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Abstract. The effect of sixteen metal ions: AI, Cd, Co(ll). Cr(lll), Cr(VI), Cu(lI), Fe(III), Li, Mg, Mn(ll), Mo(VI), Ni(II), Pb(ll), Se(IV), V(V), and Zn on the mortality and infectivity of fteterorhahditis hac'teriol~hora were observed over a 96 hr period. All ions except Pb(lI) even at natur:dly unrealistic concentrations did not cause the mortality of the nematodes. A weak vitalizing effect could eventually be observed with Mn(II), Mg, Fe(IlI) and Ni(ll) ( Table I). However, such treatment generally lowered infectivity of the nematodes with respect to wax moth caterpillars, Galh'ria melhmella. This effect was particularly signilicant with Ni(ll) and Pb(ll).

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Quantum chemical (CNDO-CI-1) simulation and theoretical analysis of UV absorption spectra of 2-amino-, 2-methylamino-, 2-anilino-, 2-acetamido-, and 2-benzamido-pyridines were carried out. A comparison of results with experiment provided information on tautomerism and rotamerim in abovementioned compounds in solution. Contrary to some literature data 2-aminopyridine in solution exists in dimeric form of 2-pyridylamine. Also 2-methylaminopyridine in solution forms a similar dimer. 2-Anilinopyridine appears in solution as cis-1 H-pyridine-2-phenylimine tautomer. Both acylamino derivatives of 2-aminopyridine tautomerize with involvement solely of the carbonyl group to form hydroxyethylideno-and hydroxybenzylideno-2-aminopyridines, respectively.

In spite of a lack of acute toxicity of single metal ions, in 96 hour laboratory tests there was a long term toxicity against S. carpocapsae and H. bacteriophora nematodes. The 96 hour laboratory tests were carried out in order to prove possible synergistic and antagonistic interactions between pairs of metal ions. Thus, the pairs of ions were arranged from each of A1, Cd, Co(If), Cr(lII), Cr(VI), Cu(lI), Fe(lll), Li, Mo(Vl), Ni(II), Se(lV), V(V) and Zn on one side and Mn(II) and Mg on the other. Mn(lI) and Mg ions considerably reduced the nematode mortality and increased their infectivity against Galleria mellonella caterpillars.