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• The Effect of Zanthium Extracts on Germination in Relation to Interior and Exterior Factors

  65-69

  István Dávid

  Views:

  83

  In Hungary, the cocklebur species significantly endanger row crops (i.e. corn, sunflower, sugar beet). Their fast spreading is caused by many reasons: long-lasting emergence, reduced sensitivity to many kinds of herbicides, vigorous competitional ability, allelopathy, fast initial growth and changes in climate. The means of allelopathy is used by many species of plants in the competition with one another, as well as by the cockleburs. But the efficiency of this is influenced by many factors. Species with allelopathical effect could show different behaviour under different conditions: they can produce compounds with retarding and stimulating effects in different quantities or compositions. The actual condition of the acceptor plant and the mediator agent (i.e. soil) influence the final effect.
  In this experiment influence of phenology and rainfall was studied on allelopathy of cockleburs in May, July and September. A stronger inhibition was observed on growth of cress before rain in July than in May, but this retarding effect disappeared after rainfall. However, the samples collected in September have significant inhibitory effect after rain. Inhibition of sugarbeet’s germination was stronger in May than in July, and the difference increased after rain.

• Effect of Water and Nutrient Supply on the Allelopathy of Abutilon theophrasti Medic. and Xanthium italicum Mor

  102-105

  István Dávid

  Views:

  70

  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 for 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.