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Allelopathic Effect of Italian Cocklebur on Sugar Beet
Published December 6, 2005
74-77

Cockleburs are noxious weeds in Hungary, where they are widespread in row crops, especially in maize, sunflower and sugarbeet. A low density population of these weeds may be harmful because of their large competitive ability, fast growth in early phenological stages, allelopathy, and persistant sprouting.
Allelopathy of Xanthium italicum Mor.... was examined during the growing season in 2004. Root and shoot samples were collected at 4 or 5 leaves stage (in the end of May and in the beginning of June) and before flowering (in the beginning of July) before and after rain. Extracts were made in tap water. The test plant was Beta vulgaris L.; its germination, root and shoot growth were evaluated at the 6th and 10th days after treatment.
Most of extracts inhibited the germination of sugar beet. In these experiments the phenological stage of the donor plant determined slightly the effectiveness of the extracts on sugar beet. Generally, significant differences existed between treatments only in cases of concentrated extracts.
Rainfall can modify the inhibitory effect of extracts (especially shoot extracts). Shoot extracts of young plants inhibited stronger germination and growth after rain than before rain. Density of cockleburs influenced the effect of extracts, as well. Generally, differences between the efficacy of extracts was larger after rain.
The results supported the hypothesis that the phenological stage and some environmental factors can modify allelopathy of cockleburs.

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Effect of Water and Nutrient Supply on the Allelopathy of Abutilon theophrasti Medic. and Xanthium italicum Mor
Published May 11, 2003
102-105

Velvetleaf (Abutilon theophrasti Medic.) and Cocklebur species (Xanthium spp.) are more and more dangerous and „difficult to control” weeds in several cultivated plants. The ground cover of these species have became larger in Hungary like other warm-philous species. There are several causes of danger of them, for example: large capability f...or competition, allelopathic effect, keeping on of emergence.
The allelopathic effect of these weeds were examined on sugarbeet (Beta vulgaris L.). Extracts of plants grown under different conditions have several effect on this species.
Abutilon theophrasti plants were grown in perlite to examine the effect of supplying with nutritive materials on production of inhibitors. The water soluble exudates of the shoots grown with no artificial fertilisers inhibit stronger than grown with them. Acid soluble exudates have contrary effect. The exudates made of roots inhibited the sugarbeet less than shoots.
Effect of drought stress on production of inhibitors was examined on Abutilon theophrasti and on Xanthium italicum. The species responded to missing of water different, and the water, acid and basic soluble exudates had different effect, as well.

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