Cytochromes of mitochondria from rice seedlings germinated under water and their changes during air adaptation

Rice seeds were germinated for up to 5 days under water (submerged) and some for another day in air (air-adapted). Control seeds were germinated for 6 days throughout in air. Low-temperature difference spectra of shoot mitochondria were compared among these three types of seedlings. All cytochromes found in the aerobic seedlings were present in the submerged seedlings. However, there were some differences in the cytochromes b₅₅₃ and c of these two types of seedlings. The cytochrome aa₃ peak height and cytochrome oxidase activity per mitochondrial protein increased 1.6- and 2.8-fold, respectively, during air adaptation. Slightly higher concentrations of the b-type cytochromes than found in air-adapted mitochondria were already present in submerged mitochondria. The computed difference between the dithionite-reduced difference spectra of mitochondria from submerged seedlings before and after air adaptation, showed that cytochromes aa₃ and c had increased more than cytochrome b₅₅₇ during air adaptation.