Difference between revisions of "Lugol's solution"

'''Lugol's solution''' ([[Category:Noun]][[:Category:Noun|noun]], [[Category:No plural]][[:Category:No plural|no plural]]) – IKI, i. e., a mixture of crystalline iodine (I) and potassium iodide (KI) in water. Recipes and recommendations for the best suited concentrations vary. Strongly concentrated solutions (''[[ca.]]'' 1.5-3%) are more reliable for spot test reactions on [[thalli]] or hyphae. These concentrated or even saturated solutions can be stored without soon loosing their staining capabilities. They are not suited, however, to examine [[ascus apical structure]]s that are easily obscured by vivid staining reactions. Better suited to resolve ascus apical structures are lower concentrations (e. g., 0.3 %), but these reagents need to be made up freshly because their iodine concentration rapidly decreases. Unlike [[Meltzer's reagent]], Lugol's iodine by itself has no clearing effect on fungal [[plectenchyma]] and thus is often used after pre-treatment with 5-10% potassium hydroxide (KOH). However, a colour change from reddish to blue that is characteristic for a [[hemiamyloid]] reaction, can only be observed, if plectenchyma are first observed in Lugol's without pre-treatment, then treated with KOH and again treated with Lugol's. This sequence of test reagents will induce the shift from reddish to blue characteristic for hemiamyloid reactions. In contrast, [[euamyloid]] reactions occur as deep blue even without pre-treatment.