Nyctinasty is a type of movement plants make. You’ve probably seen nyctinasty in action, and it’s fascinating. Leaves fold up overnight and gently lower by morning. Learn more about nyctinasty, why it happens, and the plants that experience this phenomenon.
What Causes Nyctinasty?
Nyctinasty is a natural movement based on circadian rhythm, or more accurately, diurnal rhythm. The movement is not a reaction or response but just something that happens. The movement is gradual but noticeable after time has gone by.
Why Does Nyctinasty Happen?
Scientists have not determined why some plants go through these motions, but there are theories. One theory is that moving the leaves up overnight helps the plant regulate its internal temperature. Even Charles Darwin agreed with this concept; he thought it was a method to protect against freezing temperatures.
Protection against foraging animals is another theory, and this makes a lot of sense when you consider one of the most well-known types of plants to go through these movements. Prayer Plants are named such because the folded-up leaves resemble hands held in prayer. The upper side of the leaves is often ornamental with bold and intricate patterns, but when the leaves fold up overnight, their showy display is concealed, and the plant has a more narrow and streamlined appearance. It’s possible the plant is using an ‘out of sight, out of mind’ approach to protect its foliage from hungry herbivores.
Another theory is that the leaves collect rain during the day, funneling the water to its roots as they fold up. The final hypothesis behind nyctinasty is that it is a method to protect pollen. The folded leaves provide additional protection to keep pollen dry overnight or accommodate specific pollinators.
Most of these theories have counter-theories. The movement is likely intended to provide protection; however, the part of the plant being protected and what it is being protected from are unknown.
How Does Nyctinasty Happen?
The movement occurs because of a group of cells known as pulvinae, located where the leaves attach to the stem. As the pulvinae expands or contracts, the leaves fold up or down. Why the pulvinae do what they do is a mystery, but this is how the movement happens.
Which Plants Experience Nyctinasty?
Many plants experience nyctinasty, but Prayer Plants, like Marantas and Calathea or Geoppertias, are some of the best-known plants to move. Nyctinasty is easy to see with houseplants, but this movement isn’t exclusive to indoor plants. Legumes, like beans and peas, experience nyctinasty.
Bust a Move
Nyctinasty is interesting because it’s unique. While this movement is intriguing, it’s not the only instance of plants moving. Other types of plant movement include:
- Venus fly traps snapping shut to catch prey is thigmonasty.
- Young sunflowers turning to face the sun is the result of heliotropism.
- Flowers that open during the day and close at night, like crocus and morning glory, experience photonasty. The opposite, when the flowers open at night and close during the day, like evening primrose or night phlox, are also examples of photonasty.
Plant Care
A Prayer Plant’s movement isn’t always very pronounced. Limited nyctinastic movement could be a sign that the sunlight or humidity is slightly off. The care may be good enough for the plant to survive, but just a tad off, so the foliage doesn’t move very much. If the plant has healthy foliage and pushes out new leaves during the growing season, don’t worry about a lack of movement. If the leaves have muted colors or show signs of low humidity, address the sunlight and dampness, and the prayer motion should return with time.