If I plant seeds, what must I do to make sure that they grow?
What does a plant actually need to stay alive and grow?
Conditions for growth
What do plants need to grow?
Do you remember learning about living and non-living things? We said that almost all things on earth are either living or non-living. The plants and animals that are living need to carry out the seven life processes - do you still remember what they are?
Plants make all the food that all the animals on Earth need to stay alive. If all the plants were to suddenly vanish, life on Earth would be not be possible. We need to take care of the plants on our planet because they take care of us.
In this section we are going to learn specifically what makes plants grow and keeps them alive. We will also look at growing new plants and how you can make sure that as many of your seeds as possible grow into healthy plants.
After the activity when you planted a bean seed, how did your bean grow - did it die or did it stay alive? Discuss what you think your bean plant will need to stay alive and continue growing.
Plants need sunlight, water and air to grow.
Sunlight
Plants need sunlight to grow and live.
Green plants use sunlight, water and carbon dioxide gas to make food.
The plant can use some of this food to grow and develop.
It stores the rest of the food, which animals can eat.
When animals and humans eat plants they get energy from the plant.
The plant leaf uses sunlight energy to make food and grow. The caterpillar eats the leaf.
Air
Just like animals and people, plants also need air to live and grow. Plants use carbon dioxide to make food so that they can grow.
Water
Plants need water to grow and to make food. Some plants need more water than others. The amount of water a plant needs depends on the type of plant. If the plant does not get the amount of water it needs it will die. Some plants are able to grow in very dry areas, such as cacti in the desert. These plants have adapted (changed) over many, many years to be able to survive in these conditions.
The roots of the plant absorb water from the soil. This water carries nutrients from the soil to all the parts of the plant. In the picture, the raindrops are collecting on the leaves. They will then fall down to the ground and soak into the soil. The roots will then absorb the water for the plant.
Remember: a plant needs water, sunlight and carbon dioxide to make food.
Most plants grow well if they are planted in soil.
Plants are anchored in the soil by their roots.
Their roots absorb the dissolved nutrients from the soil.
To make sure plants get enough of these mineral nutrients we often add some fertiliser or compost to the soil. We say that soil that has a lot of nutrients is rich and soil that does not have many nutrients is poor.
Plants can generally be grown from seeds or cuttings.
Seeds grow from flowers that have been fertilised with pollen from another flower. Fertilised seeds can germinate to start growing into a new plant.
A cutting is made when a piece of a plant (usually the stem) is cut off and planted in new soil to start growing roots and form a new plant.
Plants can also grow from shoots which are little roots that shoot out of special places in the stem of the plant and start to grow into a new plant.
What three really important things do plants need to grow?
sunlight, water, air
Do you remember that one of the life processes is reproduction? How do plants make new plants?
They make seeds which then germinate to grow into a new plant.
How to introduce the topic
It is recommended to do this practical task over time at school while learners engage with the next section. Give the learners the opportunity to observe the wonder of a new plant becoming alive from a seed or cutting! Let them DO the investigations; observe and record observations over time.
Presentation hints
Prior experience of the teacher will assure success. Do the prescribed investigations before you ask learners to do them. Then you will be more able to guide the learners. Consider not to do this investigation in mid-winter alow temperatures are usually not favourable for germination. Use different bean seeds and find out which germinate better. Apply the precautions as stated in the investigation in the text.
Start a class discussion by asking learners why plants are important. Possible answers can be: for food, to provide oxygen, to protect the soil (plant on dunes), plants are beautiful etc. Do we need to make more plants? Why? How?
Check learners' understanding of the words: germinate - a seed develops into a new plant, cutting a stem, leaf or part of a plant that can be used to grow a new plant.
Tell the learners that they need to find out what seeds need to germinate and grow into new plants. Go through the materials and procedures in the text. Let them work in groups. Check that every learner has the required materials and knows what to do.
You must monitor DAILY how their investigations progress. Set aside at least five minutes per day.
Guide the learners on how to keep a diary. Learners have to write the date and record their observations under headings as: what is different today (root appeared), measured root length, etc.
Revise/reinforce that drawings and labeling must be done scientifically:
the drawing must have a heading (printed in pen)
the drawing must be done with a sharp pencil
the drawing must be done using solid lines
labelling lines must be in pencil
labelling lines must be drawn using a ruler
labelling lines must be parallel to the top / bottom of the page
labelling lines must touch the part of the drawing being labelled
labelling lines must end the same distance from the drawing (i.e. the labels must be in a vertical line underneath each other)
labels must be printed in pen
The correct labels must be used in the correct place.
Assist the learners to make the following drawings:
the bean and the first root
the bean, root and first leave
the first root, the stem and the first leaf
bean plant after 2 weeks
What seeds need to germinate
You have learnt that seeds are important to grow new plants. A plant needs to germinate from the seed to start growing. This means that the seed has to develop into a new plant and grow all the necessary plant parts.
In the first chapter of this term, we germinated a seed and saw that although it seemed to be non-living, it can be revived.
Have you ever wondered what seeds need to germinate and grow into new plants? Let's find out by doing a scientific investigation!
This is the first time learners will be doing a scientific investigation. Emphasise the need for a proper scientific investigation to answer a question, such as "Can a bean germinate in a dark place?", "Can a bean germinate in a very cold place?", "Can a bean germinate without water?", etc. Each group can answer a different question and their aim and prediction will depend on what question they are answering.
What does a seed need to germinate?
You will be working in groups. Each group will investigate a different question. Your aim and prediction will depend on the question you want to answer in your investigation!
AIM:
An aim in a science investigation is where we state what the purpose (aim) of the investigation is. What do you want to find out by doing this investigation?
Group dependent answer. For example: To find out whether a seed needs light to germinate and grow", or "To find out whether a seed needs warmth to germinate and grow"
PREDICTION:
A prediction is when you predict (make a guess) what the result of your investigation will be. But it is not just any guess! You must think about what you expect will happen in your investigation. What do you think will happen to your seed and how will it change?
Group dependent answer
APPARATUS (Equipment you will need):
bean seeds for each group
a shallow container for each group, such as a saucer or the lid of a large jar or yoghurt tub
cotton wool (if no cotton wool is available, use strips of newspaper instead)
a dark cupboard
a fridge (perhaps there is one in the staff room)
a ruler
METHOD (what you must do):
Each group will have a slightly different method depending on what question they are investigating. Follow the instructions for your group.
Group - Control
NB! A control is where the bean seed is given everything that we think it needs to germinate. In the other investigations, one of these things will be left out.
It is important to have a control to compare the other groups to. The control beans should germinate and grow the best and you can then use these plants to monitor further. Once they have germinated, show learners how to measure the lengths of the stems using a ruler. Possibly measure 3 stems and then calculate an average. Record these results on the board and then use them to draw a table and then a graph in the learners book. Get all learners to make a drawing of the first beans that germinated, and again when a leaf appears. there is space later on to do these drawings.
Wrap your bean in cotton wool (or newspaper if you do not have cotton wool).
Place it in the shallow container (saucer or lid).
Wet the cotton wool (be careful not to flood it!).
Place the container with the wet cotton wool and bean in a sunny spot.
Water your cotton wool DAILY and make sure that it stays damp.
Regularly check your bean's progress.
Keep a diary during the next few weeks to write down what you see happening. This is called recording your observations.
Once the seeds germinate, measure the length of the stems each day and record your results. Your teacher will show you how to do this.
Group - No water
Wrap your bean in cotton wool (or newspaper if you do not have cotton wool).
Place it in the shallow container (saucer or lid).
DO NOT wet the cotton wool! You want to see if a plant needs water to germinate so you must not give it water.
Place the container with the cotton wool and bean in a sunny spot.
Regularly check your bean's progress.
Keep a diary during the next few weeks to write down what you see happening. This is called recording your observations.
Group - No warmth
Wrap your bean in cotton wool (or newspaper if you do not have cotton wool).
Place it in the shallow container (saucer or lid).
Wet the cotton wool (be careful not to flood it!).
Place the container with the wet cotton wool and bean in the fridge.
Water your cotton wool DAILY and make sure that it stays damp.
Regularly check your bean's progress.
Keep a diary during the next few weeks to write down what you see happening. this is called recording your observations.
RESULTS AND OBSERVATIONS (What you observed and found out):
For this section, collect all the results from all groups. A suggestion is to have "the diary" written up as a table on the board and each day you record the results for each group. The groups must look at all the different investigations taking place, otherwise those who are studying, for example, the beans with no water will have a boring time. The skills of observation are very important here. You can teach some of these skills about how to collect and record data. The plants in the control group should be measured each day, once they have germinated so you can record the growth. Measure the length of three stems and calculate an average using, average = total length of 3 stems/3. You can then use these results to plot a graph to show growth over time.
Record the results from each group in the table below.
Control
No water
No warmth
Was there a change on Day 1?
Did the seeds germinate?
When did the seeds first germinate?
Did the new plants grow once they had germinated?
Now let's focus on the data we collected from the Control Group so we can see how the plants grew over time.
In the box below, make a drawing of a bean that has just started to germinate and of the first root that appeared.
The drawing and labelling must be done scientifically. The teacher must go through / revise / reinforce this from the previous section on this:
the drawing must have a heading (printed in pen)
the drawing must be done with a sharp pencil
the drawing must be done using solid lines
labelling lines must be in pencil
labelling lines must be drawn using a ruler
labelling lines must be parallel to the top / bottom of the page
labelling lines must touch the part of the drawing being labelled
labelling lines must end the same distance from the drawing (i.e. the labels must be in a vertical line underneath each other)
labels must be written in pen
The correct labels must be used in the correct place
In the box below, make a drawing of the the plants that had grown further. Include the bean, the root and the first leaf in the drawing.
Same guidelines as for previous drawing
Use the space below to draw a table where you record the data you collected from the Control Group and the length of the stems each day after they germinated. A table is very useful in science investigations to record and present a lot of data. A table must also have a heading!
A possible outline of a table is given below. Depending on how much the beans grew, use millimetres or centimetres and include the unit of measurement in the column heading. Remember to give the table a heading! Also explain to learners why you have not recorded all the lengths of the stems, but only an average. This may be difficult at this point but it is an important science concept for later. Averages are used as they give a better representation of the whole experiment (or population). If you only chose one plant to measure, that plant might have not grown much or grown much more than the other plants and so this would not be a true reflection of the results.
Date
Average length of stems (mm)
We are now going to draw a graph! Graphs are another way of presenting (showing) our results. They are often used by scientists to show their results. Drawing graphs is a very important skill! We will use the results from the table above to draw a graph. There are also many different types of graphs, but we will draw a line graph to show the growth of the seedlings each day. If this is the first time you are drawing a graph, do not worry! Your teacher will help you.
Take learners step by step through the process of drawing a line graph. Use the steps below and draw the graph on the board for learners to see what you are doing and then draw their own in their books.
First draw the axes - one is called the horizontal axis and the other is called the vertical axis.
Next decide what will go on each axis. The horizontal axis is where the independent variable is plotted. This is confusing for learners, even in Grade 12, so the earlier we start showing them how to do it, the better. The date or day number will go along the horizontal axis. The dependent variable goes on the vertical axis. the height grown by the plants (stem length) is dependent on the day, so this goes on the vertical axis.
Label the axes.
Next decide on a scale for each - perhaps only record a measurement every two days if your seeds took a long time to grow.
Next plot each point using the "pairs" from the table. In other words for Day 1, the height should be zero so plot a point for this first. Show learners how to first read on one axis, then the other, and where these two cross, you make the point.
You can then draw a line between the points to link them up.
Give the graph a heading
A possible graph is given below to give an idea.
CONCLUSION (What we have learnt):
When we do a scientific investigation, we always have to write a conclusion at the end. This summarises what we have learnt from the results of our experiment. From this science investigation, write a conclusion where you state what you have learnt.
Seeds need water and warmth to germinate (this should be the main conclusion from learners). Evaluate any other conclusions that they might have made depending on the experiment.
Presentation hints
The investigation below provides a wonderful opportunity to revise the scientific investigative process.
Background: You may have noticed that the same vegetables grow differently in different gardens, and you may have wondered about the reason for this.
Question (to be investigated): How does the amount of water influence the growth of a plant?
Aim: I want to find out how much water a plant needs to grow fast.
Predict: What will happen if the plant gets: a) no water, b) a little water, c) plenty of water.
Planning the investigation:
Which conditions are you going to keep the same? (Same seedlings, same type and size of the container, same amount and kind of soil.
Which materials are needed?
How are you going to do the experiment? How many millilitres of water will you use for "a little water" and how many for "plenty of water"? Are you going to add the water daily or every second day?
Do the investigation:
Follow procedures 1-5 in text.
Collect and record your data (points 6 and 7). Draw a graph using the collected data.
Write down your findings.
Extension: How the amount of water influences the growth of a plant
This can be done as an extension investigation if time permits in your class.
AIM (What you want to find out):
What do you want to find out by doing this investigation.
Learner dependent answer
PREDICTION (What you think will happen):
Can you already guess what will happen in your investigation? Write a prediction of what you think will happen.
Learner dependent answer
APPARATUS (Equipment you will need):
Three of the bean plants that germinated in the previous investigation.
Three containers of exactly the same size.
Soil
METHOD (What you must do):
1. Fill the three containers with exactly the same amount of soil.
2. Plant the three seedlings in the three containers.
3. Place the three containers next to each other in a spot that gets enough sunlight during the day.
4. Label the three containers as follows:
1- No water
2 - Little water
3 - Plenty of water
5. Water the plants according to the labels.
6. Measure the three plants on the same day every week.
7. Record your findings in the table. That means you need to write the lengths of each plant in the correct block on the table below.
RESULTS (What happened?): (Answer dependent on classroom environment)
1- No water
2- A little water
3- Plenty of water
Week 1
Week 2
Week 3
Week 4
Week 5
Use the space provided below to draw a bar graph of your findings.
Fill in the scale for the vertical axis
Draw in the bars for each plant for the final height it grew after week 5.
CONCLUSION (What we learnt):
What differences could you see between the three plants after the 5 weeks? Why do you think the plants differed so much after 5 weeks?
Learner dependent answer
Plants need light, water and air to grow.
You can grow new plants from cuttings or seeds.
A cutting is a stem, leaf or part of a plant that can be used to grow a new plant.
Germinate: when seeds come alive and start to grow.
Seeds need water, warmth and air to germinate and grow.
Explain what germination means.
It means the seeds start growing and developing all the necessary parts.
What does a seed need to germinate?
Water, warmth and air.
What does a plant need to grow?
Water, food and air. Some plants need soil.
Two of the same plants were grown in different places. One plant got a lot of rain and was planted where there was a lot of sunshine. The other plant also got a lot of rain, but hardly any sunshine.
After two weeks the following measurements were taken:
Length of plant
Plant 1
15 cm
Plant 2
4cm
Which plant do you think grew in the shadowy place? Why do you say so?
Plant 2. It did not grow very well.
Complete the bar graph by choosing a different colour for each plant and colouring in the bar for each plant, as well as the little boxes on the side which tell you which plant is which (this is called a legend).
