When discussing plant lighting, two critical concepts often arise: the action spectrum and the absorption spectrum. These two terms, although closely related, are often misunderstood or used interchangeably. However, understanding their differences is key for anyone involved in plant cultivation, especially for optimizing the lighting setup for cannabis or any other crop.
Although both spectra are influenced by light, they serve distinct functions that are essential for healthy plant growth. Let’s dive deeper into these two concepts and understand how they can be used to optimize lighting strategies for your plants.
What is the Action Spectrum?
The action spectrum is a measure of how effectively specific wavelengths of light promote photosynthesis in plants. Simply put, it indicates which light colors are most useful for a plant’s photosynthetic activity.
The range of light that plants use for photosynthesis is called Photosynthetically Active Radiation (PAR), which spans from 400 to 700 nm. This spectrum includes the visible light colors – violet, blue, green, yellow, orange, and red – with red and blue being the most vital for the photosynthetic process.
The importance of understanding the action spectrum lies in the fact that it helps us maximize the efficiency of the photosynthesis process. By selecting grow lights that match the action spectrum, growers can boost plant productivity and health. Specifically, red and blue light are the most critical wavelengths for photosynthesis.
To quantify the impact of light on photosynthesis, several factors are considered:
- Oxygen production (O₂)
- Reduction of Nicotinamide Adenine Dinucleotide Phosphate (NADP+)
- Carbon dioxide fixation (CO₂)
By measuring these parameters, growers can better understand the effectiveness of specific light wavelengths in their cultivation environment.
What is the Absorption Spectrum?
On the other hand, the absorption spectrum refers to how much light different plant pigments absorb. This spectrum helps determine which light colors are absorbed by key pigments involved in photosynthesis, such as Chlorophyll A, Chlorophyll B, and Carotenoids.
- Chlorophyll A absorbs light most efficiently in the violet, blue, red, and orange ranges.
- Chlorophyll B absorbs primarily in the blue and red ranges, with some absorption in the green and orange wavelengths.
- Carotenoids absorb light primarily in the violet, blue, and green wavelengths.
Though plants absorb a broad range of colors, red and blue light are absorbed in the greatest quantities. These colors are directly involved in the process of photosynthesis, where they help convert light energy into chemical energy.
While violet, orange, and green light are absorbed less, they still play a role in the overall health of the plant. The absorption spectrum allows us to understand the light that the plant pigments are most sensitive to, helping us tailor the light source accordingly.
Key Differences Between the Action Spectrum and Absorption Spectrum
- Function:
- The action spectrum measures how effectively light wavelengths contribute to photosynthesis.
- The absorption spectrum reveals how much light is absorbed by plant pigments.
- Focus:
- The action spectrum focuses on the overall photosynthetic process, while the absorption spectrum focuses on the specific pigments within the plant that absorb light.
- Measurement:
- The action spectrum is usually measured by observing the effects of light on photosynthesis (e.g., oxygen production, carbon fixation).
- The absorption spectrum is measured using spectrometers to observe how pigments absorb light across different wavelengths.
Though both are related to light, the action spectrum is about the effectiveness of light in promoting photosynthesis, while the absorption spectrum is about the ability of pigments to capture light.
How to Use Action and Absorption Spectra to Optimize Cannabis Growth
The key to optimizing the growth of cannabis plants lies in using the right type of lighting. LED grow lights have become the go-to technology for indoor cannabis cultivation because of their ability to provide a full spectrum of light that mimics natural sunlight.
Benefits of LED Grow Lights:
- PAR Range: LED lights effectively cover the PAR range (violet, blue, green, yellow, orange, and red light), providing all the essential wavelengths for photosynthesis.
- Blue Light: Blue light is crucial for the early stages of cannabis growth. It strengthens roots and stems and helps the plant establish a solid foundation.
- Red Light: Red light is essential during the flowering stage, stimulating flower production and increasing cannabinoid content, including THC and terpenes. This light also encourages horizontal growth.
- Ultraviolet (UV) Light: UV light, while potentially harmful in excess, can stimulate resin production during the flowering stage, enhancing terpene and cannabinoid production in cannabis.
- Distant Red Light: While not as heavily absorbed as red or blue light, distant red light aids in the flowering and germination stages, promoting healthy plant development.
With their customizable spectrums, LED lights ensure that all light needs of cannabis plants are met, from germination to harvest. These lights can be fine-tuned to provide the optimal wavelengths needed at each stage of growth, ensuring plants receive everything they need to thrive.
Traditional Grow Lights vs LED Grow Lights
While traditional lights like CMH (Ceramic Metal Halide), fluorescent, HPS (High Pressure Sodium), and MH (Metal Halide) are still used, they do have limitations when it comes to optimizing the action spectrum for cannabis.
- CMH Grow Lights: These provide a broad spectrum but often over-emphasize green and yellow light, which are less beneficial for cannabis growth.
- HPS Grow Lights: While HPS lights produce a lot of red light, they lack sufficient blue light, which is essential for the vegetative stage.
- MH Grow Lights: MH lights produce good blue light but lack red wavelengths, making them less effective during the flowering phase.
LED lights, with their adjustable spectrum, provide precise control over the light conditions for each growth phase, making them superior to traditional lighting options.
Conclusion: Understanding Action vs Absorption Spectra
In conclusion, understanding the action spectrum and the absorption spectrum is crucial for optimizing plant growth. LED grow lights are the most effective technology to harness these spectra, offering a full spectrum of light that meets the specific needs of cannabis plants at every stage of growth. By choosing the right grow lights based on these principles, you can ensure healthy, productive crops with high-quality yields.
If you’re aiming for the best results in your cannabis cultivation, it’s clear: LED grow lights are your best option, combining flexibility, efficiency, and optimal light conditions for your plants.
