Mechanism of Action of Allelochemicals in Allelopathy

Abstract

The primary mode of action has not been established for any allelopathic compound, albeit some physiological actions are known. The array of compounds cuts across many chemical classes, and it is unlikely they have a common mechanism of action. Allelochemicals active against higher plants are typically characterized as suppressing seed germination, causing injury to root growth and other meristems, or inhibiting seedling growth.A primary action on ATP production is indicated for the two quinones, juglone and sorgoleone, since they inhibit chloroplast oxygen evolution (I 50 = 0.2 and 2.0 μM respectively) and strongly affect mitochondrial functions.The chloroplast block by sorgoleone is in the photosystem II complex. Cinnamic and benzoic acid derivatives alter membrane potential and have several physiological effects that suggest membrane perturbations are their initial site of action. Their thresholds (100 to 1000 μM) for inhibition of seedling growth, singly or in combinations, correlate with impairment of plant-water relationships. These phenolic compounds also alter mineral uptake, chlorophyll content, photosynthesis, carbon flow, and phytohormone activity. Phytotoxicity of many allelopathic chemicals may be from a generalized cellular disruption rather than a specific mechanism. A case study of Sorghum allelopathy suggests that inhibition of a receiving species results from the joint action of a number of allelochemicals with different cellular sites of action.Efforts to explain the phenomenon of allelopathy are ultimately challenged to identify the site, or sites, of action of the chemicals involved. However, this lofty goal has seldom come to fruition (1). Success has been greatest in localizing the subcellular target of activity for certain antibiotics and other microbial toxins (2-4).

Allelopathic activity of micropropagated Hyssopus officinalis L., Lamiaceae, water infusions

“…The results obtained from testing the germination and root elongation revealed that inhibitory effect of hyssopus was stronger in T. aestivum than in C. sativus and confirmed the observations of Einhellig (1995) that plants may be selective in their responses to allelochemicals.…”

“…There are also some data about the presence of water soluble allelopathic substances in aromatic plants (Ðikić, 2005;Economou et al, 2007). Allelochemicals may be selective in their action, or plants may be selective in their responses (Einhellig, 1995). So, determining the modes of action of allelochemicals is one of the challenging aspects in allelopathic studies (Chou, 1999).…”

Algal Decay Resistance of Conventional and Novel Wood-Based Composites

“…Additionally, previous literature also indicated that the phenolic hydroxyl group engenders an inhibition effect on algal growth. Algal cells die because of the change in and destruction of the cell membrane structure by phenolic hydroxyl groups (Einhellig 1995;Everall and Lees 1997;Li et al 2010). This study demonstrated that there were chemically volatile substances in the different wood species.…”

Estudo do potencial fitotóxico de extratos de Bauhinia ungulata L. sobre a divisão celular e atividade enzimática em plântulas de alface

“…Assim é esperado que estes flavonoides possam estar presentes na FAE, e desta forma é possível supor que tais efeitos do extrato e frações observados nos experimentos se devam em grande parte a estas substâncias. Estes compostos podem ser responsáveis, isolado ou sinergicamente, pela interferência nos processos fisiológicos durante a fase de desenvolvimento das espécies-alvo em estudo (Einhellig, 1986).…”