Rice seedlings germinated in water with normal and impeded environmental gas exchange.
Rice cv. Hokkaido-Carny was germinated in distilled water with or without impedance of surface O2 exchange by a 0.3-, 1.0- or 10-mm film of olive oil or a 10-mm film of liquid paraffin. The thick layer of olive oil reduced the O2 tension in the water after 14 days from 5.54-5.65 to 1.21-1.73 cm3/l in treatments where seeds were present; most seedlings developed no chlorophyll, leaves or roots and did not emerge above the 5.5-cm depth of water and 10-mm depth of oil. Greening occurred in 18% of seedlings in continuous light. Seedlings germinated in darkness without a layer of oil became elongated, developed leaves and roots and did not display the circumnutation-like shoot growth observed in those germinated under 10-mm olive oil. Liquid paraffin had little effect on growth. When the olive oil was removed after 14 or 24 days, normal growth resumed provided that the seedlings had not been severely damaged by microbial activity.