In order to survive and reproduce, plants compete by releasing chemicals through allelopathy to inhibit the growth of neighboring plants. This process goes beyond simple competition for survival and has a profound effect on the balance and structure of the entire ecosystem.
Animals are constantly competing for reproduction and survival. Grasses and trees are no different. To ensure their own survival, plants secrete certain chemicals from their roots, leaves, and stems that inhibit the development, growth, and reproduction of other neighboring plants. This is called allelopathy, or allelopathic behavior. And the chemicals they release are called allelochemicals.
In fact, allelopathy isn’t the only strategy plants use to defend themselves or survive. Some plants produce unique chemical reactions to pest or animal attacks, and some have even developed physical defenses. Plants that have developed thorns or microscopic hairs on the surface of their leaves are examples of these defense strategies. These physical and chemical defenses complement each other and contribute to a plant’s survival rate.
Let’s look at some specifically known allelopathies. The roots of pine trees secrete a nociceptive substance called gallotannin, which is why few other plants can live beneath the giant trees, let alone my baby asole. Salvia, a type of shrub native to California, USA, produces a volatile fence, and eucalyptus is known to inhibit the growth of other plants by exuding eucalyptol from its stems, leaves, and roots. The clover in the corner of your lawn fights relentlessly against the grass to expand its territory, thanks to the gunpowder it secretes.
Competition between plants is sometimes very intense, and the results can have a huge impact on their surroundings. For example, the inability of other plants to grow under pine trees plays an important role in maintaining the ecological balance of a forest. This leads to the dominance of certain plant groups, which in turn affects the composition of animal species in the area. So allelopathy isn’t just about competition between plants, it also has a profound effect on the structure and function of the ecosystem as a whole.
Plants like herbs and geraniums, which are commonly grown at home, have no scent when left alone, but a strong breeze or a nudge can release an unexpectedly strong scent. It’s their way of quickly warding off intruders. People think it smells good, but it’s actually a defense mechanism to protect themselves from outside forces. The toxicity of solanine in potato sprouts or the pungent odor of allicin in garlic are both nociceptive substances that protect us.
The plant’s defense against pathogens is also part of the phenomenon of allelopathy. When a pathogen attaches itself to the plant’s cell wall and embeds its harmful substance, it quickly sends out emergency signaling substances through the stomatal tubes to all cells. The wound induces protease inhibitors that prevent the cell wall proteins from dissolving, causing the cell wall to build up layers of stiff lignin and even produce antibiotics like phytoalexins.
In addition to this, plants also have the ability to adapt to environmental changes. They are constantly changing to adapt to their external environment, such as adjusting the depth of their roots or the size of their leaves in response to weather changes or the nutritional status of the soil. This adaptability is what allows them to survive in different environments.
Plants speak in chemicals. As you know, caterpillars feed on pine needles and cabbage beetles feed on cabbage leaves. But when caterpillars and cabbage beetles attack, pine needles and cabbage leaves don’t stand still. In their haste, they release volatile chemicals, such as terpenes and secterpenes, from their wounds, and the wasps smell them and rush to them. Isn’t it amazing how they signal to the wasps that they need to get rid of their natural enemies? They’re such gentle creatures.
