Leaf yields and concentrations of polyphenolic compounds in artichoke (<em>Cynara cardunculus</em> L.) affected by different row spacing and plant densities

Abstract

In Germany the artichoke (Cynara carduncuclus L., family Asteraceae) is used as leaf plant to produce extracts for dietary and medicinal applications. The quality of the leaves is characterized by caffeoylquinic acids (CQA) derived from derivatization of caffeoyl acid and quinic acid which should reach at least 2% of leaf DM. The leaf yields as well as the CQA compounds accumulated in the leaves can be affected by the growing conditions of the crop. For that reason two factorial field experiments with artichoke (cv. Green Globe) were carried out in 2001 to 2003 on sandy soils to study the effect of different row spacing and plant densities on leaf yield and polyphenolic compounds in the leaves. The leaves were harvested three times per year. Maximal leaf yields were observed with first harvest (in 2001) or with second harvest (in 2002 and 2003). In comparison with low plant densities (2 – 4 plants m^-2) the elevated plant densities of 8 to 12 plants m^-2 led to highest leaf yields. Contrary to that no clear effect on leaf yield were obtained by changing the row spacing. The concentration of polyphenolic compounds (CQA, flavonoids) in the leaves are significantly influenced by harvest time but hardly by changing the row spacing and plant density. In all three experiments maximal content of polyphenolic compounds were found in leaves harvested after the first growing phase of the plants which can be due to the later plant development and higher UV light uptake by the leaves.