In vitro cultivation of S. tuberosum plants under different illumination sources: A) Average length of the longest root during the first two weeks after replanting of plant shoots to magenta boxes. The roots became too dense for further measurement after this period. B) Total shoot length. C) Average number of leaves per plant. A-C Plots are based on data from one of two biological replicates. 12 plants were used per treatment. Error bars represent SD. Asterisks indicate statistically significant differences compared to plants grown under fluorescent lights (*P < 0.05; **P < 0.01, two tailed Student’s t-test).