Allelopathic Responses of Crop Species to Chromolaena odorata Root Exudate Extracts: A Comprehensive Study

Abstract

This study investigates the allelopathic effects of root exudate extracts from Chromolaena odorata on the germination and growth of six crop species. The results reveal variable sensitivity among the species, with the control treatment consistently exhibiting superior germination percentages. Initially, some species, including Abelmoschus esculentus (okra), Solanum lycopersicum (tomato), and Cicer arietinum (chickpea), experienced a substantial decline in germination, indicating a potential inhibitory effect of the exudates, although partial recovery was observed in subsequent treatments. Phaseolus vulgaris (common bean) displayed a moderate decrease, while Zea mays (corn) exhibited the most significant drop in germination rates, albeit with slight recovery at higher concentrations of exudates. Conversely, Cucumis sativus (cucumber) appeared least affected by the exudates. Moreover, all species demonstrated reductions in shoot and root lengths with increasing concentrations of exudates. Chlorophyll content analysis revealed a significant reduction across most treatments, highlighting concerns regarding photosynthetic efficiency and overall plant health. The species-specific response to root exudates suggests varying metabolic or adaptive mechanisms among crops. Additionally, malondialdehyde (MDA) levels, indicative of oxidative stress, varied among species, with A. esculentus and P. vulgaris showing a dose-dependent increase, while S. lycopersicum displayed a peak at intermediate treatment levels. Z. mays exhibited marginal elevation in MDA content, potentially indicating the presence of protective compounds within the exudates. Conversely, C. arietinum and C. sativus showed a steady increase in MDA, suggesting limited mitigation of allelopathic effects. These findings feature the complexity of allelopathic interactions and highlight the need for further research into active compounds and their modes of action to develop sustainable weed management strategies while safeguarding crop health. Understanding these dynamics is crucial for maximizing the potential benefits of allelopathy in agriculture.