L-3-(3,4-Dihydroxyphenyl)alanine (L-DOPA), an allelochemical exuded from velvetbean (Mucuna pruriens) roots

Abstract

We investigated whether or not lettuce growth was inhibited by diffused L-3-(3,4-dihydroxyphenyl)alanine (L-DOPA), an allelochemical exuded from the roots of velvetbean (Mucuna pruriens (L.) DC. var. utilis) cultivars using a modified plant-box bioassay. For all the cultivars and one accession examined L-DOPA diffused from the roots and caused radicle and hypocotyl growth inhibition. A high correlation co-efficient (r ¼ 0.838 to 0.982) was observed between L-DOPA concentration and lettuce seed sowing distance. L-DOPA diffused equally in all directions from roots at 0 mm position (close to root surface) in the plantbox, while the inhibition (%) of lettuce radicle growth gradually decreased with distance from the roots. For all cultivars the concentration of L-DOPA was significantly different at 0 mm position: being highest in cv. preta (167 lg/ml) and lowest in cv. jaspeada and cv. ana (13 lg/ml). The correlation between lettuce radicle growth inhibition and concentration of diffused L-DOPA was high (r ¼ 0.856 to 0.966) in all cultivars and accession examined. However, the concentration of diffused L-DOPA did not correlate with the fresh weight concentration of L-DOPA measured in roots. The lettuce radicle growth inhibition from mucuna diffused L-DOPA was very similar that induced by synthetic L-DOPA, suggesting that diffused L-DOPA was the allelochemical responsible for growth inhibition.

Allelopathy, an alternative tool to improve cropping systems. A review

“…Shiraishi et al (2002) used the method to identify seven other ground-cover plant species. Nishihara et al (2005) confirmed the influence of L-DOPA [L-3-(3,4-dihydroxyphenyl)alanine] as an allelochemical exudated from Mucuna pruriens (L.) D.C. roots using this method.…”

“…This is achieved by the use of agar as a diffusion medium, allowing the dispersion of allelochemicals exudated from roots of the donor plant to the target plant (Fujii, 1994;Nishihara et al, 2005), the latter of which is increasingly affected as it gets closer to the donor plant. The procedure consists of putting a donor plant in a cellulose (or nylon) tube and placing it in one corner of a plant box.…”

The role of L-DOPA in plants

“…This allelochemical is found in large quantities (1% and 4-7% in the leaves and seeds, respectively) 5 in velvet bean [Mucuna pruriens (L.) var. utiliz], a legume of the Fabaceae family that has a nutritional quality comparable to the soybean.…”

“…Furthermore, its ability to control weeds and nematodes greatly reduces the need to apply artificial chemicals to the crops. 5,7,8 In addition, its cultivation in tropical areas is aimed at enriching the soil due to its ability to fix nitrogen. 9 Velvet bean has been intercropped with maize and rice in Nigeria and Japan, respectively.…”

Growth and Nutrient Accumulation of Winged Bean and Velvet Bean as Cover Crops in a Subtropical Region

“…The allelochemical activity of velvet bean has been attributed to L-DOPA, which is exuded from leaves and roots. Velvet bean contributes 200-300 kg ha -1 of L-DOPA to the soil each year (Fujii et al, 1991;Fujii, 2003;Nishihara et al, 2005). However, the allelochemical compounds of winged bean remain unknown.…”