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Concept
Scarification (germination)
Résumé
Scarification in botany involves weakening, opening, or otherwise altering the coat of a seed to encourage germination. Scarification is often done mechanically, thermally, and chemically. The seeds of many plant species are often impervious to water and gases, thus preventing or delaying germination. Any process designed to make the testa (seed coat) more permeable to water and gases is known as scarification.
Scarification, regardless of type, works by speeding up the natural processes which normally make seed coats permeable to water and air. For drupes (stone fruits), scarification also extends to weakening or removal of the hard endocarp shell around the seed.
Regardless of the method, scarified seeds do not store well and need to be planted quickly, lest the seeds become unviable.
The most common type of scarification is mechanical scarification.
In mechanical scarification, the testa is physically opened to allow moisture and air in. Seed coats may be filed with a metal file, rubbed with sandpaper, nicked with a knife, cracked gently with a hammer, or weakened or opened in any other way.
The imbibition of water through seed shell membrane is affected by water temperature. Species that can withstand hot water will sprout faster under that condition than from cold tap water.
The North Carolina State University recommends placing the seeds in boiling water and letting them soak while the water cools to room temperature, and then remove the seeds from the water and sow. The buoyancy of floating seeds must be compensated with gravity to submerge them, this can be achieved with an infuser.
Hot water scarification can be combined with chemical scarification, but might require protective equipment against formed gases.
Hot water treatment is also used for removal of pathogens. Placing seeds in 90 °C for 90 seconds followed by dip in cold water for 30 seconds kills the human pathogens Escherichia coli O157:H7 and Salmonella. A variety of plant pathogens are also be killed by hot water treatment.
Source officielle
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