Many people think of plants as being passive, inert organisms that are rooted to one location and can’t react to their environment.
A new research field is challenging this assumption and demonstrating that plants can detect and adjust to environmental signals as well as animals.
The plants can detect light using specialised proteins. They also respond to vibrations, touch and sound via channels that are mechanosensitive. They recognise the chemical signals sent by their neighbouring plant and they even remember past events through DNA changes.
I am currently working on a project that examines how plants can detect time in their seasons. But this is only one part of an extensive review of the sensory capabilities of plants and their parallels to animal senses.
Colours are visible to plants
Plants can sense light. Anyone who’s seen a flower turn its head towards the sun will know this. Plants use specialised receptors to detect light, just like animals. Each one is tuned for a specific wavelength or colour of light.
Cryptochromes and Phototropins are sensitive to ultraviolet and blue light, while phytochromes respond only to red light. The sensors convert light signals into molecular messages that help plants coordinate their daily rhythms.
New research shows that trees are able to recognize the solstice of summer, which is the longest day in the year. The cue could act as a switch to trigger a change in physiological processes, such as the ageing of leaves and buds.
I have identified an Early-Flowering-3 gene in European Beech Trees (Fagus Sylvatica(which seems to regulate seasonal responses, such as the storage of energy and changes in hormone signals from plants.
Light detection is just one of the senses plants use to understand their environment.
The vibrations produced by insects can be detected by plants, like this Kawakawa. Getty Images
Listening to their surroundings
Also, plants can listen. Plants can also hear.
The plants can generate vibrations of their own. Under stress, tomato and tobacco plants produce ultrasonic clicking sounds that can provide valuable information on the condition of the plant, such as the degree of dehydration. You can record these clicks using a sound recording device.
Scientists have also observed what happens to plants when sounds are played. Scientists observed the changes to the cell membranes and chemical signals along the ion channel. These channels are similar to nerves in plants, but they act as small gateways for information transmission in and out cells.
We don’t know the exact mechanisms plants use to detect sound, but now we investigate whether they can sense vibrations by tiny hairs on leaves.
Please don’t touch me
Plants can also react directly to touch. This is often done in a striking way.
The touch-me not plant is a familiar example.Mimosa pudicaThe Venus flytrap is also known as the Venus flytrap.Dionaea muscipulaThey respond by closing their leaves quickly when touched.
Touching the Venus flytrap’s leaves will cause it to close its leaves.
Getty Images
The examples above demonstrate plants’ abilities to respond and perceive mechanical stimuli. Plants can also sense rain, and the damage done by herbivores.
Plants will then activate their defence mechanisms, such as producing toxins and depositing lignin in order to be less appealing to herbivores.
Plants, just like animals contain proteins that are specialised to detect physical forces. The mechanical-sensing proteins are able to convert the physical stimulus into biochemical signaling, usually through calcium.
The plants remember their past and decide on the future
Plants can remember that the winter is over by noticing changes in temperatures. They can flower when the spring comes by remembering that winter was cold.
These memories, as observed in animals and humans alike, are stored by epigenetic mechanisms.
The epigenetic process alters the packaging and reading of genes, creating a molecular record.
Masting is a New Zealand phenomenon where trees in entire forests remember the temperatures of previous summers.
The spread of seeds and pests can be a threat to native wildlife.
Researchers have discovered that temporary chemicals tags can be generated by removable markers. These chemical tags are able to switch off genes. It allows the masting plant to store information for more than one year.
These findings demonstrate that plants have sensory systems similar to those of humans. Plants are far from passive and unresponsive. They respond in complex, sophisticated ways to environmental cues.
This new way of thinking about plant life challenges old ideas on intelligence, communication and awareness in nature.
