Plants have long been considered a species of lower beings lacking many of the capacities assigned to animals, especially vertebrates. However, more and more studies show that, despite not being endowed with a central nervous system like we are, plants are capable of analyzing information from their environment with an extreme degree of precision and making decisions to respond to problems. And not only that: they communicate with each other and with animals, network and even sleep. In his book Sensitivity and intelligence in the plant world (2015), the expert in plant neurobiology Stefano Mancuso explains with a lot of data all the information we have about the extraordinary capacities of plants and analyzes from a very interesting perspective our relationship with these beings that they also make our life on Earth possible.
Today we know that plants also sleep but, as with other capacities such as intelligence, by the act of sleeping we do not mean that plants dream like us, but that during the night they experience a decrease in their metabolic activity and even they change position. As Mancuso explains in his book, observations regarding the rhythmic movements of plants date back to classical Greece, although it was the botanist Jean-Jacques d’Ortus de Marian who in 1729, after studying the movements of plants of mimosa, concluded that vegetables must have a kind of internal clock to control these changes in position.
It would be another botanist, Carl Linnaeus, who first spoke of the plant dream in one of his lesser-known treatises, Somnus plantarum (1755). Linnaeus gave no explanations for the phenomenon, but he systematically classified all the species that changed position throughout the day. In addition, the scientist designed a garden-clock in which it was possible to know the time by simply observing the behavior of the plants contained in it.
Another of the most curious similarities with the sleep of animals is the fact that the leaves tend to adopt a position at night similar to the one they had when they were sprouts : they roll up in the shape of a cornet, they fold into a fan shape. or they bend in two along the midribs.
The key is in the sugar
In research subsequent to the publication of Mancuso’s book, some of the unknowns related to the dream of plants have been cleared up. For example, an article published in PNAS in March 2021 sheds quite a bit of light on the metabolic processes that underlie the regulation of the circadian rhythm of plants. In previous research, a team of scientists from the University of Melbourne had shown that the accumulation of sugars produced from photosynthesis provides the plant with a lot of information about the amount of sugar generated in the morning and sends signals to the circadian clock to adjust its rhythm.
In the new work, and in collaboration with researchers from the University of York, the same authors describe another new pathway by which metabolism regulates the circadian rhythm: reactive oxygen species (ROS), molecules that are They form as a result of processes such as power generation and that are usually harmful.
Researchers have found that one of these by-products, the superoxide anion, increases as sugar levels rise in the plant and acts to adjust the circadian rhythm in the evening. This rhythmic metabolic signal is capable of changing the expression of genes that regulate such important functions as growth, nutrient transport and energy metabolism , and the authors believe that this metabolic signal could be providing information to the plant about how much energy is available. during the night and, in turn, affect the growth of the plant.
Sources:
Sensitivity and intelligence in the plant world. Stefano Mancuso and Alessandra Viola. (Trans. David Paradela López). 2015. Editorial Galaxia Gutenberg
Román et al. 2021. Superoxide is promoted by sucrose and affects amplitude of circadian rhythms in the evening PNAS March 9, 2021 118 (10) e2020646118; https://doi.org/10.1073/pnas.2020646118
