Rice (Oryza sativa L.) supports half of the human population. However, predominant rice consumption leads to malnutrition due to mineral deficiencies. The research goal was to support identification of genes responsible for the uptake/accumulation of potassium (K), iron (Fe), zinc (Zn) and molybdenum (Mo), thus promoting the breeding for rice with high grain concentrations of these elements. Prior studies identified rice genotypes with high grain-K, -Fe, -Zn or -Mo concentrations that were hypothesized to be due to differences in root traits. The research objective was to identify root traits associated with these elements. These traits could be bases for identifying genes. The first study determined if these genotypes showed similar accumulation patterns in leaves as in grains, which would hint at influences of the roots and enable identifying distinct root traits and possible genes in vegetative growth stages. The second study determined if root traits of high grain-Mo genotypes displayed an acid-tolerance mechanism as these genotypes originated from Malaysia where acidic soils strongly adsorb Mo making it unavailable for plants. The third study identified root trait differences of high grain-K, -Fe, -Zn and -Mo genotypes in hydroponics media, while the fourth determined root trait differences in these genotypes in sand-culture media including a 1-Naphthalene Acetic Acid (NAA) seed treatment for perturbation. The first study identified several high grain-Mo genotypes with similar Mo accumulation patterns in V4 to V6 stage-leaves as in grains, suggestive of a root influence. The second study established that gross morphological and physiological root traits of a high grain-Mo genotype were not part of an acid-tolerance mechanism. Neither the third nor fourth study identified root traits related to shoot K, Fe, Zn or Mo concentration, however positive associations of seedling vigor traits with several beneficial elements, including K, and negative associations with numerous toxic elements were established. Lack of correlation with root traits suggests other mechanisms (e.g. active uptake transporters) instead control the observed grain accumulation differences. Based on the fourth study, either direct effects of NAA on element uptake/transfer or indirect effects on soil pH and redox potential altered tissue Fe and Zn levels.

Okra (Abelmuschus esculentus (L) Moench.) is one of the most popular crops within the Malvaceae family of plants. It is a common vegetable eminently cultivated in regions experiencing constraints to manage climate change. In South Africa climate change coupled with aluminium-enriched soils are responsible to drawbacks crop performance. Therefore, it is worthwhile to whether okra will thrive as an alternative crop in the country. Many studies have identified potential of okra to improve yields of resource poor farmers in Africa. The physiological responses of okra seed to variations in aluminium ions and temperature were not determined. Therefore, a study with okra, cv. Clemson Spineless, seed coated and uncoated with B. subtilis, was initiated to assess germination on moist filter paper in 90mm diameter Petri plates. Germination medium consisted of various concentrations of aluminium chloride (AlCl3), 0M, 0.001M, 0.01M, 0.05M and 0.1M. Each aluminium treatment was allocated into incubators adjusted to 22°C, 25°C and 37°C temperatures. This resulted into a 5 x 3 x 2 factorial experiment with five replicates and was conducted in three cycles. Daily scores of germinated seeds were assessed from the second to the fifth day after initiation of germination. During termination, five days after the initiation of the experiment 10 seeds with the longest coleoptiles had their coleoptiles measured using a digital caliper. At the fifth day after initiation of the experiment, coleoptile lengths from 10 seeds per treatment were measured using digital caliper. A total of 50 plates (10 from 37°C in Cycle 1; 30 from 22°C, 25°C and 37°C from Cycle 2; 10 from 37°C in Cycle 3), were selected and germinated were ground and stored at - 20°C before 1H NMR analysis. Metabolites were extracted from 50mg ground seed material with 750 μL methanol-D4 and 750 μL buffer (deuterium oxide + potassium dihydrogen phosphate). The mixture was vortexed for three minutes, sonicated for 20 minutes, centrifuged at 18000 rpms for 20 minutes and the supernatant filtered through cotton wool. Then the supernatant was dispensed into NMR tubes for further 1H NMR spectroscopic processing using a 600 MHz NMR xiii Varian spectrometer to generate magnetic spectra of the fifty samples. Results of this study demonstrated that in all the experimental cycles, regardless of aluminium concentration and bacterial seed coating, 37°C inhibited germination percentages and coleoptile lengths in okra seed germination. Germination percentages and coleoptile lengths of bacteria-coated seeds growing in 25°C were most stimulated at all aluminium concentrations, but not at 0.1M. In this temperature germination percentages and coleoptile lengths were highly influenced by the interaction of aluminium concentrations and bacterial coating, respectively. 1H NMR metabolomic association showed no distinct grouping, but clusters across treatments showed to be linked through a subset of metabolites amongst aluminium concentrations, bacterial seed coating and temperatures, respectively. This infers that treatment variations in both seed and bacterial physiological responses were associated through shared metabolic pathways. In conclusion, the study proved that 25°C provide temperature environment within which B. subtilis can be able to stimulate growth and remediate physiological constraints from aluminium ions during okra seed germination. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Okra (Abelmuschus esculentus (L) Moench.) is one of the most popular crops within the Malvaceae family of plants. It is a common vegetable eminently cultivated in regions experiencing constraints to manage climate change. In South Africa climate change coupled with aluminium-enriched soils are responsible to drawbacks crop performance. Therefore, it is worthwhile to whether okra will thrive as an alternative crop in the country. Many studies have identified potential of okra to improve yields of resource poor farmers in Africa. The physiological responses of okra seed to variations in aluminium ions and temperature were not determined. Therefore, a study with okra, cv. Clemson Spineless, seed coated and uncoated with B. subtilis, was initiated to assess germination on moist filter paper in 90mm diameter Petri plates. Germination medium consisted of various concentrations of aluminium chloride (AlCl3), 0M, 0.001M, 0.01M, 0.05M and 0.1M. Each aluminium treatment was allocated into incubators adjusted to 22°C, 25°C and 37°C temperatures. This resulted into a 5 x 3 x 2 factorial experiment with five replicates and was conducted in three cycles. Daily scores of germinated seeds were assessed from the second to the fifth day after initiation of germination. During termination, five days after the initiation of the experiment 10 seeds with the longest coleoptiles had their coleoptiles measured using a digital caliper. At the fifth day after initiation of the experiment, coleoptile lengths from 10 seeds per treatment were measured using digital caliper. A total of 50 plates (10 from 37°C in Cycle 1; 30 from 22°C, 25°C and 37°C from Cycle 2; 10 from 37°C in Cycle 3), were selected and germinated were ground and stored at - 20°C before 1H NMR analysis. Metabolites were extracted from 50mg ground seed material with 750 μL methanol-D4 and 750 μL buffer (deuterium oxide + potassium dihydrogen phosphate). The mixture was vortexed for three minutes, sonicated for 20 minutes, centrifuged at 18000 rpms for 20 minutes and the supernatant filtered through cotton wool. Then the supernatant was dispensed into NMR tubes for further 1H NMR spectroscopic processing using a 600 MHz NMR xiii Varian spectrometer to generate magnetic spectra of the fifty samples. Results of this study demonstrated that in all the experimental cycles, regardless of aluminium concentration and bacterial seed coating, 37°C inhibited germination percentages and coleoptile lengths in okra seed germination. Germination percentages and coleoptile lengths of bacteria-coated seeds growing in 25°C were most stimulated at all aluminium concentrations, but not at 0.1M. In this temperature germination percentages and coleoptile lengths were highly influenced by the interaction of aluminium concentrations and bacterial coating, respectively. 1H NMR metabolomic association showed no distinct grouping, but clusters across treatments showed to be linked through a subset of metabolites amongst aluminium concentrations, bacterial seed coating and temperatures, respectively. This infers that treatment variations in both seed and bacterial physiological responses were associated through shared metabolic pathways. In conclusion, the study proved that 25°C provide temperature environment within which B. subtilis can be able to stimulate growth and remediate physiological constraints from aluminium ions during okra seed germination. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)