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Title: Studies on Zea mays infected with Striga hermonthica, with particular reference to photosynthesis
Author: Smith, Lucy Helen
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1994
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The parasitic angiosperm Striga hermonthica is native to Africa where it parasitizes maize and can reduce crop yield to zero. Pulse-chase experiments showed that carbon was assimilated in control and infected plants mainly by the C4 pathway but the distribution of 14C among photosynthetic intermediates indicated an increase in photorespiratory metabolism in leaves of infected plants. Measurements with an infra-red gas analyser showed that maize infected with Striga hermonthica had decreased rates of photosynthesis. All the leaves were affected. The decrease often began before parasitic shoots had emerged above the soil and the extent of the decrease was not correlated with the number of parasitic shoots that eventually emerged. The decrease in photosynthesis was not due to a reduction in activity of four major photosynthetic enzymes. Glutathione reductase activity was increased as a result of infection. Microscopic studies of fresh sections showed abnormalities in bundle sheath cells of leaves from infected plants. Electron micrographs showed that the bundle sheath and vascular cells of infected plants had thinner walls and were not as rounded in outline as in control plants. Immunofluorescent labelling of RuBisCO showed it to be localised in the bundle sheath cells in leaf tissue of both control and infected plants, but decreased autofluorescence indicated that the walls of the bundle sheath cells were thirmer in leaves of infected plants. The effects of extracts of leaves on cells in culture provided no evidence for the presence of a toxin, but suggested a change in growth hormone content caused by infection. Differences in the content of soluble carbohydrate, starch and α-amino nitrogen showed that Striga infection changed host resource partitioning.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available