| Abstract: | Atwell, B. J. and Green way, H. 1987. The relationship betweengrowth and oxygen uptake in hypoxic rice seedlings.—J.exp. Bot. 38: 454–465. Rice seedlings (Oryza saliva L.) were grown in the dark forup to 4 d in solutions containing various concentrations ofO2. Compared with seedlings grown at 0·250 mol O2 m–3,the dry weight of the growing seedling was 14% lower at 0·110mol O2 m–3 and 60% lower at 0 mol O2 m–3. Decreasesin fresh weight were similar but not identical to decreasesin dry weight, possibly because leaf growth was suppressed evenabove 0·110 mol O2 m–3. Oxygen deficiency inhibitedroot growth more severely than coleoptile growth. Coleoptiles from seedlings grown in aerated solution were exposedto an atmosphere of pure N2 for 30 min. Anoxia caused a declinein ATP content and energy charge, suggestive of decreased oxidativephosphorylation. It is not clear whether the decline in oxidativephosphorylation was solely responsible for impaired growth inhypoxia. In seedlings growing at O2 concentrations less than 0·110mol O2 m–3, significant amounts of ethanol were synthesized.The rate of O2 uptake decreased markedly below 0·06 molO2 m–3; this was presumably near the external O2 concentrationat which oxidative phosphorylation became limited by the supplyof O2. The stage of development of the seedlings appeared toinfluence O2 uptake, possibly through changes in conductanceof the tissue to O2. Uncouplers were used to confirm that thecritical O2 concentration was dependent on O2 diffusion ratherthan enzyme kinetics. Impaired growth above 0·110 molO2 m–3 may have been due to a decreased activity of oxygenasesof relatively low affinity for O2, which in turn altered cellmetabolism. Key words: Growth, oxygen uptake, rice seedlings, hypoxia |
