Photosynthetic development of anaerobically grown rice (Oryza sativa) after exposure to air

During anaerobic germination, rice produces a coleoptile devoid of carotenoid and chlorophyll. Further development and greening of the shoot occur upon exposure of the seedlings to air. In this study, a comparison was made between anaerobically (N2) germinated rice, greened upon exposure to air, and air/dark (A/D) germinated seedlings, greened upon exposure to light. After exposure to air, N2-grown seedlings had a 76-hour lag before net oxygen evolution occurred compared to a 6-hour lag for A/D-grown seedlings. After 98 h of greening, N2-grown seedlings reached a rate of oxygen evolution equivalent to that of A/D-grown seedlings after 24 hours. Chlorophyll and carotenoid content showed a similar lag, but did not reach the level found in A/D-grown seedlings even after 124 hours of exposure to air. RuBPcase activity also lagged in N2-grown seedlings, ultimately reaching greater values than in the 'greened' A/D-grown seedlings. Phosphoenolpyruvate carboxylase activity was constant and low in all treatments except for a transient increase after 24 hours of greening of the N2-grown seedlings.