An investigation of wild plants indicates that there are very few species which are free from possible virus infection. In comparison with this, most flowering plants growing under the surface of open water show a low but significant amount of virus. The indicated level of virus infection varies throughout each summer and from one summer to the next, but is often surprisingly high. The total annual infection under the conditions employed was approximately 10% of sample population. The amount of infection in all plants varies with species and location from 0 to 50%. Total virus infection appears to be related to the growth rates of plants. The types of virus included several common to commercial crop plants, many unidentified mixtures, and some distinctly new viruses.
The temperature dependence of the spin-lattice relaxation time T1 and of the second moment of the magnetic-resonance absorption signal has been determined for protons in powdered lithium hydrazinium sulphate over the range 80–480 °K. These measurements indicate that the hydrazinium ion is rigid only at very low temperatures. As the temperature is raised, the −NH3 group begins to undergo hindered rotation about the N–N axis with an activation energy of 4.2 kcal/mole and the effect of this motion on the line width becomes pronounced in the region of 85 °K. Further molecular reorientation begins above room temperature and is probably reorientation of the −NH2 group about either the N–N axis or the bisectrix of the H–N–H angle. Above 435 °K the hydrazinium ion begins to tumble about several axes and at 480 °K diffuses through the structure.
Even if centrifugation does not cause aggregation, completely unaggregated preparations could be expected only from plants that have been recently infected, for aggregation occurs naturally in the sap of plants that have been long infected'• We have emphasized the need for caution in interpreting centrifugal data on systems which can, in some circumstances, aggregate. It may be possible
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