Selective Influence of Chromolaena odorata Extracts on the Germination and Growth of Vegetable Crops: A Comparative Study of Aqueous and Methanolic Solutions

Abstract

This study conducted a thorough assessment of how germination and growth of shoots and roots in eight vegetable crops are influenced by aqueous and methanolic extracts from Chromolaena odorata. Findings reveal a broad spectrum of germination responses to leaf extracts (13.3% to 86.7%), signaling the intricate dynamics at play between the plant's chemical compounds and the germination mechanism. Notably, Cucumis sativus (70% at AQE 5%) and Phaseolus vulgaris (56.70% at AQE 10%), displayed remarkable resilience and even stimulation of germination under specific extract concentrations, suggesting a potential selective stimulatory effect. For root extracts, the introduction of AQE and MTE decreased germination percentages across crops. A. esculentus had the highest germination rate at AQE 20%, significantly lower than the control (60%). Solanum. melongena tolerated AQE 5% best, while MTE 20% was most inhibitory. Conversely, Solanum lycopersicum experienced complete germination inhibition in both AQE and MTE of leaf and root extracts, indicating species-specific vulnerability to the allelopathic compounds within the extracts. Shoot growth mostly declined with higher extract concentrations, except in Solanum melongena, Capsicum annuum, and Zea mays, which saw increased shoot lengths under certain conditions. Root growth responses were mixed; Abelmoschus esculentus and Zea mays showed growth increases at some concentrations, in contrast to Cucumis sativus and Solanum melongena, which had limited growth. Methanolic extracts had a stronger inhibitory effect, likely due to their potent bioactive compounds. These findings highlight the importance of extract type, concentration, and crop species in weed management, providing insights for sustainable agricultural practices.