Plant Awareness has been a controversial subject within the scientific community since it's early days. In the age of enlightenment, a general inquiry into this subject has developed into a broad field of study with many surprising findings. Even though the concept might seem somewhat silly, science has unearthed remarkable evidence of basic plant awareness, senses and even communication. This video will take a brief look at the world of plant perception. Part 2 and Part 3 will cover air and ground plant communication.
All living organisms have a certain degree of perception in order to make sense of their environment and adapt accordingly. Plants are no exception to this rule, however, the degree to which plants perceive and react is far more impressive than previously thought and is being explored ever more. The biological structure and role of a plant's senses are clearly different than those of the animal kingdom.
The basic building blocks allowing for sense may remain more or less the same, such as cryptochrome which allows for both plants and animal to perceive blue light. However, many receptors are unique to plants and distributed in the organism where applicable. Even though parallels are found in plant and animal perception, one must not anthropomorphise plant awareness since it is so very different than that of animal kind. There are three primary senses in plants that we know of, these are sight, smell and touch. Some evidence, however, suggests that plants also utilise sound, but this is not generally accepted in the academic community.
First, let us discuss plant sight. Plants require a form of sight in order to grow towards light, determine the time of day and know what season they are in. Compared to humans, plants have a greater range of light perceptible to them ranging from the 750 to 300 nm spectrum, whereas humans perceive a spectrum of 700 - 400 nm. This allows plants to perceive further into the UV and dark red spectrum where human sight fall short. Also, the number of different photoreceptors in plants are more than double that of a human being.
In general, plants have twelve photoreceptors which are phototropin, chlorophyll, zietlupe, cryptochrome, and phytochrome, with multiples of some of these in order to better perceive light frequency critical to their function. These receptors are found in all cells of the plant, unlike humans who have photoreceptors in the eyes and to a lesser extent skin. Also, such a distribution of photoreceptors throughout the plant does not allow it to see in pictures as we do but instead be sensitive enough to perceive the slightest presence of light for nourishment.
Next, the ability of plants to 'smell'. This sense serves plants in multiple beneficial ways even though the number of chemicals able to be perceived is far less than the human nose. These chemical receptors are distributed in the leaves and root system of the plant which enables them to sense both airborne and ground chemical packages. This sense has multiple roles depending on the plant species.
For example, some parasitic plants are attracted to specific host species. The chemical packages that the host plant permeates allow for the parasitic plant to easily find and consequently grow towards the host plant. The parasitic plant can then anchor onto the host plant for nourishment or support. The sense of smell is also used as a defence. When a plant is under attack by a herbivore it releases specific chemical packages for a variety of purposes. For example, some plants increase the tannin levels in their leaves when under attack to make the plant less palatable. The neighbouring plants then pick up on the chemical 'alarm signal' and increase their tannin levels preemptively.
The final confirmed sense of plants is that of touch or feeling. This is a well-recorded fact that plays an important role in plant survival. In laboratory conditions for example, if two identical sets of plants are grown and one is stroked a few times a day and the other left alone, the plant that was touched would compensate its growth pattern. Usually, this results in plants shorter and more stocky plants. The evolutionary purpose of this includes the need for plants growing in windy locations to stabilise themselves. This applies to small plants and giant trees. Plants that vine or crawl have a particularly acute sense of touch in order to feel where they can grow and anchor onto larger support structures. In the venus fly trap when a hair is touched within the 'mouth', an action potential is created, which would rapidly close when a second hair is touched within a given time frame. The exact means as to how this happens remains poorly understood.
Even though the exact functionality of some plant senses are not fully understood, it is clear that plants have a form of awareness in order to respond to their environmental challenges. As research into this fascinating field continues we will uncover a greater understanding of plant senses and functionality.
This concludes the first part of plant awareness.