ABSTRACT
Complex interactions of factors are involved in the colonization and establishment of aquatic plants. Allelopathic interactions among plants involve substances elaborated by macrophytes, algae, and bacteria whose influence in aquatic environments is largely unknwon. The second category of chemical interactions — those between plants and substances produced by the action of physical processes on natural material — has long been a subject of active research by agriculturists. The search for naturally produced chemical substances as control agents for aquatic weeds has been a very short one. The effects of sediments should not be overlooked in mixed algal assays or in the bioassays that are used for screening for natural products. In mixed cultures, C. reinhardi eliminated the second fresh-water alga within 3 to 5 days, depending upon the light intensity and nitrogen source. Control plants had an average increase of 20% or more growth, while destroyed so that the continued production of bacterial secretions would not produce artifactual material.
