Can Cannabis Plants Think?

Can plants think? and how do they feel, hear, see and smell?
01 June 2021
10 min read
Can Cannabis Plants Think?

Contents:
  • 1. How do humans think?
  • 2. What are plant tropisms?
  • 2. a. Phototropism
  • 2. b. Thigmotropism
  • 2. c. Gravitropism
  • 2. d. Hydrotropism
  • 2. e. Other types of tropisms
  • 3. Plant tropisms compared to human senses
  • 4. In conclusion

With more than 300.000 plant species on Earth, it’s obvious that they have developed and adapted to survive and thrive; Now, they cannot experience sight, smell, touch and smell like we do, which can be a huge evolutionary disadvantage but they have other ways to adapt to the different environments. Plant tropisms are mechanisms by which plants adapt to changes, making them grow towards or away from a certain stimulus, this doesn't mean that they can think like us, but it's similar in a way.

1. How Do Humans Think? 

When you think about living organisms you may think about humans, monkeys or dolphins but not plants because they don’t act like humans or other animals. The human and animal brain is super complex and has the ability to consume power, store memories, process thoughts and trigger reactions. Now, scientists still don’t understand exactly how the brain works but what they do know is that neurons are responsible for all of these actions and have connections inside the brain which are very similar to how the internet works because they are constantly exchanging information. So, for example, if you touch a hot surface, the neurons will process the information and determine what you should do next, predetermining and calculating the results a half-second (or faster) before the action is performed.

 

Can cannabis plants think?: how humans think

How do humans think?
 

But plants don't have a brain like us, so you must be wondering how do plants know in which direction to grow? Well, plants have very complex mechanisms that allow them to know how and when they should grow among other things. Now, plants don’t have brains but have time-sensitive genes that function in a similar way to our nervous system and work together to know exactly how to react to certain stimuli.

For example, if your plants are suffering from colder temperatures for a couple of days, they will slow down growth and wait for the best time to grow leaves (or slow down leaf development) or seeds, and this also happens when you perform plant training techniques such as low or high-stress training. Also, researchers claim that plants can also remember information about light exposure, for example, and transmit this information to other plants so despite not having a structure equivalent to our brain, plant intelligence is very complex and allows for super interesting behavior thanks to plant tropisms.

2. What Are Plant Tropisms? 

Just like all other animals and organisms, plants need to adapt to the different environments they’re exposed to and while other living beings can actually move from a place to another, plants cannot so they need to find other ways of dealing with unfavorable growing conditions, and this is where plant tropisms come in.

Plant Tropisms are mechanisms by which plants can adapt towards or away from certain stimuli such as light, gravity, water and touch. When this happens, the cells in one part of the plant can grow more quickly than in other parts, which will determine the direction in which your plant will grow, and, with the help of plant hormones like auxins, will help regulate this growth, causing the plant to curve or bend, for example, according to the type of stimulus. There are two types of response to a stimulus:

  • Negative tropism: Growth away from the stimulus;
  • And Positive tropism: Growth in the direction of the stimulus.

Within these two types of responses, there are several plant tropisms (or tropic responses) that can result in either negative or positive tropism and they are: Phototropism, Thigmotropism, Gravitropism, Hydrotropism, Thermotropism and Chemotropism.

Phototropism 

Phototropism is responsible for directing plant growth towards the light, meaning that when talking about phototropism in cannabis plants, this is a type of positive tropism because, due to this tropism, plants will grow in the direction of a light source. This happens because cannabis plants have photoreceptors in their cells that detect light and, when detected, will direct plant hormones such as auxins to the branches that are getting less light, which will allow them to grow more in the direction of the light source and get the light they need.

 

Can cannabis plants think?: phototropism

Phototropism is the ability to identify the light source and grow in its direction.
  

Now, phototropism is a positive tropism when talking about the branches, leaves and stem but when talking about the roots, it’s actually a negative tropism because the roots need nutrients and water to thrive which are obtained underground so they actually grow away from light, this means that a stimulus can have different tropic responses depending on the part of the plant.

Heliotropism 

Heliotropism is a type of Phototropism but, unlike Phototropism, this tropic response allows the flowers and stems to face and follow the sun as it moves across the sky, from sunrise to sunset. This type of tropic response can be easily seen with sunflower plants as they face the direction of the sun as it moves, which increases their temperature and makes them more attractive to pollinators.

 

Can cannabis plants think?: heliotropism

Heliotropism is similar to phototropism but not exactly the same!
 

Now, there has been a long debate about Heliotropism and Phototropism being the same but research has discovered that they're not actually the same, despite being very similar so make sure you don't get them confused!

Thigmotropism 

Thigmotropism refers to the response a plant has when touching it or when it encounters a solid object, for example, positive Thigmotropism occurs when a vine bends in several directions as it searches for a solid object for it to continue growing. This happens because the plant knows that certain cells (usually at the tip of the vines) are not in contact with a surface so it makes them grow faster than the other cells until they make contact with a surface that they can climb and can continue growing normally. Thigmotropism does not apply to cannabis branches but it does apply to a cannabis plant's roots.

 

Can cannabis plants think?: thigmotropism

Thigmotropism boosts growth in a certain part of the plant until it reaches a surface when it can grow on.
 

Now, as said before, depending on the part of the plant you’re talking about, a certain tropism can be positive and negative, and this is the case with Thigmotropism. As the roots grow deeper and deeper, they can find a rock or a big piece of wood that may become an obstacle for root growth and when this happens, Thigmotropism will make them change direction in order to avoid obstacles that can inhibit root growth; So despite being a positive tropism when talking about the flowers and branches, it would be a negative tropism when talking about the roots.

Gravitropism 

Gravitropism is super important because it directs a cannabis plant's root growth and overall plant growth in response to gravity, meaning that it makes the roots grow downwards while the stem, branches and leaves grow upwards. Researches believed that the statocytes (a certain type of cell) are responsible for this type of tropic response. These cells can be found in the tip of the taproot and in the roots and branches, and are responsible for this type of tropic response, this is why the roots will always grow in the same direction of gravity while the plant itself will grow in the opposite direction.

 

Can cannabis plants think?: gravitropism

Thanks to gravitropism, roots and branches will always grow in the right direction.
 

Plant hormones such as auxins also play an important role in this type of tropism because if the branches are not receiving light, the auxins will accumulate in the lower side of the branch which will induce cells in that part to grow faster until the branch starts bending upwards, this is why you have to adjust the ties when tying down the branches for example.

Hydrotropism 

Hydrotropism is a tropic response that cannabis plants have when they encounter water. This tropism is super important because plants need water to live and this tropism serves as protection against overwatering or drought. For example, this happens when the substrate is dry, resulting in positive hydrotropism which helps the roots grow in search for water or in negative hydrotropism when the substrate is oversaturated and the roots need to grow away from water.

 

Can cannabis plants think?: hydrotropism

Hydrotropism is the ability to move away or in the direction of a water source depending on what the plant needs.
 

Now, when this happens, cannabis plants actually have to overcome (or become less sensitive) gravitropism, this means that the lack or excess of water can cause plants to exhibit hydrotropism over gravitropism which can be affected by the substrate itself. For example, roots growing in a wetter substrate have a tendency to exhibit more hydrotropism than gravitropism when compared to plants grown in well-aerated substrates, which will exhibit a much greater response to gravity than to water.

Other Types Of Tropisms  

Apart from the plant tropisms mentioned, there are two more types of plant tropisms that affect how a plant grows and they’re Thermotropism and Chemotropism. These types of tropism are often harder to come by but are definitely present.

Thermotropism 

Thermotropism refers to the growth or movement in response to heat, cold or any temperature changes that may occur. For example, roots may exhibit positive thermotropism at a certain temperature but exhibit negative thermotropism in colder or hotter temperatures, but due to the roots being underground it’s harder to see.

Chemotropism 

Chemotropism is a growth response to chemicals; Roots are highly sensitive to chemicals and can respond positively or negatively to certain elements in the substrate; For example, Chemotropism helps plants reach and have access to nutrients in the soil which boost growth and overall plant development. Another example of Chemotropism happens when pollen lands on the stigmas (white hairs), when this happens, a cannabis plant will release chemical signals that directs growth to the ovaries to ensure the seeds are viable.

3. Plant Tropisms Compared To Human Senses

As mentioned, plants don’t actually think because they don’t have a brain like humans or animals but they do have tropisms that work with several hormones and direct plant growth in the case there’s a bug infestation or if they want to reach more water. This means that despite not having a brain, plants also react to stimuli just like we do but with their own kind of nervous system just not in the same way.

Can Cannabis Plants Smell? 

Plants have a sense of smell that works differently than most living beings. They have certain receptors which contain ethylene that allow them to respond to chemicals in the environment. The sense of smell in plants allows them to coordinate flower or fruit maturity to attract pollinators that disperse pollen or seeds in an attempt to perpetuate their species.

 

Can cannabis plants think?: smell

Plants can "smell" certain chemicals to attract pollinators and communicate if there's an insect attack.
 

But the main importance of these receptors is that it allows plants to communicate with other plants when they have been attacked by insects, for example because when attacked, plants release certain pheromones that warn nearby plants. This means that despite plants not using their sense of smell to smell things like we do, they definitely have one and use it to communicate.

Humans vs Plants: Sense of Smell

HumansPlants
Olfactory bulbChemotropism;
Hydrotropism.
Fossa

Can Cannabis Plants Feel Touch? 

It’s known that cannabis plants are sensitive to heat, cold or strong wind, this is why plants growing in said conditions may slow down or have difficulty growing which is a form of tactile sensitivity. However, this sense of touch is more evident in some types of plants such as the Venus Fly Trap or the Mimosa Pudica which close automatically when touched; This means that plants have a sense of touch despite working in a different way than you would imagine.

Humans vs Plants: Sense of Touch

HumansPlants
  Specialized neurons in the skinThigmotropism; 
Thermotropism.
Sensory nerves

 

Can Cannabis Plants Taste?      

Just like the other senses, plants do have a sense of taste but it works and it’s used in a different way. Just like some animals, plants have the senses of taste and smell interconnected. Plants actually have the sense of taste in the roots and can communicate with nearby roots so for example, when plants need water they will communicate to nearby plants that there is a lack of water, allowing them to close their stomata to avoid water evaporation and prepare for a drought.

 

Can cannabis plants think?: taste

The roots can "taste" nutrients in the substrate and communicate it to nearby plants.
 

Have in mind that unlike the sense of smell with which plants can respond to chemicals in the environment, the sense of taste refers to water-soluble chemicals that can be present in the substrate and can attach to the roots.

Humans vs Plants: Sense of Taste

HumansPlants
  Taste buds in the tongueChemotropism;
Hydrotropism.
Throat and esophagus

 

Can Cannabis Plants Hear? 

Even though plants cannot actually hear as we do, they do have a sense of hearing. For example, plants cannot hear music (because they don’t have ears or eardrums) but they can detect the vibration of an insect or even smaller being such as worms; Plants can also detect vibrations produced by other plants, some plants even produce ultrasonic vibrations which allows them to communicate and prepare in case there’s an insect attack or strong wind.  

Humans vs Plants: Sense of Hearing

HumansPlants
External ear Chemotropism;
Hydrotropism.
Ear canal

Can cannabis plants see?

Cannabis plants do not have eyes so they obviously don’t have a sense of sight the way we do but, thanks to phototropism, plants can sense the direction of light and can know if the light is stronger or weaker than usual. Plants also have phototropins which are light receivers that help them detect light in the blue spectrum and also have phytochromes that help them detect light in the red spectrum. Now, this doesn’t work like our eyes work because plants can definitely not form images like humans and animals but this helps them regulate their internal clock and helps them to regulate processes such as photosynthesis and transpiration, allowing them to “see” whether they’re getting more or less light than usual and what light spectrum they’re getting.

Humans vs Plants: Sense of Sight 

HumansPlants
PupilPhototropism and Heliotropism; 
Thermotropism.
Iris

8. In Conclusion       

Plants definitely think but not like we’re used to. Not only cannabis plants but all plants have mechanisms such as the mentioned above that allow them to see, hear and smell among other senses, which is essential for plant growth. Without these senses your plant will not grow properly because the roots, branches and leaves will not know in which direction, how and when to grow. 

If you have more information about plant tropisms that can help fellow growers feel free to leave a comment in the comment section below!

01 June 2021
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