Q.What is the percentage of photosynthetically active radiation (PAR) in the incident solar radiation?
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Start your 14-day free trial to unlock the full solution →Less than 50% of the total incident solar radiation is Photosynthetically Active Radiation (PAR), which is the specific range of light wavelengths plants use for photosynthesis.
To understand the percentage of Photosynthetically Active Radiation (PAR) in incident solar radiation, we first need to clarify what PAR is and how it relates to the broader spectrum of light from the sun.
Photosynthetically Active Radiation (PAR) refers to the specific range of electromagnetic radiation (light) from 400 to 700 nanometers that photosynthetic organisms, like plants, algae, and cyanobacteria, are able to use in the process of photosynthesis. This range corresponds to the visible spectrum of light, which includes violet, blue, green, yellow, orange, and red light. Plants have evolved pigments, primarily chlorophylls and carotenoids, that are highly efficient at absorbing light within these wavelengths to convert light energy into chemical energy.
The incident solar radiation is the total electromagnetic radiation emitted by the sun that reaches the Earth's surface. This radiation encompasses a very broad spectrum, including ultraviolet (UV) radiation (shorter wavelengths than visible light), the visible spectrum (PAR), and infrared (IR) radiation (longer wavelengths than visible light). Not all of this broad spectrum is useful for photosynthesis. For instance, much of the UV radiation can be harmful to biological systems, and infrared radiation primarily contributes to heat, which is not directly used for photosynthetic energy conversion.
Plants specifically utilize the visible light spectrum (400-700 nm) for photosynthesis, which is defined as Photosynthetically Active Radiation (PAR).
According to the NCERT textbook, of the total incident solar radiation that falls on Earth, less than 50 per cent of it is Photosynthetically Active Radiation (PAR). This means that more than half of the solar energy reaching our planet is either outside the visible spectrum or in wavelengths that plants cannot efficiently use for photosynthesis. …
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