As indoor gardening grows in popularity, LED grow lights have become a vital tool for achieving healthy and bountiful plants. These lights deliver the ideal light spectrum, enabling gardeners to cultivate vibrant plants year-round. However, with a wide variety of LED grow lights on the market, understanding spectrum science can be overwhelming.
That's why we've created this comprehensive guide— to equip you with the knowledge and skills necessary to select the ideal full spectrum light for your garden. So, let's dive into the fascinating world of LED grow light spectrum science!
Light Spectrum and Visible Light Spectrum
Light Spectrum, refers to the entire range of wavelengths of electromagnetic radiation that we can perceive as light, including both visible and non-visible light. This spectrum extends from gamma rays, which have the shortest wavelengths and the highest energy, to radio waves, which have the longest wavelengths and the lowest energy.
The visible light spectrum is the part of the electromagnetic spectrum that the human eye can detect, with wavelengths ranging from 380 to 750 nanometers. Within this range, light is divided into different colors, each color corresponding to a specific wavelength, from violet at the shortest wavelengths to red at the longest.
Visible Light Spectrum and Plant Photosynthesis
During photosynthesis, plants capture sunlight to convert carbon dioxide and water into glucose and oxygen. However, not all wavelengths of light are equally effective in this process. The key players in light absorption are chlorophylls, primarily chlorophyll A and chlorophyll B, which absorb specific wavelengths of light, allowing plants to efficiently convert it into chemical energy.
Chlorophyll A absorbs light most effectively in the blue-violet and red regions of the visible spectrum, with peak absorption at around 430 nm and 660 nm. Chlorophyll B, in contrast, absorbs light in the blue and orange-red regions, peaking at approximately 450 nm and 640 nm. As a result, the energy most essential for photosynthesis comes from the visible light spectrum, particularly red, blue, and yellow-green light.
The Effect of Different Light Colors on Plant Growth
The visible light spectrum includes red, blue, green, yellow, and orange light. Different colors of visible light have distinct effects on plant growth, such as germination, vegetative growth, flowering, and fruiting.
Red Light (620-750 nm)
Red light, with wavelengths ranging from approximately 620 to 750 nanometers (nm), plays a vital role in plant growth as it is a major driver of photosynthesis and overall development.
Red light is absorbed by a pigment called phytochrome, which exists in two interconvertible forms: Pr (the red light-absorbing form) and Pfr (the far-red light-absorbing form). The Pfr form activates gibberellin biosynthesis, a hormone that stimulates seed germination. Gibberellin production occurs only when both red light and water are present, ensuring seeds germinate under optimal light and moisture conditions.
Red light also stimulates the production of auxins, plant hormones that promote cell elongation and expansion, contributing to growth and development. These hormones are essential for processes like stem elongation and root development.
In terms of reproduction, red light plays a significant role in flowering. In long-day plants, red light acts as a "floral inducer," promoting the expression of genes that trigger flower development. In short-day plants, red light helps inhibit the expression of genes that suppress flowering, allowing these plants to bloom when the conditions are right.
Furthermore, plants can detect changes in the ratio of red to far-red light when they are shaded by nearby vegetation. Since chlorophyll absorbs red light while far-red light is reflected, a shift toward more far-red light signals that a plant is in the shade. This change activates the shade avoidance response, leading to stem elongation as the plant grows taller in an attempt to reach more light.
Blue Light (450-490 nm)
Blue light, approximately 450 to 490 nanometers (nm) in wavelengths, is one of the most important spectra for plant growth and development. It is characterized by a short wavelength and high energy. Specifically, Blue Light stimulates the production of chlorophyll, plays a vital role in leaf development and stem elongation, helps plants establish strong and healthy root systems, helps regulate the opening and closing of stomata, and influences phototropism.
How does it do this work? Blue light regulates these processes by stimulating the production of auxins, which are plant hormones responsible for cell elongation and division, as well as cell differentiation.
Auxins are primarily produced in the plant's apical meristem, which is the growing tip of the plant, and then accumulate on the shaded side of the plant. Therefore, they help plants' growing tips (mainly roots and leaf tips) grow towards sources of water and nutrients and help cell elongation on the shaded side of the plant stem, causing the stem to bend towards the light source.
Besides, Blue light triggers the opening of stomata by activating specific receptors in the guard cells surrounding the stomata, allowing for the uptake of carbon dioxide and release of oxygen, and water vapor loss through transpiration.
Green Light (495-570 nm)
Green light,with wavelengths ranging from approximately 495 to 570 nanometers(nm), sits in the middle of the visible light spectrum. While it isn't as crucial for plant growth as red and blue light, it still contributes to several important physiological processes.
Green light takes part in regulating plant architecture by promoting the growth of shoots and inhibiting root growth. This effect can be beneficial in controlled environments like hydroponic or aeroponic systems, where space for root expansion is limited. Additionally, green light penetrates deeper into the plant canopy than other wavelengths, reaching lower leaves that might otherwise be shaded. This increases photosynthetic activity in those leaves, boosting overall biomass production.
Moreover, green light stimulates the production of secondary metabolites, such as flavonoids, phenolic acids, and carotenoids. These compounds aren't directly involved in growth but play essential roles in plant survival, helping them respond to environmental stresses.
Yellow Light (570-590 nm)
Yellow light, with wavelengths around 570-590 nanometers (nm), is part of the visible spectrum that plants can absorb, but it is less effective in driving photosynthesis. While it may not significantly impact plant growth on its own, yellow light can interact with other wavelengths to influence growth responses.
For example, combining blue and yellow light can promote root elongation in Arabidopsis thaliana seedlings, while red and yellow light together can enhance photosynthetic pigment production in lettuce. Yellow light may also play a role in helping plants respond to environmental stresses like drought and salinity.
Orange Light (590-620 nm)
Orange light, with wavelengths between 590 and 620 nanometers (nm), may not be as crucial for plant growth as red or blue light, but it still plays an important role in promoting healthy, productive plants.
Orange light has been shown to positively affect the growth of certain plants, such as tomatoes, lettuce, and strawberries. For instance, supplementing red and blue light with orange light has been found to increase plant height, leaf number, and fresh weight in lettuce seedlings compared to using red and blue light alone.
Ultraviolet Light and Infrared Light For Plants
Although ultraviolet (UV) and infrared (IR) radiation lie outside the visible spectrum, they play crucial roles in plant growth.
Ultraviolet Light (10-400 nm)
UV light is high-energy radiation. The wavelength range of ultraviolet (UV) radiation is generally considered to be between 10 nanometers (nm) and 400 nm. However, this range can be further divided into three categories: UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm).
UV radiation can have both positive and negative effects on plants, depending on the intensity and duration of exposure. In moderate doses, UV radiation can stimulate the production of secondary metabolites, such as flavonoids and anthocyanins, which can act as antioxidants and protect plants from UV damage. These compounds can also enhance the nutritional and medicinal value of crops.
However, high levels of UV radiation can be damaging to plant tissues by causing mutations in DNA and inhibiting photosynthesis. This can result in reduced growth and yield, as well as increased susceptibility to diseases and pests. In extreme cases, excessive UV radiation can even cause cell death and plant mortality.
Infrared Light (700 nm -1000 mm)
Infrared (IR) light is a low-energy radiation. The wavelength range of IR radiation spans from 700 nm to 1 millimeter (mm) and is divided into three categories: near-infrared (NIR, 700-1400 nm), mid-infrared (MIR, 1400-3000 nm), and far-infrared (FIR, 3000 nm - 1 mm). In plant cultivation, NIR is the most commonly used.
Infrared (IR) light can also have a significant impact on plant growth and development. IR light has several significant effects on plant growth and development. One of its key roles is raising the temperature of plant tissues, which accelerates metabolic processes and enhances growth—a phenomenon known as the 'thermal effect.' IR light also influences the opening and closing of stomata, regulating water loss and gas exchange.
Additionally, it affects various developmental processes, such as promoting stem elongation, increasing leaf size and thickness, and stimulating flowering in certain species. IR light can also modulate the production of plant hormones like auxins, gibberellins, and cytokinins, which are vital for regulating overall plant growth.
Both UV light and IR light are critical "information spectrums" for plants. They're now widely applied in agricultural production and medical production. Check out our guide on How To Use UV and IR for more practical usage for your gardens.
Spectrum Science In LED Grow Light
Science has shown that plants have specific light needs for optimal growth and development, which has led to the creation of LED grow lights with tailored spectrums. By understanding the science behind these lights, growers can optimize conditions for plant growth, leading to healthier plants and more successful harvests.
How to Read LED Grow Light Spectrum Charts?
LED grow light spectrum charts are used to show the wavelength and intensity of light emitted by a particular grow light. These charts can be used to determine whether the grow light is suitable for growing plants, as well as to compare the spectral outputs of different grow lights.
When reading a spectrum chart, the x-axis represents the wavelength of light in nanometers (nm), and the y-axis represents the relative intensity of light in arbitrary units. The spectrum is typically displayed as a line graph, with different colors representing different wavelengths.
It is important to pay attention to the peaks and valleys in the spectrum, as different plant processes require specific wavelengths of light. For example, chlorophyll absorption peaks at around 450nm (blue light) and 650-680nm (red light), so a grow light with a high intensity in these ranges is ideal for photosynthesis.
In addition to peak intensities, the spectrum ratio is also an important consideration when choosing a grow light. The spectrum ratio is the ratio of the intensity of red light to blue light and is typically displayed as a single number or as a graph. The optimal ratio is different for different plant species and your cultivation goals.
Full Spectrum lights
Full-spectrum LED grow lights are designed to provide a balanced and complete spectrum of light that closely mimics natural sunlight. The spectrum characteristics of full spectrum light typically include a mix of cool and warm white LEDs, as well as specific wavelengths of blue, red, green, and sometimes UV and far-red light. The balance of each color and wavelength can vary between different brands and models of LED grow lights. But they may have a similarity in that they will have more ratio in blue and red light to emphasize their peaks.
Broad Spectrum lights
Broad-spectrum LED grow lights are similar to full-spectrum LED grow lights in that they provide a range of wavelengths that are beneficial for plant growth and development. However, broad-spectrum LED grow lights tend to have a more even distribution of wavelengths across the visible spectrum, without emphasizing specific peaks in the blue or red regions. This can make them a good choice for growers who want a balanced light source that promotes overall plant health and growth, without focusing too much on specific growth stages or plant characteristics.
Targeted Spectrum lights
Targeted Spectrum LED grow lights are designed to emit specific wavelengths that support different plant growth stages, like vegetative growth or flowering. These lights mainly focus on blue and red light, with minimal green or yellow. Some models also include UV or far-red wavelengths, which can further influence plant development. By using these lights, growers can adjust the spectrum to meet their plants' specific needs, promoting healthy growth and maximizing yields.
Color Temperature (CCT)
Color temperature is a measure of the color appearance of the light emitted by a light source and is measured in Kelvin (K). Lower color temperatures (2000-4000K) produce a warm reddish-yellow light, while higher color temperatures (5000-6500K) produce a cool blue-white light. The color temperature of grow lights affects how plants perceive and react to light, affecting their growth and development.
Ideal Spectrum Lighting For Each Plant Stage
To optimize plant growth, it's best to provide different light spectra at each growth stage. But what is the ideal spectrum for each stage?
Seedling Growth
For seedling growth, it's recommended to use a full-spectrum LED grow light with a color temperature of 5000K-6500K, offering a balanced mix of blue and red light, with a focus on more blue. This ensures seedlings get the necessary light for healthy development.
Some growers may wonder if a full-spectrum light with more red could work instead. However, Mars Hydro has researched this issue and found that if there is too much red for the seedlings, the seedlings will grow very long stems and roots with small leaves, which is not what growers want.
Vegetative Growth
The overall spectrum ratio for vegetative growth should be balanced, with a slightly higher proportion of blue light than red light, the color temperature of which should be within 4000K-5500K. Blue light stimulates the production of chlorophyll and other pigments essential for photosynthesis, while red light promotes stem and leaf growth.
Moreover, some growers add a small amount of far-red light (700-740 nm) during this phase to promote stem elongation, improve plant structure, and optimize growth patterns by influencing factors like plant height and internode spacing.
Flowering and Fruiting Stage
During the flowering and fruiting stage, plants require more red light and less blue light, with an optimal color temperature of 3000K-4000K. A full-spectrum LED grow light with a higher red-to-blue ratio is ideal. Red light stimulates flowering hormones crucial for reproduction, while too much blue light can encourage vegetative growth, leading to stretching and fewer flowers.
Some growers may also use supplemental LED lights with specific red wavelengths, like 660nm, which has been shown to particularly enhance flower and fruit production.
Final Thoughts
When choosing LED grow lights, it's important to match the spectrum to your plants' special needs at each growth stage. Mars Hydro’s LED grow lights offer a balanced spectrum with red, blue, white, and IR light, making them ideal for all stages of growth, from seedling to harvest. With different red-to-blue ratios, growers can select the best option for optimal results. Mars Hydro also offers targeted spectrum lights, including UV and IR, for specific plant growth needs. Explore ourLED Grow Lights collection and contact us for more details.
