The Dawson news. (Dawson, Ga.) 1889-current, 1920-04-13
PLANT life SEEMS
TO DEPEND ON LIGHT
DISCOVERY OF SCIENTISTS IN
BUREAU OF PLANT INDUSTRY
TEMPERATURE TESTS.

Government agricultural experts
have discovered that plant life seems
to depend on light rather than tenn
perature for nourishment and may
be controlled by regulating the hours
of light and darkness.
The principle is revolutionary; but
! it rests on actual experiments in
which it was demonstrated that
plants subjected to alternate periods
of light and darkness in carefully
determined proportions could be
brought TO maturity at any time OF
year.
Green house experiments" says
an announcement by the department
of agriculture, "prove that the flow
ering and fruiting period of practl-
cally any plant can be made to take
place at any time of year by dark
ening the green house in the morn
| ing and evening if the day is too
long, or by lengthening the day by
artificial light if the day is too short.
"Spring flowers and spring crops
happen to be spring flowers and
spring crops because the days at the
season of their Towering and fruit
ing have the proper number of hours
of day light.
The discovery may be of the high
est Importance in the future plan
ming of cropping systems for differ
ent regions. Eventually it may be
found, according to w. W. Garner
and H. A. Allard, scientists, that the
animal organism is also capable of
responding to the stimulus of certain
day lengths They believe that the
migration of birds may be an illus
tration on the ground that direct
response to such stimulus would
be more in line with modern blologl-
cal teachings than theories which as
sumo that birds ego south" as mat
ter of instinct.
Experiments were conducted with
la large variety of plants. 1t was
shown conclusively that too little
"sleep" or in other words too many
hours of daylight would prevent
MANY plants from ever reaching the
Towering and fruiting stage.
1t was found also that plants would
not reproduce except when exposed
to favorable length of day, although
too much daylight for Towering and
fruiting might stimulate profuse veg
etative growth. A length of day fav-
orable both to reproduction and
growth results in the lever bearing"
type of fruits.
By employing dark chambers the
scientists shortened or heightened
the life cycle of plants and forced
some of them to complete two cycles
in one season. Violets, which ma
turally bloom only during the com
paratively short days of spring when
covered with light-proOf boxes for a
time were made to bloom again dur
ing the summer. Biloxi soy beans
exposed to the light for only five
hours a day lowered nearly three
months earlier than plants left in the
light all day but attained only about
one-eighth the height
Temperature appeared to exert no
influence in the tests. A striking IL
luctration of the relative unimpor-
lance of temperature was given in
the fact that plants kept in the dark
for a part of the day underwent in
midsummer the changes that in ma
lure come III IH0 Idll anu JIIdI HSIS C.
tofore have been attributed to lower
temperatures. This was true even
when the dark houses registered a
higher temperature than the outside
atmosphere.
Iris kept in artificial light for 18
hours a day bloomed in two months
while others in the same atmosphere
but without artificial extension of the
day required months longer.
"The length of the day." the de-
partment's announcement said, sis
proved TO be the most potent factor"
in determining the relative proper
lions between the vegetative and
fruiting parts of many crop plants.
Indeed, fruiting may be completely
suppressed by day too long or too
short.
This new principle undoubtedly
explains the erratic behavior which
has been observed with many crops
when they are shifted to different
attitudes"
The new principle was said to ex-
plain why many plants grow most
! luxuriantly near the northern limit
of their range, where the long day
permits maximum vegetative growth
! before the short day intervenes to
start reproduction.