UNCLASSIFIED eee eee 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 -~ OD _. Uo LA SSTFIED ee eee BOE achivES