Experiment 1A – roots seek water
Large rectangular transparent dish, silver/river/washed sand, seeds (peas soaked for 24 hours) 2 markers, one labeled seeds, the other water, a pebble, watering can
Fill the dish 1/2 to 3/4 full of sand
Plant eight seeds in a furrow at one end of the dish and cover them
Carefully pour water along the furrow
Place the markers at either end of the furrow
Wait until the seeds sprout, watering them everyday
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When the seeds have become established, water them a little further away from the furrow each day and move the ‘water’ marker to show the shift.
Place the pebble to cause an obstruction
Watch the roots grow through the base of the dish
To show how roots grow, seeking water
They grow around the obstacle, towards the water
Small, solid, glazed, clay pot, seeds (peas soaked for 24 hours), watering can
In a dry outside space, dig a hole in the ground to fit the pot into and fill it with water. Plant the seeds wedged between the rim of the pot and the soil.
Keep topping up the water level in the pot
The roots, seeking the water will grow up and over the pot.
Experiment 2 – roots are shy of light
Large glazed pot with a plastic pot which firs snugly inside and a wire basket which fits neatly into it, moss, compost, cress or mustard seeds, watering can
Put the plastic container into the ceramic one and the wire container into the plastic one
Line the wire basket with moss and add a thin layer of compost
Sprinkle in some seeds and put a fine layer of compost over them, water gently
Pour water into the base of the pot 1/3 full.
Wait for the seeds to sprout, making sure the moss doesn’t dry out
When the roots emerge through the basket, remove the wire basket and hang it in a well lit area, preferably close to a window
To show the roots, seem to curl and shrivel back into the basket, as if they are ‘shy’ of the light
Experiment 3 – the direction of the roots
A straight necked jar, silver/river/washed sand, blotting paper, black construction paper, seeds (peas or beans soaked for 24 hours), an elastic band, watering can
Line the inside of the jar with blotting paper
Half fill the jar with sand to hold the shape
Put the beans or peas between the blotting paper and the glass, drawing attention to it but not using the terminology, put the micropile in different directions,say ‘We will place the seeds in all directions’.
Put in more sand
Cover the jar in black construction paper with an elastic band
Keep the sand moist, but not saturated.
After a few days remove the construction paper and observe
It does not matter what position the seeds are place in, the root appears to grow downwards.
Notes for all experiments:
The area that the roots emerge from the seed is called the micropile
When to give the lesson:
Begin all three experiments in advance of the work with the root, leaving time for the plants to grow.
After the lesson:
Give the function of the root
The story of the function of the roots including parts
We discovered that leaves need water? Where do they get it from? How do they get it in? It seems as if the plants drink with their feet, so the plants suck up water. While they are doing this they help to drain the soil. iThat is why if there are few plants in an area the are can get very marshy and bogs form. Roots are so sensitive to water it is almost as though they smell it. Let’s look at our sand tray experiment
Do you see how they are all growing towards the water
It’s as if the roots are the water seekers of the plant
Display Chart E
There is one part of the plant. The tip that really searches for water, it gores around and around searching for water. Because it has such a special job searching it might bang into things so it needs special protection, it is called a root cap. The tip is like an engineer, if it bumps into a small thing it can go around it, if it meets a large object it gives out an acid and tries to dissolve it.
It is only the tip which is this sensitive to water, it’s as though it is the ‘brains of the root’. If the tip gets broken off the root just goes down and down, it can’t look for water. The part of the root which sucks in the water is called the root hair
Showing some of the roots from the experiment, washing off the sand, or some corn seeds sprouted between layers of cotton wool; showing the cap, tip and hairs or a picture if no root is available. Allow the children to examine them and absorb this new information.
Collaboration between foliage and root hairs
Display Chart G (The leaves spread the water to the furthest extent of the root)
Say, ‘Has anyone noticed, there seems to be collaboration between the leaves and the roots, it’s as if the roots are saying to the leaves, “Give me something to drink”.
Display Chart H (it shows the leaves directing the rain down to the leaves)
‘This is another way the leaves can give the roots water’
Display Charts I and J (these give further examples; let the children imagine how the water would reach the root)
Say, ‘Some leaves seem to direct the water down and towards the roots, others seem to direct it out and down towards the roots. Different types of foliage direct water in different directions’.
Outside and with books make observations with the children, for example;
- Fir trees often live on the slopes, where there isn’t much water, they direct water down towards their ‘superficial roots’. Directly underneath them it is very dry, They have a rain shadow, they are good places to shelter if it rains.
- Deciduous trees dig one deep ‘rain root’ which goes very deep and ‘secondary roots’ branch out to the breadth of the foliage to take the water they can get. The root system underneath often mirrors the shape of the tree above the ground.
Anchoring the plant
Say, ‘Do you know that these roots, travelling around and around looking for water also keep the plant steady, they stop it falling down in the storm’
Demonstration 1 – roots keep the plant upright
Circular, polystyrene board, two identical wooden skewers, sting and thumb tacks
At first the skewer falls down, but when it is supported by the string it stays up.
‘The roots are like the pegs on a tent, they provide anchorage’
Show Chart K
‘Have you ever noticed a tree which has fallen down in a storm, it pulls up it’s roots with it, it comes down roots and all, we call it ‘up rooted’.
It does not matter what position the seeds are place in, the root appears to grow downwards.
Demonstration 2 – roots cling to soil
‘You know that roots, going around and around for water also pull soil. On mountainous or hilly areas the roots pull soil, forming terraces and preventing the soil being washed away.’
Say to the children, ‘Can you pull up a tuft of grass, I want the roots as well’, the children notice the resistance,t he blade will tear before the roots come up. If you dig up some grass, say, ’Have you noticed how much soil clings to the roots of grass, so the roots really do hold soil’.
Experiment 4 – roots cling to the soil
Soil tray, cress or mustard seeds, compost, watering can
Pass around some seeds, emphasising how tiny they are.
Place compost in the seed tray and place the seeds about 2.5 cm apart
Water them and wait for them to grow
Dig up one plant and observe, say, ‘Look at how from one tiny seed, the plant can hold so much soil, do you remember how tiny it was. Just imagine how much soil all the plants in the earth hold.’
Show Chart L
Outside with the children ask them how much soil plants are holding
Show how much soil plants hold, preparation for understanding erosion
Types of roots
Use results form previous experiments
Say, ‘Lets look at some different types of roots, tap roots have one main root with some secondary roots branching out of it, the primary root grows straight down and grows deeper than the secondary roots which come out of it laterally, tap comes from the Old English word meaning, ‘to pierce’.’
Show deciduous and dicotyledon roots
Say, ‘These are fasciculated roots, they grow like fine threads in all directions. The word comes from the Latin fascis which means ‘bundle’ or facia, meaning ‘group’, faciculus means a ‘small bundle’.
Show evergreen and monocotyledon roots
Look at further examples
- tap roots, beans, roses, mustard, dandelion,
- fasciculated root grass, corn, leek
Show how much soil plants hold, preparation for understanding erosion.
Fasciculated roots are also called reticulated.
Reinforcing the types of roots
The result of the experiment in the mesh basket, Experiment 2
Say, ‘Do you remember that we said that roots like water so much they go in search of it. For however much they like water they dislike light.
Hang the basket from the original Experiment 2 in the light,
Observe how the roots shy away from the light, they curl up. ‘When roots are exposed to the light they retreat.’
Roots really like to grow in the dark.
The result of the experiment with the beans around the outside of the jar, Experiment 3.
Remove the construction paper and observe the micropile observe that however the seed was placed the root grows downwards.
Conclusion of all work on roots so far
Say, ‘We can say that roots have been given three commands’
- grow towards the water
- grow in darkness
- grow downwards
of these commands the command to grow towards water is the strongest, roots will disobey the other two commands in order to reach water. Remember we said that if the root tip is broken off, it will always grow downwards. If it keeps going far enough it will find water
Introduce the terminology when the children are ready
- tropism – the response of a plant to an external stimulus, by growing in a direction determined by that stimulus, from the Greek ‘tropos’ for turning
- geotropism – the response of a plant to the stimulus of gravity, ‘geo’ Greek for earth (roots show positive geotropism, the stem is negatively geotropic)
- hydrotropism – the response of a plant to the stimulus of water, ‘hydro’ Greek for water (roots show positive hydrotropism)
- phototropism – the response of a plant to the stimulus of light, ‘photo’ Greek for light (roots show negative phototropism, the stem is positively phototropic)
Adaptation and other functions
To discuss and observe.
Ask, ‘Do you remember where roots grow (in soil/under the ground) they grow underground because they are the water seekers of the plant and they get their water underground’.
Recap the three commands given to the roots with the child – they grow towards water, in darkness, downwards
Discuss with the interested child, showing examples
- Some plants grow in tropical counties where the air is very moist, the grounded is crowded with other plants, so some plants may have decided to get their water from the air, they have ‘ariel roots’, for example the tree orchid
- Some plants like the climbing Ivy have little rootlets which help the plant grow up towards light, these don’t help collect the water but bring the plant up towards the light
- The Banyan tree has special roots called ‘pillar roots’, they support the weight of the tree and suck up the water
- ‘Prop roots’ used by corn and maze and in mangroves give support the plant and they push the stems up out of the damp and swampy ground, so that they won’t rot.
- ‘Swollen or tuberous roots’ can store the food for the plants, like carrots, radish.
- Sprout a variety of seeds so that children can study the parts of the root for variations and similarities
- Use Nomenclature booklets
- Explore further outside
- Study reference books
- Visit botanical gardens