dc.contributor.advisor | Berner, J.M. | |
dc.contributor.advisor | Krüger, G.H.J. | |
dc.contributor.author | Opperman, Hugo | |
dc.date.accessioned | 2018-05-17T10:50:22Z | |
dc.date.available | 2018-05-17T10:50:22Z | |
dc.date.issued | 2015 | |
dc.identifier.uri | http://hdl.handle.net/10394/26865 | |
dc.description | PhD (Environmental Science), North-West University, Potchefstroom Campus, 2016 | en_US |
dc.description.abstract | During 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 02 | en_US |
dc.description.sponsorship | National Research Foundation (NRF) | en_US |
dc.language.iso | en | en_US |
dc.publisher | North-West University (South Africa), Potchefstroom Campus | en_US |
dc.subject | Maize | en_US |
dc.subject | Abiotic stress | en_US |
dc.subject | Heavy metals | en_US |
dc.subject | Ozone | en_US |
dc.subject | Nanoparticles | en_US |
dc.subject | Photosynthesis | en_US |
dc.subject | Chlorophyll a fluorescence | en_US |
dc.subject | Photosynthetic gas exchange | en_US |
dc.title | The impact of different industrial related abiotic stresses on maize photosynthesis | en_US |
dc.type | Thesis | en_US |
dc.description.thesistype | Doctoral | en_US |
dc.contributor.researchID | 21203083 - Berner, Jacques Maynard (Supervisor) | |
dc.contributor.researchID | 20538065 - Krüger, Gert Hendrik Jacobus (Supervisor) | |