The Unseen World of Plant Communication

Written By Parag Kokane on Saturday, March 9, 2024 | 3:47 PM

In the serene yet complex ecosystem of wildlife, an intricate and largely unseen network of communication exists, not among animals, but plants. This silent communication among flora is a fascinating subject that has captivated scientists and nature enthusiasts alike. Through various means, plants convey messages to one another, influence their environment, and interact with animals and insects. This blog post delves into the mysterious world of plant communication and its significance in the natural world.

Root-to-Root Communication

One of the primary mediums through which plants communicate is their root system. Through the symbiotic relationship with mycorrhizal fungi, known as the "Wood Wide Web," plants can transfer nutrients, chemical signals, and even alarm messages to their neighbors. This underground network is crucial for the survival and health of individual plants and the ecosystem at large. It enables plants to warn each other about potential threats such as herbivores or diseases, allowing them to preemptively activate defense mechanisms.

Banyan Tree (Ficus benghalensis) and Peepal Tree (Ficus religiosa)

Both the Banyan and Peepal trees are revered in India for their spiritual significance and ecological roles. These trees engage in mycorrhizal associations predominantly with arbuscular mycorrhizal fungi (AMF). Through these connections, a Banyan or Peepal tree could share resources with other plants nearby, including other Ficus species or even completely different species. This network helps in distributing nutrients effectively, especially in nutrient-poor soils, allowing these trees to support not just themselves but a whole community of plants, fostering biodiversity.

Neem Tree (Azadirachta indica)

Neem is well-known for its medicinal properties and is also involved in mycorrhizal relationships, primarily with AMF. These fungi help the Neem tree to absorb water and nutrients more efficiently, and through the mycorrhizal network, Neem can indirectly communicate with neighboring plants. For example, in times of drought or nutrient scarcity, Neem trees can receive signals from other plants through the network, alerting them to conserve resources, a crucial adaptation for survival in the varied climates of India.

Mango Tree (Mangifera indica)

The Mango tree, another common species in India, forms associations with both ectomycorrhizal and arbuscular mycorrhizal fungi. This dual association allows Mango trees to communicate with a wide range of plant species through the mycorrhizal network. For instance, a Mango tree under attack by pests might release chemical signals into the mycorrhizal network, which could be picked up by neighboring trees, prompting them to bolster their own chemical defenses even before the pests reach them.

Sandalwood (Santalum album)

Sandalwood, highly valued for its aromatic heartwood, is an interesting case. It is a semi-parasitic tree that relies on host plants for a portion of its nutrient requirements. Sandalwood uses the mycorrhizal network to tap into the resources of nearby plants. This root-to-root communication is vital for Sandalwood’s survival, especially in the early stages of growth when it is most dependent on its host plants. The network facilitates not just nutrient transfer but also the sharing of water and signaling molecules, enabling Sandalwood to thrive alongside various hosts.

Teak (Tectona grandis)

Teak, a major forestry plant in India, forms mycorrhizal associations that enhance its growth and wood quality. Through the mycorrhizal network, Teak trees can communicate with each other, sharing information about water availability, nutrient status, and pest attacks. This communal sharing helps individual trees to adjust their resource allocation strategies, optimizing growth and survival in a competitive environment.

Chemical Signals in the Air

Plants often use chemical signals to convey messages to each other. Their communication is done through the release of volatile organic compounds (VOCs). When a plant is attacked by herbivores, it can emit specific VOCs that serve as distress signals, alerting nearby plants of the danger. These signals can prompt neighboring plants to fortify their defenses, producing chemicals that are toxic or unpalatable to herbivores. Furthermore, these VOCs can attract the predators of the pests attacking them, serving as a call for help that benefits the plant in distress.

The Acacia Trees and Mutual Protection

A compelling example can be observed in acacia trees in African savannas. When a giraffe starts eating the leaves of one acacia, the tree increases the tannin concentration in its leaves, making them bitter and potentially harmful if consumed in large quantities. Not stopping there, the acacia tree releases ethylene gas into the air, which can be absorbed by neighboring acacia trees through their leaves. Upon detecting this signal, the nearby acacias also start producing more tannins in their leaves, even before the giraffe reaches them. This preemptive mutual defense mechanism is a remarkable demonstration of plant communication, showcasing an ecosystem-wide response to herbivore threats.

The Tomato Plant's Cry for Help

Tomato plants provide another fascinating instance of chemical signal communication. When attacked by spider mites, tomato plants can emit VOCs that attract predatory mites. These predators are not interested in the tomato plant itself but are drawn to the plant by the chemical signals it emits, indicating the presence of their prey, the spider mites. This "cry for help" is a sophisticated strategy to reduce herbivore damage by indirectly engaging natural predators.

The Silent Heroes: Fig Wasps and Pollination

An intriguing aspect of chemical communication is seen in the relationship between fig trees and fig wasps. Indian fig trees, like the Cluster Fig (Ficus racemosa), emit specific chemical cues that attract fig wasps for pollination. This mutualistic relationship, essential for the reproduction of both species, showcases the nuanced ways in which chemical signals facilitate interactions beyond mere survival.

The Role of Light and Color

Plants also communicate through light and color changes that can be perceived by animals and insects. Certain plants can change their leaf color to signal their health status to pollinators, ensuring that only the healthiest plants are visited and thus promoting their chances of reproduction. The manipulation of color and light can also deter herbivores or attract beneficial species that can aid in the plant's pollination or protection.

Lotus (Nelumbo nucifera)

The Lotus flower, significant in many cultures and native to Asia, employs a unique strategy to communicate with its pollinators. The flower can increase its temperature and change its color to a more intense pink, making it more visible and attractive to pollinators like bees. The warmth provided by the flower is an additional incentive for the pollinators, especially in early mornings or cooler days, ensuring that the Lotus is effectively pollinated.

Sunflowers (Helianthus annuus)

Sunflowers are widely cultivated and have an interesting way of communicating through color changes. Sunflowers can appear more vibrant to pollinators like bees when healthy and full of nectar. Their bright yellow petals, rich in UV patterns invisible to humans but visible to bees, signal the best places to find nectar. As the flower ages and nectar becomes scarce, these UV patterns change, effectively informing pollinators from a distance about the status of its nectar supplies. This ensures that bees focus on flowers that are more likely to offer a reward, optimizing the plant's chances of being pollinated.

Himalayan Balsam (Impatiens glandulifera)

The Himalayan Balsam, although an invasive species in many parts of the world, showcases another fascinating example of plant communication through color change. The flowers of the Himalayan Balsam can change color after pollination, from bright pink to a duller hue. This color shift signals to pollinators that the flower has already been visited, guiding them towards unpollinated flowers and ensuring efficient use of the pollinators' efforts. This mechanism helps the plant spread more effectively, as pollinators are not wasting time on flowers that no longer need to be pollinated.

Touch-Me-Not (Mimosa pudica)

The Touch-Me-Not plant, widely found in India, communicates through movement rather than color change, but it influences light perception in a unique way. When touched or shaken, its leaves fold inward, reducing the surface area exposed to light. This sudden change can deter herbivores by making the plant appear less appealing. Additionally, the movement can alter the light patterns on the forest floor, potentially signaling to pollinators or other plants about the presence of herbivores or other disturbances.

Tulsi (Ocimum sanctum)

Tulsi, or Holy Basil, a plant revered in India for its medicinal properties, exhibits a subtle form of communication through its leaf color. Under certain stress conditions, such as pest attacks or diseases, the leaves of Tulsi may change color. This change can signal to beneficial insects, like predator wasps or bees, that the plant is in need of assistance, attracting these insects to help control the pests or pollinate the flowers. The specific nature of Tulsi's color change can vary, making it a subtle yet effective means of communication within its ecosystem.

The Significance of Plant Communication

The communication among plants plays a pivotal role in the balance and sustainability of ecosystems. It influences biodiversity, plant competition, and the interaction between plants and animals. Understanding how plants communicate can provide insights into ecological conservation strategies, improve agricultural practices, and even inspire innovation in technology and communication networks among humans.

About Parag Kokane

With my camera and binoculars, I wander through the beautiful landscapes of the Western Ghats, capturing the amazing wildlife and nature around us. On this blog, you'll find exciting wildlife observations, my thoughts on protecting nature, and more. Join me as we explore and help protect the beauty of our world together.


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