Plants in Action (1983)
We tend to think of plants as being essentially stationary incapable of movement other than that generated by the wind. But all plants do move as they grow and respond to aspects of their environment.
This film looks at a variety of plants in action. Some movements, like that of Mimosa, the sensitive plant, or that of the Venus flytrap are quite conspicuous.
Much plant activity, however, takes place too slowly for direct human perception it can be revealed only by time-lapse cinematography.
[Music plays, a grass field with the sun in the horizon appears on screen]
[Image changes to shots of different plants]
Narrator: Plants come in a great variety of colours, shapes and sizes. In the world of living things plants are valued for their beauty and their usefulness. Few people though think of plants as being particularly active.
[Title appears: Plants in action]
Most plants show little or no obvious movement apart from the movement of leaves and branches in the wind. 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.
[Camera zooms in on the leaves of the mimosa plant]
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.
[A finger touches the mimosa leaves and the leaves fold close]
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.
[Image changes to show an insect landing on the leaf of the Venus flytrap, and shows the leaves closing to trap the insect]
The sundew plants have sticky hairs that can close around an insect, hold it in place and digest it.
[Image changes to show an ant being trapped in the sticky hairs of the sundew plant]
Flowers of the trigger plant respond to touch in a way that helps pollinate the flower.
[Image changes to show an object being put into the centre of the flower and a trigger springs out]
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.
[Image changes to show the leaves of the albizia tree open and then close]
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.
[Image changes to show day turn to night and the albizia tree closing its leaves]
Here’s the action again. Even during the night the plant is not entirely still. With a new day the leaflets open.
[Image changes to show the oxalis plant with its leaves opening and closing]
Some other plants also close their leaves at night. This is oxalis. Its leaves respond to light changes with a display of graceful movements.
[Image changes to show the cassia bush with its leaves opened during the day and closed at night]
These are leaves of a cassia bush in daylight, at night and at dawn.
[Image changes to show bright pig face opening in the sunlight and closing at night]
Some flowers will only open in sunlight. So with time-lapse photography all sorts of plant movements become noticeable.
[Image changes to show the movements of the clovers throughout the day]
Clover leaves in a pasture move continually through the day as the sun moves across the sky. And this is leucaena a tropical plant.
[Image changes to show the leaves of the leucaena plant opening and closing]
[Image changes to shows the yellow daffodils unfolding as the sunlight warms them up]
Daffodils at dawn on a frosty morning, watch the leaves once the sun is up.
Some of the most striking activity in plants is found during growth, a developing bean.
[Image changes to show a green bean sprouting from the ground]
A young fern frond.
[Image changes to show a ferns growth using time-lapse photography]
The subtle movements of a plant can be both complex and beautiful. Climbing plants are remarkable for their growth movements.
[Image changes to show the hibbertia growing and curling around a garden stake]
This is the growing tip of a climbing hibbertia.
[Image changes to show a burnt banksia plant, the camera zooms in on the seed pod as it opens and a seed falls out.
It is even possible to watch the woody fruits of a banksia opening after a fire and releasing their seeds.
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.
[Image changes to show pink and white water lilies blooming]
A flower bud opens during the day usually in bright light and closes again later in the afternoon. Morning, afternoon, night and morning again.
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.
[Text appears: produced in association with the Australian Academy of Science Biology Project]
[Credits roll: photography and editing Roger Seccombe A.C.S. Script David Morgan. Music Tony Gould. Narration Gerard Kennedy. Production David Morgan, Nick Alexander. Thanks to Dr. Yvonne Aitken, Dr. Nan Anderson, L.R. and N.R. Gedye, Blue Dandenong Bulb Farm, Melbourne College of Advanced Education. A CSIRO film, Commonwealth Scientific and Industrial Research Organization Australia, copyright © 1983]