By Angel, Founder, Third Orbit Flora
Many of us have houseplants with special habits that have intrigued us as home urban jungle curators. Plants like Calathea, Prayer, Stromanthe and Ctenanthe* have a fascinating variety of attributes. These plants move on their own to fold and unfold their leaves with the passing of night and day. But what is it called? Why do they do that? And how is the process being studied to advance our strategies in technical solutions to create smart materials and architecture? Let’s dive in to demystify the enigma of Nyctinasty* (from Greek nux, nukt‐ ‘night’ + nastos ‘pressed together’) and maybe discover a glimpse at the ways in which it's helping shape our future.
Nyctinasty is a process that occurs in over 60 varieties of plants, including the Fabaceae* (legume) family, with its most well known member being the Mimosa Tree. Others include the Asteraceae* family, like the heliotropic Sunflower whose face follows the sun, and dandelions, known to open and close their blooms with the rising and setting sun.
How it’s achieved is still a debated topic, but in the nearly one hundred fifty years it’s been studied, scientists have made remarkable discoveries in understanding not only the how, but the why of Nyctinasty. Commonly acknowledged is the method of turgor, which is the filling, or swelling of a pulvinus, or enlarged section of the stem located just at the base of each leaf or leaflet. This rise or fall of turgor pressure is what makes the plants fold and open. This has been theorized to be caused by chemicals being released into the plants cells, typically a trade of 2 different bioactive substances. Nyctinasty was originally thought to be controlled by a common phytohormone, a hormone that is essentially the same between different plant species. Not so with the turgor chemicals. Each plant seems to have its own mix that helps the leaves open and close, according to some biologic or lunisolar clock, like our own bodies' circadian rhythms, according to research published in the MDPI open science journals.
Recent fossil findings of prehistoric plants have shed light on the fact that foliar nyctinasty evolved independently among the diverse plant groups. Which makes sense for why each plants’ biochemical mechanism to induce nyctinasty would be different.
The biggest question involving most nyctinastic plants is WHY do they fold up at night? Particularly those who live in jungles and rainforests, like that Prayer plant on your living room table. Some researchers attribute this behavior to an evolutionary response to making it more difficult for insects and small herbivorous and granivorous mammals (like mice) to forage safely from the prying eyes of predatory nocturnal birds and bats. This keeps the plant from being damaged by the tussle of an owl catching prey, or being eaten by moth caterpillars. One journal published on Pubmed shares that “nocturnal rodents exposed to too much nocturnal illumination [will] carry food back to safer locales instead of eating it in the field… by encouraging small herbivorous mammals, by a reduction in safe choices, to forage and travel amidst non‐nyctinastic competitors, FN [foliar nyctinasty]...affords a competitive advantage to those plants that exhibit it.”
The biochemical and biomechanical processes of nyctinasty, as well as photonastic and thermonastic processes, (movement in response to light or temperature) that scientists and researchers have unraveled aren’t just helping plants survive, but also paving the way for other forms of exciting research in fields like biomimicry and architecture. Development of things like passive kinetic solar shading are just one example, helping the environment they learned from by creating more energy efficient design strategies.
One paper published in HAL.Science by Natasha Chayaamor-Heil, and Nelson Montas Laracuente, states “The transformation of these [plants] strategies into technical solutions for responsive architectur[e]...requires…new technologies that include smart materials and new capabilities in simulation software. The research field of Programmable matter allows for systems to be autonomously changed according to various factors (water, light, UV ray, heat, touch, etc.)...The objective of this research is the use of shape memory alloys (SMAs) as smart actuators for the biomimetic translation of actuation systems in plants into an architectural envelope that can adapt and respond to environmental stimuli. Our aim is to develop a new type of passive kinetic solar shading device as a result of biomimetic application. Unlike traditional mechanical activation used for dynamic systems in kinetic façades, this type of responsive architectural envelope requires no complex mechanical parts, electronics or sensors, which can lead towards energy efficient design strategies.”
Nyctinasty, with its intricate mechanisms and remarkable adaptations, stands as a testament to the complexities of nature's design and plants' ability to thrive in diverse ecosystems. As scientists unravel its mysteries, gaining exciting insights, they're inspired to find innovative solutions in technology and architecture that can dynamically respond to environmental cues, shaping the future of science and technology.
-Angel, Third Orbit Flora
* Pronunciation Guide *
Nyctinasty (pronounced NICK-tuh-nass-tee)
Ctenanthe (pronounced te-NANTH-ee)
Fabaceae (pronounced fuh-bay-see-ai)
Asteraceae (pronounced aster-ay-see-ai)
To read more about the science and research of Nyctinasty and Biomimetic technology covered in this article, refer to these links:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7379275/
https://www.mdpi.com/1422-0067/2/4/156
https://academic.oup.com/aob/article/116/2/149/180655
https://www.diva-portal.org/smash/get/diva2:1817620/FULLTEXT01.pdf
https://www.sciencedirect.com/science/article/pii/S036013232301079X
https://hal.science/hal-03087330/file/BERN_FINAL.pdf
Photo credit: Adobe Stock image of plants.