Kenaf extract affects germination and post-germination development of weed, grass and vegetable seeds

Abstract

Metabolites produced by one organism can affect development of other organisms. Kenaf ( Hibiscus cannabinus L.) is used in products which put it in direct contact with other plants. This project was designed to determine whether kenaf plant extracts can affect germination and development of vegetable, grass and weed seeds. Frost-killed kenaf was chipped and either immediately frozen (weathered 0 months) or applied to the soil in mats in December and allowed to weather for 2 or 4 months. Kenaf samples, weathered from 0 to 4 months, were ground and soluble materials were extracted with distilled water. Seeds of cucumber ( Cucumis sativus L.), green bean ( Phaseolus vulgaris L.), tomato ( Lycopersicon esculentum Mill.), redroot pigweed ( Amaranthus retroflexus L.) and annual Italian ryegrass ( Lolium multiflorum Lam.) were exposed to 0, 16.7, 33.3, and 66.7 g/l of kenaf extract. Distilled water and three concentrations of polyethylene glycol (PEG) were included as controls. After 7 days, total germination and hypocotyl and radicle lengths were determined. Extracts of kenaf weathered up to 4 months, especially at the highest concentration, reduced germination in pigweed by 50–70%. Germination in tomato and ryegrass was reduced by 30% when exposed to the highest concentration of unweathered kenaf. As length of time of weathering of kenaf increased, germination and length of most plants increased. This suggests that, over time, the detrimental compounds in kenaf were leached or otherwise changed so that they had no effect or became beneficial. Non-weathered kenaf or its extracts, may be employed to suppress weeds. Alternatively, weathered kenaf tissue or extracts may stimulate germination and post-germination development of existing economic crops.