Views:9 Author:Site Editor Publish Time: 2018-10-12 Origin:Site
Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots.
The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment.
Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth.
Many higher plants release allelochemicals into the environment through root excretion or exudation, leaching, evaporation and decomposition of plant tissues/organs . These compounds can accumulate in the soil, influencing (positively or negatively) the growth and development of other species. This process is termed allelopathy and is broadly defined as any chemically-mediated interaction among plants. It also involves the contact of allelochemicals with the rhizosphere or bulk soil, and can be absorbed by receptor plants and exert its influence . Due to the multitude of potential molecular targets, the investigation of the mode of action of allelochemicals is a challenging endeavor.