What conditions are needed for the growth and development of shiitake mushrooms?

1. Nutrition The shiitake mushroom is a higher wood-rotting fungus. The carbon source it needs for growth comes from lignin and cellulose, and its nitrogen source and inorganic salts come from the bark of bed logs or from wheat bran (rice bran) added to sawdust substrate. After shiitake spawn is inoculated into bed logs (substrate logs), the substrate is decomposed into small-molecule substances that can be absorbed and used by shiitake mycelium, and mycelial biomass increases with longer cultivation time. When the substrate has been fully degraded, the shiitake mycelium has accumulated a large amount of nutrients, laying the material foundation for fruiting body formation. Under suitable conditions, shiitake switches from vegetative growth to reproductive growth, the fruiting body begins to grow and develop, and the large amount of nutrients accumulated in the shiitake mycelium is transferred into the shiitake fruiting body.

2. Temperature The growth temperature of shiitake mycelium is 5-32°C, and the temperature for robust growth is 18-22°C; at this time the mycelium grows slightly more slowly, but the mycelium is thick and dense. The temperature for rapid growth is 24-27°C; although growth is fast, the mycelium is relatively slender and sparse. Below 0°C and above 32°C, mycelial growth is poor, and at 35°C the mycelium stops growing. Shiitake mycelium has strong cold tolerance and can still survive for 8-10 weeks below 5°C. If shiitake mycelium spreads hidden inside bed logs, because it is protected by the bark, brief high temperatures or severe cold will not kill the mycelium by heat or freezing, but the effect on sawdust substrate log cultivation is relatively large. Shiitake is a fungus that fruits under low temperature and fluctuating temperature. When the mycelium reaches physiological maturity and is stimulated by the temperature difference caused by seasonal change or artificial means, the mycelium twists together to form primordia. The primordium differentiation temperature of shiitake is 8-21°C, with the optimum at 10-12°C. The required temperature difference range is determined by the shiitake strain. Generally, for low-temperature-type strains the primordium differentiation temperature is 5-15°C and the development temperature is 10-15°C; for medium-temperature-type strains the primordium differentiation temperature is 8-20°C and the development temperature is 15-20°C; for high-temperature-type strains the primordium differentiation temperature is 15-25°C and the development temperature is 20-25°C. After shiitake primordia form, the growth and development of the fruiting body does not have a high requirement for temperature difference, but an appropriate temperature difference can promote the formation of high-quality shiitake. In general, when the air temperature is high, the fruiting body develops quickly and mostly produces thin-skinned mushrooms with poor quality; at low temperature, the fruiting body develops slowly, has good quality, and is thick and richly fragrant. In production practice, the temperature type of the shiitake strain to be cultivated should be selected according to the local air temperature variation range.

3. Humidity If the water content in the culture substrate is too high, it will block the pores between sawdust particles, leading to oxygen deficiency and causing the mycelium to "drown"; if the water content is too low, the mycelium will be unable to absorb enough water needed for growth and will "die of thirst." In bed log cultivation, the appropriate water content of bed logs is 32%-42%, with 35%-40% being optimal. The optimal water content in sawdust substrate is 55%-60%. During the mycelial running stage, the air relative humidity should be maintained at about 70%; too high humidity favors the growth of contaminating microorganisms. Humidity is crucial to the differentiation and development of shiitake fruiting bodies. In the mushroom fruiting management process, the main way to control the rhythm of fruiting is by regulating temperature and humidity. The water content of the substrate logs generally required for fruiting body differentiation is 60%-65%, and the air relative humidity is generally 85%-90%. After the fruiting body primordia form, the relative humidity of the surrounding microenvironment required for sound development of the fruiting body is 80%-85%.

4. Air The shiitake mushroom is an aerobic fungus, and sufficient fresh air is an important condition for ensuring normal growth and development. Insufficient oxygen supply during the mycelial running stage will obstruct mycelial respiration; the mycelium temporarily maintains life through fermentation, nutrient consumption increases, and growth vigor weakens. Oxygen deficiency during the fruiting stage will affect primordium differentiation and growth and development, producing deformed mushrooms (long stipes, large stipes, deformed mushrooms). Therefore, only in well-ventilated places can high-quality, high-yield shiitake be obtained.

5. Light Mycelium can grow well under dark conditions, and strong light inhibits mycelial growth. Under completely dark conditions, fruiting bodies do not form. If light is insufficient, then there are few mushrooms, long stipes, small caps, pale color, and poor quality, but strong direct light causes great harm to shiitake, especially to young mushroom buds. Therefore, appropriate scattered light is very important for fruiting body development.

6. Substrate pH The shiitake mushroom, like other wood-rotting fungi, likes to grow on slightly acidic culture substrate and requires a pH of 5.5-6.5. Within the suitable pH range, different pH values have little effect on shiitake mycelial growth. In summary, whether the shiitake fungus can smoothly shift from vegetative growth to reproductive growth and form mushrooms mainly depends on temperature difference stimulation, humidity, and light. Whether the primordia can further develop after formation depends on ensuring suitable temperature and ventilation, and at the same time an appropriate relative humidity and light must also be ensured. In cultivation, only by simulating and creating as much as possible the environmental conditions most suitable for shiitake growth and development can high yield and high quality be obtained.