Jasmonic Acid Inhibits the IAA-Induced Elongation of Oat Coleoptile Segments: a Possible Mechanism Involving the Metabolism of Cell Wall Polysaccharides

Abstract

The effects of jasmonic acid (JA) on the IAA-induced elongation of segments of etiolated oat (Avena sativa L. cv. Victory) coleoptiles were studied. Exogenously applied JA substantially inhibited IAA-induced elongation of oat coleoptile segments. The inhibition of the growth of oat coleoptile segments due to JA appeared 2 h after the application of JA with IAA. JA did not affect the consumption of oxygen by the segments, the osmolarity of the cell sap or the IAA-induced loosening of cell walls, which was recognized as a decrease in the minimum stress-relaxation time (T0). JA was extremely effective in preventing increases in the amount of the cell wall polysaccharides in both the non-cellulosic fraction and the cellulosic fraction during coleoptile growth in the presence and in the absence of IAA. Inhibition of the growth of oat coleoptile segments induced by JA was partially reversed by the simultaneous addition of sucrose to the test solution. From these results, it appears that JA inhibits IAA-induced elongation of oat coleoptile segments by interfering with some aspects of sugar metabolism that are related to the degradation and/or the synthesis of cell wall polysaccharides.