Plant phenolics: Recent advances on their biosynthesis, genetics, and ecophysiology

Within the plant environment, different microorganisms can coexist that can establish various interactions with the host plant and that are often the basis for the synthesis of specific phenolic metabolites in response to these interactions. In the rhizosphere, increasing evidence suggests that root specific chemicals (exudates) might initiate and manipulate biological and physical interactions between roots and soil organisms. These interactions include signal traffic between roots of competing plants, roots and soil microbes, and one-way signals that relate the nature of chemical and physical soil properties to the roots. Plant phenolics can also modulate essential physiological processes such as transcriptional regulation and signal transduction. Some interesting effects of plant phenolics are also the ones associated with the growth hormone auxin. An additional role for flavonoids in functional pollen development has been observed. Finally, anthocyanins represent a class of flavonoids that provide the orange, red and blue/purple colors to many plant tissues. According to the coevolution theory, red is a signal of the status of the tree to insects that migrate to (or move among) the trees in autumn.