Exploring Our Senses
With Agway’s own, David Christopher
Our sensory organs are responsible for sight, sound, smell, taste, and touch, respectively.
Springtime can touch upon all of these senses.
The sight of flowers breaking dormancy.
The sound of a morning dove cooing to a new sunrise.
The smell of the outside air on a cool misty morning.
The taste of freshly picked spring greens.
The smooth touch of bark on a white birch tree.
These 5 primary senses are inherent in every living creature within the animal kingdom.
Do Plants Have Senses?
When a person doesn’t respond to stimuli we say they are “like a vegetable.” But how true is that?
Plants need to grow and survive in unpredictable conditions. To do this, they need to ‘sense’ their environment and react accordingly.
As it turns out, plants actually do possess these 5 basic senses….and even more!
Although they lack eyes, ears, tongues, noses, and brains, the senses that we tend to think of as exclusive to animals, also exist in plants. They see, hear, smell, taste, and they respond to touch.
And like us, plants make decisions according to what their senses are telling them.
How Plants Respond to Their Senses
A plants vision is rudimentary. They don’t have eyes and can’t focus images, but they detect light thanks to pigments in their cells that react to certain wavelengths or colors.
The posture of a plant in daylight is much different than night. Some plants leaves will fold up while others may slumber in sleep, during which they adopt positions different from those of the day.
And while the response of plants to light is well known, their sensitivity to sound is even more impressive!
Some plants produce defensive chemicals when attacked by a herbivorous insect. Experiments have shown that simply by recording the sound of chewing and transmitting it to the plant through vibrations, the plant reacts by secreting this same compound.
Experiments also know that plant roots move towards leaky pipes because they follow the moisture. But even if the pipe is not leaking, they are also able to find it by the sound produced by the water moving inside. They use this vibration as a first approximation, until the root touches the water.
Other studies are revealing that plants respond to airborne sounds, just like animal hearing. For example, within just a few minutes, flowers increase the sweetness of their nectar when they hear the buzzing of a flying bee!
Plants Also Use Touch to Evaluate Their Surroundings.
Climbing plants will vary their growth rate depending on whether or not they can feel a support to climb onto. Some plants also have a reaction to being touched and will close up, like the carnivorous Venus flytrap.
Plants Taste and Smell as Well.
They taste below ground, using their roots! A plant will secrete substances below ground which allows them to absorb nutrients. Other plants can use their roots to taste the secreted substance from the first plant. Based on what they taste they can tell how strong and how far away the plant is and tap in to the nutrient source.
Plants Also Release Their Own Smells
When a plant is under attack from caterpillars, slugs or other damaging bugs, it emits a chemical compound called methyl jasmonate which is a plant growth regulator. This chemical becomes air-borne and alerts other plants to raise their own chemical defenses pertaining to their own growth and development. Think of this as an early warning system…..heads up all, here come the bad guys!
How Flowers Work With Pollinators: Smell
Have you ever wondered why some flowers produce a smell and others don’t? All of this is to help the plant do one thing: attract pollinators! We all know that smells attract attention. But, just as with people, different pollinators are attracted to different scents (and some aren’t attracted to any scent at all). Some pollinators may also be attracted at different times of the day.
What attracts a bee is a sweet daytime scent that increases throughout the day with the daily rise in temperature, which is also when bees are more active. Moths pollinate at night, so the flowers that rely on them for reproduction, like jasmine and honeysuckle, release their aromas in the evening. Flowers with a spicy, musty, or fruity scent are often most attractive to beetles for pollination.
Once flowers have been pollinated, they tend to reduce their smell. This allows other unpollinated flowers a chance to attract a pollinator. Buds are less fragrant for similar reasons – they aren’t yet ready for pollination.
But what about those flowers that don’t release any smell at all?
First, it is important to note that the aromas that are noticeable to humans do not represent the full spectrum of scent in nature. Other creatures have completely different olfactory abilities to ours. It is possible that some flowers just don’t smell to us.
Lastly, other flowers can be pollinated by the wind or water. These types of plants don’t require a scent to attract their pollinator.
Some More Fun Facts!
An increasing body of evidence reveals that trees can communicate with each other through a network of underground mycelium (a root like structure of fungus) that grow around the root structures of the tree. Nicknamed the Wood Wide Web, these mycorrhizal fungus networks can be used to transport nutrients or signal that an insect enemy is nearby. A large enough network could possibly allow an entire forest to communicate much like an internet system!
Plants can learn as well and be trained to respond to stimulus.
We know plants get their energy or food source from light.
Experiments using pea plants have found that by turning on a fan each day at the same time the lights come on, the plants would lean into the direction of the light. This created an association that the breeze means food is coming.
Within just a week, researchers were 100% successful in teaching plants to respond to the fan without turning on the lights. The plants leaned towards the fan when they felt the breeze even though no lights came on.
Plant biologists have discovered up to fifteen additional senses that plants possess in addition to the five classic ones. With all these sensory systems in play and keeping in mind that plants do things like recognize their relatives, cooperate with each other, defend themselves against enemies and make decisions, it’s not unreasonable to believe that plants may after all, be more intelligent than we think!