Abstract: Plant protoplasts are suspended in a solution of sodium alginate which is thereafter thickened by the addition of a soluble calcium or lanthanum salt to produce a matrix with large pores permeable to water and gas in which the protoplasts are held. The resulting material, in tape or spheroid form, when stored in a nutrient solution, will prolong the senescence of the protoplasts and increase their sensitivity to polluting materials. When such ribbons or particles are exposed to a polluting environment for a particular period of time, the effect of pollution can be detected by measuring the evolution of ethane or measuring the blocking of the enzyme ribulose-diphosphate-carboxylase, in the latter case using carbon dioxide marked with .sup.14 C. A control experiment in which an identical indicator treated in an equivalent environment without pollutants reveals, by comparison, the effect of the pollution.

Abstract: A target containing vanadium, either of natural isotopic constitution or enriched either with respect to .sup.50 vanadium or .sup.51 vanadium, is bombarded with .sup.3 helium of an energy of about 14 MeV producing .sup.52 manganese by nuclear reaction from both of these isotopes of vanadium. After a waiting period for the disappearance of short-lived intermediates, the target foil is dissolved in acid and the .sup.52 manganese is extracted with a solution of a hydroxychinolin in chloroform. The oxinate complex of .sup.52 manganese thus extracted can be used directly as a source of .sup.52 manganese in the preparation of compositions for radiochemical or radiopharaceutical purposes.