Evening star., 1936-08-20
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY.

places over most of the earth. 1t has
high melting point. is strong, can easily
be worked and Is liked by jewellers and
dentists. It makes stronger Jewelry than
does white gold. 1t alloys with gold
to make a superior white gold, which is
highly resistant to tarnish, as well as
very tough. 1t also alloys well with
other metals for special applications.
y -
Curious and hitherto unsuspected spe-
cific effects of wave-lengthS of visible
light on the growth and behavior of
plants are reported from the division of
radiation and organisms of the Smith
sonian Institution.
In the experiment oat seedlings were
exposed to the light of an electric lamp
which was split up into its constituent
wave lengths by passing through
prism. The exposure was arranged IN
such a way that only a narrow band OF
visible wave lengths of light fell upon
each plant, and from a horizontal
direction.
As was expected by Enoch Karrer,
who conducted the experiment, the
seedlings exposed to the blue region
were bent toward the source Of the
illumination-the ordinary phenomenon
of. phototropism. But, In addition, he
found the tips of these seedlings were
bent toward each other, while in the
red region of the spectrum they were
bent away from each other. He also
noted the following specific effects:
The greatest growth IN length was In
the two regions where were found the
greatest conveyance and the greatest
divergence of the tips.
The greenest growth was in those
plants illuminated only by the orange
part Of the spectrum. The yellowest
growth was in the blue-green region.
Roots grew longest in the extreme blue
and shortest in the orange-red.
The leaf sheaf, or coleoptile, was most
filled out by the first leaf in the green
and orange regions and least in the
blue and deepest red. In the green the
growth Of the leaf sheaf appeared to be
stunted and the leaf broke through pre-
maturely, but its growth was rapid when
exposed to full white light.
The implication Of these findings Is
that different wave length bands OF
light give rise to different forces in the
physiology of plant development
This renders much more complex the
already extremely complicated relation
ships Of life and light. The basic phe-
nomenon is photosynthesis, the keystone
of all life on earth. 1t is the process
by which the plants synthesize carbo-
hydrates out of carbon -dioxide and water,
with the energy of sunlight made avail
able through the medium Of chlorophyll,
the green pigment of leaves. This makes
plant growth possible, and plants pro-
vide food for the rest of creation.
But there apparently is much more
to plant development than synthesis OF
carbohydrates, Mr.. Karrer points out.
Carbohydrates, fats, proteins, water and
minerals must be mobilized and oxidized.
There are reactions with ammonia and
other nitrogen compounds and chemical
changes in the synthesized products.
It now appears that many OF these
processes may be specifically activated
by specific bands of radiation. At differ
ent stages Of growth q plant may have
need of all the wave lengths in the
visible light spectrum, with one or an
other exerting the dominant influence
st any one period