Evening star., 1939-03-16
Of Sturs, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
p And Study
By Thomas {. Henry.

p And Study
By Thomas i. Henri.
Nitrogen, which constitutes about 30
per cent Of the atmosphere, is natures
milk for the plant world, sucked from
the breasts Of Mother Earth by the
sprouting seedlings.
The function of this cosmic baby food
Is indicated by experiments reported to
the Soviet Academy of Sciences by Drs.
v. P. Popov and T. L. Demidenko of the
Voronej Agricultural Experiment Sta
ton. Plants were grown in liquid solu-
tions containing proper proportions Of
the three indispensable elements for
plant growth, nitrogen, phosphorus and
potassium. Then, at various periods in
the life Of the plants, one or another
element was removed from the solution
and the effects on mature growth and
crop yield noted
They found that 1t was the nitrogen
that gave the plants strong bodies with
which to do their work in the world, the
production Of basic food for men and
animals. After they had passed through
the period of plant adolescence it made
little difference whether they had any
Of this milk gas diet. Without it, in
fact, they did little better. They had
to make up its food value in the red
meat and potatoes of plant diet, phos-
phorus and potassium, and were the bet
ter for the change.
Experiments with sugar beets grown
in liquid solutions are reported in the
journal of the academy by DR.. Popov.
The solution contained at first proper
proportions of all three elements. He
found that up to the time the plant had
eight pairs of leaves the elimination Of
nitrogen from the solution materially
decreased the root weight and sugar con-
tent. After that the presence of this
baby food element appeared to be detri-
mental and the later it was eliminated
from the mixture the lower the percent
age of sugar yielded by the root.
The potassium and phosphorus, how
ever, were required throughout life. and
the earlier they were eliminated from
the solution the less the sugar obtained.
His conclusion is that the essential func-
ton of nitrogen is in building up the
mature plant organism. Once this has
been accomplished the demand for the
element ends and 1t has slightly detri-
mental effect. All through its life, DR..
Popov found, the plant likes nitrogen
and will suck 1t in if it gets a chance.
But in the mature days of its life it has
no use for it and simply stores 1t up in
the root, where it serves no real purpose.
From the same experimental station
are reported similar results with sun
flowers When the sunflower plant was
deprived of nitrogen before the forma-
ton of the bud the seed yield dropped
8 per cent below normal. II it was taken
of nitrogen diet after the bud had
formed the decrease was less than per
cent. When the nitrogen was taken
away at the time of blossoming the yield
jumped per cent above the average.
When the deprivation was delayed until
the seeds were forming the crop was
per cent greater than for the plants
given throughout life a good proportion
of all three elements.
Here also. as in the case of the sugar
beets, the function of the nitrogen was
evidently for infantile and adolescent
growth. When the plant reached ma
turity and started to do its assigned Job
in the world-the formation of sun
flower seeds for birds to eat-it didn't
need natures milk any more and got
along better without It,
Deprivation of phosphorus at various
stages showed an almost specifically op-
posite effect. The first vital need for
this element, as measured by the size
of the experimental crop, was at the
stage of seed formation The need for
potassium was shown when the bud be-
gan to develop.
At the same time were reported expert
ments which may make possible the
growing Of peaches far north of their
present limits. Occasionally a peach
seeding appears in nature which is ex-
traordinarily resistant to cold and, ac-
cording to the report to the Soviet
Academy by Drs. G. D. Pratassenja and
E. M. Turbitzina Of the Molotov Botanic
Gardens, in such cases it usually is found
that the hardy plant is a polyploid, or
plant whose pollen cells contain more
than two sets Of chromosomes, the bun
dies OF genes which are the units of
heredity.
The two Russian botanists carefully
picked out Of the peach pollen of more
than 100 varieties the giant grains"
which presumably were two-chromosome
bearing cells, and with these fertilized
other peaches of the same variety. Out
OF 800 such trials they obtained five
fertile seeds, all of which came up. One
died In few days but four are still
growing. All these are "triploids," plants
whose body cells contain three chro-
mosomes each. Increasing the number
OF chromosomes, they found, is a highly
lethal process but they believe that they
have established that 1t can be accom-
plshed by the methods they used.
These four peach seedlings, they hope,
Will provide a jumping off point for
further breeding experiments to produce
an Arctic peach.
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Janitors and Window Washers.