Download Plants: What do plants need to grow?

Plants: What do plants need to grow?
Objectives
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Find out and describe how plants need water, light and a suitable temperature to grow
and stay healthy.
Plenary
Ask the pupils to list things that humans need to survive. They should be able to differentiate
between essentials (food, water, air, sleep, warmth) and non-essentials (exercise, showers).
Explain that just like humans, plants have things that they cannot survive without.
Growing healthily
Revise how a healthy plant grows from a seed. Say that this can only happen when a plant is
provided with some essentials. For germination, they need water and warmth. A seed will
remain dormant unless it has water and warmth.
Once a plant has germinated, it needs water, warmth and light. Plants need energy from light
to make its food (through a process called photosynthesis). Pupils should discuss the
following questions:
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Why don’t you get many plants in caves?
Why don’t you get many plants in the desert?
What would have happened in Jack and the Beanstalk if Jack had lived in the Arctic?
Why is the rainforest a good place for plants to grow?
To demonstrate that plants need light, put a young runner bean plant in a dark environment
with a single light source. It will grow towards the light.
Pupils must note:
Seeds need water and warmth to germinate. Plants need water, warmth and light to stay healthy.
Note that pupils do not need to learn about plant respiration in KS1, but it is valuable to
explain that plants also breathe, although they breathe a different part of the air to humans.
Testing the health of plants
Ask pupils to suggest ways of seeing that a plant is healthy. They may suggest that healthy
plants are green, perky, and if it has petals they will be colourful and undamaged.
EXPERIMENT: In table groups, pupils should set up three sets of cress seeds by unrolling
small pieces of cotton wool and pouring some cress seeds onto each. Put each set of seeds
either in a small transparent tray or, if resources are available, place them inside empty
eggshells which can be decorated to make cress heads.
© Education Umbrella 2015
The pupils should give one lot of seeds light and water (placed on a windowsill and
dampened), one just light (placed on a windowsill) and one lot just water (placed in a dark
cupboard and dampened). Label the sets of cress seeds with the pupils’ names and the
conditions that they have been placed in.
Check on the cress seeds every few days. After two weeks, the groups should look at the sets
of cress, draw simple diagrams, make notes about the health of the cress (considering colour,
wilting, how much it has grown) and draw a simple conclusion about the best way to keep
plants healthy.
Pupils should find that the cress with water and light grows green and upright. Without
water, the cress wilts or doesn’t germinate at all and without light it goes yellow.
Pupils should fill in the columns in the worksheet, identifying which things are necessary for
plants, humans, both or neither. Pupils may need guidance while sorting ‘food’ and ‘air’;
food is essential for a plant (although it makes its own) and both humans and plants need air
(although they breathe different constituent gases).
Essential for plants: sunlight. Essential for plants and humans: water, warmth, air, food.
Essential for humans: sleep. Non-essential: TV, garden gnome, husband/wife, clothes.
Possible extra-curricular questions
Why does a plant need water?
A seed needs water to begin germination. A plant needs water to help make food. It is soaked
up by the roots and travels up the stem to the leaves, where the plant carries out
photosynthesis to make its food. Water travelling up a plant’s stem is what makes it stand
upright; this is why an unwatered plant goes floppy.
Why does a plant need light?
Plants need light to help make food. They use the energy from light to carry out
photosynthesis so without light they will starve.
Why does a plant need heat?
All living things need some warmth. This is because all life processes (respiration, digestion,
reproduction, etc) are controlled by important chemicals which cannot carry out their work
when it is too cold.
© Education Umbrella 2015