Resistance to Water Absorption in Germinating Rapeseed (<i>Brassica napus</i>L.)

Williams, J.T.

doi:10.1093/jxb/22.1.19

Cited by 26 publications

(15 citation statements)

References 4 publications

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“…Low hydraulic conductivities may be responsible for relatively slow rates of water entry into dry seeds even though there is a larger water potential gradient between the seed and the surroundings. The abrupt increase in hydraulic conductivity measured by Shaykewich and Williams (8) in rapeseed occurs at a moisture content comparable to the content at which PEG no longer enhances water entry rates into soybean (Fig. 6).…”

Section: Vertucci and Leopoldmentioning

confidence: 79%

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Dynamics of Imbibition by Soybean Embryos

Vertucci¹,

Leopold²

1983

Plant Physiol.

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Mea emts ofthe rate of Imbtn by Isolated cotyledons ofsoybean (GbAcia max (L.) Meff cv Wayne) Indicated that water uptake rates were slowed by low temperatures and by low initial moisture contents of the tisue. The role of water viscosity In the temperature effects on imbibition was examined, and a linear relation between mbbition rate and the reciprocal of viscosity was found only for seeds of very high initial moisture content. Adding solutes which lowered the surface tension, or increased the wetting ability of the water, yielded markedly increased rates of imbibiton, especially for tssue of low initial moisture content The data are interpreted as Indicating a first compeneat of water entry which is a wetting reaction influenced by the surface tension of the water, and a second compot which resembles water flow through a porous matrix and is Inluenced by the water viscosity. We speculate that damage to soybeans during mbton, such as in the cse of chilng injury, may be particularl related to the Iitial wetting reaction rather than to the logerterm hnbbtional rate.The period of imbibition by seeds is a period of sensitivity to stresses, especially to low temperatures (2, 7). Protection against chilling damage to soybeans during imbibition is provided by higher initial moisture contents (5) or by treatments or conditions which retard the initial rate of imbibition (10, 13). Thus, the features of initial moisture content and rates of water entry are of particular interest in terms of the success of germination.It has been known for some time that imbibition proceeds more slowly at lower temperatures (9). Recent evidence (4) time course, kinetic analyses can be misleading. The kinematic viscosity of water at 0 to 40°C and the viscosities of solutions with different concentrations of PEG, Tween 20, and PAM were determined using a calibrated Cannon-Fenske Routine viscometer. Solutes were used at concentrations which provided the same range of viscosity as is shown by water between 0 and 25°C. At these concentrations, the solutes had no measurable effects on the water potential as determined by a dew-point psychrometer.Surface tensions of the solutions, or the related function of wetting ability, were estimated by measuring the spreading characteristics of a I-Il droplet of solution on a polyethylene film (3).The droplet size was visually enlarged by a Nikon shadowgraph instrument, and its area was determined. RESULTSFor analyses of the dynamics of water uptake, it is important that the parameters be measured as rates. As has been described earlier (2), water entry into soybean seeds proceeds at a linear rate between the first 5 and 35 min ofimbibition. As a routine measure of the rate of water entry, time course curves such as those in Figure 1 were utilized. Actual rates were calculated from the regression lines during the early period of linear water uptake. Figure 1 illustrates that the rate of water entry into soybean embryos is decreased at lower temperatures.Water entry rates were studied for soybean ...

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Section: Vertucci and Leopoldmentioning

confidence: 79%

“…Past work (8) has shown that hydraulic conductivity changes dramatically with moisture content in rapeseed. When rapeseed is very dry, hydraulic conductivity ranges from 10-15 to 10-13 cm/d.…”

Section: Vertucci and Leopoldmentioning

confidence: 99%

Dynamics of Imbibition by Soybean Embryos

Vertucci¹,

Leopold²

1983

Plant Physiol.

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“…The equation so far used (8,10) to model uptake by spherical seed was derived from three assumptions: (a) constant diffusivity, (b) no swelling, (c) constant water content near the surface after the first wetting. These are not borne out by observations; thus, a variable diffusivity was required to fit observations (8,10).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…These are not borne out by observations; thus, a variable diffusivity was required to fit observations (8,10). The seeds swelled to about double their size (8,10,11), and such swelling requires a different definition of coordinates (9). Finally, the swelling makes more room for water, the flux through the surface scarcely changes for a long time (11), and the water content near the surface increases for a long time (6 original distance r(o) from the center and by a swelling factor X: X = 8r(t)/0r(o) (1) where Fr(o) and Mr(t) are the distances between nearby locations before and after wetting for time t. In general, X varies with water content and temperature.…”

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Water Uptake and Water Diffusivity of Seeds

Waggoner¹,

Parlange²

1976

Plant Physiol.

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When pea (Pisum sativum) seeds were wetted, a sharp front separated the wet and dry portions, the seeds swelled, and the water content in the wetted portion continued to increase for a long time. A model was proposed and tested that takes into account these three characteristics and in particular does not postulate a constant diffusivity. The parameters of the model are simply the rate of penetration of the wetting front and a swelling factor.Recently the early water uptake and swelling of phloem has been examined. The uptake was interpreted in terms of both a constant diffusivity (5) and of a diffusivity that varied rapidly with water content (7). Although the variable diffusivity fitted the observations somewhat better, the total water uptake by the entire structure is insensitive to the effect of water content upon diffusivity, and the nature of diffusion in plant tissue can be solved only by observing the water profile in the tissue. The water content and profile vary smoothly when diffusivity is constant and abruptly when diffusivity increases rapidly with moisture. Because phloem or leaves are so thin that the water profile cannot be observed easily in them, we decided to observe water uptake and the profile of wetting in large seeds.As in any other living tissue, water uptake in dry seed is first controlled by permeation and then by growth (1). Since permeation and growth in seed occur on different time scales, they are easily separated. In addition, dead seeds, e.g., split peas (11), or swelling in water too cold for growth (4) can be observed.The equation so far used (8, 10) to model uptake by spherical seed was derived from three assumptions: (a) constant diffusivity, (b) no swelling, (c) constant water content near the surface after the first wetting. These are not borne out by observations; thus, a variable diffusivity was required to fit observations (8, 10). The seeds swelled to about double their size (8, 10, 11), and such swelling requires a different definition of coordinates (9). Finally, the swelling makes more room for water, the flux through the surface scarcely changes for a long time (11), and the water content near the surface increases for a long time (6).Our task is to observe the water profile in seed to show the inconstancy of the diffusivity and then to propose a model that does not require a constant diffusivity but does take into account swelling and the continuing change of water content as the surface expands. THEORY Fundamentally, our theory depends upon two things. First, see Figure 1, a location in the spherical seed is identified by its I This investigation of water movement into seeds is dedicated to Leon Bernstein whose investigations, scholarship, and editing have advanced knowledge of how plants get water and exchange salt.original distance r(o) from the center and by a swelling factor X: X = 8r(t)/0r(o)( 1) where Fr(o) and Mr(t) are the distances between nearby locations before and after wetting for time t. In general, X varies with water content and temperature....

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Imbibition, Leakage and Membranes

Simon¹,

Mills²

1983

Mobilization of Reserves in Germination

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Resistance to Water Absorption in Germinating Rapeseed (Brassica napusL.)

Cited by 26 publications

References 4 publications

Dynamics of Imbibition by Soybean Embryos

Dynamics of Imbibition by Soybean Embryos

Water Uptake and Water Diffusivity of Seeds

Imbibition, Leakage and Membranes

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