Soluble sugar content, soluble protein content, and root activity in tissue culture seedlings of D. officinale under different light qualities. Different letters (a, b, c, d, e, f) indicate significant differences between treatments at P≤0.05 by using Duncan’s test. Vertical bars represent the standard deviation of the means (n = 10) in soluble sugar and protein, whereas the standard deviation of the means (n = 6) in root activity.