Improvements in technology over the past couple of centuries has revealed plants in a light that may never have been thought possible in the times of the early philosophers.
The 18th and 19th century studies into electricity allowed for the closer study of plants while time-lapse footage of plants in Sir David Attenborough's 1995 series The Private Life of Plants displayed the incredible process of growing, the day-to-day opening and closing of flowers and the way roots branch out in the soil in a way that we can visually appreciate.
However, it is the recent lab-based studies into the communication methods used by plants that touch on a curiously complex world in which plants communicate with members of their species, attempt to out-compete rivals and attract animals to do their handiwork.
Carnivorous plants, like venus fly traps and pitcher plants, behave more like an animal in the way that they catch and digest their food.
The "wonderful" venus fly trap, or Dionaea as quoted below, was a favourite plant of Charles Darwin, and he was impressed by their incredible ability to capture their prey. He also saw that the movement of the trap was very different to that of plant growth - being relatively fast and repeatable.
Darwin noted that the traps were triggered by a very specific stimulation of the trap's hairs. The plant was able to distinguish between a rain drop and a likely prey species, such as a buzzing fly.
This plant, commonly called Venus’ fly-trap, from the rapidity and force of its movements, is one of the most wonderful in the world.
Consulting on his naturalist friend Dr. Burdon Sanderson, Darwin learned that the electrical discharge recorded in animal muscles was very similar to that of fly trap shutting. This electrical stimulation allows the plant to modify the pressure of cell sap, which can provide movement of a venus fly trap hinge or the sticky tentacle of a sundew.
This discovery changed the way we think about plants, leading to further research into their hidden abilities.
We all know about the close relationship nectar-drinking bees have with pollinator-requiring flowering plants. But did you know that the relationship stretches further than the bee simply responding to a brightly-coloured flower?
Plants are rooted to the ground and have a small negative charge, one which gets greater the higher up the plant you get. Meanwhile, bees generate a positive charge as they actively lose electrons due to friction whilst flapping their wings.
When a positively-charged bee flies past the negatively-charged flower this electric field changes, something which it seems the bees can perceive, providing the bee with an extra stimulus to land. Having landed on the flower charge is then cancelled out.
However, the bees have to fly very close to the flower in order to detect a change in the electric field, so how useful can this be?
It seems that the plant's negatively-charged pollen will actually jump on to and stick to the positively-charged bee, to be carried to the next flower. Plants don't just have to rely on the incidental rubbing of bee on stamen or hoping that the pollen doesn't accidentally drop off.
In addition, the now altered electrical charge of the flower acts as a signal to the next bee to return later when the pollen stocks have been replenished!
Plants may be communicating in extraordinary ways above ground, but we mustn't forget the rest of the plant. What is going on underground?
Recent studies have suggested that plant roots are able to communicate with the roots of other plants.
Corn seedling roots have been shown to emit a clicking sound whilst growing which, when played back through a speaker, attracts other corn seedling roots towards it.
However, although we can clearly see this direct response, we do not quite understand its purpose. It could possibly be for echolocation, allowing the root to avoid hard objects or to grow towards preferable soils. It could also be that this demonstrated a tactic for avoiding competition, or to outcompete as a group of plants. Put simply; are they listening out for their own echoed clicks or those clicks of other plant roots?
Whatever the purpose, we now know that plants can not only hear and make a sound, but they can also respond to this stimulus. Plants are quite remarkable, aren't they?