Abstract

The present study was conducted to investigate the phytotixic effects of aqueous extracts of dry and fresh leaf, stem and inflorescence of sunflower (Helianthus annuus L.) var. Hysun 33against germination and early seedling growth of four varieties of rice, namly Basmati Pak, Basmati Supper, Basmati 385 and IRRI-fine. Extracts of all the three parts of sunflower showed toxicity against germination and seedling growth of different rice varieties. Leaf extract exhibited the highest toxicity against germination followed by root and stem extracts, respectively. With respect to seed germination, rice varieties Basmati 385 and IRRI Fine were more resistant against various types of sunflower extracts while Basmati Pak was found to be the most susceptible one. None of the extract exhibited any significant effect on shoot length of Basmati supper and IRRI Fine. Root growth in Basmati 385 showed the most susceptible response to sunflower extracts toxicity followed by Basmati supper and Basmati Pak, respectively. Results of the present study suggest that rice variety IRRI Fine is the most tolerant to sunflower phytotoxicity followed by Basmati supper and thus may be suitable for cultivation under sunflower allelopathic stress. Basmati 385 showed highly tolerant germination behaviour and can be sown for raising of rice nursery under allelopathic stress of sunflower.

Key words: Helianthus annuus, phytotoxicity, rice varieties, sunflower.