You have probably heard that plants can be affected by human emotions and that you should probably talk to your plant if you have one!
Although there is no scientific evidence that plants are affected by the emotions of humans, it is true that they are able to communicate with other plants, either to coordinate their processes or to warn them when there is danger nearby. So without further ado, let us take a closer look at the process of plant communication as well as some examples!
Cell communication in plants
As a starting point, let's take a look at the structure of plant cells. Remember that plants are a part of the kingdom Plantae and the domain Eukarya.
Although plant and animal cells have some similarities, plant cells have some structures that animal cells don't.
Plant cells have a cell wall of cellulose that gives the cell support.
They also have a central vacuole containing a weak solution of sugars and salts. The central vacuole is used for storage, waste breakdown, and also aids in metabolism. The tonoplast is the membrane enclosing the central vacuole.
Chloroplasts are photosynthetic organelles that contain chlorophyll for photosynthesis.
Plasmodesmata are channels that connect adjacent cells' cytoplasm through the cell wall and plasma membrane.
Plants can communicate in various ways, such as through direct contact, plant hormones, and electrical signaling. Different activities are coordinated based on environmental stimuli through communication.
In addition, they can communicate with other plant cells to let them know what is happening in other parts of the plant, such as roots and leaves.
These junctions called plasmodesmata between plant cells are where cellular communication takes place through direct contact (cell-to-cell contact). The plasmodesmata transport materials from cell to cell through the cytoplasm.
Local signaling in plants
Although there is a lot that researchers still do not understand about local signaling in plants, they do know that just like animals, plants can use hormones for signaling. Most plant hormones reach their target cells by moving cell-to-cell.
Some important plant hormones include:
- Auxin (IAA) - Stimulates stem elongation, root growth, and branching. It also regulates fruit development and enhances functions in phototropism and gravitropism.
- Cytokinin - Stimulates cell growth, cell division, and germination.
- Gibberellins - Promotes seed and bus germination, shoot elongation, and leaf growth. It also promotes flowering and fruit maturation.
- Ethylene - Promotes fruit ripening and leaf fall.
Plant communication electrical signaling
As a response to environmental stimuli or hormones, plants generate electrical signals as a form of communication. These signals affect plants in different forms, including photosynthesis, respiration, flowering, and wound healing.
In plants, signal transduction is the pathway through which chemical or physical signals are transmitted through a plant cell in response to environmental stimuli, and linked to cellular responses.
Step 1: Reception - The first stage of signal transduction in plants is reception. Here, signals such as hormones (chemical signals) or environmental stimuli are detected by receptors usually located in the plasma membrane. These receptors are proteins that change in shape in response to a specific stimulus.
Step 2: Transduction - Following the reception of the signal, transduction occurs. The transduction of these signals involves second messengers.
Second messengers are small molecules and ions in the cell whose job is to amplify the signal from the receptor and transfer it to other proteins that carry out the response.
Examples of second messengers involved in plant communication are cytosolic calcium ions (Ca2+) and cyclic GMP (cGMP).
Step 3: Response - When second messengers transfer the signal to proteins that produce a physiological and cellular response.
Plants communicate through roots
Scientists have viewed plants very differently ever since one research changed the way they thought about them. It has been discovered that plants are capable of communicating through their roots! They do this by secreting root exudates into the soil through the rhizosphere (the plant's root zone).
Root exudates are organic compounds exuded by plant roots into surrounding substrates.
This form of communication is the primary way in which plants communicate with their rhizosphere microbiome to facilitate nutrient absorption, plant-to-plant signaling, the recruitment of beneficial microorganisms and even parasitism!
For example, wounded tomatoes can send signals to let neighboring tomato plants know about any herbivore infestation so that they can prepare some kind of defense.
A plant can also use roots to "listen in" on their neighbors! Pretty cool, right?
Do plants have any help when it comes to communicating with other plants? The answer to this question is yes! Plant communication can be enhanced by the presence of mycorrhizal fungi.
Mycorrhizal fungi are fungi that form symbiotic associations with plant root.
These mycorrhizal fungi contain big mycelial networks that are very efficient in transmitting signals between the roots of plants, and also help the plant's root to acquire water and minerals from the soil.
For example, if a plant that is further from another plant finds itself in the need for some nutrients, the nutrients can be transported from another plants to that plant through the underground mycelial network!
Plant communication examples
Let's look at examples of how plants use communication to respond to different environmental stimuli.
In drought seasons, plant cells communicate with other plant cells to reduce the rate of transpiration and conserve water. This is done by the release of abscisic acid (a plant hormone) in the leaves, which helps keep a plant's stomata closed.
Some plants can communicate through impulses known as action potentials.
For example, the Venus flytrap plant transmits action potentials from the sensory hairs in the trap that respond by closing the trap!
Figure 6. Venus flytrap.
During cold conditions, plants might respond by adjusting membrane fluidity and producing antifreeze proteins. On the other hand, a plant can respond to severe heat stress by producing heat-shock proteins that reduce protein denaturation.
Plant communication impact factor
One of the most popular journals regarding plant biology is called plant communications. This journal publishes research involving technical advances and resources in plant evolution, ecology, plant physiology, plant biochemistry and many other areas of plant biology.
This year (2022), the journal of plant communications has had an impact factor of 8.625.
The impact factor is calculated based on how many citations it has received from papers published within the past two years.
Plant communication research
To finish off, let's explore some interesting research on plant communication. Researchers have found that elevated levels of ozone (O3) cause disruption in the communication between plants and insects in urban areas by degrading volatiles involved in the communication.
Another research found that melon plants that have been infected by a type of potyvirus (watermelon mosaic virus) are able to emit volatiles that induces gene deregulation in healthy plants nearby, similar to preparing them for incoming infections!
Plant Communication - Key takeaways
- Plants use communication to coordinate different activities based on environmental stimuli, and also to let other plant cells know that is going on in the roots, leaves or other areas of the plant.
- In plant cells, communication via direct contact (cell-to-cell contact) happens in these junctions between plants cells called plasmodesmata.
- As a response to environmental stimuli or hormones, plants generate electrical signals as a form of communication. These signals affect plants in different forms, including photosynthesis, respiration, flowering, and wound healing.
- Mycorrhizal fungi are fungi that form symbiotic associations with plant root.
References
- Impello® Biosciences, Root Exudates, (n.d.).
- Biology Discussion, Plant Signal Transduction | Biotechnology, 23 Dec. 2016.
- Elhakeem, A., Markovic, D., Broberg, A., Anten, N. P. R., & Ninkovic, V., Aboveground mechanical stimuli affect belowground plant-plant communication. PLOS ONE, 13(5), 2018.
- Cell, Issue: Plant Communications, (n.d.).
- Masui, N., Agathokleous, E., Mochizuki, T., Tani, A., Matsuura, H., & Koike, T., Ozone disrupts the communication between plants and insects in urban and suburban areas: an updated insight on plant volatiles, Journal of Forestry Research, 2021.
- López-Berenguer, C., Donaire, L., González-Ibeas, D., Gómez-Aix, C., Truniger, V., Pechar, G. S., & Aranda, M. A., Virus-Infected Melon Plants Emit Volatiles that Induce Gene Deregulation in Neighboring Healthy Plants. Phytopathology®, 111(5), 862–869, 2021.
- AP Biology - AP Central | College Board, AP Central, 30 May 2017.
- Mary Ann Clark, Jung Ho Choi, Douglas, M. M., & College, O., Biology. Openstax, Rice University, 2018.
- Pack, P. E., AP biology, 2013.
- Figure 6: Venus Flytrap (https://www.flickr.com/photos/192952371@N05/51177629780/) by Gemma Sarracenia (https://www.flickr.com/photos/192952371@N05/). Licensed by CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/).
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