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:: Volume 13, Issue 1 (2-2012) ::
علوم زراعی 2012, 13(1): 32-48 Back to browse issues page
Effect of the timing of emergence of seedling on morphological characteristics and seed production of redroot pigweed (Amaranthus retroflexus L.) in competition with sunflower (Helianthus annus L.)
Abstract:   (1770 Views)
To investigate the morphological and structural changes of Redroot pigweed (Amaranthus retroflexus L.) in competition with sunflower (Helianthus annus L.) under different timing of seedling emergence, a field experiment was conducted in , Weed Research Department, Iranian Research Institute of Plant Protection in 2008 using Randomized Complete Block Design with three replications. Experimental treatments included five times of emergence for redroot pigweed (with 0, 2, 4, 6, and 8 weeks after sunflower emergence) planted at a density of eight plants per meter of row length. Lateral branch number and length, leaf area in different canopy layers, leaf, stem and head dry mater weights, seed per plant in redroot pigweed and sunflower yield were measured at the end of the growing season. Results indicated that redroot pigweed leaf area number of lateral branches, branches length, leaf, stem, and head weight significantly decreased with delay- in redroot pigweed emergence. Delayed seedling emergence in redroot pigweed (> 4 weeks after sunflower emergence) lost lateral branches and had more leaf area to upper layers of canopy. Increasing the redroot pigweed leaf area index (up to 0.08) and dry matter (up to 10 g.plant-1) increased the seed number.plant-1 up to 4 to 5 folds. Stem and leaf partitioning coefficient, did not vary over all of emergence times for redroot pigweed, but seed partitioning coefficient decreased with delaying seedling emergence. However, the seed yield of sunflower did not decrease in competition with redroot pigweed. In conclusion, weed control in early season (two weeks after sunflower emergence) is suggested to avoid enrichment of redroot pigweed seed bank in the field.
Keywords: Dry matter, LAI, Redroot pigweed, Sunflower, and Timing of seedling emergence.
Full-Text [PDF 297 kb]   (323 Downloads)    
Type of Study: Scientific & Research | Subject: Special
Received: 2015/02/17 | Accepted: 2015/02/17 | Published: 2015/02/17
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Effect of the timing of emergence of seedling on morphological characteristics and seed production of redroot pigweed (Amaranthus retroflexus L.) in competition with sunflower (Helianthus annus L.). علوم زراعی. 2012; 13 (1) :32-48
URL: http://agrobreedjournal.ir/article-1-140-en.html


Volume 13, Issue 1 (2-2012) Back to browse issues page
مجله علوم زراعی ایران Iranian Journal of Crop Sciences
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