Seed mass variation potentially masks a single critical water content in recalcitrant seeds

2004 ◽  
Vol 14 (2) ◽  
pp. 185-195 ◽  
Author(s):  
Matthew I. Daws ◽  
Christiane S. Gaméné ◽  
Sheila M. Glidewell ◽  
Hugh W. Pritchard
Keyword(s):  
Water Content ◽  
Seed Mass ◽  
Tropical Tree ◽  
Recalcitrant Seeds ◽  
Seed Population ◽  
Wide Range ◽  
Critical Water Content ◽  
Whole Seed ◽  
Water Contents ◽  
Seed Water Content

For recalcitrant seeds, mortality curves of germination versus water content typically imply a wide range of desiccation sensitivities within a seed population. However, seed to seed differences in water content, during desiccation, may confound our interpretation of these mortality plots. Here, we illustrate this problem for two batches ofVitellaria paradoxa(Sapotaceae) seeds collected in 1996 and 2002. Whole seeds were desiccated to various target water contents (TWCs) using silica gel. During desiccation, smaller seeds in the population dried most rapidly. Consequently, there was a significant linear relationship between whole-seed water content and seed mass during the drying process. In addition, following desiccation to low TWCs, only the largest seeds in the population retained viability. Taken together, this suggests that the larger seeds survived, not as a consequence of great relative desiccation tolerance, but as a result of taking longer to desiccate. Subsequently, the critical water content (CWC) for viability loss was calculated, based on the assumptions that in the seed population whole-seed water content during desiccation was normally distributed and the smallest, and hence driest, seeds were killed first. Using this approach, the driest seeds in the population that were killed, at each TWC, were always below a single CWC (c. 20% and 26% in 1996 and 2002, respectively). In subsequent experiments the effect of seed size variation on the response to desiccation was confirmed by conducting desiccation screens on seeds sorted into two discrete size classes, i.e. the seed-lot heterogeneity in mass was reduced. Using this approach, the mortality curves had a steeper slope. Furthermore, data for 24 tropical tree species from the Database of Tropical Tree Seed Research (DABATTS) revealed that seed lots with less variability in mass had steeper mortality curves. Thus, taken together, the data suggest that, at least for whole seeds, the wide range of desiccation sensitivities typically inferred is an artefact of seed to seed variation in mass, and hence water contents, during drying.

WATER TOLERANCE OF MIXTURES OF GASOLINE WITH ETHYL ALCOHOL, ISOPROPYL ALCOHOL AND BENZENE

1934 ◽  
Vol 11 (4) ◽  
pp. 505-519
Author(s):  
Colin H. Bayley ◽  
Clarence Yardley Hopkins
Keyword(s):  
Water Content ◽  
Ethyl Alcohol ◽  
Isopropyl Alcohol ◽  
The Other ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Water Tolerance ◽  
Wide Range ◽  
Critical Water Content ◽  
Water Contents

The relation between water content and critical solution temperature of mixtures of gasoline with ethanol and isopropanol and with ethanol and benzene has been determined. Curves are presented which show the critical water contents of a wide range of mixtures at any temperature between + 20° and − 50 °C. Three gasolines were used, two being straight-run and one a cracked gasoline. The mixtures contained 60 to 90% of gasoline with varying proportions of the other two components. Isopropanol has been found to bring about a marked increase in the critical water content of gasoline-ethanol mixtures to which it is added. Benzene is shown to be of little value for this purpose within the range of mixtures studied.

Effects of differential drying rates on viability retention of recalcitrant seeds of Ekebergia capensis

1998 ◽  
Vol 8 (4) ◽  
pp. 463-471 ◽  
Author(s):  
N. W. Pammenter ◽  
Valerie Greggains ◽  
J. I. Kioko ◽  
J. Wesley-Smith ◽  
Patricia Berjak ◽  
...  
Keyword(s):  
Water Content ◽  
Exponential Function ◽  
Time Course ◽  
Drying Rate ◽  
Recalcitrant Seeds ◽  
Tissue Water ◽  
Initial Water ◽  
Viability Loss ◽  
Drying Rates ◽  
Water Contents

AbstractThe drying rate of whole seeds of Ekebergia capensis (Meliaceae) was shown to influence the response to desiccation, with rapidly dried seeds surviving to lower water contents. Short-term rapid drying (to water contents higher than those leading to viability loss) actually increased the rate of germination. The form of the time course of decline of axis water content varied with drying rate; slow drying could be described by an exponential function, whereas with rapid drying initial water loss was faster than predicted by an exponential function. These observations suggest that slow drying brought about homogeneous dehydration and that the rapid drying was uneven across the tissue. This raised the possibility that the different responses to dehydration were a function of different distributions of water in the axis tissue under the two drying regimes. However, ultrastructural observations indicated that different deleterious processes may be occurring under the different drying treatments. It was tentatively concluded that a major cause of viability loss in slowly dried material was likely to be a consequence of aqueous-based processes leading to considerable membrane degradation. Uneven distribution of tissue water could not be rejected as a contributory cause of the survival of rapidly dried seeds to low bulk water contents. The differential response to dehydration at different drying rates implies that it is not possible to determine a ‘critical water content’ for viability loss by recalcitrant seeds.

Desiccation sensitivity and activities of free radical-scavenging enzymes in recalcitrant Theobroma cacao seeds

1999 ◽  
Vol 9 (3) ◽  
pp. 209-217 ◽  
Author(s):  
Changrun Li ◽  
Wendell Q. Sun
Keyword(s):  
Lipid Peroxidation ◽  
Superoxide Dismutase ◽  
Water Content ◽  
Theobroma Cacao ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Desiccation Sensitivity ◽  
Critical Water Content ◽  
Scavenging Enzymes ◽  
Water Contents

AbstractMature and immature axes of Theobroma cacao (cocoa) seeds tolerated desiccation under a rapid-drying regime to critical water contents of 1.0 and 1.7 g g-1 dw, respectively. These critical water contents corresponded to water contents below which activities of free radical-scavenging enzymes (ascorbate peroxidase, peroxidase and superoxide dismutase) decreased rapidly during desiccation. The decline in axis viability below the critical water content was correlated with sharp increases in lipid peroxidation and cellular leakage. Cotyledon tissues were more desiccation-tolerant than axes, with a low critical water content of 0.24 g g–1dw. Desiccation sensitivity in cotyledon tissues was also correlated with the decrease in superoxide dismutase activity and increased lipid peroxidation products. However, in the cotyledons, no ascorbate peroxidase activity was detected at any water content, and peroxidase activity was gradually reduced as desiccation proceeded. Cocoa embryonic axes contained large amounts of sucrose, raffinose and stachyose but only traces of reducing monosaccharides. Desiccation sensitivity of recalcitrant cocoa axes did not appear to be due to the lack of sugar-related protective mechanisms during desiccation, and it was more likely related to the decrease of enzymic protection against desiccation-induced oxidative stresses.

Effects of water content and temperature on the surface conductivity of bentonite clay

Soil Research ◽  
2012 ◽  
Vol 50 (1) ◽  
pp. 44 ◽  
Author(s):  
M. A. Mojid ◽  
H. Cho
Keyword(s):  
Water Content ◽  
Bentonite Clay ◽  
Ionic Mobility ◽  
Surface Conductivity ◽  
Temperature Correction ◽  
Hydration Layer ◽  
Temperature Range ◽  
Wide Range ◽  
Hydration Layers ◽  
Water Contents

This study explored the effects of water content and temperature on the mobility of exchangeable cations (termed the surface ionic mobility and hereafter ionic mobility) in the hydration layers of bentonite clay. The ionic mobility directly governs the surface conductivity of the clay. The investigation was done by measuring the bulk electrical conductivity (EC) of four sand–bentonite mixtures of different proportions for a wide range of water contents under constant temperature, and three bentonite samples at different water contents over 5–90°C. The ionic mobility was determined from the surface conductivity at the mean ionic strength of the hydration layers. The ionic mobility in the sand–bentonite samples increased with an increase in hydration layer thickness. For a given thickness of the hydration layer, the greater the bentonite content of a sample, the smaller was the ionic mobility. The ionic mobility in the bentonite samples at different water contents also increased, at reduced rates, with a rise in temperature. Consequently, the surface conductivity of the samples increased non-uniformly, at two different rates, with an increase in temperature. The increasing rate of this conductivity depended on temperature; over the low temperature range which depended on the water content, the rate was 0.013 dS/m.K, and over higher temperature range, the rate decreased to 0.008 dS/m.K. The commonly used temperature correction factor, 0.019 dS/m.K, for EC therefore did not hold true for the bentonite samples.

Spectrophotometrical pod colour measurement: a non-destructive method for monitoring seed drying?

2005 ◽  
Vol 143 (2-3) ◽  
pp. 183-192 ◽  
Author(s):  
F. COSTE ◽  
M. P. RAVENEAU ◽  
Y. CROZAT
Keyword(s):  
Water Content ◽  
Sharp Decrease ◽  
Quality Criteria ◽  
Visual Assessment ◽  
Grain Legumes ◽  
Grain Legume ◽  
Seed Filling ◽  
Wide Range ◽  
Non Destructive ◽  
Seed Water Content

A non-destructive indicator of seed water content could significantly help crop scientists with assessment of the effects of environmental conditions during drying on grain qualities or on seed physiological quality. This is particularly important for grain legumes which simultaneously bear pods of different ages. Visual assessment of pod colour has so far been used to date grain legume stages, but now colour can be easily and accurately measured with a portable spectrophotometer. Relationships between the spectrophotometer measurements and the pod and seed water contents were tested in various climatic contexts (3 years: 2000, 2001, 2002; field or greenhouse, two or three sowing dates) for two bean cultivars (Booster and Calypso) and also for one pea cultivar (Baccara) in 2003 near Angers, France. Among the different spectrophotometer measurements, hue angle (h) clearly shows the transition from green (h=180 °) to yellow (h=90 °) and then to red (h=0 °). In each context, h and seed water content (SWC) relationships showed the same pattern of three linear phases: first a steady state; then a sharp decrease from green (h=106–108 °) to yellow (h=85–93 °) just before the end of the seed filling stage for Booster or between the end of the seed filling phase and the beginning of seed drying for Calypso and pea; finally, a slow decrease from yellow to ochre (h=75–78 °) during seed drying. For each bean cultivar, the parameters of the linear relationships showed no differences between maturation conditions. Therefore, 6 h classes matching six SWC classes could be defined over a wide range of SWC between 0·56 and 0·2 g/g for Booster. However for Calypso and pea, only 3 h classes could be defined because of the tight relationships between h and SWC during the end of seed drying, which can be explained by pod walls drying faster than seeds. Hence, spectrophotometer measurements, if calibrated for a given cultivar of a species, could now be used to select pods with seeds of the same water content and therefore to study environmental effects on quality criteria either in controlled conditions or in the field.

ANALYSIS OF EMPIRICAL COMPRESSION INDEX EQUATIONS USING THE WATER CONTENT

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Amir W. Al-Khafaji ◽  
Krishnanand Y. Maillacheruvu ◽  
Melissa Hoerber
Keyword(s):  
Water Content ◽  
Empirical Models ◽  
Soil Types ◽  
Data Sets ◽  
Regression Equations ◽  
Compression Index ◽  
Empirical Formulas ◽  
Wide Range ◽  
Compression Data ◽  
Water Contents

This paper proposes a new method to evaluate the reliability of published empirical formulas in terms of accuracy and applicability to different soil types. Different empirical models are proposed to properly approximate the compression index for a wide range of water contents and soil types. They were developed using a unique technique and a substantial number of published regression equations and compression data. Familiar empirical equations were examined for their reliability in predicting the compression index of clay for any water content. A comparison was made between available and newly-proposed empirical formulas using combined regression data sets compiled independently by several authors. The newly proposed empirical compression index equations are applicable to a wide range of clay soils, and in validating other published relationships. The degree of scatter and variations in the computed compression index values are minimized for any water content.

scholarly journals Morphological and germination response variability in seeds of wild yellow gentian (Gentiana lutea L.) accessions from northwest Spain

Botany ◽  
2012 ◽  
Vol 90 (8) ◽  
pp. 731-742 ◽  
Author(s):  
Félix Pérez-García ◽  
Federico Varela ◽  
M. Elena González-Benito
Keyword(s):  
Seed Germination ◽  
Water Content ◽  
Germination Rate ◽  
Seed Mass ◽  
Germination Percentage ◽  
Gentiana Lutea ◽  
Moist Chilling ◽  
Mean Germination Time ◽  
Wild Accessions ◽  
Seed Water Content

Gentiana lutea L. (yellow gentian, Gentianaceae) is an important medicinal plant under protection as endangered species in most European countries. The aim of this work was to evaluate variation in seed mass, seed water content, and seed germination among 56 wild accessions of G. lutea. The effect of gibberellic acid (GA3), putrescine, moist chilling, and level of ripeness of seeds on subsequent germination was also investigated. Seeds of G. lutea showed physiological dormancy (final germination percentages ranged from 0% to 11%, depending on the accession) and GA3 enhanced seed germination drastically in all the accessions. The highest germination (99%) of GA3-treated seeds was reached at 15 °C. Final germination percentage and germination rate (as expressed by mean germination time), as well as seed mass and seed water content, varied significantly among accessions. In general, 1 year moist chilling did not significantly enhance G. lutea seed germination. For most accessions, no significant differences were found between fully ripe seeds and less ripe seeds for seed water content, seed mass, and seed germination. Applications of GA3 were always most effective than those of putrescine for increasing seed germination.

Dormancy release in Lolium rigidum seeds is a function of thermal after-ripening time and seed water content

2003 ◽  
Vol 30 (3) ◽  
pp. 345 ◽  
Author(s):  
Kathryn J. Steadman ◽  
Andrew D. Crawford ◽  
Robert S. Gallagher
Keyword(s):  
Water Content ◽  
Dry Weight ◽  
Base Temperature ◽  
Dormancy Release ◽  
Lolium Rigidum ◽  
Time Model ◽  
Ripening Time ◽  
Seed Moisture ◽  
Water Contents ◽  
Seed Water Content

Dormancy release in seeds of Lolium rigidum Gaud. (annual ryegrass) was investigated in relation to temperature and seed water content. Freshly matured seeds were collected from cropping fields at Wongan Hills and Merredin, Western Australia. Seeds from Wongan Hills were equilibrated to water contents between 6 and 18% dry weight and after-ripened at constant temperatures between 9 and 50°C for up to 23 weeks. Wongan Hills and Merredin seeds at water contents between 7 and 17% were also after-ripened in full sun or shade conditions. Dormancy was tested at regular intervals during after-ripening by germinating seeds on agar at 12-h alternating 15°C (dark) and 25°C (light) periods.Rate of dormancy release for Wongan Hills seeds was a positive linear function of after-ripening temperature above a base temperature (Tb) of 5.4°C. A thermal after-ripening time model for dormancy loss accounting for seed moisture in the range 6–18% was developed using germination data for Wongan Hills seeds after-ripened at constant temperatures. The model accurately predicted dormancy release for Wongan Hills seeds after-ripened under naturally fluctuating temperatures. Seeds from Merredin responded similarly but had lower dormancy at collection and a faster rate of dormancy release in seeds below 9% water content.

Water Diffusion in Silicate Glasses and Melts

2006 ◽  
Vol 46 ◽  
pp. 79-88 ◽  
Author(s):  
Harald Behrens
Keyword(s):  
Water Content ◽  
Ambient Pressure ◽  
High Water ◽  
Float Glass ◽  
Water Diffusion ◽  
Experimental Investigations ◽  
Melt Structure ◽  
Water Diffusivity ◽  
Wide Range ◽  
Water Contents

Knowledge on diffusion of water in glasses and melts is important for glass sciences as well as for Earth sciences. The ranges of water contents differ widely in both research domains. Industrial glass contain typically less than 0.1 wt% H2O whereas natural glasses may even contain up to 10 wt% H2O. Dissolved water strongly modifies physical and chemical properties of the melts and, hence, water diffusion studies at low water contents often cannot be transferred to high water contents and vice versa. Pressure effect on water diffusion, on the other hand, is small so that high pressure data can be applied also at ambient pressure without significant error. At low water contents the assumption of constant water diffusivity is often justified whereas at high water contents the H2O diffusivity increases strongly (often linearly or exponentially) with water content. Combining experimental data over a wide range of water contents allows getting deeper understanding of the mechanisms of water diffusion and of the effect of dissolved water on melt structure. In this paper an overview is given on experimental investigations on water diffusivity in aluminosilicate and silicate systems. Effects of base compositions and water content on water diffusivities are discussed. New experimental results for water diffusion in soda lime silica glass, float glass and borosilicate glass are presented.

Determining the virgin compression lines of reconstituted clays at different initial water contents

2015 ◽  
Vol 52 (9) ◽  
pp. 1408-1415 ◽  
Author(s):  
Ling-Ling Zeng ◽  
Zhen-Shun Hong ◽  
Yu-Jun Cui
Keyword(s):  
Regression Analysis ◽  
Water Content ◽  
Liquid Limit ◽  
Initial Water Content ◽  
Initial Water ◽  
Kaolinite Clay ◽  
Soil Particles ◽  
Wide Range ◽  
Natural Clays ◽  
Water Contents

Forty-eight consolidometer tests were performed on various natural clays and a kaolinite clay reconstituted in the laboratory at different initial water contents using a modified consolidometer apparatus. These data together with those published previously allow a multi-regression analysis for the development of an approach for determining the intrinsic compression parameters that depend on initial water content and liquid limit. The approach proposed by Burland can be thereby extended to provide an expression describing the compression response of a wide range of clays. Based on the intrinsic concept, a simple way of determining the virgin compression lines of reconstituted clays is also proposed using the density of soil particles, initial water content, and liquid limit.

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