|Wu, How-Chiun - UNIVERSITY OF PRETORIA-SA|
|Du Toit, Elsa - UNIVERSITY OF PRETORIA-SA|
|Reinhardt, Charlie - UNIVERSITY OF PRETORIA-SA|
|Van Der Kooy, Frank - UNIVERSITY OF PRETORIA-SA|
|Meyer, J.J. Marion - UNIVERSITY OF PRETORIA-SA|
Submitted to: Journal of Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 28, 2007
Publication Date: July 1, 2007
Citation: Wu, H., Du Toit, E.S., Reinhardt, C.F., Rimando, A.M., Van Der Kooy, F., Meyer, J. 2007. The Phenolic, 3,4-Dihydroxybenzoic Acid, is an Endogenous Regulator of Rooting in Protea Cynaroides. Journal of Plant Growth Regulation. 52(3):207-215. Interpretive Summary: Analysis of the extracts of stems of Protea cynaroides showed large amounts of the phenolic compound 3,4-dihydroxybenzoic acid. When tissues of Protea cynaroides grown in culture medium were treated with this compound at a concentration of 100 mg per liter root growth was stimulated, but not at lower concentrations; at 500 mg per liter concentration, the compound inhibited root growth. Analysis of plant cuttings during the growing stages showed an increase in the levels of this compound from initial planting to when root formation took place, indicating that this compound may be important in regulating root formation. Other phenolic compounds were also identified in the cuttings, namely caffeic acid, ferulic acid, gallic acid and salicylic acid.
Technical Abstract: Bioassays indicated the presence of allelochemicals in Protea cynaroides stem cuttings. Analysis of stem extracts identified large quantities of 3,4-dihydroxybenzoic acid and other simlar phenolics. Phytotoxicity bioassay showed that 3,4-dihydroxybenzoic acid both stimulated and inhibited root growth of lettuce seedlings, depending on concentration. The exogenous application of 3,4-dihydroxybenzoic acid on P. cynaroides explants in vitro stimulated root growth at 100 mg 1-1, but not at lower concentrations, while root inhibition was observed at concentrations of 500 mg 1-1. HPLC analysis of cuttings during vegetative propagation showed a considerable increase in 3,4-dihydroxybenzoic acid levels from initial planting to when root formation took place, inidicating that 3,4-dihydroxybenzoic acid may be an important phenolic compound in regulating root formation in P. cynaroides cuttings. HPLC analysis also identified caffeic, ferulic, gallic and salicylic acids in the cuttings.