The mechanism of NH3 and SO2 uptake by leaves and its physiological effects = [Het mechanisme van de NH3 en SO2 opname door bladeren en hierdoor veroorzaakte fysiologische effecten]

    Research output: Thesisinternal PhD, WU

    Abstract

    <p>The relation between uptake of atmospheric ammonia (NH <sub><font size="-2">3</font></sub> ) and sulphur dioxide (SO <sub><font size="-2">2</font></sub> ) by individual leaves, photosynthesis and stomatal conductance was examined. The experiments were carried out with bean plants ( <em>Phaseolus vulgaris L.</em> ) and poplar shoots ( <em>Populus euramericana L.</em> ). The method of analysis was derived from methods used in photosynthetic research. The uptake of NH <sub><font size="-2">3</font></sub> or SO <sub><font size="-2">2</font></sub> was experimentally determined by using a leaf chamber specially developed for this research. Simultaneously, transpiration and carbondioxide (CO <sub><font size="-2">2</font></sub> ) assimilation of leaves were measured.<p>The adsorption of NH <sub><font size="-2">3</font></sub> and SO <sub><font size="-2">2</font></sub> strongly increased with increasing air humidity, indicating a major role of water in the adsorption process. A descriptive model for the adsorption in the cuticle-watersystem is proposed. The affinity of SO <sub><font size="-2">2</font></sub> for the leaf surface was found to be approximately twice that of NH <sub><font size="-2">3</font></sub> . A mixture of these gases in the air mutually stimulated their adsorption on the leaf surface. No significant desorption or transport of these gases through the cuticle could be detected.<p>The uptake of NH <sub><font size="-2">3</font></sub> into leaves appeared to be dependent on the leaf boundary layer and stomatal resistance and NH <sub><font size="-2">3</font></sub> concentration at the leaf surface. In contrast, a less clear relation between SO <sub><font size="-2">2</font></sub> uptake and stomatal resistance was found, in particular at a low vapor pressure deficit (VPD). The measured flux was larger than can be calculated from the boundary layer and stomatal resistance for H <sub><font size="-2">2</font></sub> O, suggesting a lower resistance of the diffusion pathway. The same was observed for NH <sub><font size="-2">3</font></sub> at a low temperature and VPD. It is postulated that this discrepancy is due to a difference in path length.<p>Under the conditions of the present research the physiological effects caused by a prolonged exposure to NH <sub><font size="-2">3</font></sub> or SO <sub><font size="-2">2</font></sub> became notable at concentrations of about 100 μg.m <sup><font size="-2">-3</font></SUP>. The NH <sub><font size="-2">3</font></sub> exposure had a positive effect on photosynthesis, stomatal conductance and NH <sub><font size="-2">3</font></sub> uptake, whereas a small irreversible inhibition of photosynthesis and stomatal conductance was induced by the SO <sub><font size="-2">2</font></sub> exposure.<p>The relations assessed in this study can be used to construct a descriptive model for NH <sub><font size="-2">3</font></sub> and SO <sub><font size="-2">2</font></sub> transfer into leaves as a function of wind velocity, light intensity, air temperature and humidity.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Adema, E.H., Promotor, External person
    • Vredenberg, W.J., Promotor
    Award date18 Oct 1989
    Place of PublicationS.l.
    Publisher
    Publication statusPublished - 1989

    Keywords

    • precipitation
    • chemical properties
    • acidity
    • acid rain
    • crop damage
    • air pollution
    • sulfur dioxide
    • ammonia

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