You may not have heard of etiolation before, but we would bet money you’ve encountered it at some point, especially with houseplants.
Etiolation isn’t a disease, but a condition caused by insufficient light.
It can affect just about any sun-loving plant, as well as shade-loving plants in the right circumstances.
The term etiolate (ee-tee-uh-leyt) comes from the French étiolé, meaning “to blanch”. Indeed, the process of purposely inducing etiolation in garden vegetables is known as blanching.
The effect is not so desirable in your flower garden, though.
It’s important to note that etiolation occurs naturally in plants during germination and when covered in leaves or other debris.
It only becomes a problem when etiolation affects adult or flowering plants, where the pale color, fewer leaves, and weak stems may lead to disease or damage.
What is Etiolation?
The name of this condition is in reference to etioplasts. Plant tissue contains chlorophyll, which converts sunlight into food for the plant. When there’s inadequate sunlight, etioplasts develop instead of tissue containing chlorophyll (or lack of chlorophyll) or stacked thylakoid membranes.
An etioplast (or plastid) is created as a byproduct of auxin and may evolve into chloroplasts through a process called de-etiolation (or greening).
Auxin, a plant hormone, controls how long a stem grows. It’s produced at the tip and travels downwards, diffusing along the way. The auxins are key in preventing lateral buds and other important functions.
When light is present, auxins will also stimulate proton pumps that, in turn, increase the acidity of cell walls. This causes an enzyme known as expansin to activate, which weakens the cell wall and allows it to expand.
What Damage Does It Cause?
Etiolation doesn’t directly damage a plant. However, it significantly affects the plant’s appearance and makes it more susceptible to damage from other sources.
One concern is how etiolation affects the stem. Affected stems become spindly (or leggy), appearing long, thin, and with a pale color. This makes them more prone to breakage, especially with the cell walls weakened by expansin.
This isn’t as problematic for seedlings, which go through de-etiolation once the sprout has reached sunlight.
Another symptom is the appearance of pale, sparse leaves due to elongated internodes. The sickly pale yellowish-white color is known as chlorosis and is due to the lack of chlorophyll present.
Without enough chlorophyll, the plant becomes more reliant upon soil nutrients and will become malnourished in time.
Of course, this unattractive appearance can signal a much higher risk in adult plants of contracting diseases or being killed off from any infestations that might occur.
The lower health may result in less serious infestations killing the plant or reduced resistance to temperature changes.
How To Control Etoliation?
It’s important to remember that etiolation is a normal biological reaction of plants to help them reach sunlight. Under normal circumstances, a seed will germinate and naturally de-etiolate upon breaking through the ground.
However, it may become necessary to assist plants that are suffering from etiolation.
De-etiolation, also known as greening, is the reversal of an etiolated plant that has reached adequate lighting. As with etiolation, the reversal is regulated by chemicals, in this case, the photoreceptor pigments known as phytochrome A, phytochrome B, and cryptochrome.
These pigments are inactive in the absence of light but become increasingly responsive as they come into more contact with light. The phytochromes respond to red light, while cryptochromes respond to blue light.
As a result, etioplasts will develop into chloroplasts and begin producing chlorophyll. Production of expansin will cease, allowing an elongated plant cell to regain strength and return to a normal shape. The restoration of chlorophyll will also lead to a healthy, green plant.
When you see etiolated plants in your garden, try to determine what’s interfering with their light source. Remove any debris such as leaf litter and thin out any neighboring plants which are blocking access to sunlight.
In many cases, a younger plant will be able to simply outgrow such obstructions and will naturally de-etiolate, but adult plants may need your assistance.