How to Prevent Photobleaching in Your Indoor Farms or Greenhouses

Modern indoor farms and greenhouses utilize the power of LED grow lights to grow crops year-round. However, along with their numerous advantages, LEDs also present a new challenge - the risk of photobleaching your precious plants.

Photobleaching is a common problem that many commercial growers face. It occurs when plants are exposed to too much wrong light, which destroys their chlorophyll and other pigments. The result is a noticeable fading or bleaching of leaves and flowers. Photobleaching can not only affects the appearance and market value of your crops but also reduce their overall quality.

But fear not! With the right lighting strategies, you can largely prevent photobleaching.

What is photobleaching in plants

Photobleaching happens when plants are exposed to excessive light, which damages their photosynthetic pigment and reduces their color and potency. It’s similar to a sunburn but caused by light, not the sun. Photosynthetic pigments, such as chlorophyll, are responsible for absorbing light energy and converting it into chemical energy for plant growth and development. However, when the light intensity exceeds the plant’s capacity to use it, the excess light energy can destroy the chlorophyll molecules and impair the photosynthesis process.

What causes photobleaching

The primary cause of photobleaching is an imbalance between the amount of light received by the plant and its capacity to utilize that light for photosynthesis. Here are some factors that contribute to the occurrence of photobleaching:

• High light intensity: Intense light can overwhelm the plant’s photosynthetic machinery. This excess energy leads to the generation of reactive oxygen species, causing damage to the chlorophyll and cellular structures.
• Light spectrum: Insufficient or excessive amounts of certain wavelengths can disrupt the plant’s metabolic processes and trigger photobleaching. For example, an imbalance in blue or red light can lead to chlorophyll degradation and reduced photosynthetic efficiency.
• Uneven light distribution: Uneven light distribution across the growing area can create localized areas of intense light. These hotpots increase the risk of photobleaching in the affected plant parts while leaving other areas under-illuminated.
• Distance from plants to lights: The proximity of the light source to the plants also plays a role in photobleaching. LED lights positioned close to leaves emit a higher photon flux compared to those placed further away, potentially increasing the risk of photobleaching.
• Heat: The combination of excessive heat and light can further stress the plants, exacerbating the effects of photobleaching.

How does photobleaching affect plant quality?

Photobleaching can have a negative impact on the quality and marketability of your crops, especially if you are growing high-value plants. Take cannabis as an example. Photobleached cannabis plants may suffer from a decline in flavor, aroma, potency, and visual appeal, which can lower their consumer demand and price.

Here are some of the potential effects of photobleaching:

Reduced chlorophyll content

Photobleaching damages chlorophyll, the pigment responsible for capturing light energy during photosynthesis. As a result, plants experiencing photobleaching show a decline in chlorophyll content. This not only affects the plant’s ability to convert light into energy but also leads to visual changes in foliage color, often appearing pale.

Impaired photosynthetic efficiency

Photobleaching disrupts the photosynthetic process, reducing the plant’s ability to produce energy for growth and development. With compromised photosynthetic efficiency, plants may experience stunted growth, reduced biomass accumulation, and a decrease in overall vigor.

Altered nutrient uptake and metabolism

Excessive light exposure can negatively impact the plant’s nutrient uptake and metabolism. Photobleached plants may struggle to absorb essential nutrients efficiently, leading to nutrient deficiencies or imbalances. This can compromise the plant’s ability to synthesize essential compounds, resulting in lower nutritional value and compromised flavor in the harvested produce.

Increased susceptibility to pests and diseases

Weakened plants due to photobleaching become more vulnerable to pests and diseases. The stress induced by excessive light exposure compromises the plant’s defense mechanisms, making it more susceptible to insect infestation, fungal infections, and other pathogenic attacks. This can further impact the quality and marketability of the produce.

Reduce market value

Consumers are naturally drawn to crops that appear fresh. The vibrant color of plants contributes to their visual appeal. In contrast, photobleaching causes plants to appear pale and blemished. This visual appearance can negatively impact a consumer's overall experience and their likelihood of purchasing the produce.

How to prevent photobleaching in your indoor farms or greenhouses

Let’s get back to what causes photobleaching. Photobleaching occurs when plants are exposed to too much light. Therefore, the key to preventing photobleaching is to avoid excessive light for plants. Here are possible tips to prevent photobleaching in your indoor farms or greenhouses.

Use a balanced spectrum

Choosing the appropriate light spectrum is essential to provide plants with optimal wavelengths for photosynthesis while minimizing the risk of photobleaching. The easiest way to avoid photobleaching is to use a balanced, broad white spectrum.

Reduce light intensity

Reducing the light intensity can prevent plants from getting overwhelmed by excessive light. According to the research by Fluence, reducing PPFD down to 500 μmol/mˉ²/sˉ¹ will help some cultivars remain unbleached even when the supplemental light intensity contains up to 95% red photons. However low light intensities can result in reduced final yields. Invest in dimmable LED grow lights to distribute the right light intensity throughout the life cycle of plants.

Use high-quality LED grow lights

Another way to reduce the risk of photobleaching is to use high-quality LED grow lights with less heat generation. According to the research by Fluence, pre-heating treatments induce photobleaching in cucumbers, showing the possibility that cooling treatments might help reduce excess photobleaching. Therefore, a high-quality LED grow light can reduce the risk of photobleaching and other problems caused by overheating or aging of the light source.

Monitor and adjust lighting parameter

Regularly monitor light intensity, spectrum, and duration. Continuously observe how your plants respond to the lighting and make any necessary adjustments to optimize growing conditions. Lighting needs can change as plants mature, so remain vigilant and adapt the lighting levels and exposure times to keep your crops healthy and thriving.

Preventing photobleaching in your indoor farms or greenhouses is crucial for maintaining healthy plant growth and ensuring high-quality produce. Remember to select the balanced spectrum and pay attention to light intensity and heat for the plant.

If you need any customized horticulture lighting solutions for your commercial grow rooms, please feel free to contact us. We are ready to help you create a better lighting environment for your plants.