How Heat Impacts Mushroom Spores And Their Growth

Mushroom spores are known for their resilience and can last for years, even when exposed to high temperatures. However, extreme heat can affect mushroom spores, with some sources suggesting that temperatures above 100°F can kill spores. Higher temperatures can also cause contamination by allowing certain contaminant spores to germinate faster. The ideal temperature range for growing mycelium, for example, is between 75-80°F (24-27°C) for P. cubensis, with temperatures above this range potentially killing the mycelium. While mushrooms are known to maintain colder temperatures than their surroundings, the impact of heat on mushroom spores is still a subject of discussion among mushroom enthusiasts and growers.

Heat can kill mushroom spores

Mushrooms are known to be colder than the air around them due to evapotranspiration. Infrared imaging has revealed that mushrooms, molds, and yeasts all stay colder than their environment through this process. On average, fungal specimens are about 2.5 °C colder than the ambient temperature. This relatively cold temperature can be observed throughout the fruiting process and at the level of mycelium.

The ability of fungi to maintain a lower temperature is important for spore production and discharge. The frequency of S. cerevisiae sporulation and tetrad formation is higher at 22 °C than at 30 °C. This suggests that the relatively cold temperatures enhance the discharge and production of spores.

However, excessive heat can kill mushroom spores. While PC temperatures may not kill all spores, they can kill enough to allow for inoculation with mushroom mycelium or spores. Boiling temperatures of about 100 °C can kill spores in as little as 12 hours. At 250 °C, it takes about five hours to kill spores, while at 300 °C, it takes approximately one hour.

It is important to note that the resilience of mushroom spores can vary. Some growers have reported that their spores did not survive being left in a hot mailbox, while others have found that their spores began to colonize even after being exposed to high temperatures.

Spores are more heat-resistant when dry

It is important to understand the thermal biology of mushrooms, mycelium, moulds, and yeasts. Mushrooms were previously observed to be colder than the surrounding air, and this can be attributed to evaporative cooling or evapotranspiration. However, the impact of heat on mushroom spores is a more complex topic.

Firstly, it is crucial to distinguish between dry spores and spores that have been activated in water. Dry spores are significantly more heat-resistant than those in water. In fact, dry spores can withstand high temperatures, as evidenced by a Reddit user who reported receiving spores that were exposed to 100-degree Fahrenheit weather and sat in a mailbox for hours, yet remained viable.

On the other hand, mushroom spores activated in water are more susceptible to heat damage. High temperatures can kill spores in water, with temperatures reaching 100 degrees Fahrenheit or above. This was observed in a user's experience with inoculating jars that were still hot from sterilisation, leading to concerns about potential harm to the spores.

To optimise the viability of mushroom spores, it is recommended to allow sterilised jars to cool for an extended period, such as 8 hours, before inoculation. Additionally, maintaining the ideal temperature range is crucial for successful colonisation. For example, P. cubensis colonises most rapidly between 75-80°F (24-27°C), and temperatures outside this range can be detrimental.

In conclusion, mushroom spores exhibit varying levels of heat resistance depending on their state. Dry spores possess a remarkable ability to withstand high temperatures, whereas spores in water are more delicate and prone to damage at elevated temperatures. By understanding this distinction and implementing proper handling techniques, growers can maximise the chances of successful mushroom cultivation.

Heat affects mushroom growth

The ideal temperature range for growing mycelium, for example, is between 75-80°F (24-27°C) for P. cubensis. If the temperature is too high, the mycelium may die, and contaminants are more likely to grow. Lower temperatures may slow down colonisation. The ambient air temperature around a jar containing growing mycelium should not be allowed to rise too high, as the mycelium inside will be warmer.

In terms of mushroom spores, dry spores are more resistant to heat. However, when spores are in an aqueous solution, they are more susceptible to heat damage. Spores are relatively resilient, but high temperatures, particularly above 100°F, will kill them.

It is worth noting that light also plays a role in mushroom growth. While significant exposure to direct UV light from the sun can be detrimental, artificial or ambient light is sufficient during the incubation period.

Heat can cause contamination

In terms of specific temperature ranges, temperatures above 75-80°F (24-27°C) may be detrimental to mycelium growth and can encourage the growth of contaminants. At temperatures above 100°F, spores are at risk of dying, and certain contaminant spores may germinate faster or better in these conditions. Therefore, it is crucial to allow sterilized jars to cool for a significant amount of time, such as 8 hours, before inoculation to prevent contamination and ensure optimal spore health.

Additionally, heat can affect the moisture content, which is critical for spore survival. Dry spores are more resistant to heat, while spores in water are more susceptible to heat-related issues. This is an important consideration when storing spores and maintaining their viability over the long term.

Furthermore, the application of heat during the inoculation process itself requires careful consideration. Heating the syringe during inoculation can cause the fluid in the needle to boil and spurt, potentially damaging the spores. As a result, it is recommended to let the needle cool down before inoculating the jars to avoid any adverse effects on the spores.

Overall, heat can indeed cause contamination and negatively impact mushroom spores. By understanding the temperature thresholds and taking the necessary precautions, such as allowing adequate cooling periods and maintaining proper moisture levels, growers can mitigate the risks associated with heat and optimize the conditions for healthy spore development.

Thermal biology of mushrooms

Mushrooms, along with other fungi, play a crucial role in maintaining the Earth's ecology. They break down decaying organic matter and provide nutrients for new growth. Fungi can be a source of food, medicine, and biomaterials. However, some can also be harmful to plants and animals, causing agricultural and public health issues. Given their ecological and economic importance, understanding their thermal biology is essential, especially in the context of global warming.

The thermal biology of mushrooms and other fungi is not well understood. Mushrooms have been observed to be colder than the surrounding air, a phenomenon known as evaporative cooling or evapotranspiration. Infrared imaging has confirmed that mushrooms maintain a temperature of around 2.5 °C lower than their surroundings. This hypothermic state is also observed in molds and yeasts, which are part of the fungal kingdom. The relatively cold temperature of mushrooms has been observed throughout the fruiting process and at the level of mycelium.

The ability of mushrooms to maintain a colder temperature than their surroundings is believed to be important for spore detachment, release, and dispersal. The frequency of S. cerevisiae sporulation and tetrad formation is higher at 22 °C than at 30 °C, indicating that colder temperatures enhance spore production and discharge. The cold temperature of mushrooms may also attract insects, which contribute to spore dispersal. Additionally, maintaining a colder temperature may be a defense mechanism against infectious diseases.

While mushrooms are generally considered hypothermic, there are some thermophilic fungi that can thrive at temperatures between 45 °C and 55 °C. These thermophilic and thermotolerant fungi have different minimum and maximum temperature requirements for growth. However, thermophily in fungi is not as extreme as in some bacteria or archaea, which can grow at temperatures above 100 °C.

In conclusion, the thermal biology of mushrooms is a complex and relatively unexplored area of study. Mushrooms exhibit hypothermic properties and maintain a colder temperature than their surroundings through evaporative cooling. This phenomenon appears to be important for spore production, dispersal, and ecological functions. However, there are also thermophilic fungi that can survive at much higher temperatures. Further research is needed to fully understand the thermal biology of mushrooms and its implications for their growth, reproduction, and ecological distribution.

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