Evening star., 1932-07-11
TASTE Of SUGAR
AFFECTSFL0WERS
Opening and Closing of Bios
SONS Governed by Many
External Factors.
BY THOMAS r. HENRY
overs fond of sugar?

Are flowers iona OF sugar!
Some of them, at least, show decided
reactions to this substance, experiments
lust reported by Carnegie Institution OF
Washington show.
The blossom, of course, is not aware
of liking or disliking anything, but 1t
sometimes acts rs if it did. G. w.
Goldsmith and A. L. Hafenrichter of the
Carnegie Institution staff, found this
out in a long series of experiments to
discover the mechanism of the semi
rythmic opening and closing of flowers.
When tulip blossom was placed In
pure distilled water the effect was TO
make it close in approximately one
hour Then a closed blossom was placed
in the same distilled water with very
small amount of sugar in solution, but
at the same time constant temperature,
and exactly the opposite effect was OBJ
served The blossom opened. but almost
twice as long was required for 1t to
added the faster and fuller the opening.
Dandelion Similar.
A similar effect was observed in the
dandelion, but in the opposite direction.
Water caused the blossoms to open, but
the addition of sugar solution caused
them to close, the greater the amount
of sugar the greater the closing In a
given time. The same effects. either In
one direction or another, was observed
in many other flowers studied under
laboratory conditions.
Because the nerveless blossom can
have no Sensory awareneSS, a purely
mechanical explanation of its response
to stimulation of any kind is necessary.
The opening and closing of blossoms,
it is explained in the Carnegie report,
is due to bending of the bractS SepalS
and petals. The experiments show this
occurs mainly in very limited region
near the base of these regions which.
because of its structure, becomes a site
Of extreme SenSitivity.
The explanation is probably to be
found, it is explained, in the water con-
tent of the cells in this region. Some
plants are so constituted that when
these cells are turgid with water there
will be bending effect which will tend
to open the blossom. In others the
bending effect will tend to close the
blossom When the flower is immersed
in water this turgidity is effected and
movement results in one way OF an
other. But when sugar is added the
effect may be to draw the water out of
the tissues it is explained, causing the
opposite effect. 1t is considered i'm
possible for the sugar to permeate the
cells themselves.
Responses Delicate.
AS rule, it is stated, movements of
this kind can be caused repeatedly.
They also can be produced by artifi-
cial manipulation af the cells in the
sensitive area. Delicate responses
were found to light, temperature and
humidity of the surroundings, the bios
som movements varying according to
species and some flowers showing even
individual differences.
Cutting, they found, rarely produces
any change in the behavior OF a BIOS
som for "a hours or more, indicating
that the mechanism involved is largely
confined to the flower and has no tie
up with the general structure of the
plant Flowers cut Immediately before
opening and left in the field without
any water supply. the experimenterS
found, frequently opened at the usual
time Studies of the water content of
the flowers indicated general decrease
with age, but no change which could be
directly correlated with the movements
except in a few species.
The dependence of the flower move
ments upon the conditions of the en-
vlronment was shown by observations
Il. L
regularly in the morning and close at
night, but on exceptionally cool days
the flowers may remain closed all the
periods-that is, when the, drying-out
time. while curing hot and windy
process would be more rapid-they may
close early in the forenoon instead of
waiting for darkness.
Plant Matches Weather.
The dandelion, they found may be
an early or late riser. Under favorable
conditions its blossom will open as early
as S am, but on bad day-that is,
q bad day for dandelions-it may re-
main asleep until 10 O'Clock. And it
may quit it's days work of looking pretty
any time from am. to 6 pm. Dande-
hons in the shade, or protected from
the wind, show quite different bios
som movements from those in less
favorable positions. =
They conclude that closing or open
ing, according to the nature of the
plant, is likely to occur, not according
70 any mysterious inner rythm of be-
havior, but whenever the rate of trans
piration of water from the tissues con-
cerned in movement equals or exceeds
the water conduction to the tissues.
Temperature, light and humidity all
contribute to this result.
The opening and closing of flowers,
the experimenterS explain, may seem
to be independent of these factors in
their environment because they must
reach a critical intensity or be pro-
longed over long periods before they
will produce easily noted changes.