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Part 1: Which Wavelengths do Chlorophylls Absorb?

In order to choose the best light for growing your plants, it’s essential to understand which wavelengths of light are required for normal plant growth.  Plants are experts at capturing light energy and converting it into sugars through the process of photosynthesis.  The first step of photosynthesis is the absorption of light by specialized molecules called pigments that are found in plant cells.  In addition to pigments, plants have a number of other light receptor molecules known as photoreceptors.  We will explore the range and function of key plant pigments and photoreceptors and identify the wavelengths of light they absorb and respond to.  This article, which will cover chlorophyll pigments is the first in a 4-part series.

Words of caution: a complex network of factors control plant growth and development.  This article focuses on just one of these factors: light spectrum.  When deciding which wavelengths of light will be best for your plants, consider how all factors (light intensity, temperature, soil, etc.) interact together.  It’s also important to remember that most of what we know about pigments and photoreceptors is derived from studies with the model plant Arabidopsis (the plant equivalent of the lab mouse) and much remains to be learned about other species.  Different plant species have variations in the chemical composition of their pigments and photoreceptors.  For this reason, pigments and photoreceptors from different species can have slightly different absorption peaks than the values listed here.

Figure 1: Diagram of a light harvesting complex (LHC) within the chloroplast of a plant cell. The LHC is made up of the reaction centre (a single chlA molecule) and the antenna (a mix of chlorophylls, xanthophylls, and carotenes).