ALLELOPATHIC EFFECTS OF AQUEOUS EXTRACT OF PHRAGMITES AUSTRALIS ON GERMINATION AND GROWTH OF BRASSICA NIGRA

Abstract

Brassica nigra was most negatively affected by the allelopathic effects of Phragmites australis aqueous extracts, especially at higher extract concentrations. Higher quantities, particularly of stem extracts, consistently hindered biomass production, root and shoot elongation, and germination, while low doses of leaf extracts marginally promoted germination and growth parameters. Furthermore, biochemical tests showed that whereas leaf extracts at lower concentrations encouraged the formation of flavonoids, high concentrations of stem extracts decreased levels of chlorophyll, carotenoids, and IAA, suggesting stress and repression of metabolic activities. These results support the idea that allelopathy is a mechanism for the invasive success of P. australis, as demonstrated by the considerable inhibitory (phytotoxic) impact of leaf and stem extracts on the germination, growth, and physiological characteristics of nearby plants. Allelochemicals from P. australis had a detrimental overall effect on B. nigra, particularly at higher extract concentrations, underscoring the invasive species' potential danger to agricultural production and plant community structure.