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North-West University (2020)

Comparing the photochemical potential of quinoa to maize under water stress conditions

Malan, C.

Titre : Comparing the photochemical potential of quinoa to maize under water stress conditions

Auteur : Malan, C.

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Science with Botany 2020

In the current context of climate change, drought events are one of the major causes of yield reduction in crops. Seeing that South Africa is a water scarce country and along with the future climate change predictions, the introduction of climate resilient crops is needed. Quinoa has been identified as a climate resilient crop that could provide farmers with an alternative option to mitigate the impact of climate change on crop production. Nevertheless, the question stands, whether the cultivation of quinoa would be successful in South Africa. The aim of this study is to investigate the physiological acclimation of quinoa, while subjected to water stress and compare it to the main staple crop, maize. In this trial, both quinoa and maize were planted in glasshouses at two different temperature regimes (20 ?C and 30 ?C) while subjected to water stress. The photochemical potential of PSII was measured by means of chlorophyll a fluorescence and the photochemical potential of PSI was measured by means of 820 nm reflection. The antioxidative capacity of the crops was assessed by measuring the superoxide dismutase (SOD) and glutathione reductase (GR) activities and proline content. In addition, the stomatal conductance, chlorophyll content, leaf water potential and membrane leakage was determined for both the crops. The higher proline levels of the water- stressed quinoa contributed to the ability of PSII to tolerate water deficit stress. PSI activity of the water- stressed quinoa was more stable under the water- stressed conditions compared to the water-stressed maize plants. The SOD and GR activities were higher in the water stressed quinoa, thereby playing an active role in minimizing oxidative damage. The physiological acclimation strategy of quinoa also included a decrease in the stomatal conductance, total leaf area, membrane leakage and higher leaf water content. Compared to the water stressed maize, quinoa was able to acclimate more successfully to water deficit stress. The ability of quinoa to protect its photosystems is a crucial acclimation strategy to ensure optimal photochemistry under water deficit conditions.


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