LED Light Stress on Plants

LED Light Stress on Plants

We all know light is the only source for plants to process photosynthesis, but sometimes, it may become a problem.

Plants can only absorb a specific amount of light; exceeding the limit may lead to light stress on plants. It often happens in indoor environments where plants grow under artificial lights.

In outdoor environments, plants adapt to the natural conditions and react accordingly. However, in controlled surroundings, you may have to face different challenges, and one of them is LED light stress on plants, which affects plants’ growth and productivity.

This guide will help you identify the signs of light pressure on plants so you can handle the cause before it gets catastrophic.


What is LED Light Stress on Plants?

Before diving into the main course, you need to know the story behind the light stress on cannabis plants.

Whether it’s a natural or artificial environment, too much heat/light can damage the plant cells, leading them to progress slowly and eventually die.

Plants experience light stress when stability between absorbed energy and energy to optimize the metabolic process is disturbed, leading to a decrease in the capacity of photosynthesis and production of oxygen.

This phenomenon leads to discoloring in cannabis plant leaves, often confused with iron or nutrient deficiency.

The symptoms of light stress in plants are so similar to nutrient deficiency that many don’t focus on the main symptoms, leading to an overfeeding of chemical fertilizers.


LED Light Stress on Plants


Why do Plants Experience Light Burn and Light Stress?

Light burn and light stress are different things, but both are closely related to each other.

Light stress is a broader term and manifests a range of symptoms in cannabis plants when they are exposed to unbalanced lighting conditions. Too much or too compact light can put light stress on plants.

On the other hand, light burn is a more specific term related to an only cause: too much direct heat from the source may result in light burn in plants. It’s like getting sunburned from overexposing yourself to the sun. The same goes for the plants, leading them to turn leaves yellow, brownish, or crispy.

Light burn is more likely to happen indoors because of over-optimizing the use of resources by growers in search of higher crop production. They keep focusing on chemical fertilizers, unaware that too much heat would dry the plant's surface, leading to overwatering. Such extreme conditions can cause permanent damage to plants' health.

Recognizing Signs of Light Stress in Plants

Plants can exhibit different symptoms when suffering from light stress. There are many ways to identify the signs of LED light stress on plants, including leaves curling, discoloring, stunted growth, leaf drop, etc.


  • Leaves pointed upwards: Generally, the leaves pointing upwards suggest healthy growth and a sweet spot for getting optimal light, which is a good sign. But sometimes, it triggers the light stress in indoor cannabis plants—nothing to worry about if your plants get a lot of heat and have lush green leaves. The below image depicts the sign of light stress.
Leaves pointed upwards

 Image Source: growweedeasy.com


  • Pale Leaves: Pale leaves are another sign of light stress in plants. This is a sign that the plant is near the light source and getting more light than usual. You’ll see this stress sign only in those plants nearer to the light; others will be fine. The leaves of the plants closer to the light have a pale color, followed by burnt and twisted tips.

Pale leavesImage source: semillas-de-marihuana.com


  • Bleaching of leaves: Bleaching or yellowing is the most common sign of light stress in plants, especially in matured leaves. The causes of bleaching in plants due to the malfunction of chlorophyll. It’s because the plant can’t absorb the light to process photosynthesis, leading to discoloring of leaves.
bleaching of leaves

Image Source: jonjoseeds.in


  • Change of Leave shape: Cannabis plants can also change the shape of their leaves to respond to light stress, i.e., cupping or curling leaves.

Change of Leave shape

Image Source: cannabisbusinesstimes.com


  • Discoloring leaves: Many growers misunderstand the discoloration in marijuana plants with nutrient deficiency. It’s not always the case that plants suffer from nutrient deficiency. Sometimes, you see only plants suffer from discoloration that is getting too much light. The plants suffering from light stress may change the leaves’ color to yellow, red, purple, and possibly brown spotting.

 Discoloring leaves

Image Source: growweedeasy.com



Types of Light Stress in Plants: A Brief Overview

Generally, there are two types of light stress in plants, i.e., high LED light stress and low LED light stress. Both types are entirely different, but their agenda is similar.

If you identify the cause of light stress at early stages, you can easily prevent or reverse the reasons that slow down the healthy growth of plants.


High LED Light Stress

Excess light is not the problem; too much heat generated by the light is the main reason that causes light stress in plants.

Plants use water to cool their internal temperature (tissues) when the outside environment gets too hot; plants use all reservoirs to cool their internal tissues.

Continuously cooling the temperature when nothing is left behind at the bank leads to high light stress in plants.

When plants suffer from light stress, leaves start to look yellow, burnt, curled, or falling off. And when things get too intense, the soil may dry, too.

In rare instances, the outdoor plants get light stress due to extreme climatic conditions—when the outdoor weather gets too hot, plants consume too much water, and the defensive system stops working.

Well, it’s a rare event in outdoor environments and most probably happens in the summertime, where the temperature constantly hits more than 40 degrees Celsius.


Low LED Light Stress

Low light stress is entirely opposite to high light stress and occurs when a plant lacks light.

Plants should receive the optimal intensity of heat and light to grow faster and healthier; otherwise, it affects the whole growth cycle. Too much or too little can be problematic for plants. 

The heat and light intensity are interconnected—one helps make chlorophyll, and the other benefits to process photosynthesis. If your plant doesn’t get both of these, it will stunt the growth.


Plant Defense Mechanism Against LED Light Stress

When plants trigger any kind of stress, they have to start different mechanisms to defend against that stress.

When plants get light stress, they tend to use different strategies to defend against light stress. Here are different strategies for high light and low light stress:


Strategies for Plants to Defend Against High Light Stress 

So far, you may be well aware of the fact that too much light can be catastrophic for plants. For that reason, plants use multiple mechanisms to drive off the light stress, which helps them to have stable physiological functions to live under difficult conditions. 

The first mechanism that plants use is photoprotection, which filters the excessive heat as energy; as a result, reducing the development of ROS (reactive oxygen species).

The plants can only achieve this by expanding the number of carotenoids, i.e., lutein and zeaxanthin, which protect against high light.

Furthermore, plants can also generate antioxidant enzymes like SOD (superoxide dismutase), catalase, and peroxidase, which play an essential role in stopping the ROS and protecting against oxidative stress.

Another mechanism involves the circulation of photosynthesis that plants use to fight against light stress. They can slow down the regulating process of genes that are involved in the photosynthetic reaction.

This helps the plants prevent the build-up of excessive energy and ROS and minimizes the risk of photodamage in plants.

Lastly, plants can stop their growth as an act of defense against high-light stress. They grow smaller, followed by thicker leaves, which helps them absorb heat energy and minimize light penetration. This process also allows them to enhance their water and nutrient intake.


Strategies for Plants to Defend Against Low Light Stress

Similar to high light stress, plants do have a defense mechanism for low light stress as well. These mechanisms help them maintain physiological activity and live under low light conditions.

Unlike plant defense systems against high-light stress, it tunes photosynthesis to defend against low stress.

It increases the production of genes associated with light-dependent response to photosynthesis, concealing the PSI reaction center. This process will help the plants to enhance and utilize the energy properly.

Plants can alter their growth in reply to low-light stress. They may develop larger and thinner leaves, which absorb more light and less interaction (less dense). In this process, plants take more resources than usual because their primary objective is to get as light as possible.

Lastly, plants also adjust their metabolism in response to low stress. They may store more energy to support the development when plants get low light.


LED Light Stress Vs. Nitrogen Deficiency

Light stress and nitrogen deficiency are different, but their symptoms are quite similar. Sometimes, cannabis growers mix both because the deficiencies are pretty relevant to each other.

To understand the difference between LED light stress and nitrogen deficiency, you need to discover the cause troubling the plants.

Nitrogen deficiency is caused because of unhealthy soil. On the other hand, light stress is caused by the uncertain presence of light, either low or high intensity. Like high intensity of light causes problems, too much nitrogen or toxicity in the soil can make your plant sick and delay the fruit ripening.

Confusing light burn with a Nitrogen deficiency is a common mistake that can cause wilting and yellowing of the leaves.

However, there are key differences: Nitrogen-deficient leaves typically fall off by themselves, while light-burned leaves tend to remain attached and can be difficult to remove.

Additionally, Nitrogen deficiency usually starts at the bottom of the plant and progresses upwards, whereas light burn may be more pronounced at the top of the plant.


Tips for Avoiding Light Stress

Prevention is better than cure, and it is a more straightforward thing to do before things get out of control. Here are some tips for avoiding light stress in your indoor plants:

  • Optimal Light Intensity: Do artificial lights put light stress on plants? Yes, if you don’t use the optimal intensity of LED lights, it will burn your plants. That’s why it’s important to use proper LED grow lights to give plants the right amount of light.
  • Light Duration: Give your plants an exact amount of light for dark periods.
  • Temperature Control: Too much heat can lead to high stress, and too little leads to slow plant stress. It’s essential to monitor the temperature constantly with a temperature controller.
  • Prevent Overwatering: Overwatering may lessen the oxygen levels in plants, which can cause light stress in plants.
  • Gradually Adjust Plants to New Environment: If you are planning to move your new plants from low levels of light to high levels, make sure to move them slowly to adapt to the environment.
  • Conventional Ventilation: Ventilation plays a vital role in the development of indoor plants. Maintaining the ideal humidity and temperature may also minimize the risk of disease.
  • Proper Nutrients: Plants need nutrients to defend against light stress.


Caring for LED Stressed Plants: 

LED light-stress plants require care, starting with what is causing the issue and then going for the fix. If something goes sideways while caring, here’s how to fix it:


  1. Solving High Light Stress Issues

  • If your plant is under the pump due to high light stress, move the plant to a spot with less direct light. Dim the lights or put the cloth above it to reduce the light intensity.
  • Too much heat may increase evaporation and lead to plants becoming parched; raising the humidity levels may help you reduce the stress levels.
  • Prune your damaged leaves to avoid additional damage to other leaves. This will allow plants to regenerate more energy.


  1. Solving Low Light Stress Issues

  • If your plant seems dull and not getting much light, move it to a spot with better lighting. You can also move the LED grow light near the affected plant.
  • If your plants suffer from low light stress due to nutrient deficiency, give balanced fertilizers to reduce the deficit.
  • If the daylight hours are not fulfilling the need, increase the duration to provide more light intensity to plants. But this way is not recommended because changing the natural order would disturb the plant’s other factors.


Final Thoughts On LED Light Stress on Plants

Light stress is a challenging issue for indoor environments that directly impacts plant’s growth, health, and overall development. Both high and low stress can be fatal for plants.

Although, with proper care and adjustments, you can minimize the effects of light stress on plants. By following the preventive measures and tips mentioned above, you can easily avoid anything terrible happening to your plants.