Effects of extremely weak alternating magnetic fields on the plant gravitropism

It was shown that the rate of gravitropic response in apical segments excised from the 4-day-old seedlings of flax (Linum bienne) may be substantially influenced by combined magnetic fields (CMF) of two different types: 1) CMF tuned to the parametric resonance for Ca2+; 2) CMF containing extremely weak alternating component with the values of magnetic density ranging from 10(-6) to 10(-10) T. Our experimental data indicate that CMF affect the gravitropic response via at least two different mechanisms. The first one corresponds to the ion parametric resonance well established earlier in studies with test-systems prepared from animals. The origin of the bioeffects induced by CMF containing extremely weak alternating component remains to be established.