Plant Communication: Into the Roots

by on
Share:

Abstract

A previous article discussed plant communication and how plants are able to warn other plants of impending herbivory above ground. The warning occurs through airborne chemicals called volatiles. However, plants communicate for a variety of reasons and in many more ways than we have probably discovered. This article discusses some of the documented “under-the-table” communications. In every case, their communicative abilities point back to God’s very good world that he created in Genesis 1.

Plant Communication in Different Scenarios

In some cases, plants communicate but are not exchanging warnings. A parasitic plant may communicate with its host plant. A parasitic plant is a plant that uses resources obtained from other plants to survive. One type of parasitic plant, genus Striga, attaches to the host plant underground using a special organ called a haustorium. This allows the parasitic plant to siphon nutrients from the host plant. However, to form the haustorium, parasitic plants require the presence of special chemicals called haustoria inducing factors (HIFs). HIFs are produced by the host plants and are diverted by the parasite for other purposes.. When a parasitic plant root senses HIFs, it quickly produces a haustorium, which will attach to the host plant.1 Though parasitism is typically seen as negative, this kind of communication could have taken place in the pre-fall world since plants are not living in a biblical sense, though it may also have been commensal, causing no damage to the host, rather than parasitic at that time.

Other plants communicate with one another in less competitive ways. Sometimes, below ground, plants interconnect through a network of fungus called a mycorrhizal network. Mycorrhiza is the term for the relationship between plant roots and small fungal colonies that attach to the plant roots and interconnect the roots. It is estimated that eighty percent of land plants have a relationship with mycorrhiza.2 Many plants will only partner with a specific type of fungus to form their network, while most fungi have a wide range of plants they will partner with to form networks.3 Theoretically, since there is not a one-to-one correlation, some mycorrhizal networks could contain multiple species.

Tomato plants were grown in a common mycorrhizal network (CMN) with a fungus until the network was well established. Then one of the plants was given a disease, causing the uninfected plants to turn on genes associated with defense, as well as produce disease-fighting enzymes.4 Clearly, the neighboring plants were receiving information from the infected plants, which caused them to prepare to be attacked with a disease.

the ability to communicate underground about potential herbivore threats could still have been useful in a pre-fall world since plants would have been eaten at that time.

Mycorrhizal communication fits very well with the Bible’s description of the pre-fall world. In Genesis 1, God gave the plants to both man and animals as food. Thus, the ability to communicate underground about potential herbivore threats could still have been useful in a pre-fall world since plants would have been eaten at that time.

Plants do not just communicate with one another using the mycorrhizal network. They also communicate directly to the mycorrhiza themselves. The roots of a species of lotus were shown to induce the formation of fungal hyphae, the branching filaments that make up a fungus, in the mycorrhizal network.5 Given that this is a symbiotic relationship in which the plants gain nutrients and the fungi gain carbon, it is hardly surprising that there is at least some level of communication involved. The fungi need carbon which, due to their lifestyle, they do not have the ability to uptake. The plants need nutrients, which the fungi can extract from the ground more easily than the plants. The trade benefits both.

Plant Communication Using Microbes and Chemicals

Plants also communicate directly to microbes in the ground around them. Legumes are often found with nodules on their roots containing symbiotic nitrogen-fixing bacteria. These bacteria extract nitrogen from the environment, which plants need, then give it to the plants in exchange for nutrients the microbes need. The legumes release chemicals called flavonoids into the soils, which the microbes can sense.6 These cause the microbes to congregate on the roots and begin to trade resources with the plant. The nodules provide a safe haven for the bacteria. The plant benefits by gaining resources from the bacteria.

It is well known that plant roots exude chemicals into surrounding soils. Less well understood is the ability of these chemical signals to attract or deter certain microbes. Plants like rockcress, potatoes, sugar cane, and members of the mustard family have been demonstrated to have these effects on the microbe populations in the soil around them.7 Sometimes, microbes return the favor, producing what amounts to growth hormones for rockcress plants.8 It appears plants are not having a one-sided conversation with their microbe counterparts. Mutually beneficial symbiosis makes sense with God’s originally created “very good” world, and we still see some of this today.

Communication Across Kinds

In a multiple plant species study, researchers demonstrated that plants could communicate stress cues to their neighbors that were in direct contact underground. Further, unstressed plants receiving stress cues were able to pass those cues to other nearby plants whose roots they touched. Using three types of grasses and the common garden pea plant, the researchers planted multiple of each in pots. They then subjected one of the plants in the pot to drought, while the others were watered. The two nearby plants both responded to the stress they sensed in their neighbors by closing their stomata to minimize water loss. However, within 24 hours, the neighboring plants had acclimated to the stress cues from their neighbor and lack of stress and reopened their stomata.9 While this study did not involve mycorrhiza, the researchers did speculate about the role mycorrhizal networks play in plant communication. It would be interesting to repeat this experiment but replace the root touch with a mycorrhizal network.

Plant Communication: A Mystery to Evolutionists

there is no known mechanism for this form of communication to evolve, nor is it favored by the normal course of evolution.

Like plant-to-plant above-ground communication, below-ground plant communication is mystifying to evolutionists. One paper, commenting on the potential evolution of plant-microbe communication, admitted, “However, we know little about the next level of specificity, namely how selection for quality (rather than just identity) can evolve. In general, discriminating partners based on actual resources received, rather than signals, is evolutionarily more robust.”10 In other words, there is no known mechanism for this form of communication to evolve, nor is it favored by the normal course of evolution. Natural selection and mutation cannot account for it. Evolution would predict that, once a fungus had partnered with a plant, it would begin exploiting its host for additional resources. It does not do so. This mutualistic relationship is neither expected nor explainable by evolutionary dogma.

By contrast, plant communication in the roots and above ground makes perfect sense in light of a creationist worldview. Given that the pre-fall world was created perfect, and that plants were very much on the menu for humans and animals, it makes sense that God would give plants the ability to defend themselves to the extent that plant life would not go extinct. These methods of communication detailed in this and the preceding article should be viewed as mechanisms of God’s provision for plants in a pre-fall world that have persisted—and in some cases have become increasingly aggressive in the harsh post-fall and post-flood environment.

Answers in Depth

2019 Volume 14

Answers in Depth explores the biblical worldview in addressing modern scientific research, history, current events, popular media, theology, and much more.

Browse Volume

Footnotes

  1. Elizabeth M. Estabrook and John I. Yoder, “Plant-Plant Communications: Rhizosphere Signaling between Parasitic Angiosperms and Their Hosts,” Plant Physiology 116 (1998): 1–7, http://www.plantphysiol.org/content/plantphysiol/116/1/1.full.pdf.
  2. Yuan Yuan Song et al., “Interplant Communication of Tomato Plants through Underground Common Mycorrhizal Networks.” PLOS One (2010), https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013324.
  3. Monika A. Gorzelak et al., “Inter-plant communication through mycorrhizal networks mediates complex adaptive behavior in plant communitie,” AoB Plants 7 (2015), https://academic.oup.com/aobpla/article/doi/10.1093/aobpla/plv050/201398.
  4. Song et al., 2010.
  5. Harro J. Bouwmeester et al., “Rhizosphere communication of plants, parasitic plants, and AM fungi.” TRENDS in Plant Science 12, no. 5 (2007): 224–230, https://www2.eez.csic.es/mycorrhizaandbioticstresslab/Rhizosphere communication (Bouwmeester et al 2007).pdf.
  6. Ann M. Hirsch and Nancy A. Fujishige, “Molecular Signals and Receptors: Communication Between Nitrogen-Fixing Bacteria and Their Plant Hosts,” in Biocommunication of Plants edited by Günther Witzany and Frantisek Baluska, 255–280, Berlin: Springer, 2012, https://link.springer.com/chapter/10.1007/978-3-642-23524-5_14.
  7. Andrew Lareen, Frances Burton, and Patrick Schäfer, “Plant root-microbe communication in shaping root microbiomes,” Plant Molecular Biology 90, no. 6 (2016): 575–587, https://link.springer.com/article/10.1007/s11103-015-0417-8.
  8. Ibid.
  9. Omer Falik et al., “Plant responsiveness to root-root communication of stress cues,” Annals of Botany 110, no.2 (2012): 271–280, https://academic.oup.com/aob/article/110/2/271/2769210.
  10. Anouk van’t Padje, Matthew D. Whiteside, and E. Toby Kiers, “Signals and cues in the evolution of plant–microbe communication,” Current Opinion in Plant Biology 32, (2016): 47–52, https://doi.org/10.1016/j.pbi.2016.06.006.

Newsletter

Get the latest answers emailed to you or sign up for our free print newsletter.

I agree to the current Privacy Policy.

Answers in Genesis is an apologetics ministry, dedicated to helping Christians defend their faith and proclaim the gospel of Jesus Christ.

Learn more

  • Customer Service 800.778.3390