Bluefield Daily Telegraph, Bluefield, WV

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February 6, 2013

Some seeds need coaxing to sprout

(Continued)

In places with consistent moisture throughout the year, it is winter cold that would snuff out any young sprout that began growing in the fall. So seeds of many of our native plants won't sprout until they feel that winter is over, a condition that could be mimicked by a couple of months in the refrigerator in a sandwich bag along with moist potting soil. While doing time in the refrigerator, it's not unusual for a whole batch of seeds to sprout in unison, as if a switch has been turned on, even before they're released into warmth.

Hormones in seeds are what bring them to life at the appropriate moment. Although the seeds appear to be lying lifeless in a bag on a refrigerator shelf, all sorts of things are going on hormonally. Levels, for instance, of a germination inhibitor called abscisic acid are decreasing, while levels of another hormone, gibberellic acid, are increasing. These hormones have been extracted from seeds or synthesized, and some seeds shed their normal reluctance to sprout with nothing more than a dip in an appropriate concentration of gibberellic acid. All is not so simple, though, because other hormones also are at work and other compounds, such as potassium nitrate, can, for unknown reasons, also promote germination.

MECHANICAL INHIBITION

Let's not blame dormancy only on hormones; some seeds stay asleep for purely mechanical reasons. The tough seedcoats of honeylocust, black locust and black cohosh are among those that cannot imbibe water as soon as their seeds hit the ground. And a seed that remains dry inside will not sprout.

In nature, these tough coats are eventually softened as soil microbes chew away at them, by cycles of freezing and thawing, by abrasion and by passage through animals. Microbes work best at warm temperatures, so a couple of months in a sandwich bag along with some moist potting soil could awaken these seeds just as they do those of tree peonies.

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