Allelopathic effects of water extracts from sweet potato on the growth of invasive alien species Alternanthera philoxeroides

Abstract

It is an effective approach to control invasive plants based on the allelopathic effect of native plants with higher economic values, from the perspective of allelopathy. The aim of this study was to test the allelopathic effect of a local crop, sweet potato (Ipomoea batatas), on the invasive plant Alternanthera philoxeroides. Water extracts from different organs of sweet potato (roots, stems, leaves) with three concentrations (0.025, 0.05, 0.1 g·mL-1) were used in the study. To test the effect of sweet potato on rhizome growth of A. philoxeroides, the morphological index (ramet number, node number, leaf number, leaf area, plant height, total dry weight and root number of new ramets), allelopathic response index, trait values (succulent degree, root-shoot ratio, specific leaf area, leaf mass ratio, stem mass ratio, root mass ratio), CAT, POD, MDA and SOD in young leaves were measured. The results showed that 1) Water extracts from different organs of sweet potato with different concentrations differed in their effects on the growth of A. philoxeroides. Water extract from root with 0.1 g·mL-1 significantly inhibited all morphological indices. Except total dry weight and root number, other morphological indices decreased significantly with increasing concentration of water extract from all organs. 2) The synthetic allelopathic response index (RI) was negative under all treatments, indicating that water extract of sweet potato had negative effects on all indices of A. philoxeroides and thus inhibited their growth. Among all the treatments, water extract from root with a concentration of 0.1 g·mL-1 had the strongest allelopathic inhibition (RI=-0.73), followed by that from stem with a concentration of 0.1 g·mL-1(RI=-0.44) and from root with a concentration of 0.05 g·mL-1(RI=-0.44). 3) Water extract of sweet potato had significant inhibitory effects on the degree of succulence, root-shoot ratio, specific leaf area, and leaf mass ratio, but did not affect stem mass ratio and root mass ratio. 4) Water extract of sweet potato significantly increased the contents of MDA and SOD in the fresh leaves of A. philoxeroides, while had no effect on the contents of CAT and POD. All these results indicates that water extract of sweet potato significantly suppress the ramet growth of A. philoxeroides.