Changes in transcript levels in 4-week-old, short-day-grown Arabidopsis plants after further treatment for 0, 3, 6, and 9 d in extended darkness. Transcript abundance is shown for genes associated with the alternative pathways of respiration, including ETFβ (A), ETFQO (B), IVDH (C), D2HGDH (D), LKR/SDH (E), SAG12 (F), SAG13 (G), and CV (H). The y axis values represent the metabolite level relative to the wild type (WT). Data were normalized with respect to the mean response calculated for the 0-d dark-treated leaves of the wild type. Values presented are means ± se of three independent biological replicates. Asterisks indicate values that were determined by Student’s t test to be significantly different (P < 0.05) from the wild type at each time point analyzed.