Carbohydrate contents in leaves of adk1−/adk1− Arabidopsis plants. Diurnal changes in Suc (A, B, and C) and starch (D, E, and F) contents in leaves of 2-week-old plants growing under different growth regimes (A and D, photoperiod 16/8; B and E, continuous light; and C and F, continuous darkness). At each time point, samples were taken from mature source leaves, and the data represent the mean ± se of measurements from four to six plants per genotype. Black squares, Col-0; white circles, adk1−/adk1−. Asterisk indicates values determined by the Student's t test to be significantly different (P < 0.05) from the control.