How Plants Sense - A Social Network ( Rough Draft )

This project began with questioning how plants sense their surroundings. With realizing how broad a topic this can be, the decision was made to highlight one specific sense; communication. The question is not if plants can communicate, that was already a given. The question is, how exactly does this occur?  The hypothesized scenario was that the roots somehow intertwine, and transmit genetic messages from plant to plant, then operational functions are sent to specific organs of the plant via the vascular system.

Defining Senses

             Most people would think that to see, means to have the ability to form pixelated images within the mind, by ways of optical mechanics connected to the brain. In the kingdom of plantae, this obviously is not the case. Understanding that plants do not have eyes and therefore cannot see images demands that the definitions must be expounded. For this project senses are defined as; the way that a living thing perceives, and innately responds to an external force. Communicate is the idea of an exchange of nutrients from plant-plant. It is fun to imagine plants as being capable of communicating with audible speech, or seeing as humans do. However, it is vital to understand that this language is figurative, used to describe the biochemical awareness plants possess. Though the language is figurative, the function is not. Plants unquestionably sense light, touch, odor, and can even communicate (Chamovitz, 2017).

Light, Touch, Odor

            Biologically plants and animals have many parallels. They both contain many of the same biochemical compounds, such as calcium, and glutamate. Interestingly enough, glutamate is a neurotransmitter in animals. Similarly, in plants glutamate also functions as a transmitter. When the leaves are touched glutamate goes on to alert receptors that release a calcium signal. The calcium flows through the plant via its vascular system to the roots, which act as the center for response. The roots then trigger defense hormones; salicylic acid, jasmonic acid, and ethylene which voyage to a prescribed organ to counter the force. Simply put, when a plant is touched, hormones are the messengers which carry the message of biochemicals. Each of these chemicals cause a different reaction. In the specific biochemicals of these hormones the plant goes on alert for the possibility of danger near (Plant Hormones 2009).

            When light is detected within its leaves, there are many different chemical compounds that respond. Photoreceptors and stomata are altered by the light and send encrypted chemical messages to the roots using the vascular system. The same principal process occurs for sensing touch and odor. It begins in the leaves, contacts the roots, then ends with a specific organ receiving messenger proteins to perform a response to the surrounding force (Secondary plant nutrients: Calcium, magnesium, and Sulfur 2021).

            Fungi & Root Symbiosis. Plantae communication can be viewed in two spectrums; internal and external communication. Internal would resemble one of the senses using the vascular system as seen above. External communication is an entirely different condition. Beneath the surface in the soil, roots far outstretch branches. Their main intention is to extend upon as much surface area as possible in order to soak up all the water and nutrients it can. When elongating often, roots and fungi will bind together. Fungi are parasitic in nature and need a host for survival.  Thousands of species of fungi exist; however, mycorrhizal fungi generate a symbiotic association with plants. Mycorrhiza is a term used to describe how the filament-like structures of fungi called hyphae, connect to the root hairs. Eighty to ninety percent of plants form mycorrhizal relationships, and a substantial number of fungi will do the same (Mycorrhiza 2013). Amongst the many different kinds, I chose to study ectomycorrhizal relationships, which work to connect the tips of the mycorrhizal roots of the plant to the reproductive structures of the fungi using the mycelium (a collection of hyphae). These relationships make up the majority of an ecosystem’s biomass (Brundrett, 2008). Fungi tends to be host specific, not all will acclimate to every plant. The same goes for the hosts, not all plants welcome relationships with all fungi.

            Structural Breakdown of Ectomycorrhizal Fungi associations with Plant Roots.  Ectomycorrhizal relationships occur when the “host roots and compatible fungi synchronize”. The Ectomycorrhizal (ECM) hosts roots are primarily heterorhizic in form meaning their shape resembles a lateral branching pattern. They are composed of shorter mycorrhizal roots which branch out of longer roots. These two roots are mostly identical, with the exception that smaller roots grow slower. It is speculated that this slower growth rate enables the fungi to associate, because this process can be timely (Brundrett, 2008).

            A hyphal network is built of single strands or collective groups of hyphae (mycelial strands). This system operates to retrieve sustenance from the soil, transport resources throughout the organism, and is the center for mycorrhizal connections and trading of goods between fungi and plant (Brundrett, 2008). When connection occurs, the hyphal network will act as a propagule, meaning it begins to grow with the plant in a bound formation on the outside of the roots (Propagule definition & meaning 2012).

            The connection is initiated by the hyphae which glues itself to the outermost cells of the short roots. The hyphae will sprout two days on average after the connection first commenced. The mycorrhizal established roots will vary in branching design because of the numerous kinds of root-fungi connections (Brundrett, 2008).

            Hyphal networks can attach not only to one plant, but to as many as it can reach and often found in relationship with multiple species. In addition, they can link up with other kinds of mycorrhizal fungi. This can create a truly enormous and diverse network of roots, in an ecosystem which is referred to as “plant-mycelium-plant association”. Similar to the way a telephone line works, the roots carry messages back and forth between neighboring plants. To be quite imaginative, in this way, plants do talk to one another. If one plant is suffering, adjoining plants will send the resources it needs from their own supply to maintain the health of the ecosystem (Mycorrhiza 2013).

            An example of this phenomenon is found in a study done by students at RWTH Aachen University in Germany. The cite of this research was the Eifel National Park home to an abundant community of Fagus sylvatica, commonly known as the European beech trees. These deciduous trees “showed highly distinct macrofungal communities together with a two times higher fungal species richness compared to ~70 years old Norway spruce forests.” (Heine et al., 2016).  Forester Peter Wohlleben deduces that “the trees synchronize their performance so that they are all equally successful” (Wohlleben et al., 2018). This beech community thrived because if any lack was found, resources were dispersed.

            The social network that ectomycorrhizal fungi-host roots can create could have tremendous applications in forest conservation. Science has only touched the tip of this iceberg, the possibilities that mycorrhizal fungi present could truly transform entire biomes.

           

           

           

 

 

 

 

 

 

 

References

Australian National Botanic Gardens. (2013, January 22). Mycorrhiza. Retrieved November 3, 2021, from https://www.anbg.gov.au/fungi/mycorrhiza.html.

 

Brundrett, M. (2008). Mycorrhizal Associations: The web resource. Mycorrhizal Associations: Ectomycorrhizas. Retrieved October 15, 2021, from http://mycorrhizas.info/ecm.html.

 

Collins English Dictionary. (2012). Propagule definition & meaning. Dictionary.com. Retrieved November 1, 2021, from https://www.dictionary.com/browse/propagule.

Chamovitz, D. (2017). What a plant knows: A field guide to the Senses. Scientific American/Farrar, Straus and Giroux.

 

Heine, P., Hausen, J., Ottermannas, R., Schaffer, A., & Rols-Nickoll, M. (2016). (Elsiver). Forest conversion from Norway spruce to European beech species richness and functional structure aboveground macrofungal communities (pp. 1–9). Elsevier.

 

Mississippi State University. (2021). Secondary plant nutrients: Calcium, magnesium, and Sulfur. Mississippi State University Extension Service. Retrieved November 4, 2021, from http://extension.msstate.edu/publications/secondary-plant-nutrients-calcium-magnesium-and-sulfur#:~:text=The%20primary%20function%20of%20calcium,normally%20not%20deficient%20in%20calcium.

 

Science Direct. (2009). Plant Hormones. Plant Hormones - an overview | ScienceDirect Topics. Retrieved November 4, 2021, from https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/plant-hormones.

 

Wohlleben, P., Billinghurst, J., & Wohlleben, P. (2018). The Hidden Life of Trees: The illustrated edition. Black Inc.