EFFECTS OF AQUOUS EXTRACTS OF SUNFLOWER (HELIANTHUS ANNUUS L.) ON GERMINATION AND SEEDLING GROWTH OF THE SELECTED WHEAT (TRITICUM AESTIVUM L.) VARIETIES

Farmers generally incorporate the sunflower (Helianthus annuus L.) residue in the soil without taking into account the ill effects of sunflower allelopathy on germination and growth of subsequent crop. Since crop response to allelopathy varies with the genotype, the present study was carried out to evaluate the germination and seedling growth response of four varieties of wheat (Triticum aestivum L.) viz. MH 97, Inqalab 91, Punjab 96 and Pasban to aqueous extracts of sunflower var. Hysun 33, an allelopathic crop of family Asteraceae. In laboratory bioassays, the effect of different concentrations (5, 10 and 15% on dry weight bases) of aqueous extracts of fresh and dried leaf, stem and roots of sunflower were studied on germination and seedling growth of the selected wheat varieties. Aqueous extract of fresh stem exhibited the highest inhibitory effect on germination of wheat seeds. The highest concentration 15% of this extract significantly reduced germination of various wheat varieties by 21 - 67%. With respect to germination, Inqlab 91 was found the most tolerant to sunflower phytotoxicity followed by MH 97. Fresh stem extract significantly enhanced shoot length and/or shoot dry weight in different wheat varieties. In contrast, 15% dry leaf and fresh root extracts significantly reduced shoot length and shoot dry weight, respectively, in Inqalab 91. Study showed that sunflower extracts stimulated root dry weight in MH 97 and adversely affected this parameter in Pasban.