American Falls press. [volume] (American Falls, Idaho) 1907-1937, 1911-03-25

ly passing into these minute grow
ing root hairs. The explanation of
this inward movement is complicat-
ed. 1t Is sufficient to say that the
concentration strength OF the solu-
ton within the root hair Is of diff
ferent degree from that of the soil
water solution. The water tends.
therefore to move from the soil in
to the root, In order to made the
solution outside and inside of the
root of the same concentration. 1t
is clear that under these circumstan-
ces not only water enters the root
hair, but many of the substances
found in solution in the soil water
under the plant also. Among these
are the mineral substances. which
are indispensable for the proper life
and growth of plants.
The soil water holding in solution
a great variety of plant nutrients,
passes gradually from the root hairs
through the root hairs through the
roots and stems into the leaves,
where 1t is finally ev~aporated. The
rapidity of this current Is often con-
siderable. Ordinarily it varies from
one to six feet per hour, though
OUSCIb dtiOuS dT0 vi TCCOIu
that the movement often reaches the
rate of Is feet per hour. 1t is
evident, then, that in an actively
growing plant it does take long for
the water which is in the soil to
find its way to the uppermost parts
Of the plant.
The water which is thus passed
through the plants escapes into the
air through countless small open
ings, which exist chiefly on the sur
face Of the leaves and known as
stomata. The stomata are deli
cately balanced valves, exceedingly
sensitive to external influences.
They are more mer on the low
err side than on the upper side Of
plants In fact there are often five
times more on the under side than
on the upper side of the leaf. 1t
has been estimated that $50, 900
stomata or more are often found
pei square inch on the under side
Of the leaves on the ordinary cul-
tivated plants. Stomata, or breath
Ing pores are SO constructed that
they may open and close readily
In wilted leaves they are practically
closed; often they close Immediately
after rain; but in sunlight they are
usually wide open.
1t Is through the stomata that
the water which is drawn from the
sol by the roots through the stems
Is evaporated into the air. There
Is some evaporation of water from
the stems and branches OF the plants
but 1t seldom more than a thirtieth
or a forthieth of the total transpir-
alton. The evaporation of water
from the leaves through the breath
Ing pores Is sO-called Transportation,
which is the greatest cause of the
loss OF water under dry farming con
dttions. 1t Is to the prevention of
tn Transportation that much inves-
tigation must be given by future stu
dents of dry farming. Transpira-
ton. or the movement of water
through the plant, appears to be a
process wholly necessary for plant
life. and 1t Is a question to what ex-
tent 1t may be dimished without in
: juring plant growth. or one thing
only we are fairly sure. II the up
ward stream Of water Is wholly
stopped for even a few hours the
plant Is likely to be so severity injur-
ed as to be greatly handicapped in
Its future growth.
The conditions that determine the
evaporation of water from plant
leaves are in general the same as
those that favor direct evaporation
OF water from the soil. Especially
does this form of water use increase
with a dry air, an abundance of sun
shine and a high temperature-fac-
tors which prevail in all dry farming
districts. and are practically beyond
the control OF the farmer.
Further. it has been observed re-
peatedly that the amount of water
which actually e%vaporates from
plant leaves depends materially up
on the kind and quantity of the
substances held in solution by the
SOIL water; that is Transportation
depends upon the nature and concen
tration of the soil solution. This
fact, which is fundamentally i'm
portant in dry farming, though not
commonly applied at the present
time, has really been known for a
very long time. Woodward, in 1893
observed hat the amount of water
transpired by a plant growing in
rain water was 1928 grains; in
spring water, 1886 grains, and in
water from the river Thames 159.
grains: that is, the amount of water
TRANSFERRED by the plant in the COM
paratively pure rain water was near
ly 20 per cen higher than hat used
by the plant growing in the motor
iously impure water of the river
Thames. The latest investigators
of a generation. or two ago likewise
determined beyond a doubt that vor-
ious chemical substances added to
solutions In which plants were grow
ing reduced the evaporation from
plant leaves from 10 to rs per cent.
In particular was 1t determined that
the substances commonly known as
alkaline and which characterize dry
farming districts tended to reduce
Transportation.
The investigators OF almost q gem
,..tt~r 49, a. Io.-~l ~v~~