The utilization of chemically derived herbicides has caused many negative impacts, it
is essential to investigate some biosynthetic products, being an alternative for inhibiting weeds.
The inhibition of Leucaena leucocephala (Lamk.) de Wit. extract on plant germination and
growth is reported. Many components belonging to the allelochemical group were found in
distinctive parts’ extract of L. leucocephala, mostly detected in leaves with flavonoid 292.7 mg
QE/g extract and phenolic 397.6 mg GA/g extract. The findings proved that the extract
inhibited the plant germination and growth in various test concentrations, being the highest
point at the concentration of 20 mg/mL extract. In this condition, the inhibitory effects
regarding each parameter were 70% (seed germination), 91.46% (root length), 69.89% (stem
length), 78.73% (fresh weight), and 49.53% (dry weight). Furthermore, this study also revealed
the inhibitory concentration of 50% (IC50) of the extract on germination, starting the inhibition
at 17.40 mg/mL. The content of photosynthetic pigments and water uptake decreased gradually
after 7-day treatment, suggesting that the ethanol extract from L. leucocephala influenced these
biological processes which directly caused the plant growth inhibition.