Water potentials and soluble carbohydrate concentrations in tissues of freshly harvested and stored mushrooms (Agaricus bisporus)

The mechanism of water uptake in the cultivated mushroom, Agaricus bisporus was investigated by examining the relationship between total water potenti al (psi (w)), component osmotic (psi (s)) and turgor (psi (p)) potentials o n the one hand and sugar and sugar alcohols concentrations on the other, in different tissues during storage for up to 5 days at 18 and 25 degreesC an d 90 and 95% relative humidity. Storage humidity had no effect on tissue wa ter relations in the five tissues examined, although significant temporal c hanges in water relations over the 5-day storage period were observed. The gills had the highest mean psi (w) (- 1.0 to - 1.5 MPa), while the peel had the lowest mean level (- 1.5 to - 2.5 MPa). The mean turgor potential was approximately + 0.5 MPa. Rising psi (p) often coincided with declining psi (s) in the upper stipe. inner cap and gill tissue. Sugar (glucose and treha lose) and polyol (mannitol, arabitol, erythritol and glycerol) concentratio ns ill these various sporophore tissues also produced distinct patterns ove r time. The disaccharide trehalose was present at 5-10 mM concentration thr oughout the storage period. In contrast, glucose concentrations were highes t in the lower stipe tissue immediately after harvesting. The predominant p olyol was mannitol (60-100 mM), which decreased in concentration after harv est, for up to 3 or 4 days of storage, depending on the tissue. Glycerol wa s only present in the gills initially, but concentrations rose significantl y in inner cap tissue after 5 days storage. Statistically significant corre lations between psi (w), its components and sugar/polyol concentrations wer e found on specific days of storage. (C) 2001 Elsevier Science B.V. All rig hts reserved.