Cold hardiness in plants: molecular genetics, cell biology and physiology. Seventh International Plant Cold Hardiness Seminar, Sapporo, Japan, 10-15 July 2004.

Chapter 15 (Page no: 219)

Dehydration in model membranes and protoplasts: contrasting effects at low, intermediate and high hydrations.

Upon studying the effects of dehydration on model membranes and protoplasts at low (water potentials less than -60 MPa), intermediate (water potentials between -6 and -60 MPa) and high hydration levels (water potentials between 0 and -6 MPa), results showed that sugars can exert several different protective effects in dehydrating systems. At high hydrations, sugars have osmotic effects that enable cells to resist water loss in the face of dehydrating environments. Sugars also contribute to the freezing-point depression of cellular solutions, which may facilitate survival of mild subzero temperatures. There is also evidence that sugars can act as scavengers of free radicals, which may be generated during episodes of dehydration stress. At intermediate and low hydrations, the protective role of sugars is likely to be more physical than physiological. The protection afforded by sugars is due to their ability to act as volumetric spacers that hinder the close approach of membranes and other surfaces and thereby, diminish the physical stresses that would otherwise damage cellular structures.

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