How does wavelength affect the efficiency of photosynthesis?

Wavelength affects photosynthesis efficiency as different wavelengths of light are absorbed differently by chlorophyll in plants.

Photosynthesis is the process by which green plants, algae and some bacteria convert light energy, usually from the sun, into chemical energy in the form of glucose. This process is facilitated by pigments, primarily chlorophyll a and b, which absorb light energy at specific wavelengths. The efficiency of photosynthesis is therefore directly influenced by the wavelength of light the plant is exposed to.

The absorption of light by chlorophyll pigments follows a specific pattern known as the absorption spectrum. According to this spectrum, chlorophyll a absorbs light most efficiently in the blue-violet and red regions of the light spectrum (approximately 430-450nm and 640-680nm respectively), while chlorophyll b absorbs light most efficiently in the blue and red-orange regions (approximately 455-470nm and 640-660nm respectively). This means that these wavelengths of light are most effective at driving photosynthesis.

However, it's important to note that green light (around 500-570nm) is least absorbed by chlorophyll and is instead reflected, which is why plants appear green. While green light is less efficient at driving photosynthesis, research has shown that it can still contribute to photosynthesis, particularly in deeper layers of leaves where it can penetrate more effectively than shorter wavelengths.

In addition to chlorophyll, plants also contain accessory pigments such as carotenoids and phycobilins. These pigments absorb light at different wavelengths than chlorophyll, allowing the plant to utilise a broader range of the light spectrum for photosynthesis. For example, carotenoids absorb light most efficiently in the blue-green region of the spectrum, while phycobilins absorb light in the green-yellow region.

In summary, the wavelength of light affects the efficiency of photosynthesis by determining how much light energy can be absorbed by the plant's pigments. The most efficient wavelengths for photosynthesis are those that are best absorbed by chlorophyll and other pigments, primarily in the blue and red regions of the spectrum. However, all wavelengths of light can contribute to photosynthesis to some extent, thanks to the range of pigments present in plants.