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d. Light

As non-photosynthetic organisms the influence of light upon fungi comes as a surprise to some, but there are numerous examples of such influence. There are reports that vegetative growth of some species on agar may be inhibited by light.  It is a common laboratory practice to grow the mycelium of shiitake mushroom (Lentinula edodes) in the dark to obtain better growth than in light grown cultures.  More frequent is the observation of zones of dense and light hyphal growth, or zones of vegetative growth alternating with zones of sporualation.  Such zonation may also be genetically controlled, as has been shown in Neurospora and Schizophyllum.  The death of fungi in dished places in direct sunlight has also been reported, but, in the absence of experimental studies, this death is probably attributable to excessive temperatures brought about by the sunlight.  Just as high temperature may result in the inability of a species to synthesize a needed vitamin and inhibit mycelial growth, so may strong light induce the same effect by light destruction of vitamins, which may be overcome by the addition of natural mineral, such as yeast extract, which is a rich in vitamins, to the medium.

While phototropic responses in the sporangiophores of Phycomyces and Piloblous of the class Zygomycetes are well known and have been the subject of much experimental study, the light effects of greatest interest in mushroom biology involve the development of the furiting bodies.  Light may trigger the initiation of primordia in some species and be required for the development of other stages of fruiting body development. The positioning of the stipe and pileus, which is essential for the basidiosproes to fall free from the hymenial surface of the gills of the agaric or tubes of the polypore, has been shown in a number of mushrooms to be controlled by phototropic reposes.  It is well known that the button mushroom (Agaricus bisporus) is grown in caves or mushroom houses in the dark.  This is because light is actually inhibitory to the development of primordia and affect stipe elongation and pileus expansion of this spices.

It should also be mentioned that light in the ultra violate region of 200-300 nm [i.e., UV-C; bad stuff] has an effect upon vegetative growth.  The effect may be lethal or it may be to induce mutations [Fastfred as written about mutation via UV-C of cubes] since these are the wavelengths absorbed by DNA (deoxyribonucleic acid).  The effects of ultraviolet light can be revered by exposure to visible light in the range of 360-420 nm [i.e., UV-A to PAR range blue light].  This process is called photoreactivation.  These wavelengths (360-420 nm) activate an enzyme which splits the thymine and cytosine dimers, which are formed as a consequence of the ultraviolet radiation creating covalent bonds between adjacent pyrimidine nucleotides.  The dimers inhibit normal DNA synthesis, and thus in photoreactivation the enzymes that splits the dimer permits normal DNA synthesis to take place.

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HerbBaker said:

Does anyone know the equivalent of 65000k in nanometers?

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