The influence of the allelochemicals ferulic (FA) and vanillic (VA) acids on peroxidase (POD, EC 1.11.1.7) and phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activities and their relationships with phenolic acid (PhAs) contents and root growth of soybean (Glycine max (L.) Merr.) were examined. Three-day-old seedlings were cultivated in nutrient solution containing FA or VA (0.1 to 1 mM) for 48 h. Both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) and increased PhAs contents. At 0.5 and 1 mM, FA increased soluble POD activity (18% and 47%, respectively) and cell wall (CW)-bound POD activity (61% and 34%), while VA increased soluble POD activity (33% and 17%) but did not affect CW-bound POD activity. At 1 mM, FA increased (82%) while VA reduced (32%) PAL activities. The results are discussed on the basis of the role of these compounds on phenylpropanoid metabolism and root growth and suggest that the effects caused on POD and PAL activities are some of the many mechanisms by which allelochemicals influence plant growth

A técnica de depleção foi usada para determinar como raízes de soja consomem os ácidos ferúlico e p-hidroxibenzóico em solução nutritiva. Os resultados mostraram que extremidades excisadas de raízes de soja consumiram rapidamente estes aleloquímicos. Entre concentrações de 0,1 e 1,0 mM, 50% ou mais de ácido ferúlico foi consumido após 6 h de depleção. Embora o consumo tenha iniciado somente após 3 h, comportamento idêntico foi encontrado com ácido p-hidroxibenzóico.

Depletion method was used to describe how soybean root consumed ferulic and p-hydroxybenzoic acids in nutrient culture. The results showed that excised cultured soybean roots consumed these allelochemicals very rapidly. At concentrations between 0.1 and 1.0 mM, roots consumed 50% or more of ferulic acid after 6-h depletion. Although consumption started only after 3 h, similar behavior was verified with p-hydroxybenzoic acid.

Plântulas de soja cultivadas em meio nutriente foram utilizadas para investigar como glicose ou metionina influenciam a depleção de ácido ferúlico. Plântulas de três dias foram cultivadas em meio hidropônico contendo ácido ferúlico e glicose ou metionina e os níveis de ácido ferúlico foram monitorados no meio nutriente. Os resultados mostraram que as raízes de soja depletaram ácido ferúlico mais rapidamente na presença dos compostos. Após 6 horas, o aumento causado pela glicose (0,01 e 0,05 mM) foi mais pronunciado que na presença de metionina, nas mesmas concentrações. Por seu lado, metionina, a 0,1 e 0,2 mM, aumentou a depleção mais significativamente que a glicose. Os resultados sugerem que ambos os compostos podem aumentar os efeitos alelopáticos do ácido ferúlico nas plântulas.

Cultured soybean seedlings were used to investigate how glucose or methionine influenced depletion of ferulic acid. Three-day-old seedlings were grown in hydroponic solution containing ferulic acid plus glucose or methionine, and the level of the phenolic acid were monitored in the nutrient culture. The results showed that ferulic acid depletion was more rapid in the presence of those compounds. After 6 h, the increase caused by glucose (0.01 and 0.05 mM) was more pronounced than methionine in the same concentrations. On the other hand, methionine (0.1 and 0.2 mM) increased depletion more significantly than glucose. Results suggested that both compounds might to increase the allelopathic effects of ferulic acid in the seedlings.