In: Biology
Which wavelengths penetrate shallower and deeper layers of leaves? Why?
Red and blue light (longer wavelengths) can penetrate the upper adaxial layers of the leaves. Green light (shorter wavelength) has more penetrance and therefore can penetrate into deeper abaxial layer of the leaves. Red and blue light has higher wavelength than green light. Photosynthetic efficiency is higher for red and green light as compared to blue light. However, in the deeper layer, photosynthesis efficiency is higher for green light as compared to blue and red light.
In top layer of leaf (shallower), blue light is absorbed very quickly by the multiple pigments that are present. Only chlorophylls can absorb red light. Hence, red light is absorbed a little further than the blue light but still in the shallower regions. The bottom deeper layer of plant cells can absorb green light. This is because chlorophyll has weak absorption spectra for green light. Further, green light is scattered by chlorophyll in leaves. Thus, green light can transmit through the chloroplast, allowing more light to reach the mesophyll layer. Weak absorption of green lights by chlorophyll (green window) and the high refractive property of leaf allows green light to reach the deeper layer of the leaves. Further, scattering of green light allows its path through green leaf to become wide. Thus, there are greater chances of being absorbed by chlorophyll, increasing its efficiency of photosynthesis.