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dc.contributor.advisorBerner, J.M.
dc.contributor.advisorKrüger, G.H.J.
dc.contributor.authorOpperman, Hugo
dc.date.accessioned2018-05-17T10:50:22Z
dc.date.available2018-05-17T10:50:22Z
dc.date.issued2015
dc.identifier.urihttp://hdl.handle.net/10394/26865
dc.descriptionPhD (Environmental Science), North-West University, Potchefstroom Campus, 2016en_US
dc.description.abstractDuring the past few decades, a sharp rise in industrial activity in the mineral rich Highveld region of South Africa has been seen. Together with this increase in industrial activity, an accompanying increase in urbanization is also evident. As a result of increased industrial activity and urbanization, a large increase in environmental pollution followed, which resulted in the area being declared a priority area. In this study, three distinct types of industrial related pollution sources (ionic metal species, ozone and nano-fine particle matter) were investigated in terms of their impact on maize photosynthesis. Maize was chosen because most of the maize in South Africa is produced in the heavily industrialized Highveld area. The efficiency of the partial processes of photosynthesis is often used as abiotic stress indicators. The influence of different concentrations of Cu, Fe, Mn and Zn on PSII and PSI electron transport was investigated for a South African maize cultivar (IMP 52-11). The non-invasive (in vivo) techniques of chlorophyll a fluorescence induction (JIP-test) and modulated reflection at 820 nm (MR8200m) were measured simultaneously to follow the PSII and PSI activity, respectively. We could demonstrate that both deficient and excess heavy metals concentrations resulted in significant decreases (p:S0.05) in PSII and PSI activity, which has never been presented before in so much detail. Metal deficiency induced down-regulation was attributed to a lowering in metal specific electron carriers containing these metals as co-factors, resulting in lower PSII and PSI activity. The photosynthetic sensitivity of two popular South African maize cultivars (IMP 52-11 and PAN 6411) to chronic 0 3 exposure was also investigated. Two different cultivars were used in order to determine whether or not these cultivars have similar sensitivities to 0 3 induced stress. The effect of 0 3 on both photosynthetic electron transport and photosynthetic gas exchange was monitoried (in parallel) by means of chlorophyll a fluorescence, MR82onm reflection and infrared gas analysis, in both cultivars. Although a concentration dependent inhibitory effect was found in both cultivars, the data suggested that PAN 6411 was less sensitive to the chronic 0 3 exposure than IMP 52-11, showing lower stomatal, mesophyll and electron transport limitation. Furthermore, a simple and novel decoupling model was proposed for the first time, with which a new parameter, e, could be obtained. The % decoupling (e) is indicative of the amount of decoupling (electron losses) between PSI and COrassimilation. Furthermore, chlorophyll a fluorescence, MR8201101 reflection, photosynthetic gas exchange and antioxidant capacity studies were also used to evaluate the influence of increasing concentrations of nano-Ti02 and nano-Si02 foliar sprays, with regard to the photosynthetic efficiency of the IMP 52-11 maize cultivar. Both particles caused significant (p:S0.05) reductions in both the photochemical (electron transport) and biochemical (Calvin Benson Cycle) phases of photosynthesis. The negative effect of Ti02 was ascribed to its photocatalytic activity, which induced increased ROS formation. Given that Si02 is rather inert, the decrease in photosynthetic efficiency at high Si02 concentration was attributed to the increased stomata! closure. This increased stomata! limitation caused a decrease in the electron demand for COrassirnilation and subsequent electron buildup. The decoupling model was used to determine e under increasing stress conditions. The increase in ROS formation and the consequent increase in antioxidant activity, which coincided with an increase in e, suggested that the electrons lost between PSI and COr assimilation were being lost to alternative electron acceptors such as 02en_US
dc.description.sponsorshipNational Research Foundation (NRF)en_US
dc.language.isoenen_US
dc.publisherNorth-West University (South Africa), Potchefstroom Campusen_US
dc.subjectMaizeen_US
dc.subjectAbiotic stressen_US
dc.subjectHeavy metalsen_US
dc.subjectOzoneen_US
dc.subjectNanoparticlesen_US
dc.subjectPhotosynthesisen_US
dc.subjectChlorophyll a fluorescenceen_US
dc.subjectPhotosynthetic gas exchangeen_US
dc.titleThe impact of different industrial related abiotic stresses on maize photosynthesisen_US
dc.typeThesisen_US
dc.description.thesistypeDoctoralen_US
dc.contributor.researchID21203083 - Berner, Jacques Maynard (Supervisor)
dc.contributor.researchID20538065 - Krüger, Gert Hendrik Jacobus (Supervisor)


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