Effect of osmotic stress on microstructure and mass transfer in onion and strawberry tissue

• Autores: Montserrat Ferrando, W.E.L. Spiess
• Localización: Journal of the science of food and agriculture, ISSN 0022-5142, Vol. 83, Nº 9, 2003, págs. 951-959
• Idioma: inglés
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• Resumen

  • We investigated the structural changes in onion epidermis and strawberry cortex tissue due to osmotic stress during osmotic treatment (OT) with sucrose solutions of concentrations ranging from 300 to 600 g kg−1. We used miniaturised experiments with confocal scanning laser microscopy (CSLM) to monitor microstructural changes—cellular shrinkage and viability—during OT. The overall cellular shrinkage of these plant tissues was not significantly different under the same conditions of osmotic stress. For onion epidermis we determined the transmembrane water flux from the cellular shrinkage and found that the coefficient of water membrane permeability was (1.0 ± 0.39) × 10−6 mol2 J−1 m−2 s−1. Osmotic stress did not affect the cellular viability of onion epidermis but significantly reduced the viability of protoplasts of strawberry in the whole range of solution concentrations. We used Fick's unsteady state second-order diffusion equation to describe cellular water transport under transient conditions. The pseudo-diffusional approximation led to water diffusivity values in the range (3–10) × 10−12 m2 s−1 for both onion epidermis and strawberry cortex tissue. The concentration of the solution did not significantly affect the values of effective water diffusivity, which indicated the primary role of the plasma membrane during the initial stages of OT.