Stem senses
HEaring
Whilst you may never have thought plants could listen in on your conversations, you'll be surprised to hear that plants have been recorded responding to different sounds and changing their behaviour based upon what they hear. The mechanism behind plants hearing capabilities is not yet fully understood. However, it is evident that plants use sound in a wide variety of ways to make sense of their environment.
Chatty plants
Research suggests that plants may not only be able to hear sounds, but they may be able to release them too. The young roots of corn plants have been shown to release sounds, but why they do this is not yet known.
Key definitions
Pollinator: an organism which carries pollen from one flower to another.
Species: a group of similar organisms which are able to breed and produce fertile offspring.
What do you think?
Could certain flower shapes be better at "hearing" sounds? Think about the shapes of animal ears and how they are adapted to collecting acoustic information.
What do you think?
(Hover over me)
The hungry caterpillar
A study conducted by scientists in Missouri discovered that plants release chemical defences when they hear caterpillars munching on their leaves. Their methods:
-
The researchers recorded the small vibrations made by a caterpillar eating the leaves of a plant;
-
Then they played back the sound of the caterpillar eating to one set of plants and only silence to another set of plants;
-
They then played the recording to both sets of plants.
They found that the plants which had previously heard the sound of caterpillars eating quickly produced a chemical defence to prevent the caterpillar from eating their leaves, when they heard the recording for the second time. Whereas the plants which had not heard the sound of the caterpillars before produced no extra defence chemicals. It is thought that using hearing to identify danger is one of the fastest ways plants can protect themselves.
Sweet treats
The flowers of the plant Oenothera drummondii, have been shown to respond to airborne vibrations released by approaching pollinators. Research has shown that in response to the vibrations caused by the beating wings of bees, flowers produced nectar which had a higher concentration of sugar. It appears that the flowers themselves "hear" the approaching pollinator. The researchers found that the flowers of the plant were the most more sensitive than the stem and leaves of the plant to sound. This response is beneficial to both the plant and the pollinator involved because:
-
By increasing the reward the pollinator receives when it visits the plant, it is likely they will return to a plant of the same species, in turn increasing the chance of successful pollination and reproduction.
-
The pollinator is likely to spend longer at individual flowers, increasing the likelihood that it collects pollen or deposits more pollen.
follow the water
Watch this video to see how researchers at the University of Western Australia discovered that plants can use their hearing capabilities to locate water sources.
acoustic pollution
New understanding of the ways plants use sound within their environment has thrown into question whether noise pollution is having a greater effect on plants than originally thought. Research has already found that the sound sensitive pollinators and seed dispersers which plants rely upon are affected by noise pollution. Effects have been shown to be both positive and negative. However the long-term effects of noise pollution are not yet known and as sources of noise pollution only increase, it is likely the ecological impacts will become more apparent.
Summary
-
Different sounds have been found to trigger different plant behaviours
-
Plants can distinguish potential predators or pollinators based upon individual frequencies
-
Plants can link previous harm to vibrations and respond to defend themselves when they next hear the vibration
-
Acoustic pollution affects plants indirectly by affecting the animals which visit the plant
-
It is likely that increasing noise pollution will have greater affect on plants in the future