An analysis of the diurnal course of growth, carbon dioxide exchange and carbohydrate reserve content of cucumber

H. Challa

    Research output: Thesisexternal PhD, WU


    A detailed study was made of the diurnal course of carbon dioxide exchange, transpiration and carbohydrate reserve levels in different organs of young cucumberplants, cultivated in climate rooms under 'spring' or 'winter' conditions. Under spring conditions the stomata closed after about 8 hours light, causing a decrease in the rate of CO <sub>2</sub> uptake. This closure could not be ascribed to water shortage. Under winter conditions CO <sub>2</sub> production rapidly decreased after about 12 hours darkness, as a result of carbohydrate depletion. Additional respiration substrates were provided by protein breakdown. Reducing the air temperature during that period from 25 °C to 12 °C caused an increase in rate of plant growth, probably by reducing the amount of protein breakdown. The moment at which starch reserves were depleted was, under the conditions studied, independent of the amounts formed and seems to be 'preprogrammed'. Majority of the carbohydrate reserves formed during the day were used as respiration substrates. A comparison of the measured amounts of CO <sub>2</sub> production with theoretically derived values, showed a discrepancy which may be explained by underestimation of the amount of protein turnover.<br/>Furthermore a new method is described for calibration of differential water vapour analysers and also for mixing pure CO <sub>2</sub> with CO <sub>2</sub> -free air to obtain air mixtures with various constant CO <sub>2</sub> -concentrations.<p/>
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • de Wit, C.T., Promotor
    • Brouwer, R., Co-promotor, External person
    Award date7 Jan 1977
    Place of PublicationWageningen
    Print ISBNs9789022006238
    Publication statusPublished - 1977


    • cucumis sativus
    • cucumbers


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