Stem senses
Taste
Just as humans are able to distinguish between salty and sweet it has been discovered that plants are also able to distinguish between the "tastes" of different organic compounds released by other plants. These compounds may allow for plant-plant communication without them having to speak a single word.
How plants taste
On the surface of a plant are many receptors which allow for soluble molecules to dissolve into them. Certain tissues of plants such as the roots are already covered with receptors for the absorption of water and minerals from the soil. This makes them the perfect area for tasting different organic compounds. Not only can plants 'taste' organic compounds using their roots, but plant roots can also release their own soluble organic compounds known as exudates. These exudates travel through the soil and can then dissolve into the roots of neighbouring plants.
Key definitions
Organic compounds: Chemical compounds, which make up the majority of living organisms e.g. proteins.
Receptors: cells which detect environmental change and respond to the change.
Soluble: a substance that dissolves.
Exudates: substances secreted by an organ, in this case plant roots
Abiotic: non-living factors such as wind, water or temperature.
Control group: a group within an experiment that receives no treatment from the researchers, so that treated groups can be compared.
Root-root communication
Studies have shown that plants use root exudates to communicate to other plants that are close by. The root exudates act as messages which can be sent by one plant and received by another. These messages give off different pieces of information about the sender. From these messages plants can determine if they are near to relatives or competitors. Depending on the information they receive plants will then change their behaviour accordingly. These messages can be wide-reaching, allowing for long distance communication between plants.
The corn maize experiment
A well known experiment examining plant-plant communication was conducted by researchers in 2018 on maize seedlings. It explored whether above ground abiotic stresses on plants would cause growth changes in nearby plants. They did multiple tests to observe plant behaviour changes.
Test 1
-
Plants were touched to recreate naturally occurring mechanical stimulations e.g. wind;
-
The chemical exudates released by the touched plants were collected, these were known as growth solutions;
-
Maize seedlings were then allowed to grow either towards the control group (not touched) or the stressed (touched) groups growth solution.
The results showed that the maize seedlings preferentially grew towards the control groups solution, who had not been touched within the experiment. This demonstrated that plants can differentiate between the exudates released by stressed and non-stressed plants, with plants choosing to grow in the direction avoiding stress.
Test 2
-
Maize leaves were touched to produce a stress response;
-
The researchers collected the growth solution produced by stressed plants.;
-
They then placed non-stressed plants into the the stressed plants growth solution.
This test found that not only do plants avoid stress, but they can change their growth patterns to reduce potential stress on certain tissues for example stems or roots. The researchers found that when non-stressed plants were placed into the stressed plants growth solution, the non-stressed plants started to grow more leaves and fewer new roots. They hypothesised that this response was due to the touching being an indication of close competition. In response to potential competition plants appear to redirect their resources to stressed tissues (in this experiment these tissues were the leaves). By helping stressed tissues, plants are then better able to tolerate any potential environmental changes.
Summary
-
Plants use receptors on the surface on their tissues to detect soluble organic compounds.
-
Plants can use different combinations of organic compounds known as exudates to communicate to neighbouring plants.
-
Neighbouring plants detect the composition of root exudates and alter their growth pattern or behaviour accordingly.
Explore the academic literature...