Mushrooms and Light: A Deep Dive Into the Fungi's "Eyes"
Mushrooms are fascinating and have been used by societies all over the globe for thousands of years. This was usually for their psychedelic effects, medicinal properties, or their use as food. Though use was common, fungi were not cultivated until the 17th century.
Because of late cultivation, there is a lot about mushrooms that we simply do not know. So much of the information about them that you read online may be lacking in source information or context. I am hoping to clear that up with this article. A previous article I authored discussed that at least some mushrooms use light in some way. In this article, we are going to take a deeper look into this fascinating ability.
Different mushrooms may react in different ways to light. It is dependent on the species. Other factors in light utilization may also play a role, such as moisture, the amount of light, heat, soil composition, course of development, etc. Most studies on mushroom growth in different conditions are done on commonly cultivated mushrooms, such as the shiitake (Lentinula edodes) or the button mushroom (Agaricus bisporus). That said, studies on many other genera and species are providing similar results.
How mushrooms detect light
Since fungi do not photosynthesize and do not tend to be phototropic, one may wonder how they detect light. But studies have shown that they are able to detect light through the use of up to 11 photoreceptors, the same kind of receptors we have in our eyes.
This light detection is vitally important for most fungi, as it tells the mushroom when it is time to start fruiting. Fruiting is the stage in the mushroom's life where it turns from a link of spores into the toadstool we know and love.
These photoreceptors were not discovered in mushrooms until very recently, and further tests reveal surprising results. For instance, mushrooms tend to not just have a blue-light photoreceptor, but many color receptors. They also tend to have red light-absorbing photoreceptors, phytochromes, cryptochromes, and rhodopsins.
This means that mushrooms don't just detect light, but can detect them in various wavelengths, and can even compute that information. But more on that later when talking about genes.
How light affects mushrooms
Unlike plants, mushrooms do not need sunlight to convert materials into nutrients. However, that does not mean that mushrooms can grow correctly without the presence of light. Most mushrooms need a small amount of light to determine how and what to grow. Without this light, mushrooms rarely grow and the ones that do are often smaller and deformed.
It seems that the majority of mushrooms tend to prefer light on the blue end of the spectrum. Studies have shown that mushrooms that grow on high-calcium surfaces grow better, faster, and larger, under blue light, and are inhibited by red light. This becomes reversed for mushrooms that tend to grow on low-calcium surfaces. This depends on the stage of its lifecycle, and different effects can happen in different stages.
UV light can be a big benefit when it comes to the cultivation of mushrooms. Mushrooms exposed to UV light create quite a significant amount of ergocalciferol, commonly known as Vitamin D2. This form of Vitamin D is less effective at being absorbed and utilized in our bodies as opposed to the common Vitamin D3, but at higher amounts can be a good plant-based alternative.
How light influences fungi genetics
Odd as this may sound, the genetics of mushrooms are intimately interwoven with certain wavelengths of light. This is why specific wavelengths can affect the growth of the mushrooms, or cause them to overproduce certain products like the Vitamin D3 mentioned before.
Other aspects can also influence the genetics of mushrooms when growing such as gravity, wind, and touch. All of these can be seen in action in the fungi's sporophores, which are tiny 'hairs' that mushrooms use to spread spores, which will later turn into new mushrooms. But light is one that we have the least amount of information.
Much of the effects of light on the rest of the genome have to do with two proteins labeled WC-1 and WC-2. These often work together to form a complex that determine the development of the fungi. Also, in many species, both the blue light and red light photoreceptors are necessary for complete development. And in some species, like Neurospora crassa, these receptors can set their circadian clock and determine what pigments are produced.
Due to the infancy of this field, more information about mushrooms and light should come up in the future. It would be amazing to see how this affects many scientific studies on medications and more in the coming years.
Learn a little bit more about mushrooms and light by checking out this video below.