Investigation of allelopathic effects of barnyardgrass (Echinochloa cruss- galli L.) weed on some anatomical triats of rice (Oryza sativa L.) Tarommahalli variety of Iran at flowering and grain ripening stages

Rice (Oryza sativa L.) and Barnyardgrass (Echinochloa crus- galli L.) are annual plants and belong to Gramineae. Barnyardgrass is the most important weeds of rice paddies in Iran and the world. In this study, the effects of barnyardgrass allelopathy on anatomical characteristics of rice (Tarommahalli) at flowering and grain-ripening stages were investigated. Experiment were conducted to evaluate the effects of aqueous extracts obtained from root and shoot of barnyardgrass at 50% and 100% concentrations on anatomy traits of rice. The results of treatments with aqueous extracts of root of barnyardgrass at 100% concentration at both flowering and grain ripening stages showed an increase in number and size of silica grains on epidermal cells of stem and lower layer of leaf and well as increased size of stomata files. The cross-section of the rice stem showed that the number and size of silica knobs on its surface and also size of vascular bundles have increased. Rice treated with aqueous extracts of root from barnyardgrass indicated that as silica on the leaf and stem of rice increased, stem elongation was augmented and production yield also increased. Moreover, the treatment caused resistance to stem borer (Chilo suppressalis) and stem strength against lodging (stem stooping by wind and rain) occurred. The results revealed that the aqueous root extracts from barnyardgrass had positive effects on number and size of silica grains and silica knobs of leaf and stem which resulted in higher resistance and strength of rice stems leading to higher production yields of rice.