title: Enhanced lignin monomer production caused by cinnamic Acid and its hydroxylated derivatives inhibits soybean root growth.
abstract: Cinnamic acid and its hydroxylated derivatives (p-coumaric, caffeic, ferulic and sinapic acids) are known allelochemicals that affect the seed germination and root growth of many plant species. Recent studies have indicated that the reduction of root growth by these allelochemicals is associated with premature cell wall lignification. We hypothesized that an influx of these compounds into the phenylpropanoid pathway increases the lignin monomer content and reduces the root growth. To confirm this hypothesis, we evaluated the effects of cinnamic, p-coumaric, caffeic, ferulic and sinapic acids on soybean root growth, lignin and the composition of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monomers. To this end, three-day-old seedlings were cultivated in nutrient solution with or without allelochemical (or selective enzymatic inhibitors of the phenylpropanoid pathway) in a growth chamber for 24 h. In general, the results showed that 1) cinnamic, p-coumaric, caffeic and ferulic acids reduced root growth and increased lignin content; 2) cinnamic and p-coumaric acids increased p-hydroxyphenyl (H) monomer content, whereas p-coumaric, caffeic and ferulic acids increased guaiacyl (G) content, and sinapic acid increased sinapyl (S) content; 3) when applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), cinnamic acid reduced H, G and S contents; and 4) when applied in conjunction with 3,4-(methylenedioxy)cinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL), p-coumaric acid reduced H, G and S contents, whereas caffeic, ferulic and sinapic acids reduced G and S contents. These results confirm our hypothesis that exogenously applied allelochemicals are channeled into the phenylpropanoid pathway causing excessive production of lignin and its main monomers. By consequence, an enhanced stiffening of the cell wall restricts soybean root growth.
authors: Laboratory of Plant Biochemistry, University of Maringá, Maringá, Paraná, Brazil.
authors: Rogério Barbosa
authors: RB
authors: Lima
authors: Victor Hugo
authors: VH
authors: Salvador
authors: Wanderley Dantas
authors: WD
authors: dos Santos
authors: Gisele Adriana
authors: GA
authors: Bubna
authors: Aline
authors: A
authors: Finger-Teixeira
authors: Anderson Ricardo
authors: AR
authors: Soares
authors: Rogério
authors: R
authors: Marchiosi
authors: Maria de Lourdes Lucio
authors: Mde L
authors: Ferrarese
authors: Osvaldo
authors: O
authors: Ferrarese-Filho
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D002934:Cinnamates / Q000378:metabolism / Q000494:pharmacology; D008031:Lignin / Q000096:biosynthesis*; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development*; D013025:Glycine max / Q000166:cytology / Q000254:growth & development*
chemical_list: D002934:Cinnamates; C029010:cinnamic acid; D008031:Lignin