Effect of low frequency pulsed magnetic field on gravitropic response and cell elongation in coleoptiles of maize seedlings.

The effect of pulsed magnetic field (PMF) on gravitropic response, endogenous growth and growth in the presence of indole-3-acetic acid (IAA) was studied in coleoptiles of maize (Zea mays L.) seedlings. Medium pH changes, measured simultaneously with growth of coleoptile segments, were also determined. In seedlings grown in the presence of PMF, elongation growth of coleoptiles was inhibited by 16%, while growth of roots and mesocotyls did not depend on PMF. Magnetic field also inhibited (by 36%) the gravitropic response of maize seedlings. However, when PMF was applied only during gravistimulation (within 6 h), it suppressed the gravitropic reaction only by 8% at 6 h. It was also found that endogenous growth and IAA-induced growth of maize coleoptile segments excised from seedlings treated with the PMF was stimulated by 52% and 30%, respectively, as compared to control (segments untreated with the PMF). Values of medium pH, measured simultaneously with growth, indicated that PMF-treated coleoptile segments extruded much more protons than untreated segments. In contrast, coleoptile segments treated with the PMF and subsequently incubated in the presence of IAA extruded 2.5-fold less protons as compared to segments treated with IAA only. The data presented here have been discussed with consideration of mechanisms by which auxin (IAA) regulates plant cell growth.