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Density-Dependent Interactions Between Zinnia (Zinnia elegans J.) and Red-Root Amaranth (Amaranthus retroflexus) in Ornamental Planting Systems
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Ammar Maan Abdulameer Mudhafar Ammar Maan Abdulameer Mudhafar   , Marjan Diyanat * , Sepideh Kalatejari |
| Associate Professor of Department of Agricultural Sciences and Food Industries, Science and Research Branch, Islamic Azad University, Tehran, Iran |
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Abstract: (15 Views) |
One of the challenges currently faced by officials in green space management is the proliferation of weeds in parks, particularly in gardens where ornamental plants, such as flowers, are cultivated. To investigate the impact of red-root amaranth (Amaranthus retroflexus) on zinnia (Zinnia elegans), an experiment was conducted in 2023 using a randomized complete block design in the greenhouse of the Tehran Agriculture and Natural Resources Campus (Karaj). The study evaluated different density ratios of zinnia and red-root amaranth, specifically 4:0, 1:3, 2:2, 3:1, and 0:4 in each pot. The results showed that all observed traits of zinnia flowers were significantly influenced by the density ratio of red-root amaranth and zinnia. Notably, the flower diameter of zinnia decreased compared to the control treatment (4:0 ratio) 120 days after planting. The reductions observed were 13%, 16%, and 22% for the density ratios of 75% zinnia and 25% red-root amaranth, 50% zinnia and 50% red-root amaranth, and 25% zinnia and 75% red-root amaranth, respectively. The Relative Crowding Coefficient (RCC) of red-root amaranth was slightly lower than that of zinnia at density ratios of 25% and 50%, indicating that both species exhibited similar competitive interactions under these conditions. However, at a density ratio of 75%, red-root amaranth demonstrated a stronger competitive ability. Light availability was identified as the most critical factor contributing to competition in this system. The dominance of red-root amaranth at higher density ratios underscores its competitive advantage in terms of height and canopy expansion. These results suggest that effective weed management strategies are crucial in ornamental plant cultivation to minimize competition and maintain the aesthetic and ecological value of green spaces. Targeted control measures, such as reducing red-root amaranth density, could help mitigate its adverse effects on ornamental plants like zinnia.
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| Keywords: Competition, relative crowding factor, relative performance, flower fresh weight |
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Type of Study: Research |
Subject:
General
Received: 2024/08/13 | Accepted: 2026/08/10 | Published: 2026/09/9
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