ALLELOPATHIC ACTIVITY OF NIGHTSHADE (Solanum nigrum L.) ON SEEDLING GROWTH OF CERTAIN WEEDS AND CROPS

The allelopathic activity of nightshade, Solanum nigrum L. extract and residue on the seedling growth and chlorophyll content of certain weeds and crops was investigated. Obtained results indicated that shoot length of London rocket and root length of sowthistle were the most sensitive plants based on l50 and l90 values to the aqueous extract of nightshade, whereas wheat was the least sensitive plant. Nightshade residue was more phytotoxic to dicotyledonous plants than monocotyledonous. Moreover, wheat and onion crops have greater tolerance than londonrocket and sowthistle weeds. Addition of 2% (w/w) of dried nightshade leaves to 500 g soil severely reduced the seedling length and dry weight of sowthistle seedling by 21.6 and 16.8% of the control, respectively beside occurrence of complete inhibition (100%) for sowthistle growth at a higher rates (4 and 8%, w/w). Also, chlorophyll a and b contents in the dicotyledonous plants were decreased with increasing the residue, in contrast to the monocotyledonous plants which were not affected. Allelochemicals in nightshade leaves were identified as alkaloids such as atropine, hyoscine and solanine in addition to capric, myristic, palmitic and oleic fatty acids. These results suggest that nightshade may have allelopathic activity and that alkaloids and fatty acids may be responsible for the growth reduction or inhibition in the affected plants.