Can plants see?

Author: Miranda Hitchens
Artist: Lola Artiles
Editor: Altay Shaw

Over a century ago, a theory was proposed by botanist Gottlieb Haberlandt, which subsequently fell into relative obscurity. The idea he devised was a method by which plants may be able to see, not in an abstract way, but by a similar mechanism as an animal’s eyes. He posited that the epidermis of many leaves was suspiciously lens-shaped, focussing light onto a light-sensitive mesophyll below, much like our eyes to our retinas. The validity of this theory has been debated by botanists ever since, but a key discovery has reignited interest in so-called ‘plant ocelli’. 

The Boquila Trifoliolata, a climbing vine native to South America, has a remarkable ability to mimic the leaves of a wide range of plants; climbing and disguising itself to avoid predation. However, the plant doesn’t need to climb, or even contact the plant that it mimics. It is also capable of a range of transformations, including colour, shape and vein pattern changes, with quite remarkable accuracy. The question is, how? 

Ernesto Gianoli and Fernando Carrasco-Urra, the researchers who discovered the plant in 2014, have introduced several theories by which it may mimic its hosts. In 2016, it was proposed that the vine may be receptive to volatile chemicals which arise from the host plant, from which it can determine information about the host’s phenotypes and commence its shape-shifting. 

However, it was not confirmed if enough genetic information could be conveyed by these volatiles.This theory was later superseded by the possibility of bacteria transfer between the Boquila Trifoliolata and its host. The bacterial communities on the leaves of the host, the mimicking Boquila Trifoliolata plant and another Boquila Trifoliolata plant which was not mimicking were studied, showing the non-mimicking vine had very different bacterial content than the other two.The mimicking vine had a large cross-over with the host, indicating that there may be exchange of genetic information via the common microorganisms. 

These findings seemed convincing given this evidence, but what if there were no bacteria to transfer? In 2020, an experiment showed that the Boquila Trifoliolata could mimic the leaves of an artificial plastic plant – a host with no genetic information to offer. This indicates that the vine has some degree of sensory capability, which lended much more credence to the plant ocelli theory. The shape of the leaves of all vines placed significantly close to the plant showed some degree of mimicry, though the vines improved their ability to mimic the shape of the host as time went on, seemingly learning and even demonstrating an ability to remember the shapes over the months of exposure. 
This study leaves plant ocelli as potentially the only theory standing, as there are limited options beyond sensory perception that could explain this phenomenon. However, further studies of the Boquila Trifoliolata and leaf anatomy will be essential to explore this enigmatic plant and the extent to which the similarities between leaf cells and lenses can be shown. We may not have definitive proof that plants can see, but it looks remarkably similar.

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