Back in the 1960s, during a tense time known as the Cold War, a CIA interrogator named Cleve Baxter did something unusual. He connected a polygraph machine, which is usually used to detect lies, to a house plant. Baxter noticed changes in the plant’s electrical resistance when it was harmed or threatened, leading him to wonder if plants could feel or even read minds. While this idea sounds fascinating, it’s not true. Plants can’t see, hear, or read minds, but they do have some amazing ways of sensing their surroundings and communicating with each other.
Plants can’t move around like animals, so they’ve developed special ways to survive. One of the first things a plant figures out is its position in space, a sense called proprioception. This helps them know which way is up and which way is down. Even seeds that start growing in the dark can correctly orient their shoots and roots. Scientists have seen that if you plant a seedling upside down, it will turn itself around. Plants can even sense gravity, as shown by experiments where plants grown on spinning wheels point their roots in the direction of the force. Charles Darwin discovered that the cells that sense gravity are at the tips of roots. If these tips are removed, the plant can’t tell which way is down.
Plants also show phototropism, which means they bend toward light. Darwin experimented by cutting off the tips of seedlings, and he found that without these tips, the plants didn’t change direction. The tips have cells that detect light and tell the rest of the plant how to grow. Plants also use a process called photoperiodism to measure how much light they get, which helps them track the seasons. At night, the last light a plant sees is in the far red spectrum, which turns off a light-sensing molecule until morning. This cycle helps plants know when the seasons are changing.
Even though plants don’t have noses, they can detect chemical signals in the air, similar to how we smell things. For example, ancient Egyptians ripened figs by cutting open a few in each bunch, and Florida farmers used kerosene lamps to ripen oranges. These methods work because of ethylene gas, a plant hormone that helps synchronize ripening and tells leaves when it’s time to fall off.
Some plants have developed the ability to “steal” nutrients from nearby plants. A growing seedling can sense the presence of a preferred plant, like a tomato, and grow toward it to access nutrients. Plants can also warn each other of danger. When caterpillars attack, injured leaves release chemicals into the air that signal nearby leaves to produce toxic compounds, making them less tasty to herbivores.
Plants can feel touch too. For example, a vine can sense when it touches something and will wrap around it. This sensitivity is so precise that even the weight of a single thread can trigger a response. Some plants, like the sensitive plant, fold their leaves when touched, using tiny hydraulic pumps to make the leaves droop.
So, the next time you admire a flower, remember that it might be sensing its environment in ways we’re just starting to understand. Stay curious! And while the idea that plants enjoy classical music is a myth, playing a little Mozart certainly can’t hurt.
Try planting seeds in different orientations (right-side up, upside down, and sideways) in small pots. Over a few weeks, observe and record how the seedlings adjust their growth direction. Discuss how this demonstrates the concept of proprioception and gravity sensing in plants.
Create a simple maze using cardboard and place a plant at the start. Shine a light at the end of the maze and observe how the plant grows toward the light over time. Document the plant’s growth and discuss how phototropism helps plants find light in their environment.
Place a ripe banana in a sealed bag with unripe fruits like apples or avocados. Over several days, observe how the ethylene gas from the banana affects the ripening process of the other fruits. Discuss how plants use chemical signals to communicate and synchronize ripening.
Role-play a scenario where some students are plants and others are herbivores. When a “plant” is “attacked,” they must signal nearby “plants” to produce defenses. Discuss how real plants use chemical signals to warn each other of danger and how this helps them survive.
Observe a sensitive plant (Mimosa pudica) and gently touch its leaves to see how they fold. Discuss how plants sense touch and the potential benefits of this sensitivity in their natural environment. Consider how this might help them avoid damage or capture sunlight more effectively.
In the 1960s, during the Cold War, CIA interrogator Cleve Baxter connected his polygraph machine to a house plant. Through his experiments, Baxter observed changes in electrical resistance when the plants were harmed or threatened. This led to the idea that plants might possess sentience or even extra-sensory perception (ESP). However, there is no truth to this notion. Plants cannot see, hear, or read minds, but they do have fascinating ways of sensing their environment and communicating with each other.
Plants are rooted in one place and cannot escape danger or move toward sunlight, so they have developed unique adaptations. One of the first things a plant determines is its orientation in space, known as proprioception. This ability allows them to sense which way is up and down. Even seeds that germinate in darkness can correctly orient their shoots and roots. Botanists have observed that upside-down seedlings reorient themselves, and plants grown on spinning wheels point their roots in the direction of centrifugal force, indicating they can sense gravity. Charles Darwin demonstrated that gravity-sensing cells are located at the tips of roots; if these cells are cut off, the plant cannot determine which way is down.
Plants also exhibit phototropism, bending toward light. Darwin tested this by cutting off the tips of seedlings, which resulted in the plants not changing direction. The growth tips contain cells that sense light and inform the rest of the plant how to grow in response. Additionally, plants can measure the amount of light they receive, a process known as photoperiodism, which helps them track the seasons. The last light a plant perceives at night is in the far red spectrum, which inactivates a light-sensing molecule until the next morning. This cycle helps plants determine the changing seasons.
While plants do not have noses, they can detect chemical signals in the air, similar to how humans smell. For example, ancient Egyptians would ripen figs by cutting open a few in each bunch, and farmers in Florida used kerosene lamps to ripen oranges. These methods rely on ethylene gas, a plant hormone that synchronizes ripening and signals leaves when their job is done for the year.
Some plants have even developed the ability to “steal” nutrients from their neighbors. A growing seedling can detect the scent of a preferred plant, such as a tomato, and aim for it to access nutrients. Additionally, plants can warn each other of danger through airborne signals. When caterpillars appear, injured leaves release volatile chemicals that prompt nearby leaves to produce toxic compounds, making them less appealing to herbivores.
Plants also possess a sense of touch. For instance, a vine can detect when it touches an object and signal cells to coil around it. This sensitivity is remarkable; even the weight of a single thread can trigger a response. Some plants, like the sensitive plant, fold their leaves when touched, activating hydraulic pumps that cause the leaves to go limp.
Next time you stop to admire flowers, consider that they may be sensing their environment in ways we are just beginning to understand. Stay curious! And while the idea that plants respond to classical music is a myth, enjoying a little Mozart never hurts.
Plants – Living organisms that typically grow in soil, have stems, leaves, and roots, and use sunlight to make their own food through photosynthesis. – Example sentence: Plants are essential to life on Earth because they produce oxygen and provide food for many organisms.
Light – A form of energy that is visible to the human eye and is essential for the process of photosynthesis in plants. – Example sentence: Without light, plants cannot perform photosynthesis and produce the energy they need to grow.
Gravity – A natural force that pulls objects toward the center of the Earth, affecting how plants grow and orient themselves. – Example sentence: Gravity causes plant roots to grow downward into the soil, anchoring the plant and seeking water and nutrients.
Nutrients – Substances that provide the essential elements needed for growth and survival of living organisms, including plants. – Example sentence: Plants absorb nutrients from the soil through their roots to help them grow and stay healthy.
Communication – The process by which organisms exchange information, which can occur through chemical signals, sounds, or other means. – Example sentence: Plants use chemical signals to communicate with each other and warn of potential threats like insect attacks.
Phototropism – The growth response of a plant in direction to a light source. – Example sentence: Phototropism causes a plant to bend toward the light, ensuring it receives enough energy for photosynthesis.
Proprioception – The ability of an organism to sense the position and movement of its body parts, important for animals but also relevant in how plants sense their orientation. – Example sentence: While proprioception is well-known in animals, plants also have a form of it to sense their position and adjust growth accordingly.
Ethylene – A plant hormone that regulates growth and development, including fruit ripening and response to stress. – Example sentence: Ethylene is released by fruits like bananas and apples, causing them to ripen faster.
Seasons – Periods of the year characterized by specific weather conditions and daylight hours, affecting plant growth and animal behavior. – Example sentence: Many plants have adapted to the changing seasons by shedding leaves in autumn and blooming in spring.
Touch – A sense that allows organisms to perceive physical contact, which can trigger responses in both animals and plants. – Example sentence: Some plants, like the Venus flytrap, respond to touch by closing their leaves to capture prey.
