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Detecting and overcoming water-impermeable barriers in prickly sida (Sida spinosa L.) seeds

Published online by Cambridge University Press:  19 September 2008

G. H. Egley  and
R. N. Paul Jr
G. H. Egley*
Affiliation:
Southern Weed Science Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Stoneville, MS 38776, USA
R. N. Paul Jr
Affiliation:
Southern Weed Science Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Stoneville, MS 38776, USA
*
* Correspondence
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Abstract

Barriers to water permeability in prickly sida seeds were characterized using solvents and water-soluble salts. The seeds imbibed water when barriers in the chalazal area broke down. The major barrier was in the distal region of the palisade layer bordered internally by the light line. Soaking dormant seeds in certain organic solvents overcame the barrier and enabled the seeds to imbibe water. The most active were non-polar solvents with dielectric constants between 3.7 and 18.5, and with a high ability to hydrate and swell cellulosic materials. We concluded that the most active solvents (pyridine, diethylamine) overcame the major barrier, entered the proximal portion of the palisade layer and caused the swelling of cellulosic cell components. The cellular expansion created stresses that broke thin walls of the underlying subpalisade cells in the chalazal area. The breakage resulted in separation of the cell layers and rapid entry of water into the seed. Highly non-polar or highly polar solvents had little or no activity. Some solvents overcame the barrier but did not cause swelling and disruption of the cell layers. We propose that the natural breakdown of impermeability in prickly sida seeds was due to the gradual seepage of water past the barrier in the distal portion of the coat in the chalazal area and into the inner portions where swelling of hygroscopic components triggered the breakage of subpalisade cell walls resulting in cell layer separation.

Keywords

Dormancyimbibitionpalisade layerSida spinosawater impermeable barriers
Type
Research Papers
Information
Seed Science Research , Volume 3 , Issue 2 , June 1993 , pp. 119 - 127
Copyright
Copyright © Cambridge University Press 1993

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Footnotes

1

Plant Physiologist

2

Biologist

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