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(Narrator) Plants come in a great variety
of colours, shapes and sizes.
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In the world of living things
plants are valued for their beauty and their usefulness.
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Few people though think of plants as being particularly active.
[Birds chirping and Music plays]
Most plants show little or no obvious movement
apart from the movement of leaves and branches in the wind.
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Yet when we look more closely at plants
or change the way we look at them
we find they show a great deal of activity.
These are leaves of mimosa,
a sensitive plant which is common in warmer parts of the world.
Watch what happens when a mimosa leaf is touched.
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The leaves of some plants such as the Venus flytrap
can capture and digest insects and other small animals.
The leaf responds when sensitive hairs inside it are touched.
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The sundew plants have sticky hairs that can close around an insect,
hold it in place and digest it.
Flowers of the trigger plant respond to touch
in a way that helps pollinate the flower.
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Not many plants move in such ways
yet all plants do move.
Their movements
are not as obvious because they take place much more slowly.
These are leaves of an albizia tree during the day.
At night it looks like this.
The leaflets have closed.
Slow movements can be made to look faster by a filming technique called
time-lapse photography.
At 60 times normal speed
patterns of movement become obvious.
The same technique can be used to film the leaves of the albizia tree
as day ends and night begins.
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Here's the action again.
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Even during the night the plant is not entirely still.
With a new day the leaflets open.
Some other plants also close their leaves at night.
This is oxalis.
Its leaves respond to light changes with a display of graceful movements.
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These are leaves of a cassia bush in daylight,
at night and at dawn.
Some flowers will only open in sunlight.
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So with time-lapse photography
all sorts of plant movements become noticeable.
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Clover leaves in a pasture move continually through the day
as the sun moves across the sky.
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And this is leucaena a tropical plant.
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Daffodils at dawn on a frosty morning,
watch the leaves once the sun is up.
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Some of the most striking activity in plants is found during growth,
a developing bean.
A young fern frond.
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The subtle movements of a plant can be both complex
and beautiful.
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Climbing plants are remarkable for their growth movements.
This is the growing tip of a climbing hibbertia.
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It is even possible to watch the woody fruits
of a banksia opening after a fire
and releasing their seeds.
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With some plants the daily cycle of movement
combined with growth movements
is very striking.
These are water lilies
at 10,000 times normal speed.
A flower bud opens during the day
usually in bright light
and closes again later in the afternoon.
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Morning,
afternoon,
night
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and morning again.
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At first glance then most plants look inactive
but a great deal of movement is in fact taking place
as the plants grow and respond to changes in their surroundings.
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