| This experiment is about the adaptive capacity of three species of edible fungi, Flammulina velutipes, Pleurotus eryngii, Hgpsiygus marmoreu to environmental stress. Plant-physiology research methods were modeled to study the changes of enzyme's activeness in the mycelium (cell defense enzyme, exocellular enzyme) of three different species of edible fungi in the different environmental stresses (temperature, moisture of medium, pH). Discussion on adaptive capacity to environmental stress from the perspective of enzyme was carried out, the results showed that:1. Under high temperatures, the superoxide dismutases (SODs), the peroxidases (PODs) showed relevance with the nature of three kind of edible fungi. But catalases (CATs) in the three kinds of edible fungi differed in a relatively large way, i.e., heterogenous edible fungi have certain difference in their responses to high temperatures.While under low temperatures, both SODs, PODs of the three kind of edible fungi have certain response: the performance was stable. Likewise, the CAT of the three kind of edible fungi showed marked changes, i.e., all mycelium of the three kinds of edible fungi had a certain defense mechanism to injuries caused by low temperatures.2. When the moisture of the medium was 45%, the activeness of the SOD in the mycelium of the three tested fungi was close or surpassed the control strains during the late period of growing. The activeness of the POD in Flammulina velutipes and Hgpsiygus marmoreus showed fierce undulation, while the CAT of Pleurotus eryngii showed a certain undulation. When the moisture of the medium was 75%, the SOD of Plewotas eryngii became sensitive; and the activeness of POD of Flammulina velutipes and Hgpsiygus marmoreus had greater undulation, and the activeness of CAT of Flammulina velutipes showed greater ujdulation, but the activeness of CAT Hgpsiygus marmoreus showed greater changes in both of these two kinds of processing, i.e. the three kind of edible fungi are particular to the moisture of culture medium.3. Under low pH, the changing rate of the activeness of POD and CAT in Flammulina velutipes was close to the control group, likewise, the changing rate of SOD, POD activeness in Plewotas eryngii, as well as the changing rate of SOD, CAT activeness of Hgpsiygus marmoreus was also close to the control group., i.e. all the mycelium of the three kind of edible fungi like meta-acid habitats.Under high pH, the activeness of SOD, POD, CAT in Flammulina velutipes had relatively large changes, but the changes of the the SOD and POD of Plewotas eryngii and Hgpsiygus marmoreus remained steady. This showed that the resistance of Plewotaseryngii and Hgpsiygus marmoreus to high pH is greater than that of Flammulina velutipes.4. The change of the MDA content is one of the important indicators of damages of the protoplasmic membrane. With the environmental stress of moisture of medium, pH and high temperature, there was certain relevance between the change of MDA content and the change of protection enzyme in the early stage of the environmental stress, but in the later stage, the MDA content of the mycelium of the edible fungi increased dramatically, the peroxidation of membrane fat intensified, causing the damage to the membrane system.5. During the experiment using low temperature against the mycelium of the edible fungi, it was found that: during the low temperature process, the content of MDA in earlier stage went through a period of undulation, however, as time went, the activeness of the protection enzymes (SOD, POD, CAT) (probably as well as the accumulation substances, the level of hormone and fat acid) of the mycelium became adaptive, which brought about the dynamical equilibrium of the production and elimination of the free radical in the cell, which maintained the basal metabolism of the cell under low temperature to prevent the injuries caused by low temperature. This experiment has confirmed from the perspective of enzyme the feasibility of preserving culture of edible fungi in low temp...
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