Saprotrophic Responses by Ectomycorrhizal Fungi

9318568米勒在实验室研究中，许多研究发现真菌（与树木根系共生的真菌）中的酶可以分解有机物。其他研究表明，这些共生真菌在田间不能进行这样的分解，即使它们在土壤中可能比真正的腐养真菌生长得更快。这种明显的矛盾存在着几种可能性。共生关系可能改变菌根真菌的行为，使酶的产生成为不可能。另一种可能性是，外生菌根真菌可能只有在其宿主产生的糖量不足时才能够分解有机物。在这种情况下，菌根真菌的腐坏机制可能能够从有机基质中获得能量以及所需的矿物元素。第三种可能是，至少一些实验室里的酶活性报告受到了批评，因为这些研究是在与这些真菌最有可能遇到的条件非常不同的条件下完成的。我们建议研究外生菌根真菌的机制，使它们能够更好地与腐养真菌竞争。我们将通过在实验室进行实验来实现这一目标，使用特别设计的根室，允许从根和生根基质中分离出一部分真菌生长和操纵，同时仍与树木共生。这种方法将使我们能够在迄今为止尚未达到的水平上研究外生菌根真菌的腐坏性沉积。* * *

9318568 Miller Many studies have detected enzymes in fungi (fungi that are symbiotically associated with the roots of trees) that may decompose organic matter in laboratory studies. Other studies imply that these symbiotic fungi are not capable of such decomposition in the field even though they may outgrow true saprotrophic fungi in the soil. Several possibilities exist for this apparent contradiction. The symbiotic association may alter the behavior of mycorrhizal fungi so that enzyme production is not possible. Another possibility is that ectomycorrhizal fungi may only be able to decompose organic matter during times when sugars produced by their host are not being produced in sufficient quantities. At such times, the saprotrophic machinery of mycorrhizal fungi may be able to obtain energy along with required mineral elements from organic substrates. A third possibility is that at least some reports of enzymatic activity in the laboratory are subject to criticism because the research has been accomplished under conditions that are very different from what would most likely be encountered by these fungi. We propose to examine the mechanisms of ectomycorrhizal fungi that may allow them to better compete with saprotrophic fungi. We will accomplish this by conducting experiments in the laboratory using specially designed root chambers that allow growth and manipulation of a portion of the fungus separate from the roots and rooting substrate while still in symbiosis with the tree. This approach will allow us to investigate the saprotrophic reposes by ectomycorrhizal fungi at a level that heretofore has not been achieved. ***