Dynamics of Imbibition by Soybean Embryos

Abstract

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 ...

Water Uptake by Seeds in Yellow-seeded Soybean (Glycine max(L.) Merrill) Cultivars with Contrasting Imbibition Behaviors

“…Of interest is that 12%-moisture Tamahomare embryos imbibed faster than 8%-moisture embryos, even though the water potential gradient between the embryo and its surroundings should be higher in the drier embryos. A similar observation has been reported by Vertucci and Leopold (1983). Since the low initial seed moisture content had little promotive effect on either the dorsal hydration of the intact seeds or the ventral hydration of the partially decoated seeds (Figs.…”

Temperature, Osmotic Pressure and Seed Treatments Influence Imbibition Rates in Sorghum Seeds

“…Additionally, the 40 °C regime may have reduced the water viscosity surrounding the seed and, thus, increased its diffusion (Woodstock 1988). Vertucci and Leopold (1983) suggested two components of early imbibition: an initial wetting reaction, which is influenced by the surface tension of the water, and a subsequent flow of water through seed tissue, which is influenced by water viscosity. Consequently, the higher imbibition rate at 40 °C may also be explained on the basis of lower water viscosity and, thus, higher water diffusion into the seed.…”

Role of exogenous folic acid in alleviation of morphological and anatomical inhibition on salinity-induced stress in barley

“…Soil salinity (Bewley, 1997) particularly affects the germination process (Fredj et al, 2013), which is one of the most important periods of plant growth, by delaying germination and decreasing germination rate (Ashraf and Foolad, 2005). A period of sensitivity to stress started with the imbibition of dry seeds during seed germination (Vertucci and Leopold, 1983). The negative impact of salt stress on seed germination occurs as a reduction of water absorption from the environment (Long et al, 2013) as a result of hyper-osmotic stress (Farsiani and Ghobadi, 2009) caused by the reduction of osmotic potential in soil solution by salt.…”