[NAFEX] FW: Vapor, Not Water, Sprouts Seeds

Lon J. Rombough lonrom at hevanet.com
Tue Jan 7 10:33:01 EST 2003

From: ARS News Service <NewsService at ars.usda.gov>
Reply-To: ARS News Service <NewsService at ars.usda.gov>
Date: Tue, 07 Jan 2003 07:42:33 -0500
To: ARS News subscriber <lonrom at hevanet.com>
Subject: Vapor, Not Water, Sprouts Seeds

Vapor--Not Liquid Water--Spurs Seeds' Sprouting


ARS News Service
Agricultural Research Service, USDA
David Elstein, (301) 504-1654, delstein at ars.usda.gov
January 7, 2003

A new finding by Agricultural Research Service soil scientist Stewart B.
Wuest has stunned many plant scientists. Until recently, it was generally
believed that seeds must be in direct contact with soil to obtain liquid
water needed for germination. Then Wuest discovered the importance of water

>From his research on wheat seeds at ARS' Columbia Plateau Conservation Research
Center in Pendleton, Ore., as well as from studying previously published
data, Wuest concluded that water vapor in the soil is actually what makes
seeds germinate. With a relative humidity of close to 99 percent in soil,
the seeds didn't need to be tightly compacted in the soil to grow. In fact,
seeds that were separated from the soil by crop residue still germinated,
because the vapor was able to reach them.

Wuest also found that, thanks to water vapor, seeds separated from soil by a
layer of fiberglass cloth germinated just as well as those touching the
soil. He was even able to germinate seeds suspended in air above water,
using just the vapor rising from it.

Water vapor is all around us, measured as humidity. That's what makes a dry
cracker left out in a room with high humidity turn soggy from absorption of
water from the air. Similarly, seeds are able to absorb their needed water
from vapor in the soil. In fact, liquid water is not nearly as important as
previously thought and may only account for 15 percent of water taken up by
germinating seeds.

In light of this discovery, approaches to water absorption models and
measurement techniques may need to be changed. The design of some seeding
equipment may also change, since actual seed-soil contact is not as
important as earlier believed. Emphasis is likely to shift to tactics for
retaining water vapor near the seed.

Findings from Wuest's research were published in a recent issue of the Soil
Science Society of America Journal.

ARS is the U.S. Department of Agriculture's chief scientific research

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