Plant communication
[1] Therefore, in order to respond or be ready for any kind of physiological state, they need to develop some sort of system for their survival in the moment and/or for the future.
[7] Due to the physical/chemical constraints most VOCs are of low molecular mass (< 300 Da), are hydrophobic, and have high vapor pressures.
As such, whether neighboring plants have evolved the capability to "eavesdrop" or whether there is an unknown tradeoff occurring is subject to much scientific debate.
[12] In Runyon et al. 2006, the researchers demonstrate how the parasitic plant, Cuscuta pentagona (field dodder), uses VOCs to interact with various hosts and determine locations.
Their experiments also showed that the dodder weed seedlings could distinguish between wheat (Triticum aestivum) VOCs and tomato plant volatiles.
Plant receptors are most commonly found on plasma membranes as well as within the cytosol, endoplasmic reticulum, nucleus, and other cellular compartments.
VOCs that bind to plant receptors often induce signal amplification by action of secondary messengers including calcium influx as seen in response to neighboring herbivory.
Starting in the late 1800s scientists, such as Charles Darwin, examined ferns and Venus fly traps because they showed excitation patterns similar to animal nerves.
[40] Alternatively, the transport of action potentials over short, local distances is distributed throughout the plant via plasmodesmatal connections between cells.
[43] Additionally, ethylene has shown quick upregulation in the fruit of a plant as well as jasmonate in neighboring leaves to a wound.
[50] Falik et al. subjected the root of an externally-induced plant to mannitol in order to inflict osmotic stress and drought-like conditions.
[50] Therefore, neighboring plants demonstrate the ability to sense, integrate, and respond to stress cues transmitted through roots.
They found that plant roots synthesize and release a wide array of organic compounds including solutes and volatiles (i.e.
[51] They cited additional research demonstrating that root-emitted molecules have the potential to induce physiological responses in neighboring plants either directly or indirectly by modifying the soil chemistry.
[51] Moreover, Kegge et al. demonstrated that plants perceive the presence of neighbors through changes in water/nutrient availability, root exudates, and soil microorganisms.
[50] Further research is needed to identify a well-defined mechanism and the potential adaptive implications for priming neighbors in preparation for forthcoming abiotic stresses; however, a literature review by Robbins et al. published in 2014 characterized the root endodermis as a signaling control center in response to abiotic environmental stresses including drought.
[53] They found that the plant hormone ABA regulates the root endodermal response under certain environmental conditions.
In 2016 Rowe et al. experimentally validated this claim by showing that ABA regulated root growth under osmotic stress conditions.
[54] Additionally, changes in cytosolic calcium concentrations act as signals to close stomata in response to drought stress cues.
Therefore, the flux of solutes, volatiles, hormones, and ions are likely involved in the integration of the response to stress cues emitted by roots.
[55] The researchers followed seedlings of paper birch and Douglas-fir in a greenhouse for 8 months, where hyphal linkages that crossed their roots were either severed or left intact.
[56] Through root systems and common mycorrhizal networks, plants are able to communicate with one another below ground and alter behaviors or even share nutrients depending on different environmental cues.
