Allelopathic effects of aqueous extract of invasive alien cactus on seed germination and seedling growth of an invasive alien legume – Leucaena leucocephala

Abstract

One impact of Alien invasive plants (AIP) on the ecosystems is allelopathy. The allelopathic activity of the aqueous extract of an AIP, Opuntia stricta on seed germination and seedling growth of Leucaena leucocephala (AIP) were studied in this research. Selection of these two AIP based control of AIP by utilization. A concentration series of 10, 25, 50, and 75 g L-1 O. stricta was tested with distilled water as the control to assess seed germination percentages, mean shoot lengths and mean root lengths of L. leucocephala. The viability of the L. leucocephala seed lots were 80%. A pot experiment was conducted to investigate the seedling growth performance of L. leucocephala. All the data were subjected to the One-way ANOVA test at p ≤ 0.05 followed by Tukey pairwise comparison using the “R” software. The highest and lowest germination percentages were recorded in control (60.0 ± 2.9) and 50 g L-1 treatment (43.3 ± 1.6) respectively after four weeks. Seed germination percentages of L. leucocephala were decreased under the different concentrations of O. stricta extract compared to the control. However, the difference was not significant (One-way ANOVA, p ≤ 0.05). The lowest mean shoot (37.6 ± 3.5 cm) and root (11.3 ± 0.3 cm) lengths of L. leucocephala were observed at 50 g L-1 concentration after 12 weeks. There was no significant difference among the shoot length of L. leucocephala plants in all treatments. There was a significant difference in the mean root length of L. leucocephala plants between 10 and 75 g L-1 treatments. The highest mean shoot (49.7 ± 1.9 cm) and root (13.5 ± 0.8 cm) lengths were observed at 75 g L-1 concentration indicating allelochemicals enhanced the seedling growth of L. leucocephala. The 75 g L-1 concentration showed a fertilizer effect by increases in the mean shoot length and mean root length of L. leucocephala. As an AIP, L. leucocephala may also possess allelopathic compounds of its own, which could interact with those of allelochemicals in O. stricta extracts and neutralized the allopathy. Therefore, the growth performance of L. leucocephala was enhanced. The findings of the study provide novel knowledge and understanding of the competitive nature of both AIP studied in relation to their allelopathy.