Ana Paula Ferro, Rogério Marchiosi, Rita de Cássia Siqueira-Soares, Edicléia Aparecida Bonini, Maria de Lourdes Lucio Ferrarese and Osvaldo Ferrarese-Filho*
Laboratory of Plant Biochemistry, University of Maringá, Av. Colombo, 5790, 87020-900, Brazil.
* Correspondence author.
Cinnamic acid and its hydroxylated derivative, ferulic acid, are known allelochemicals that affect the root growth of several plant species. Some studies have indicated that the impairment of root growth by allelochemicals is associated with lignification of the cell walls. However, this hypothesis has not been tested in monocot plants. Here, we evaluated the effects of these two allelochemicals on growth, activities of phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL), lignin content and the composition of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monomers in maize roots. Cinnamic acid reduced root growth, TAL activity and lignin (H+G+S) content. When applied in conjunction with piperonylic acid, cinnamic acid reduced total lignin and H, G and S content. Ferulic acid reduced root growth and PAL/TAL activities, but it increased G monomer and lignin (H+G+S). When applied in conjunction with 3,4-(methylenedioxy)cinnamic acid, ferulic acid reduced total lignin and G and S content. The results indicated that decreased maize root growth by the cinnamic acid was not related to the lignin production while exogenous ferulic acid could be channeled into the phenylpropanoid pathway and resulted in an excessive production of lignin, thus solidifying the cell wall and restricting the plant growth.
Keywords: Allelochemical, lignin, monolignol, phenylpropanoid pathway, root growth, Zea mays L.
RECEIVED: March 1, 2015
ACCEPTED: March 30, 2015