Table I. Pigment contents and chlorophyll fluorescence parameters in wild-type and orrm6 mutant plants

Chlorophyll was extracted and determined as described by Wellburn (1994). Measurements of chlorophyll fluorescence parameters were performed with the IMAGING-PAM M-Series chlorophyll fluorescence system (Heinz Waltz) on dark-adapted plants. For NPQ, qE, and qI measurements, an actinic light treatment (531 μmol photons m−2 s−1) was performed for 715 s. After termination of actinic light, recovery of Fm′ was monitored for 14 min. Data are presented as means ± se (n = 5 for pigment contents and n = 4 for chlorophyll fluorescence parameters). Asterisks indicate significant differences between the mutant and the wild type (Student’s t test: *, P < 0.05; **, P < 0.01; and ***, P < 0.001). Plants used for pigment extraction and chlorophyll fluorescence analysis were grown on a 12-h-light/12-h-dark photoperiod with an irradiance of 150 μmol photons m−2 s−1 during the light period.

ParameterWild Typeorrm6-1orrm6-2
Chlorophyll a (mg g−1 fresh weight)1.097 ± 0.0160.944 ± 0.024***1.022 ± 0.010**
Chlorophyll b (mg g−1 fresh weight)0.263 ± 0.0040.241 ± 0.007*0.255 ± 0.004
Total chlorophyll (mg g−1 fresh weight)1.360 ± 0.0201.184 ± 0.031**1.277 ± 0.014*
Chlorophyll a/b4.179 ± 0.0313.922 ± 0.029***4.004 ± 0.026**
Fv/Fm0.827 ± 0.0040.598 ± 0.013***0.538 ± 0.003***
NPQ2.263 ± 0.1171.099 ± 0.043***1.325 ± 0.085***
qE1.861 ± 0.0900.676 ± 0.055***0.920 ± 0.092***
qI0.402 ± 0.0290.423 ± 0.0220.405 ± 0.014