Silent Symphony, The Language Of Plants
Summer is in full swing and our local meadows, woodlands and wetlands are alive with the lush growth and green goodness of solar-powered warmth, light and renewed life.
Songbirds fill the air with calls and melodies signaling territoriality, courtship and connection with mates and youngsters, while squirrels and chipmunks scamper and chatter as they busily gather goodies from our backyard trees and shrubs.
Bees and wasps buzz among the wildflowers, and ruby-throated hummingbirds chirp and whiz in and out of our gardens and nectar-feeders. Voices of happy children echo through the neighborhood, and rumbling lawnmowers fill the air with the fragrance of cut grass and gasoline.
Such is the sensory symphony of summertime.
But there is another summer chorus that we humans cannot hear, sung by the ancient voices of the green “standing ones.” Evidence abounds that plants converse and exchange information, not via sounds, but via chemical whispers on the wind and warnings through the network of roots and their fungal partners in the soil.
Plants have been shown to warn neighbors of impending attacks by hungry caterpillars and other herbivores and alert others of looming droughts. Some, such as pine, oak and redwood trees, as well as mustards, ragweed and jewelweed, can preferentially recognize and share essential resources with kin in times of trouble. Still others can even call in predatory wasps to attack specific caterpillars munching on their leaves.
How can this be?
It’s really about resilience and survival within the challenges of complex community life. To avoid being eaten, plants must protect themselves with spines, prickles, wax, glassy crystals, stony tissues, bitter-tasting tannins and even glue traps and immobilizing resins.
They may secrete spicy scents, noxious oils, phenols and enzymes. They may imbed poisons in their tissues including nicotine, cardiac glycosides, latex and photosensitizers. But life is difficult, and sometimes even these measures are not enough to prevent the onslaught of attack by hungry herbivores. When assaulted by aphids, thrips, caterpillars, pathogens or other enemies, damaged leaves not only trigger a ramping up of plant-wide defenses but also release specific volatile organic compounds (VOCs) based on the chemical signature of the saliva of the attacker. These VOCs serve as an air-borne early warning system to neighboring plants, alerting them to augment their defenses in advance of attack. Such cooperative communication has been documented in a variety of species, including poplar, alder, birch, willow, beech, maple, wild tobacco, barley, tomato, beans, garden peas and sagebrush.
Some VOCs additionally serve as chemical “cries for help,” calling in enemies of the enemies of plants. For example, parasitic wasps may be enlisted to sting, immobilize and lay eggs within the tissues of an offending caterpillar. The unfortunate creature will then become paralyzed and zombie-like, serving as “fresh meat” destined to be devoured from the inside out by hungry wasp larvae. Still other body guards, the ants, may also be recruited to defend against a munching menace, attracted by sugary wound nectar and offerings of methyl salicylate (oil of wintergreen), which provide the ants useful food, pheromones for reproduction and antiseptic oils for their nest.
While above-ground defense and the exchange of chemical information is critical for plant survival in the midst of threats, still deeper conversation occurs below ground within the intricate network of plant roots and symbiotically-associated fungal filaments that enshroud them.
Water-soluble chemical messages warning of impending drought, disease, herbivore damage and other stresses have been shown to efficiently pass between plant roots via the underground fungal highway, such that unstressed neighbors physically prepare for the threat in advance and pass the warning on to others. This ancient, intimate relationship between plant roots and mycorrhizal fungi is mutually beneficial: the fungi provide plants with much needed nitrates and phosphates in exchange for nutritious sugars provided by the plants. Within the microbial complexity of healthy soils, such fungal friends connect the roots of neighboring plants and form “common mycelial networks” (CMNs) critical to the recycling of nutrients and water and creating a potentially vast communication highway within a stable ecosystem – the so-called “wood wide web.”
Good communication matters. The botanical world is brimming with conversation and critical information exchange, all of which help maintain the stability of the community and integrity of the larger ecosystem. Perhaps someday a better understanding of plant communication will lead to revolutionary changes in agriculture and a kinder, more sustainable and neighborly-way to live. We have much to learn from the leafy language of the green ones, and only now are beginning to listen to the messages they are sending.
Becky Nystrom is a Professor of Biology at Jamestown Community College, a founding trustee and board director of the CWC, and a longtime CWC supporter and volunteer.
The Chautauqua Watershed Conservancy is a local not-for-profit organization dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region. For more information, call 664-2166 or visit chautauquawatershed.org or facebook.com/chautauquawatershed.