Light is composed of tiny particles called photons, which are the most basic units of light. As particles,
photons are discrete and each wavelength(colour)of light has its own independent photons.
In the context of plant growth, the energy carried by photons is what powers photosynthesis. Different
pigments in plants absorb different wavelengths (or colors) of light, each of which is composed of photons with a
specific energy level. This energy is used to power the chemical reactions that convert carbon dioxide and water into glucose and oxygen.
Moreover, specific wavelengths of light (and thus, photons of specific wavelengths)
can trigger different morphological (shape, size, quality) responses in plants. This is why manipulating the light spectrum,
and thus the energy levels of the photons reaching the plant, can influence plant growth and development.
Power refers to the intensity of light that plants receive. Light intensity,
often measured in lumens(for human viewing capabilities) or more appropriately for
plants in Photosynthetically Active Radiation (PAR) values, is a critical component
of plant growth as it fuels photosynthesis. This process enables plants to convert water
and carbon dioxide into oxygen and glucose, a type of sugar that serves as the main energy source for plants.
In essence, the greater the light intensity, the more energy plants have at their disposal to
carry out photosynthesis and grow. It's crucial to strike a balance where the light intensity is
high enough to promote robust growth, but not so high that it causes stress or damage. Power is
the primary and most important contribution of light to plant growth and govern over 80% of your growth results.
The ratio and composition of light colours(colour ratios) in a grow light spectrum provides control of the light over a plant shape and size. This ability of light to control plant morphology (shape, quality, texture) is independent of photosynthesis and is known as photomorphogenesis. This is why different colour ratios can trigger different growth characteristics when activated by photons of specific wavelengths. So, by controlling your light spectrum you can affect powerful changes in plant growth. LED Grow lights are uniquely suited for facilitating these morphological processes in plants due to their capacity to emit specific wavelengths of light. Plants mainly have two specific photoreceptors - phytochrome and cryptochrome.
1. Phytochrome - These pigments are particularly sensitive to red (600-700 nm) and far-red (700-800 nm) light. They play a crucial role in seed germination, the timing of flowering, and shade avoidance, amongst other things. Far-red light, in particular, is important for processes like shade avoidance, where plants growing under the shade of others will grow longer stems to reach the light.
2. Cryptochrome - These pigments are sensitive to blue (400-500 nm) and UV-A light. They have several roles in plants, including the regulation of growth, the timing of flowering, and the orientation of growth to optimize light capture. These two photoreceptors allow plants to sense and respond to their light environment in a distinctive way. By using LED lights of specific wavelengths, we can optimize plant growth and development. For example, by providing the right mix of red and blue light, we can influence the plant's photosynthesis efficiency, and potentially even characteristics such as taste in certain crops.
Our understanding of plant photoreceptors and their function is still growing, and there may be more complexities to this interaction than we currently understand. However, the use of LED lights in horticulture is a promising area of research and has the potential to greatly improve our ability to grow plants in a variety of conditions, from indoor vertical farms to outer space.
Read more about PAR (Photosynthetically Active Radiation) range.