GROWING GOURMET - Anto2ni.it

of the surface, the region supporting the creation
of primordia.
Light: In nature, light acts as a signal alerting
the mycelium to an open-air environment
where, should mushrooms form, spores can be
spread into the air. Light controls stem elongation
and cap development. Ideal light
conditions—intensity and wavelength—vary
with each species and strain. Indirect natural
light, or the dappled light filtering through a
forest canopy, is considered ideal for woodland
mushrooms. Specific photo-periods and spectral
frequencies have not yet been established
for all mushroom species. In these cases, cultivators
resort to providing the lighting
necessary to the most sensitive of the gourmet
mushrooms, the Pleurotus species. Modest
light is not harmful to developing mushroom
mycelium; it seems unaffected by its presence.
Direct sunlight or high intensity exposure is
harmful. The fluorescent lights used in indoor
facilities do not inhibit mycelial growth, and in
some circumstances may stimulate early primordia
formation. For most species, light
levels between and 50-1000 lux and 3 80-480
nanometers (green to blue) seem most stimulatory
to primordia formation. (I use six 8 ft.
long, "Daylight" 6500 Kelvin fluorescents to
light each 1000 sq. ft. growing room which also
gets supplemental natural light through a row
of diffusion panels.) For specific light requirements,
please consult the growth parameters
for the species being cultivated.
Leatham and Stahlman (1987, 1989) conducted
trials with Shiitake on chemically
defined media which showed that the absence
of calcium made the mycelium unresponsive to
light stimulation. At low calcium levels (130
GROWTH PARAMETERS 215
Figure 190. Lack of light causes Oyster mushrooms
to malform into coral-like structures.
pg/mg.) levels, the wavelengths most stimulatory
for primordia formation were between
400-500 nanometers, what we know as blue to
ultraviolet light. Calcium is naturally present in
woods in sufficient quantities to allow fruiting.
Just as strains of Shiitake differ in their fruiting
cycles, I suspect that the "calcium factor" in
triggering Shiitake formation may be strain
specific. Nevertheless, the interplay between
light and calcium concentrations continues to
be a subject of great interest. Further studies
are needed to compare the many strains, on
various woods, with varying levels of calcium,
and at different wavelengths.
The body of mycelium is not as sensitive to
these environmental stimuli until the substrate,
its impending food source, has become fully
captured by it. Where there are zones of
uncolonized substrate, the mycelium continues
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