Morphometric analysis of ageing mushrooms (Agaricus bisporus) during postharvest development

During postharvest development of the basidiocarp of Agaricus bisporus cv.U1, growth takes place in the pileus, stipe and gills. The average cell area in periclinal sections of pileus tissue increases about 5-6 fold. Although the morphology changes, the pileus of the mushroom as a whole does not enlarge, implying that only a minority, estimated to be less than 20% of the cells, are destined to grow by vacuolar expansion at the cost of other cells. This is in contrast with growth of the gill tissue, as measured in the supporting tissue (the trama), where cells are enlarging in a radial direction by increasing both vacuole volume and cytoplasm content. However, the absence of an increase in average cell size in the longitudinal direction does not match the growth and growth direction of the gill tissue as a whole. This can only be explained by assuming that each cell in the gill tissue has to divide in the longitudinal direction. Since the stipe architecture shows large variation, observed changes in cell size at one specific point cannot be used to explain macroscopic changes of the stipe as a whole. A new method for correcting shrinkage due to fixation and dehydration procedures has also been developed. This method might be useful for a range of organisms in which measurements of absolute or relative cell sizes and intercellular space are required. (C) 1998 Elsevier Science B.V. All rights reserved.