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Tree Facts - How Plants See Hear Taste Smell And Touch

Courtesy of Public Domain Photos

Courtesy of Public Domain Photos

Have you ever wondered what a tree feels? Or whether it can sense other plants around it, and smell the apple growing from its branches? The thought of trees being sensory beings never really crosses our mind. To us, a tree is just a large plant growing in the field or in our gardens. In fact senses are extremely important to all plants.

They are constantly rooted to one spot. They can't move whatever the weather or climate throws at them. So they have had to develop their own real senses to cope with this strange and sometimes harsh world.

What you have to remember is that Trees have to eat, escape predatory insects and know how to shelter from storms or fire.

You may find it rather strange that trees can actually see, hear, taste, smell and touch. In fact it does seem rather odd. But to survive, Trees do indeed use these five senses.

public domain

public domain

Tree Sight.

How do plants see? We are talking about trees, but we do need to include all types of plants and flowers, as they all act similarly.

According to recent research, trees can see in a similar way that we use our eyes. They see light just as we have photo receptors in our eyes. They have similar receptors in their leaves and stems.

These allow them to see different wavelengths, red and blue mainly, but others that we can't see ourselves. These occur in the red and ultraviolet parts of the light spectrum.

The clever thing is that plants and trees can can also see the direction where light is coming from. They can also tell how long the lights were off, and how dim the light is.

Plants, as we know, bend towards the light as if hungry for the suns rays, which in fact is true.The process of Photosynthesis uses light as energy to turn carbon dioxide and the plants water into sugars. So in reality the sun is actually starting the process for the tree or plant to eat.

The actual light sensors are called phototropins. These are light receptors in the membranes of the cells in the tree. When the tree senses blue light, they start a cascade of signals that ends up modulating the activity of auxin, a hormone.

Plants see red light also using receptors in their leaves. These are called phytochromes. These will allow the plant to detect far red light, so after soaking up the red light, it then changes back to its lower level red light.

The reason for this is to allow it close down at night, or turn off. Far red light is predominant at sunset. And then reverse the process in the morning when the red light is strong enough for the plant to open its leaves again and soak up the sun.

The leaves can also tell when they are in shade. And adapt accordingly.

Using these processes, the plant or tree can actually regulate itself to tell the time of day.

public domain Acorns

public domain Acorns

Smell

Did you know that all plants have a sense of smell? There is one particular vine called a dodder which is referred to as the sniffer dog of the plant world. As it contains hardly any chlorophyll it has to eat by by sucking the sap from other plants. The dodder vine uses smell to hunt down its prey or food. It can tell by smelling the plants whether they are poison or edible. It trails towards the edible plant to wrap itself around it to eat.

In animals sensors in the nose bind with the molecules in the air to produce smell. And its very similar with plants and trees. They have receptors that respond to chemicals. But what do they smell?

All ripening fruit emits something called ethylene in large amounts which the plants can smell. And then they respond to it and ripen too. This clever process means that all the similar plants and trees know at the same time and then ripen together. This is perfect for plants because it then attracts animals which will then eat the fruit and disperse the seeds. Ethylene is a plant hormone, that not only helps to ripen the flower or plant, but also helps to coordinate the leaf changing color in the Autumn.

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Dodder Vine public domain

Dodder Vine public domain

Fascinating Facts

Back in the 1980s, research showed that trees can communicate. Healthy trees that were in the vicinity of caterpillar infested ones were resistant to pests because their leaves had produced a chemical to protect them. In other words their leaves were producing a chemical that tasted nasty.

Other trees that were farther away, did not produce the chemical. The infected trees had therefore sent out an airborne pheromonal message to healthy trees to get them ready for an attack by the insects.

Touch

Trees are never still. The wind blows through the branches and leaves, insects crawl across the canopy and vines search out the best way to grow. So it seems obvious that trees and plants can and do touch and feel.

They are also sensitive to changing weather conditions. By changing their growth rate and being careful on how much water they use. Research has shown that by even shaking or touching a plant, it will modify its behaviour to keep itself safe. For example trees in windswept parts of the world will be much more stunted than plants that grow in a more moderate climate. We only see the top part of the trees and plants, but a lot of the behaviour is unseen. The roots are very sensitive and can grow vast distances reaching other plants to see if they are healthy or unsafe.

The most obvious plants that respond to touch are the Venus Fly Trap and other similar plants. These work by acute sensitivity in the hairs on the leaves. As a fly or beetle lands, it will get trapped because the sensors will snap the hard leaves together. The plant will know whether the insect is too large or just the right size because the feet of the insect will have to touch two hairs before the plant will react. This way it will know whether its too large to keep the insect inside.

The actual process that produces a response is an electrical current that radiates up through the leaves. This will activate ion channels in the cell membrane. All this can happen in less that one tenth of a second.

Not all plants are as sensitive as the Venus Fly Trap, but they all react in a similar way when touched but on a much smaller level. As plants do not have a brain, this process is carried by currents up and through the plants and trees.

Venus Fly Trap Dionaea  muscipula public domain

Venus Fly Trap Dionaea muscipula public domain

Taste

Plants have a similar taste structure to ours. With humans our sense of smell and taste are entwined. Smells can enhance or take away the taste of food. Smell deals with volatile chemicals, and taste with soluble.

The same two senses are connected in plants. This has been seen when the trees or plants are attacked by insects or bacteria. We have seen that plants emanate a chemical response when under threat, but there is one chemical called methyl jasmonate that is particularly important. This is the taste chemical.

It is a gas, so its not so effective as an airborne deterrent, but when it diffuses through the stomata the pores in the surface of leaves, it gets converted into the soluble water jasmonic acid. This is then attached to a receptor in the plants cells and helps to trigger the leafs defences. Most of the sensors are once again in the roots where it is surrounded by soil and water.

Did You Know?

Plants use underground chemical messages to recognise their close relatives nearby! There is also root to root communication between relative plants and unrelated plants. Scientists discovered that when a row of plants were subjected to drought, it took just one hour for the message to travel to the other plants that were five rows away. This caused them to close their cells or stomata to be prepared for lack of water.