Residue allelopathy in Parthenium hysterophorus L.—Does parthenin play a leading role?

TLDR: The level of involvement of parthenin in overall phytotoxicity of decomposing leaf material in a South African population of P. hysterophorus was investigated and the natural release of inhibitors during decomposition was simulated.

About: This article is published in Crop Protection.The article was published on 2007-03-01 and is currently open access. It has received 142 citations till now. The article focuses on the topics: Parthenium hysterophorus & Ageratum conyzoides.

Figures

Fig. 2. Phytotoxicity of parthenin on germination of Lactuca sativa depending on the time after exposure (a) and the association between ED50 (dose causing 50% reduction in germination) and slope B of normalized dose–response curves (b). R2=coefficient of determination; r=Pearson correlation coefficient (significant at P=0.01). Results revealed a significant decrease in inhibition of germination by parthenin with increasing time of exposure, which suggests that the currently applied length of exposure (7 days) was too long to have captured a considerable effect on germination for most test plant species. This indicates that the phytotoxicity of parthenin is characterized by a widely reversible inhibition of germination leading to a significant delay even at low concentrations, as well as growth stimulation at low, and inhibition at higher doses. Therefore, the subsequent comparison between the phytotoxicity of pure parthenin and the quantified contents of parthenin in the aqueous leaf extracts of P. hysterophorus considered merely root length as being the more reliable response parameter to estimate the role of parthenin.

Table 1. Phytotoxicity of aqueous leaf extracts of Parthenium hysterophorus on five different plant species

Fig. 3. Association between the amounts of parthenin extracted from leaves of Parthenium hysterophorus and its contribution to the overall phytotoxicity of aqueous leaf extracts on five different plant species; aratio of ED50-values of dose–response curves of pure parthenin and parthenin in leaf extracts; bamount of parthenin extracted by water from fresh leaves of P. hysterophorus within 24 h; R2=coefficient of determination; r=Pearson correlation coefficient (significant at P=0.01). Parthenin was isolated as one of the most important phytotoxins in the leaf material of P. hysterophorus, however, other toxic, water-soluble metabolites were present as well. Kanchan and Jayachandra (1980a) isolated several organic and phenolic acids, with phydroxybenzoic acid being most phytotoxic (Pandey et al., 1993a; Pandey, 1994a). Furthermore, although the amounts of other sesquiterpene lactones in the leaf material, in particular coronopilin and tetraneurin-A for the ‘parthenin race’, are comparably low (Picman et al., 1980; Picman and Towers, 1982), they could have contributed to the observed effects. Considering the apparent variable portion of parthenin within leaf extracts, that in case of A. conyzoides did not change the overall phytotoxicity of leaf extracts, it is most likely that a fluctuating phytotoxic mixture of sesquiterpene lactones and phenolic acids was responsible for the observed effects. The relative contribution of each of the individual compounds will depend on the qualitative and quantitative

Table 2. Phytotoxicity of parthenin on five different plant species

Fig. 1. Stimulation of root growth of Eragrostis tef at low doses of aqueous leaf extracts of Parthenium hysterophorus (a) and of Eragrostis curvula at low doses of parthenin (b). F=initial rate of increase in response (asymptotic 95% confidence interval in parentheses); M=dose giving maximum response; LDS=limited dose for stimulation; R2=1-residual SS/corrected SS; aamount of fresh leaf material extracted for 24 h per ml water. As evident for root length, the dose–response curves for germination were parallel for all species (average B=2.6), but differed in ED50-values. A. conyzoides was most sensitive with an ED50-value for germination of 53.5 mg/ml, which was more than four times

Table 3. Contribution of parthenin to the overall phytotoxicity of aqueous leaf extracts of Parthenium hysterophorus on root growth of five different species

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Residue allelopathy in parthenium hysterophorus l.— does parthenin play a leading role?" ?

Because leaf residues are believed to deliver large amounts of parthenin to soils during decomposition, the authors investigated the level of involvement of parthenin in overall phytotoxicity of decomposing leaf material in a South African population of P. hysterophorus.