get some useful results?

2 days

4 days

2 weeks

4 months

1 year

At the end of the investigation Mrs. Bates asked each student to calculate how much their plant had grown. She then pooled their results on the board and worked out an average.

 

Here is what the class found out:

  WATERED NOT WATERED WARM COLD LEAVES NO LEAVES
Height at start/cm 20 22 18 19 23 20
Height at end/cm 25 23 24 20 30 20
Change in height/cm ? ? ? ? ? ?

 

Complete the table by working out the change in height for each plant.

 Change in Height/cm
Watered
Not Watered
Warm
Cold
Leaves
No Leaves

From what you worked out, which factor do you think had the greatest effect upon how well the plants grew?

watering

warmth

leaves

By cutting off all the leaves, which important requirement are the students preventing the plant from absorbing?

light

water

warmth

minerals

air

  • Question 1

Here is a list if different things (called factors or variables) that might affect how well a plant grows.

 

What do you think is most important for a plant to grow?

Tick three answers.

 

Seedling

CORRECT ANSWER
light
warmth
water
EDDIE SAYS
If a plant is going to grow successfully it needs plenty of light, which its leaves absorb, as well as sufficient water and a warm temperature, amongst other factors.
The smells in the room and the noise level won't affect it (although some gardeners play music to their plants!) and the type of pot is not important as long as the plant has enough room.
  • Question 2

Why do you think Mrs. Bates is giving each student in her class a plant to test? Wouldn't it be just as good to have just one plant to investigate?

CORRECT ANSWER
No, you need several plants to get results that mean anything.
EDDIE SAYS
The concept of a 'Fair Test' in scientific investigations is really important: just like each of us are individuals, plants are too and each one will react differently as conditions change. So you need lots of plants to get an idea of how that type of plant behaves under different conditions. That way you get results that mean something.
  • Question 3

First Mrs. Bates shows her class how to measure the growth of a plant by measuring its height each day.

 

Which of these pictures do you think represents the best way of measuring the plant so that the students can discover whether it's growing?

 

Measuring plants

CORRECT ANSWER
B
EDDIE SAYS
Measuring one leaf (C) will only tell you about the growth of that one leaf. Measuring the plant and pot (A) is OK but if you wanted to find out about the growth of the plant itself you're going to have to subtract the height of the pot. B is best as you're measuring just the height of the plant.
  • Question 4

Mrs. Bates divides her students up into groups who will be investigating whether leaves, water and warmth are important to growth.

 

In the group investigating whether leaves are important to a plant's growth, half the students cut all the leaves off their plant while the other half are instructed to leave their plant as it is.

 

Scissors

 

Why do you think that Mrs. Bates made half of the group cut their plant's leaves off?

CORRECT ANSWER
So the growth of the plants with and without leaves could be compared.
EDDIE SAYS
If leaves are important to a plant's growth the easiest way to find out is to remove them - that way you can compare the group of plants without leaves to the group of plants with leaves. Don't worry - the plant will be able to grow some more fairly quickly!
  • Question 5

The group studying the effect of water on the growth of plants were also divided into two groups. The first group added 100 cm3 of water to their plant each day and the other group added no extra water.

 

Watering can

 

What do you predict will happen to the two groups of plants?

CORRECT ANSWER
The watered ones will grow better.
EDDIE SAYS
It's likely that over time the plants given a little water each day will grow better: plants are mostly water (even more than we are!) and water is vital to most of what's going on inside a plant like transporting substances around it.
  • Question 6

The group studying the effect of warmth on the growth of plants were divided into two groups – one was to keep their plants in a cold, bright room (at 10°C) and the other group were to put their plants in the classroom near the heater (at 20°C). The classroom was also very bright.

 

Lottie wanted to know why their plants couldn't go in the fridge to make them even colder.

 

Fridge

 

What do you think?

CORRECT ANSWER
In a fair test only one factor should be changed, but if they put the plants in the fridge both warmth and light will be changed.
EDDIE SAYS
If the students put their plants in the fridge, they are keeping one set of plants cold AND dark (fridge) and another set warm AND light (windowsill). This means that TWO factors are being changed. If the plants grow differently the students won't know what was most important: warmth or light???
So both sets of plants need to be in light in this investigation.
  • Question 7

How long do you think Mrs. Bates should allow her students to carry on their investigation for in order to get some useful results?

CORRECT ANSWER
2 weeks
EDDIE SAYS
Obviously the longer they carry it on the more accurate their results will be, but remember that this is a classroom situation and Mrs. Bates's students will be involved in a good deal of other work. After 2 weeks they will have gathered enough data to get worthwhile results.
  • Question 8

At the end of the investigation Mrs. Bates asked each student to calculate how much their plant had grown. She then pooled their results on the board and worked out an average.

 

Here is what the class found out:

  WATERED NOT WATERED WARM COLD LEAVES NO LEAVES
Height at start/cm 20 22 18 19 23 20
Height at end/cm 25 23 24 20 30 20
Change in height/cm ? ? ? ? ? ?

 

Complete the table by working out the change in height for each plant.

CORRECT ANSWER
 Change in Height/cm
Watered
Not Watered
Warm
Cold
Leaves
No Leaves
EDDIE SAYS
You can work this out by subtracting (taking away) the start height from the end height. So for the watered plants that's 25cm-20cm=5cm. Simples!
  • Question 9

From what you worked out, which factor do you think had the greatest effect upon how well the plants grew?

CORRECT ANSWER
leaves
EDDIE SAYS
The results suggest that the greatest difference is between those which had leaves and those which didn't (7cm of growth) so that would suggest that the amount of leaves a plant possesses has the greatest effect upon how well it grows. However, many more tests would have to be carried out in order to decide whether this is actually true.
  • Question 10

By cutting off all the leaves, which important requirement are the students preventing the plant from absorbing?

CORRECT ANSWER
light
EDDIE SAYS
Leaves are what a plant uses to absorb the light it needs in order to make its food, so without leaves its growth is going to be poor. In fact, its leaves also absorb gases from the air (well done if you put that!) but as it can also do that through its stem it is light that is the more important in this investigation.
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