hrvatski

Učinak ekstrakata uspolđa ploda crnog oraha (Juglans nigra L.) na različite biljne vrste

It is known that black walnut (Juglans nigra L.) actively secretes various allelochemicals that may negatively affect germination, growth and development of other plant species. However, mechanisms of allelochemical’s action at physiological levels are poorly explored. The aim of this study was to investigate allelopathic effect of aqueous extract (10% and 20%, w/v) of black walnut pericarp on tomato (Lycopersicon esculentum L.), chicory (Cichorium intybus L.) and wheat (Triticum aestivum L.). To determine allelopathic effect on germination and growth of seedlings, seeds were exposed to extract for six days, after which rate of germination and length of roots and shoots of seedlings were measured . In the second part of the experiment in four weeks old plants that were exposed to extract for seven days the efficiency of photosynthesis using chlorophyll a fluorescence and in vivo as well as activity of antioxidant enzyme guaiacol peroxidase were determined. Exposure to higher concentrations (20% w/v) of extract significantly lowered the rate of germination of seeds of all species examined, and reduced growth of roots and shoots of wheat and tomato, especially chicory. Exposure to lower concentrations (10% w/v) of extract reduced the rate of germination of tomato and chicory seeds and reduced root growth of all species, especially tomato while reduced shoot growth was observed in tomato and wheat. Optimum yield of photosynthesis and rate of electron transfer were significantly decreased in all plants growing in the 20% solution of extract while at lower concentration of extract rate of electron transfer was lower only in tomato. Increase in guaiacol peroxidase activity observed in the shoots of chicory and tomato exposed to extract and in the roots of wheat and chicory at a higher concentration of extract as well as increased activity of individual isoforms in tomato roots exposed to higher concentration of extract indicate the occurrence of oxidative stress. From the results obtained it can be concluded that the extract of black walnut pericarp had a negative impact on seed germination and seedling growth, but also on the process of photosynthesis in all species examined, and that it can be due to oxidative stress.

alelopatija ; fotosinteza ; klijanje ; oksidativni stres

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