Nitrogen content in control/test barley plants and R. padi aphids (Mean ± standard deviation).

Different measures of nitrogen are presented as percentage of 15N [atom%]; abundance of 15N [δ15N ‰]; excess of 15N [µg] per plant or aphid; amount of total N [µg] per plant or aphid as well as concentration of total N [mg gDW−1] and uptake of total N [%] (% of total plant nitrogen coming from fertiliser or total aphid nitrogen coming from plant). Calculated values subtracted by the natural background label are 15N excess [µg] and total N uptake [%], therefore no values for control plants and aphids are given and rows are denoted by -.