Abstract
Oxygen uptake and energy charge were monitored during aging of excised maize root tips and related to the soluble sugar content and exogenous sugar supply.
Oxygen uptake declined immediately after excision to 50 to 30% of its initial value after 8 and 24 hours of aging at 25 C. There was also a sharp decline of the total sugar content (glucose, fructose, and sucrose). Starch content was very low at the time of excision and almost negligible 5 hours later. During the same period, the respiratory quotient declined from 1 to 0.75 and then remained stable.
The addition of exogenous sugars induced a rapid rise of the respiratory rate which stabilized at a level correlated to the external sugar concentration. Addition of 0.2 molar glucose was necessary to restore the respiratory rate to the initial, also the maximum, level. These results indicate that metabolic activity of root tips is highly reliant on sugar import and carbohydrate reserves at the time of excision cannot compensate for the cessation of import. The control of respiration by substrate supply is in good agreement with the failure for dinitrophenol to stimulate oxygen uptake in aged sugar-depleted root tips.
The energy charge remained constant at about 0.9, irrespective of the presence or absence of glucose and in spite of a large decline of respiratory activity in aged, sugar-depleted tissues.
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Selected References
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- Lin W., Hanson J. B. Phosphate absorption rates and adenosine 5'-triphosphate concentrations in corn root tissue. Plant Physiol. 1974 Sep;54(3):250–256. doi: 10.1104/pp.54.3.250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ohmura T., Howell R. W. Inhibitory Effect of Water on Oxygen Consumption by Plant Materials. Plant Physiol. 1960 Mar;35(2):184–188. doi: 10.1104/pp.35.2.184. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raymond P., Pradet A. Stabilization of adenine nucleotide ratios at various values by an oxygen limitation of respiration in germinating lettuce (Lactuca sativa) seeds. Biochem J. 1980 Jul 15;190(1):39–44. doi: 10.1042/bj1900039. [DOI] [PMC free article] [PubMed] [Google Scholar]
- STREHLER B. L., TOTTER J. R. Firefly luminescence in the study of energy transfer mechanisms. I. Substrate and enzyme determination. Arch Biochem Biophys. 1952 Sep;40(1):28–41. doi: 10.1016/0003-9861(52)90070-2. [DOI] [PubMed] [Google Scholar]
- Troughton J. H., Currie B. G. Relations between Light Level, Sucrose Concentration, and Translocation of Carbon 11 in Zea mays Leaves. Plant Physiol. 1977 May;59(5):808–820. doi: 10.1104/pp.59.5.808. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wilson A. M., Harris G. A. Hexose-, inositol-, and nucleoside phosphate esters in germinating seeds of crested wheatgrass. Plant Physiol. 1966 Nov;41(9):1416–1419. doi: 10.1104/pp.41.9.1416. [DOI] [PMC free article] [PubMed] [Google Scholar]