Oxygen stress and coleoptile growth and plastogenesis in light-germinated rice (Oryza sativaL.) seedlings

Summary Three different oxygen-containing germination environments demonstrate the profound influence exerted by environmental oxygen (02) on growth and plastogenesis in coleoptiles of light-germinated rice seedlings. Coleoptile greening is extensive in low numbers of seedlings germinated in a sealed, initially air-saturated, static water environment and in large numbers of seedlings germinated under unagitated water underambient gaseous exchange conditions. In seedlings germinated in air (≅21% 02), coleoptile greening is sparse and extension growth is much reduced compared with coleoptile extension growth of the submerged seedlings. Coleoptile greening and shoot and root growth are completely inhibited under hypoxia resulting from large numbers of germinating seedlings competing for the limited 02 supply in the sealed, initially air-saturated, static water environment. Coleoptile extension growth is highest under hypoxia and lowest under ≅21% 02. The observations presented here demonstrate that 02 stress and non- stress conditions serve as environmental signals which influence growth behaviour and plastogenesis in coleoptiles of light-germinated rice seedlings.