Allelopathic Effects of Vachellia nubica, Vachellia tortilis and Hyphaene compressa on Germination and Seedling Growth of Prosopis juliflora

Background: Prosopis juliflora (Sw.) DC is an invasive species negatively impacting plant ecology and livelihoods in introduced areas. Native tree species may produce allelochemicals that can inhibit growth of invasive species, resulting in a natural management technique.

Aim: This study aimed to determine allelopathic effect of three native tree species (V. tortilis, V. nubica, and H. compressa) on seed germination and early seedling growth of P. juliflora to identify the tree species that can be used to suppress P. juliflora invasion as part of its management strategy.

Methodology: Crude Leaf and root extracts of the native trees at 0%, 1%, 2.5%, 5%, and 10% concentrations were prepared. P. juliflora seeds were subjected to 24 crude extract treatments and a control in a completely randomized design in Petri dishes. The seeds were uniformly moistened with 10 ml extracts daily in a germination chamber for 14 days, and germination counts were done after every 2 days. Shoot and root length and wet weight were measured after 14 days. The data were subjected to three-way ANOVA and means separated by Tukey.

Results: Prosopis seed coats treated with V. tortilis and V. nubica leaf extracts turned darkish before germination while germination of seeds in 10% leaf extracts of V. nubica aborted. Seed germination percentage in 10% leaf extracts of V. tortilis (30%) and V. nubica (23%) were the lowest compared to control (90%). P. juliflora seedlings under 5% V. nubica and 10% V. tortilis died before the experiment period. Depending on crude extract concentrations, percent inhibition on germination characteristics were; percent germination (21-74%), wet weight (6-49%), plumule length (10-47%), and radicle length (7-86%) of germinating P. juliflora.

Conclusion: The native tree species studied have allelopathic effects on the germination of P. juliflora and thus can be promoted to suppress invasiveness of P. juliflora.