Qualitative and quantitative response of artichoke to irrigation treatments and planting densities.

• Polyphenol, Caffeic and chlorogenic yield were increased by plant density. • Drought resulted in a decrease in polyphenol, caffeic and chlorogenic yields. • Caffeic and chlorogenic yields were completely influenced by dry matter yield. To study the effects of water stress and plant density on the qualitative and quantitative characteristics of artichoke (Cynara cardunculus var. scolymus), a two-year field experiment was carried out in a semi-arid region in 2016 and 2017. The experimental treatments were arranged as split-plot in a randomized complete block design with three replications. The main plots were three irrigation treatments of 40, 60 and 80% field capacity and sub-plots consisted of four planting densities of 2, 4, 6 and 8 plant m−2. The results showed leaf area, dry matter, and chlorophyll (a, b, and total) concentration decreased by water deficit stress, whereas proline concentration was increased by water deficit stress. Dry matter and LAI were significantly affected by plant density, so that the highest dry matter and LAI in all irrigation treatments were observed at the populations of 6 plants m−2. An increase of plant density decreased concentrations of chlorophyll a and b and total chlorophyll in artichoke leaves. The various irrigation treatments and plant densities influenced total polyphenol and yields of caffeic and chlorogenic acids. Among irrigation treatments, the highest yield of caffeic acid, chlorogenic acid and total polyphenol (5.14, 8.24, and 5.01 g m−2, respectively) belonged to the non-stressed control. In addition, the highest yield of caffeic acid, chlorogenic acids and total polyphenol (5.90, 9.38, and 5.60 g m−2, respectively) were observed at the population of 6 plants m−2. For both of these factors, the yields of these compounds were completely affected by dry matter yield. [ABSTRACT FROM AUTHOR]