UNCLASSIFIED
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interpreted as dite to its action uponmolecules which affect mltin-.
molecular turn-over, that is, the’enzymes.
2
If the enzyme system Involved —
_ in euxinsupply1is Tedtosensitirey. the.free auxinreservoir. woul: ‘be. atin
synthesis. | Exposure of the ‘plant to radiation doses caused decréased-
growth and decreased auxin concentration. The effect of the lowjradiation doses can be reversed by applying synthetic growth hormone fo the
plant following irradiation. The effect of higher radiation dosks cannot be reversed, implying that a more profound biochemical inj
has
taken place such.as on the enzymes.
Morphological changes due to irradiation can likewise be
fshown
to be due, in part, to radiation sensitivity of the hormone sys fem.
Plant workers are familiar with the phenomenon of apical domi
terminal growing point, or bud, suppresses the growth of lateral]
ce.
The
buds.
When the terminal meristem is cut off, or severely injured, the] lateral
buds immediately leave their "dormant" state and begin growing.|
by the auxin produced by the terminal bud.
Thus, when the stem
removed and auxin alone is applied to the stump, the laterals
pressed as long as the auxin source is allowed to remain.
If
applied source is in turn removed, normal growth of the later
immediately initiated.
This
tip is
gtay supthe |
is
i
Terminal growing points of the cocklebur were irradiated with
single low‘doses of X-irradiation, the remainder of the plant feing
shielded with lead.
Lateral bud growthensued, the buds increksing over -
100 percent in size within 2 days. When auxin was applied to Ehe tips
immediately after irradiation, lateral buds stayed suppressed.{| We can
therefore conclude. that these apical dominance responses to ixfradiation
are chiefly, if not wholly, due to radiation sensitivity of tHe
auxin
supply system.
When growth hormone is present in tissues, it is relat}vely in-
sensitive to ionizing radiation: Auxin itself in plant tissug
appear to be unduly radiosensitive.
However, the process of
does not
Buxin forma-
tion is relatively sensitive to radiation, and provides an explanation,
in part, for changes in growth and development of higher pl
to relatively intense, low doses of ionizing radiation.
s exposed
Medicine
Red Cross research contract (Harvard) on separation of white blood
celis and platelets. Within the past month investigators woyking on the.
above AEC-supported contract have devised means of separati
white blood
cells from other blood constituents. The separated white ceflis remain
viable for approximately 2 weeks, whereas white cells handlefi by ordinary
methods are destroyed almost immediately.
This development
fnarks a real
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