Evening star., 1939-07-11
Of Stors, Men
And Atoms
In Field, Laboratory
Notebook Of Science Progress
And Study
By Thomas r. Henri.

By Thomas r. Henry.
Demonstration Of the existence of an
hitherto unobserved basic life chemical
IN plants, by means of which they are
able to breathe" carbon dioxide out of
the atmosphere, has just been an
nounced by DR.. E. D. McAlster bio
physicist of the Smithsonian Institution.
This carbon dioxide combining in
termediate' has an indispensable role
in the process of photosynthesis, the
corner stone of all life on earth. Chloro-
phyH, the green coloring matter in
vegetation, enables a plant to manufac-
ture out of water and carbon dioxide
the various hydrocarbons which consti-
tute its own substance by utilizing the
boundless energy of sunlight. =.
Thus the suns heat is trapped and
preserved on earth. Animals eat the
plants, or other animals who have eaten
the plants, and thus obtain the fuel
for their own bodies. Or the sun energy.
trapped by photosynthesis, is preserved
hundreds of million of years in the form
OF coal or oil to heat the homes and
run the machines of mankind
All this depends on the ability of the
chlorophyll to get grip on the carbon
dioxide molecule. Hitherto it has been
supposed that the two molecules acted
directly upon each other-one unit of
the gas entering into combination with
one or more units of the chlorophyll and
that this could happen, generally speak
ing. only when the leaves were illumi-
mated.
DR.. McAlister worked with an ex-
tremely delicate measuring device of his
own invention which determines accu-
rately the amount of carbon dioxide in
a given volume of atmosphere surround
Ing plant. He experimental with
wheat seedlings, with lights flashed on
ana OH every 80 seconds, and made ex-
tremely accurate measurements of the
varying amount of the gas.
Up to definite limits the rate of the
photosynthesis process, all other things
being equal, depends on the degree of
light available. DR.. McAlister found.
however. that after a plant had been
intensely Illuminated, with a corre-
spending high rate of photosynthesis
Tor few minutes the ABSORPTION of
carbon dloxlde continued for a brief
period when all lights were turned off
ana that the amount of gas taken from
the air was altogether too great to be
accounted for by any minor adjustment
process. That is. part of the process of
photosynthesis was going on without
hght, contrary to previously accepted
contentious
The phenomenon could be explained
ne found, by postulating an intermedi-
ate chemical, chlorophyllous in nature,
which combines directly with carbon
oloxide and which is itself created in
the photosynthesis process. It presum-
ably will be forever impossible to isolate
chemically any of the stuff itself It's
creatlon serves as pacemaker for the
oaslc process of life. 1t must first be
created in order for photosynthesis to 90
on and is destroyed as soon as it has
fulfilled its purpose.
When light is turned off the whole
process stops, but enough of the hitherto
unknown substance has been formed
SO that the absorption of carbon dioxide
stlil can go on for a brief interval
AT the other end of the phenomenon
Dr. McAllster found a brief lag after
hghts were turned on before photosvn-
tnesls could be detected in proper pro-
portion to the intensity of the illumina.
llon. Ihls supposedly is the interval
required for production of the initial
supply OF the intermediate. It must
get in the lead.
Inc conditions under which this
phenomenon has so far been observed
says DR.. McAlister, indicate that the
intermediate is formed in relatively
large quantities during the actual proc
esS OF photosynthesis and not before.
simple order of unity is found to exis1
between the number of carbon dioxide
nlolecules taken up and the total num-
per OF chlorophyll molecules present in
the plant. This is in opposition to the
loea OF a large photosynthetic unit of
some 1000 molecules operating together
IN the reduction of one carbon dioxide
molecule, as has sometimes been as
sumed. Chlorophyll, it would seem, par
tlclpates in photosynthesis as an in
olVloual molecule and not as part of a
very large miltomolecular unit"
DR.. McAlister's experiments have inst
been reported, together with a wealth
OF complex detail supporting his deduc-
tons, in the Journal of General Physi-
ology. They constitute part of an in.
tenslve study being carried on by the
Institutions Division of Radiation and
Organisms to get at the Fundamental
mechanisms OF the effects of light on
life.