ALLELOPATHIC EFFECTS OF HERBACEOUS AND WOODY PLANT SPECIES ON SEED GERMINATION AND SEEDLING GROWTH OF WHEAT

A laboratory experiment conducted at the agricultural research institute, dera ismail khan during 2011 investigated the allelopathic effects of water extracts from the leaves of eucalyptus camaldulensis, acacia nilotica, helianthus annuus and parthenium hysterophorus on 20 different wheat varieties. results revealed significant effects of the aqueous extracts from leaves upon the seed germination of all the investigated wheat varieties. the maximum number of days to germination (13.7 and 13.3) was recorded for the untreated control treatments and h. annuus followed by e. camaldulensis, p. hysterophorus and a. nilotica extracts. among wheat varieties, the maximum days to germination (13.9) were recorded for meraj-2006 while the minimum days to germination (11.4) were noted for khirman variety. aqueous extracts reduced all growth parameters (shoot length, root length, fresh and dry weight of shoot, fresh and dry weight of root). the variable performance among the wheat varieties found during the experiment indicates that some varieties had tolerance against the allelochemicals. in general, hashim-8 variety was more resistant while moomal-2002 and saleem-2000 were both susceptible. based on this investigation, it can be suggested that the tested plant species may hinder both seed germination and seedling growth of wheat varieties; however, some wheat varieties may show resistance to the allelochemicals that may be released by the test plant species.