Allelopathic effects of umbrella sedge (Cyperus difformis L.) weed on tillering, flowering and grain ripening stages of rice (Oryza sativa L. cv. Tarom mahalli)

Rice is an important crop and main food of more than half of the word and Umbrella sedge is one of the weeds growing in the rice paddies at North provinces of Iran. An experiment was set up in order to investigate the allopathic effects of aqueous extracts 50 % and 100 % of roots and shoots of umbrella sedge on tillering, flowering and grain ripening stages of rice. Experiment based on completely randomized in a factorial design with three replications was conducted in 2011 at the Rice Research Institute of Iran, Amol. The results showed that at tillering stage, with aqueous extract 100 % of umbrella sedge shoot was shoot fresh weight of rice 68.71g and its root dry weight 4.26g that compared to control plant (respectively 85.59g and 7.48g) decreased. At the flowering stage the fresh weights of root and leaf and dry weights of root, stem and leaf of rice were decreased by extracts of umbrella sedge and the fresh and dry weights of cluster increased. At grain ripening stage, extracts of umbrella sedge reduced the fresh and dry weights of rice and the weight of brown and white rice increased by 50 % root aqueous extracts. At this stage the percent of amylose, protein and lipid by all aqueous extracts significantly increased (P≤0.05) and control was 18.3, 7.705 and 0.505 % respective. The overall results showed that the aqueous extracts of umbrella sedge had different effects on triple stages of rice that depended on growth stages and the kind of organs.