Background:

Hydrocinnamic acid is the major rhizospheric compound with known growth regulatory activities.

The major compound, Hydroxyhydrocinnamic acid, is found to have a strong inhibitory effect on the elongation of radish root. The richness of Hydrocinnamic acids in the mixture is interesting, because they have synergistic effects on the gibberellic acid-induced hypocotyl elongation of lettuce seedlings[1].

[1]. Tang CS, et al. Collection and Identification of Allelopathic Compounds from the Undisturbed Root System of Bigalta Limpograss (Hemarthria altissima). Plant Physiol. 1982 Jan;69(1):155-60.