Metabolic Activity and Energy Charge of Excised Maize Root Tips under Anoxia

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Abstract
Energy charge and fermentative metabolism under anoxia were monitored in excised maize root tips after various times of aging in air and were related to their soluble sugar content. The energy charge value, which was 0.9 in air irrespective of the time of aging, dropped to a lower value within minutes of transfer to a N atmosphere. This value was dependent upon sugar content of the tissues which was itself a function of aging. The energy charge value after transfer to N was 0.6 in freshly excised tissue but only 0.2 in tissue aged for 4 h. When aged tissues supplied with 0.2 M glucose were transferred to N, the energy charge was 0.6, irrespective of the time of aging. When 0.2 M glucose was added under N, energy charge rose to 0.6. This rise was faster in root tips aged for 8 h than those aged for 24 h. The rate of ethanol plus lactate production (representing 60 and 10%, respectively, of the total sugar consumption in anoxia) was closely correlated to the level of energy charge. In anoxia, there is a quantitative relationship between the energy charge value and the level of metabolic activity via fermentative pathways.