Calorimetric studies of the state of water in seed tissues

Vertucci, Christina W.

doi:10.1016/s0006-3495(90)82491-7

Cited by 100 publications

(85 citation statements)

References 24 publications

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“…The sensitivity of L. kirkii axes to desiccation differed with drying regimen, and yet the drying treatments had no effect on either the types of water present or the water contents at which the different types could be detected. The water contents at which the melting and freezing transitions become apparent in soybean and pea seed tissue (0.22 and 0.33; 0.24 and 0.35 g/g, respectively [12]) are similar to the water contents at which these transitions become apparent in L. kirkii (0.28 and 0.37 g/g). These data suggest that the desiccation tolerance of seed tissue may not be related to the amount of nonfreezable water.…”

Section: Discussionmentioning

confidence: 53%

“…In addition to the three types of water mentioned, there is a discrepancy between the amount of nonfreezable water calculated from freezing and melting transitions. Although this difference may be a result of energy dissipation during an exothermic event (and not measured in a heat-compensated DSC), it also may be relevant to the expression of freezing injury, as has been suggested for orthodox seeds ( 12).…”

Section: Discussionmentioning

confidence: 99%

“…that present below 0.28 g/g, cannot be tolerated, even if it is removed very rapidly. Vertucci (12) established that the moisture content at which water is not observed to freeze under the given protocols corresponds to a relative humidity ofapproximately 92% (equivalent to water potential of -1 1.3 MPa). This is similar to the water potential at which mitochondrial electron transport is facilitated (14) and at which membranes are believed to undergo conformational changes (9,15).…”

Section: Discussionmentioning

confidence: 99%

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Homeohydrous (Recalcitrant) Seeds: Dehydration, the State of Water and Viability Characteristics in Landolphia kirkii

Pammenter

Vertucci²,

Berjak³

1991

Plant Physiol.

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107

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Differential scanning calorimetry was used to study the relationships among drying rate, desiccation sensitivity, and the properties of water in homeohydrous (recalcitrant) seeds of Landolphia kirkW. Slow drying of intact seeds to axis moisture contents of approximately 0.9 to 0.7 gram/gram caused lethal damage, whereas very rapid (flash) drying of excised embryonic axes permitted removal of water to approximately 0.3 gram/gram. The amount of nonfreezable water in embryonic axes (0.28 gram H20/ gram dry mass) did not change with drying rate and was similar to that of desiccation-tolerant seeds. These results suggest that the amount of nonfreezable water per se is not an important factor in desiccation sensitivity. However, flash drying that removed all freezable water damaged embryonic axes. Differences between desiccation-sensitive and -tolerant seeds occur at two levels: (a) tolerant seeds naturally lose freezable water, and sensitive seeds can lose this water without obvious damage only if it is removed very rapidly; (b) tolerant seeds can withstand the loss of a substantial proportion of nonfreezable water, whereas sensitive seeds are damaged if nonfreezable water is removed.In this paper, we address (a) to what extent drying rate can affect the minimum moisture content that homeohydric tissues can survive, (b) whether the rate of water removal affects the thermal properties of water remaining in the tissues, and (c) whether there is a correlation between the thermal properties of water and expression of desiccation sensitivity. If desiccation tolerance is related to the ability of tissue to lose "bound" water without the denaturation of macromolecules, there may be differences in the thermal characteristics of water in axes of homeohydrous seeds flash dried and those dried more slowly. The relationships among dehydration rate, desiccation tolerance, and the state of water were studied using embryonic axes ofthe homeohydric seeds ofLandolphia kirkii Dyer. This species is a viny shrub native to Mozambique and the inland region of northeastern South Africa. Its large (approximately 1.5 g) endospermic seeds are typical of many other seeds from tropical species in that they are intolerant to chilling and desiccation, the embryonic axis is fully developed when it sheds, and there are no tendencies toward dormancy. If maintained at their original water content, the seed will lose viability in approximately 1 month.Desiccation tolerance of organisms involves, inter alia, the ability to withstand loss of water sorbed to macromolecular structures, particularly the surfaces of membranes, without irreversible denaturation (3, 4). A current theory, the "water replacement hypothesis," suggests that, in desiccation-tolerant tissues, water closely associated with macromolecular surfaces can be replaced by polyhydroxyl compounds that stabilize the macromolecules as water is withdrawn (3, 4). This hypothesis implies that such water replacement does not occur in desiccation-sensitive tissue.Recalcitrant, or "homeohydr...

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Homeohydrous (Recalcitrant) Seeds: Dehydration, the State of Water and Viability Characteristics in Landolphia kirkii

Pammenter

Vertucci²,

Berjak³

1991

Plant Physiol.

Self Cite

107

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“…Bean axes contain about 10% lipid, and there appears to be no interference between the water-dependent thermal transitions and those associated with lipids (Williams and Vertucci, 1990). Embryonic axes were dissected and placed in jars over salt-saturated solutions at room temperature for 4 to 7 d. The WC after equilibration ranged from O to 0.45 g/g.…”

Section: Plant Materials and Sample Preparationmentioning

confidence: 99%

“…The motional and thermal properties of intracellular water in seeds change as a function of the WC and temperature of the tissue (Vertucci, 1990;Bruni and Leopold, 1992b). The WC/temperature combinations at which these changes occur have been described using equilibrium thermodynamic principles assessed by measurements of water sorption and chemical potential (Vertucci and Roos, 1993;Vertucci et al, 1994a).…”

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confidence: 99%

A Calorimetric Study of the Glass Transition Behaviors in Axes of Bean Seeds with Relevance to Storage Stability

Leprince

Walters

1995

Plant Physiol.

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Although the presence of intracellular aqueous glasses has been established in seeds, their physiological role in storage stability is s t i l l conjectural. Therefore, we examined, using differential scanning calorimetry, the thermal behavior of glass transitions in axes of bean (Phaseolus vulgaris 1.) with water contents (WC) between O and 1 g H,O/g dry weight (g/g) and temperatures between -120 and +120°C. Three types of thermal behaviors associated with the glass transition were observed. The appearance, the glass + liquid transition temperature, and the amount of energy released during these transitions were dependent on the tissue WC. No glass transitions were observed at WC lower than 0.03 and higher than 0.45 g/g. A brief exposure to 100°C altered the glass properties of tissues with WC between 0.03 and 0.08 g/g but did not affect the thermal behavior of glasses with higher WC, demonstrating that thermal history is important t o the intracellular glass behavior at lower WC. Correspondence of data from bean to models predicting the effects of glass components on the glass --z liquid transition temperature suggests that the intracellular glasses are composed of a highly complex sugar matrix, in which sugar and water molecules interact together and influence the glass properties. Our data provide evidente that additional glass properties must be characterized to understand the implications of a glassy state in storage stability of seeds.Water and temperature play a significant and fundamental role in determining the storage longevity of orthodox seeds. Early models developed from storage experiments suggested that water and temperature were independent variables (Justice and Bass, 1978; Roberts and Ellis, 1989). However, theoretical considerations (Vertucci, 1992;Vertucci and Roos, 1993) and experimental data (Vertucci and Roos, 1993;Vertucci et al., 1994aVertucci et al., , 1994b have demonstrated that the effects of water and temperature on seed aging are interdependent. Conceptual models have been introduced to describe the interdependencies of WC and temperature on seed longevity. They rely on the findings that the nature and kinetics of degradative reactions in seeds change according to the physical properties of water

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Plant Desiccation Tolerance

Jenks

Wood²

2007

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Calorimetric studies of the state of water in seed tissues

Cited by 100 publications

References 24 publications

Homeohydrous (Recalcitrant) Seeds: Dehydration, the State of Water and Viability Characteristics in Landolphia kirkii

Homeohydrous (Recalcitrant) Seeds: Dehydration, the State of Water and Viability Characteristics in Landolphia kirkii

A Calorimetric Study of the Glass Transition Behaviors in Axes of Bean Seeds with Relevance to Storage Stability

Plant Desiccation Tolerance

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