Quantitative and qualitative performance of globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori) influenced by plant density and weed competition

To investigate the effect of planting density on quantitative and qualitative characteristics of globe artichoke (Cynara cardunculus L. var. Scolymus (L.) Fiori) under weedy and weed-free conditions, a field experiment was conducted at Tarbiat Modares University, Tehran in 2016 growing season. A factorial arrangement of the experimental treatments was studied in a randomized complete block design with three replications. The factors included four crop planting densities (2, 4, 6 and 8 plants m-2) under two conditions of presence and absence of weeds. Different traits including leaf number per plant, leaf area index, total dry weight, chlorophylls a, b and total chlorophyll, caffeic acid, chlorogenic acid and total polyphenol contents were measured. The results showed that leaf number and dry weight were significantly affected by plant density and weed competition in artichoke, so that the weed competition reduced the artichoke dry weight by 22.4%. The highest leaf area index (2.29) and dry weight of artichoke (253.44 g m-2) were observed at 6 plants m-2, while the highest number of leaves per plant (16.33) belonged to the density of 2 plants m-2. Among qualitative traits chlorophylls a, b and total chlorophyll were only affected by weed presence while caffeic acid, chlorogenic acid and total polyphenol contents were only affected by plant density. The effect of crop plant density on weed leaf area and dry weight was also significant. Overall, the highest performance of the main secondary metabolites in artichoke including caffeic acid, chlorogenic acid and total polyphenol (5.99, 9.55 and 5.89 g m-2, respectively) were obtained at 6 plants m-2, completely affected by crop dry matter yield.