The Effects of Naturally Occurring Phenolic Compounds on Seed Germination

Caffeic acid, chlorogenic acid, coumarin, p -coumaric acid, ferulic acid, fumaric acid, gallic acid, hydrocinnamic acid, p -hydroxybenzoic acid, juglone, and pyrocatechol were examined for effects on germination of nine crop and weed species: cotton ( Gossypium hirsutum L.), cantaloupe ( Cucumis melo L.), corn ( Zea mays L.), sorghum [ Sorghum bicolor (L.) Moench], hemp sesbania [ Sesbania exaltata (Raf.) Cary], sicklepod ( Cassia obtusifolia L.), velvetleaf ( Abutilon theophrasti Medic), prickly sida ( Sida spinosa L.), and redroot pigweed ( Amaranthus retroflexus L.). Germination tests with 10- 3 and 10- 5 M solutions were conducted under controlled conditions in petri dishes at 25 C in the dark. At 10- 3 M, coumarin, hydrocinnamic acid, juglone and pyrocatechol inhibited germination, but p -hydroxybenzaldehyde and p -hydroxybenzoic acid were not effective and others had intermediate effects. There was little effect by any compound at 10- 5 M. Chlorogenic acid, p -hydroxybenzaldehyde, and pyrocatechol, each combined with coumarin, inhibited germination. The combination of coumarin plus p -hydroxybenzaldehyde had an additive effect on hemp sesbania and prickly sida, inhibiting germination to a greater extent than either compound alone. The lack of inhibitory action at the higher concentration of some of these chemicals suggests they may not exhibit a high allelopathic potential.