Allelopathic Activity of the Invasive Plant Polygonum chinense Linn. and Its Allelopathic Substances

Abstract

Polygonum chinense Linn., belonging to the Polygonaceae family, is distributed mostly in northern temperate climates. This species is a high-risk invasive plant and is thought to possess allelopathic potential. This study aimed to isolate and identify the allelopathic substances from P. chinense. Aqueous methanol extracts of P. chinense significantly inhibited the growth of alfalfa and Italian ryegrass seedlings in a species- and concentration-dependent manner. Activity-guided fractionation led to the isolation of two active compounds: dehydrovomifoliol and loliolide. A cress bioassay was used to determine the biological activity of dehydrovomifoliol, and cress, alfalfa, and Italian ryegrass were used to determine loliolide. Dehydrovomifoliol significantly suppressed the seedling growth of cress at the concentration of 1 mM, and the concentrations necessary for 50% growth inhibition (I₅₀ values) of the roots and shoots were 1.2 and 2 mM, respectively. Loliolide significantly suppressed the shoot growth of cress, alfalfa, and Italian ryegrass at the concentration of 1 mM, and the concentrations necessary for I₅₀ values of the shoots and roots were 0.15 to 2.33 and 0.33 to 2.23 mM, respectively. The findings of our study suggest the extracts of P. chinense might have growth-inhibitory potential and that dehydrovomifoliol and loliolide might contribute as allelopathic agents.

Keywords: Polygonum chinense; allelopathic substances; invasive plant.

Figure 1

Polygonum chinense.

Figure 2

Effect of the Polygonum chinense above plant parts extracts on the seedling growth of alfalfa and Italian ryegrass at six concentrations. Each bar expresses mean ± SE with six replicates (n = 60). The letters on the bars signify significant differences (Tukey’s HSD test, at 0.05 probability level).

Figure 3

Procedure for isolation and purification of allelopathic active compounds from the extracts of the above plant parts Polygonum chinense.

Figure 4

Effects of the distilled water (aqueous) and ethyl acetate (EtOAc) fractions on the seedling growth of cress obtained by partitioning the extracts of Polygonum chinense at the concentrations of 0.1 and 0.3 g DW equivalent extract/mL. Each bar expresses mean ± standard error with three replicates (n = 30). Different letters on the bars signify significant differences (Tukey’s HSD test, at 0.05 probability level).

Figure 5

The inhibitory effect of the P. chinense above plant parts extracts on the shoot and root growth of cress. The cress seeds were treated with different ratios of EtOAc in n-hexane (v/v) at the concentration of 0.6 g DW equivalent extract/mL using nine fractions and the last fraction eluted with MeOH. Each bar expresses mean ± standard error with three replicates (n = 30). *, **, *** Asterisks signify significant differences (Tukey’s HSD test at 0.05, 0.01, 0.001 probability level, respectively). NS: Non-significant differences.

Figure 6

The structure of dehydrovomifoliol isolated from the above plant parts of P. chinense extract.

Figure 7

Effects of dehydrovomifoliol against the growth of cress seedlings. Each bar expresses mean ± SE with three replicates (n = 30). Different letters on the bars signify significant differences, but any two means having a common letter are not significant differences within the group (Turkey’s HSD test, at 0.05 probability level).

Figure 8

The structure of loliolide isolated from the above plant parts of P. chinense extract.

Figure 9

Effects of loliolide against the growth of cress, alfalfa, and Italian ryegrass. Each bar expresses mean ± standard error with three replicates (n = 30). Different letters on the bars signify significant differences, and any two means having a common letter are not significant differences within the group (Turkey’s HSD test, at 0.05 probability level).