*The major pinning triggers are in order of importance, full colonization, a decrease in CO2 levels due to increased air exchange (not gas exchange which is minimal), a steady rate of evaporation from the substrate or casing layer, and lastly, light. Hyphal knots form best in 100% humidity, but I didn't list that because it's not a pinning trigger, but rather an environmental condition that is necessary. That's why we use casing layers. The casing helps to provide the 100% humidity right at the surface of the substrate where the hyphal knots form. I have seen no correlation with temperature drop whatsoever. In the summer, my growing chambers are 10 or more degrees warmer than the open shelves I incubate on due to the heating effects of the lights. Even with a temperature increase, I still get wall-to-wall pinsets, so I don't consider temp drop relevant at all to tropical species. Other growers disagree of course, but that's just my observation after many years. Full colonization of the substrate is the number 1 pinning trigger. Full colonization can be when the mycelium reaches the physical border of the container they are in, or when they run up against a biological border, such as a contaminant species. Either way, they see they have colonized all of what is available to them, so they then enter the next phase, which is reproduction. There must be evaporation of moisture from the substrate for pins to form. A waterlogged substrate will just sit there forever without pinning. Even in 99% humidity, as long as you provide fresh air, moisture will be evaporating away from the substrate, and this is necessary for pinning. We mist to replenish the lost moisture, and then allow it to dry slightly before misting again. This keeps the moisture content high, and keeps the humidity at the casing surface near 100%, but at the same time provides the evaporation of moisture that is a very important pinning trigger. During colonization, we provide very small holes in the jars or tubs for gas exchange. We want a high CO2 environment during colonization, because this prevents the mycelium from consuming all of the substrate. The mycelium colonizes the substrate, but doesn't 'eat it all up' due to the high CO2 levels. During fruiting, we remove the covers to provide air exchange, which is at a much higher level then the minimal gas exchange provided during colonization. This increase in air exchange lowers the CO2 levels, and is a major pinning trigger. At this time, the mycelium begins to consume the substrate it has previously colonized, and we notice during fruiting that our substrates pull away from the sides of the container. This is not due to moisture loss, but rather due to the mycelium 'eating' the substrate and turning it into CO2, a waste product. It is easily proved that this shrinking isn't related to moisture loss, because even when we dunk a bulk substrate, it doesn't return to its pre-flush size. Last, but not by any means least is exposure to light. Light does much more than just tell the mushrooms which way to grow. There are mechanisms in the light that stimulate the formation of hyphal knots as well, and light at the higher end of the spectrum (blue) definitely, absolutely stimulate more hyphal knots (which grow into primordia, which then morph into pins) than light at the lower end of the spectrum (red) This does not mean to get a 'mood light' with a blue lens, but rather to select lights such as metal halide, or much more economical is 'natural daylight' fluorescent that emit light at around 6,000 Kelvin to 7,500 Kelvin depending on the brand. Cool white fluorescent emit light at around 5,000 Kelvin and the 'red' incandescent emit light at around 3,000 Kelvin. The higher the light temperature in Kelvin, the more stimulatory it is to hyphal knot formation. I hope this helps. CONDITIONS TO INDUCE FRUITING
*I rarely start new threads anymore, but the same questions and misunderstandings seem to keep popping up regarding what makes our fungi enter the pinning stage. The reply below is one I posted in another thread earlier, so I'll take the liberty of cutting and pasting it here for those who would otherwise miss it. Hopefully it will stimulate some more research and discussion on everyone's part and clear up a few things. Here it is: LIGHT IS NOT THE MAJOR PINNING TRIGGER FOR MUSHROOMS! In fact, light isn't even the major factor in which direction mushrooms grow. Wind or other air currents is the first. Light is the second, and then finally gravity is the third. As for pinning, full colonization of the substrate is the most important pinning trigger. If there are contaminants present in a substrate, the mushroom mycelium generally stops growing when it contacts them. This represents full colonization because the mycelium has hit a natural barrier, and often pins begin to develop, whether light is present or not. The second most important pinning trigger is an increase in air exchange, with the corresponding drop in CO2 levels that occurs simultaneously. When you uncover a tray to look at it, you allow the CO2 to escape and be replaced by fresh air. THIS is a pinning trigger, even if you do it in the dark. Third, which goes along with second, is a steady rate of evaporation of moisture from the substrate or casing layer. In the artificial environment of a small tray, we must mist to keep the substrate or casing from drying out, but we also must allow that moisture to evaporate off between mistings. Fourth, when the above three triggers are active, light becomes a pinning/growth initiation factor. If one waits too long to apply the casing layer, or the other factors listed above are in effect prior to light OR the casing layer being applied, primordia will begin to form, which will then push up through to the surface, whether or not it has been fully or even partially colonized. By the same token, if light is applied and the other, more important factors have not been met, primordia will NOT form. This is why experienced growers, such as commercial spawn producers who make their entire living incubating mushroom mycelium, make absolutely NO effort to incubate in the dark. It isn't necessary. People will have much more success in the hobby when they understand that. PINSET INITIATION FACTORS
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