Osmotic Adjustment and the Development of Freezing Resistance in <i>Fragaria virginiana</i>

O’Neill, Sharman D.

doi:10.1104/pp.72.4.938

Cited by 30 publications

(12 citation statements)

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“…Cold acclimation of Fragaria also caused an accumulation of soluble carbohydrates and decreased osmotic potential (22). With the increase in sugars and decrease in water content, the lower osmotic potentials observed during winter appear to be a variation on an osmotic adjustment theme (22).…”

Section: Resultsmentioning

confidence: 99%

“…When the effects of the winter reductions in water content and increases in soluble sugars on osmotic potential were estimated, the difference in leaf osmotic potential between summer and winter could be fully accounted for by the changes in water and soluble sugars (36). Cold acclimation of Fragaria also caused an accumulation of soluble carbohydrates and decreased osmotic potential (22). With the increase in sugars and decrease in water content, the lower osmotic potentials observed during winter appear to be a variation on an osmotic adjustment theme (22).…”

Section: Resultsmentioning

confidence: 99%

“…The relatively small increase in freezing tolerance of (2-4°C) following cold acclimation of many species, of which C. sinensis is one example, suggests that osmotic adjustment could be a major factor in the increased hardiness (12,18,22). It is well documented, for many plants, that tissue water content decreases while soluble carbohydrates, proline, polyamines, and other soluble solutes increase in concentration during cold acclimation (19,21).…”

Section: Introductionmentioning

confidence: 99%

“…The reduction of cellular dehydration will be directly proportional to the decrease in osmotic potential. However, the freezing of the tissue water must approximate the freezing of water of an ideal solution to accurately estimate the degree of cellular dehydration at a given subzero temperature and osmotic potential (15 OSMOTIC ADJUSTMENT AND FREEZING TOLERANCE leaf hardiness increases may be limited to about 2°C or less (36).The relatively small increase in freezing tolerance of (2-4°C) following cold acclimation of many species, of which C. sinensis is one example, suggests that osmotic adjustment could be a major factor in the increased hardiness (12,18,22). It is well documented, for many plants, that tissue water content decreases while soluble carbohydrates, proline, polyamines, and other soluble solutes increase in concentration during cold acclimation (19,21).…”

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confidence: 99%

“…The most sensitive species have little freezing tolerance (LT502 -2°C) and no significant capacity to undergo cold acclimation (3,34). More hardy species have modest freezing tolerance (LT5o -3 to -6°C) and some capacity to increase freezing tolerance during cold acclimation (1,3,10,12,22). For example, the commercially important sweet orange, C. sinensis, has the ability to increase in freezing tolerance during cold acclimation.…”

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Freezing Tolerance of Citrus, Spinach, and Petunia Leaf Tissue

Yelenosky¹,

Guy²

1989

Plant Physiol.

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Seasonal variations in freezing tolerance, water content, water and osmotic potential, and levels of soluble sugars of leaves of field-grown Valencia orange (Citrus sinensis) trees were studied to determine the ability of citrus trees to cold acclimate under natural conditions. Controlled environmental studies of young potted citrus trees, spinach (Spinacia pleracea), and petunia (Petunia hybrids) were carried out to study the water relations during cold acclimation under less variable conditions. During the coolest weeks of the winter, leaf water content and osmotic potential of field-grown trees decreased about 20 to 25%, while soluble sugars increased by 100%. At the same time, freezing tolerance increased from lethal temperature for 50% (LTso) of -2.8 to -3.80C. In contrast, citrus leaves cold acclimated at a constant 100C in growth chambers were freezing tolerant to about -60C. The calculated freezing induced cellular dehydration at the LT5o remained relatively constant for field-grown leaves throughout the year, but increased for leaves of plants cold acclimated at 100C in a controlled environment. Spinach leaves cold acclimated at 50C tolerated increased cellular dehydration compared to nonacclimated leaves. Cold acclimated petunia leaves increased in freezing tolerance by decreasing osmotic potential, but had no capacity to change cellular dehydration sensitivity. The result suggest that two cold acclimation mechanisms are involved in both citrus and spinach leaves and only one in petunia leaves. The common mechanism in all three species tested was a minor increase in tolerance (about -10C) resulting from low temperature induced osmotic adjustment, and the second in citrus and spinach was a noncolligative mechanism that increased the cellular resistance to freeze hydration.During extracellular freezing, ice first forms in the dilute apoplastic solution and a water potential gradient is established between the extracellular ice crystal and the intracellular liquid water. The lower water potential of ice as compared to that of liquid cellular water at the same temperature will cause liquid water to move from the cell to the extracellular ice (19). This process, depending on the temperature and concentration of the cell sap imposes a dehydration stress 'Part of this work was supported by a U.S. Department of Agriculture competitive research grant 85-CRCR-1-1649. University of Florida Agricultural Experiment Station Technical paper 8889. on the cell. When the cellular water potential of the partially dehydrated cell equals that of the extracellular ice, an equilibrium is established and further dehydration will not occur provided the temperature remains constant (15,23). If the temperature further declines or increases, water will flow out of or back into the cell. During such equilibrium freezing a tissue can behave either as an ideal solution or as a nonideal solution (15,23). In nonideal equilibrium freezing, negative wall pressure is believed to reduce the degree of cell dehydration and solute co...

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Section: Resultsmentioning

confidence: 99%