Allelopathic potancial of Ziziphora clinopodioides on germination indices and initial growth of Sinapis arvensis and Avena fatua

Introduction: Weeds are a serious threat to crop production because they interfere with the crop growth and development and result in significant crop losses. Weeds actually cause yield loss higher than any other pest in crop production. As a result, chemical synthetic herbicides have been widely used for weed management. Heavy usage of chemical synthetic herbicides, however, has resulted in public concerns over the impact of herbicides on human health and the environment (Xuan, et al. ۲۰۰۴). Therefore, unconventional weed control strategies, especially those based on ecological principles, are very much needed in modern agriculture. Allelopathy is considered a multi-dimensional phenomenon occurring constantly in natural and anthropogenic ecosystems, by which one organism produces bio-chemicals that influence the growth, survival, development, and reproduction of other organisms (Rice, ۱۹۸۴). Allelochemicals (chemical compounds) found in different organs of plants (leaves, flowers, stems, roots, buds and even seeds) can greatly slow or stop the germination and growth of weeds (Rezvani & Dadkhah, ۲۰۲۳). The multiple effects resulting from allelochemicals include effect on cell division, plant hormones production, membrane permeability, mineral uptake, movement of stomata, photosynthesis, respiration, specific enzyme activities and etc. (Dadkhah, ۲۰۱۲). Materials and methods: In order to study the allelopathic potential of Ziziphora clinopodioides on seed germination and seedling growth of Sinapis arvensis and Avena fatua in laboratory condition, an experiment based on completely randomized design with four replications was carried out. The experimental treatments including distilled water as control, aqueous extract concentrations of Z. clinopodioides ۱۰ and ۲۰% (w/v) were used. The aerial parts of Z. clinopodioides were collected from rangeland of Shirvan city, North Khorasan province, Iran. The foliar parts were washed with distilled water and dried in the shade at room temperature. Then the aerial parts (stem and leaves) were fine powdered (using an electrical mill). Twenty g of the powdered organ was placed in a ۲ L Erlenmeyer flask and ۱L deionized water was added. Flask was covered with aluminum foil to protect photo decomposition and placed on a rotary shaker (~۲۰۰ revolutions per min.) for ۲۴ h. The mixtures were filtered through Whatman No.۱ filter paper using a vacuum pump. The pH and electrical conductivity (EC) of extracts were determined using a digital pH meter and conductivity meter. The pH (from ۶.۷ to ۶.۰) and EC (from ۲.۲۰ to ۲.۶ mS/cm) were within the tolerance range of target plants. Data were transformed using arcsine prior to statistical analysis if needed. The data for all measured parameters were analyzed using the analysis of variance procedure of Statistical Analysis System (SAS), version ۹.۱. Means were compared by Duncan’s multiple range test at the ۰.۰۱ probability level for all comparisons. Results and Discussion: The results of experiment showed that the aqueous extracts of Z. clinopodioides inhibited the germination and seedlings growth of S. arvensis and A. fatua. The inhibitory effect was concentration-dependent. The low concentration (۱۰%) of aqueous extract of Z. clinopodioides inhibited the germination of S. arvensis and A. fatua by ۲۳.۳% and ۳۰.۴%, respectively. However, the highest concentration (۲۰%) of Z. clinopodioides inhibited the germination of S. arvensis and A. fatua by ۶۵.۱ and ۷۴.۲%, respectively than control (Table ۱). The seedlings growth of S. arvensis and A. fatua were severely inhibited at the higher concentration (۲۰%) of Z. clinopodioides extract. The low (۱۰%) and high (۲۰%) concentrations of Z. clinopodioides extract, decreased the seedling length of S. arvensis by ۳۶.۱% and ۶۴.۱%, and the seedling length of A. fatua by ۴۷.۲% and ۷۴.۵%, respectively, than control (Table ۱). However, the root length of S. arvensis decreased by ۴۲.۳% and ۷۵.۵%, and the root length of A. fatua decreased by ۴۵% and ۸۰.۷%, respectively, than control. Shoot length of S. arvensis and A. fatua seedlings were also decreased by ۳۱.۵% and ۳۸.۱% at low concentration (۱۰%) and ۵۸.۱% and ۶۹.۵% at highest aqueous extract concentration (۲۰%). Some researchers reported that allelochemicals inhibit the physiological processes that lead to reduced growth (Dadkhah, ۲۰۱۵; Jefferson & Pennacchio, ۲۰۰۳). The effects of allelopathy on germination and growth of plants may occur through various mechanisms such as reduced mitotic activity in roots and hypocotyls, suppressed hormone activity, reduced rate of nutrients uptake, reduction in permeability of cell membranes and inhibition of enzyme action (Rice, ۱۹۸۴). The stronger inhibitory effects of extract on roots might be due to the direct contact with the extract and its chemicals (Dadkhah, ۲۰۱۲). Conclusion: The results of this experiment showed that the aqueous extract of Z. clinopodioides inhibited the germination and seedlings growth of both weeds due to its phytotoxic effects. However, further studies are necessary to find out the mechanism involved in its specific recognition ability.

کلیدواژه ها:

Allelopathy ، Ziziphora clinopodioides ، Sinapis arvensis ، Avena fatua ، germination ، seedling growth ، phytotoxic effects