OICC Press Journal of Rangeland Science 2423-642X 15 4 2025 09 14 Exploring the allelopathic impact of leaf extracts from three desert flora on roman chamomile (Chamaemelum nobile L. (All.)) under three experimental conditions 1 10 10.57647/j.jrs.2025.1504.40 EN Ahmad Sadeghipour Department of Range management, Faculty of Desert Studies, Semnan University, Semnan, Iran Davoud Kartoolinejad Department of Forestry, Faculty of Desert Studies, Semnan University, Semnan, Iran Journal Article 2025 09 14 This study aimed to assess the allelopathic effects of leaf extracts from Prosopis juliflora (an invasive species), Acacia nilotica, and Ziziphus spina-christi (native species) on seed germination and seedling growth of Chamaemelum nobile (L) All. (Roman chamomile) under three vegetative conditions (laboratory, greenhouse, and field). The germination percentage, germination rate, and seedling growth of Roman chamomile were evaluated under both laboratory and greenhouse conditions. In the laboratory, the effects of various concentrations of leaf powder (30%, 50%, and 100%) were assessed, with distilled water used as the control. During the greenhouse stage, different litter-to-sand ratios (1:15, 1:10, and 1:5) were utilized for evaluation. The study was conducted using a completely randomized design with four replications. Field experiment was performed utilizing a randomized systematic design, in which 10 randomly selected seedlings of each species were planted at distances of 0, 1, and 2 m from selected trees. The results indicated that leaf extracts of P. juliflora, A. nilotica, and Z. spina-christi reduced the germination percentage, radicle length, and plumule length of Roman chamomile across all concentrations compared to the control. Moreover, an increase in leaf extract concentrations led to a decrease in germination percentage, germinationrate, radicle length, and plumule length. P. juliflora's leaf extract exhibited a more pronounced impact on all variables compared to the other species. In this context, the treatment with 100% leaf extract of P. juliflora yielded the lowest percentage of germination (24%), the lowest germination rate (3 seeds per day), the shortest plumule length (0 mm), and the shortest radicle length (3.5 mm) for Roman chamomile. In the greenhouse treatment, the litter-to-sand ratio significantly influenced the germination and radicle length of Roman chamomile, with all variables showing an increase with higher sand proportions relative to leaves. The highest allelopathic effects were observed in the P. juliflora leaf extract mixed with sand. These findings were supported by the results of field treatments. The field study confirmed the results of the experiments conducted in both laboratory and greenhouse. Additionally, the frequency of Roman chamomile was found to increase as the distance from A. nilotica and P. juliflora increased, suggesting an influence over the plant's spread. Conversely, Z. spina-christi exhibited a different behavior, indicating its supportive role in enhancing the presence of Roman chamomile in natural settings. Regarding the significant medicinal value of Roman chamomile in Iran, along with the allelopathic impact of A. nilotica and P. juliflora on other plants, it is advisable to prioritize the cultivation of species like Z. spina-christi which are better adapted to local soil and climate conditions.