Amyloid (mycology)

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In mycology the term amyloid refers to a crude chemical test using iodine in either Melzer's reagent or Lugol's solution, to produce a black to blue-black positive reaction. It is called amyloid because starch gives a similar reaction, and that reaction for starch is also called an amyloid reaction. The test can either be on microscopic features, such as spore walls or hyphal walls, or the apical apparatus on an ascus, or be a macroscopic reaction on tissue where a drop of the reagent is applied. Negative reactions, called inamyloid or nonamyloid reactions are for structures that remain pale brown or clear. A deep reddish to reddish brown reaction is termed either a pseudoamyloid reaction or a dextrinoid reaction.