M.Tech. (Electrical Engineering) / For securing food production it is essential that every possible method should be investigated. This study is about utilising low power radio frequency (RF) energy signals from leaky transmission lines for the benefit of plant growth and production in hydroponic systems. Using these lines eliminates common problems like radiation interference and licence application protocols. Plant cell walls are covered with tightly-bonded, positively-charged calcium ions that affect the inflow of nutrients into the cell. As calcium ions have a mass twice that of the potassium ion, the fundamental harmonic of calcium is equal to the first harmonic of potassium (32Hz). Thousands (10k : 1) fewer positive potassium ions also exist around the cell wall and when stimulated at their resonance frequency (16Hz), they will bounce against the tightly bonded calcium ions so these calcium ions become dislodged from the cell wall. If this happens more nutrients can enter the cell causing acceleration in plant growth. A suitable electromagnetic wave for such an action is the amplitude modulated wave especially if it is modulated near the cyclotron resonance frequency of potassium (16Hz) or its even-harmonics of 32,64Hz etc. Applying sufficient energy in the lower modulated frequency when it is the same as the vibration frequency of the potassium ions surrounding the cell wall, these ions will then acquire some energy from the electrical wave. Controlling the process is important because if too many calcium ions are released it would cause plant stress and plant structure breakdown. The amplitude modulated wave will allow sufficient time for the calcium ions to return to the cell wall during the period without energy. To apply radio energy to a plant in the form of amplitude modulated signals requires a medium. One such medium is the use of transmitting energy into two leaky transmission lines to cause worse case standing waves, which could then be absorbed by the plants that are placed in between these transmission lines. The energy from the radio waves is then used to create window periods during which the calcium ions are dislodged allowing additional nutrients to enter the plant cell, enhancing plant growth and production.

Existing evidence suggested that nursery inoculation with Trichoderma harzianum and arbuscular mycorrhizal fungi (AMF) could reduce deleterious effects of biotic and abiotic stresses and improve seedling quality, fruit yield and quality of tomato (Solanum lycopersicum L.). However, studies of their combined inoculation on seedling growth, fruit yield and quality of tomato plants are not well-documented. Experiments were carried out to investigate the combined effect of T. harzianum and AMF on tomato crop performance under various conditions. When combined with a T. harzianum and AMF mixture, seaweed extract from Ecklonia maxiama inhibited AMF root colonisation of tomato seedlings. Treating seedlings with a mixture of T. harzianum and AMF reduced the incidence of Verticillium wilt in tomato grown in a nethouse at early season, with negligible effect on fruit yield. Further investigations were initiated to find out whether T. harzianum and AMF were efficient when applied as a mixture or alone, at different inoculation times. Co-inoculation with T. harzianum and AMF (Glomus mosseae) improved seedling growth and development, except when both fungi were simultaneously applied two weeks after sowing. When the seedlings were allowed to grow up until full harvest in a greenhouse, both fungal inoculants increased total yield and marketable yield, but these increases were not significant. Furthermore, inoculation with AMF increased the percentage of extra-large fruit. Field experiments conducted under commercial tomato production confirmed greenhouse studies. Inoculation of tomato with T. harzianum and AMF, either alone or in combination increased early fruit yield (four first harvesting weeks). Throughout the studies, percentage AMF root colonisation in seedlings and plants remained low, despite nursery inoculation. Field experiments investigated the effects of AMF-inoculated transplants combined with biochar-amended soils on AMF root colonisation and their resultant effects on overall crop performance and microbial community structure. Biochar had no effect on AMF root colonisation, and also when combined with AMF, it had no influence on tomato productivity. Interestingly, biochar altered the fungal community while AMF might have influenced the bacterial community such as plant-growth promoting rhizobacteria, which are associated with improved plant growth, nutrient uptake and disease control in the rhizosphere. These benefits could contribute to improved yield and fruit quality. In conclusion, although the results were variable, there was a clear indication that T. harzianum and AMF can play an important role in tomato production. / Thesis (PhD)--University of Pretoria, 2012. / Plant Production and Soil Science / unrestricted

In South Africa, most of the surface coal mines are situated on the Highveld of the Mpumalanga Province. The mining industry plays a vital role and contributes to the economy of the country. Very often the mining activities change the physical nature of the soil which results in soil compaction. In mine soils, compaction is of great importance in plant growth and the environment because its high levels may adversely result in the degradation of soil structure, reduced nutrient distribution and reduced root growth, which eventually decreases plant growth. To ensure a productive vegetation, compacted mine soils has to be ameliorated effectively. A combination of practices is suggested to alleviate soil compaction, but some of them are costly and not ecologically stable particularly the use of conventional methods. Therefore, the challenge is to use the potential practices to ameliorate compacted soils. The proposed investigations, which are envisaged to solve harmful effects of soil compaction on plant growth, include biological activities, achieved through appropriate application of cattle manure and planting of pasture species. A review on literature, some studies indicate that the application of organic manure amendments such as cattle manure may overcome the negative effects of compaction, due to the beneficial effects on soil physical, chemical and biological properties in the zone of incorporation. Other studies has shown that pastures are linked with improvements in soil structure, soil organic matter content, rooting depths, consequently, reductions in bulk density. The focus of this study were to monitor the root biomass of irrigated Tall Fescue (F. arundinacea cv Dovey) and dryland Smuts Fingergrass (D. eriantha cv Irene) on mine soils, and to describe soil bulk density and soil nutrient concentrations in such soils. This study were also determining the effects of incorporating cattle manure into compacted (mine soils) and non compacted (agricultural soils) and evaluating its effects on the seedling growth rate, dry matter and root biomass production of Tall Fescue and Smuts Fingergrass. In addition, the influence of different rates of cattle manure on soil bulk density and nutrient concentration in such compacted soil was also measured. These parameters are relevant to the sustainable rehabilitation of mine soils. Based on the results obtained in this study, it was concluded that the use of two grass species, Tall Fescue and Smuts Fingergrass, with vigorous root systems have extended their roots in compacted mine soil layers over two growing seasons. Other results have demonstrated that application of cattle manure revealed a significant decrease in soil bulk density of compacted mine soils planted to Tall Fescue and Smuts Fingergrass. The bulk density was at a minimum in the 80 tha-1 cattle manure-treated plots and followed by the 40 tha-1 cattle manure treatment, and the maximum bulk density was recorded for the control treatment (0 tha-1). The application of cattle manure resulted in a large input of nutrients to the soil as compared to untreated control and significantly increased Tall Fescue and Smuts Fingergrass growth and production. This research has illustrated that use of plant roots and cattle manure as soil organic amendments to reduce soil compaction may be environmentally and economically beneficial leading to a more sustainable agricultural system. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Plant Production and Soil Science / Unrestricted

Carotenoids are the precursor of several metabolites with regulatory functions, which include the plant hormones abscisic acid (ABA) and strigolactones (SLs), and signaling molecules, such as β-cyclocitral. These carotenoid-derivatives originate from oxidative breakdown of the double bond resulting in carbonyl cleavage-products designated as apocarotenoids. The cleavage reaction causing apocarotenoid formation is catalyzed frequently by Carotenoid Cleavage Dioxygenases (CCDs). Several lines of evidence indicate the presence of yet unidentified apocarotenoids with regulatory or signaling function. Here, we first characterized the biological functions of the apocarotenoid zaxinone formed by ZAXINONE SYNTHASE (ZAS), a member of an overlooked, widely distributed plant CCD clade. The loss-of-function rice zas mutant contains less zaxinone, exhibiting retarded growth with elevated levels of SLs that determines plant architecture, mediates mycorrhization, and facilitates the germination of root parasitic seeds, such as Striga spp. The zaxinone treatment rescued zas phenotypes, down-regulated SL biosynthesis and release, and enhanced root growth in the wild-type rice seedlings. Next, we performed multi-omics analysis demonstrating zaxinone increased sugar metabolism and induced photosynthesis in a manner that led to phenotypical changes in rice roots. Besides, transcriptome analysis showed that zaxinone upregulated CYTOKININ GLUCOSYLTRANSFERASES expression in roots, which might explain the increase in the apex and meristem length, and in the number of cellular layers. Finally, the investigation of zaxinone biology and the utilization of its application is constrained by its laborious organic synthesis and low abundance in natural sources. Therefore, we developed easy-to-synthesize and highly efficient Mimic of Zaxinone (MiZax), based on the structure-activity-relationship study using a series of apocarotenoids. Activity-based experiments unraveled MiZax3 and MiZax5 were at least as active as zaxinone in rescuing root phenotypes of the zas mutant, promoting root growth in wild-type seedlings, and reducing SL biosynthesis and release. Taken together, zaxinone is a key regulator of rice growth and development, which regulates sugar metabolism, suppresses SL biosynthesis, fine-tunes cytokinins level, and modulates biotic interactions with arbuscular mycorrhizal (AM) fungi. Our work also provides easy-to-synthesize mimics for illuminating zaxinone biology and as a tool to improve crop growth and reduce the infestation by Striga hermonthica, a severe threat to food security worldwide.

A greenhouse study was conducted involving interactive effects on bean yield of three levels of irrigation water salinity, three frequencies of irrigation water app li cation, two level s of nitrogen, and seven levels of phosphorus fertilization to determine if the effects of adverse saline conditions or water stress could be overcome by fertility and / or saline water management. Dry matter and bean yields were reduced with decreasing irrigation frequency (2 days to B days} and increasing salinity of irrigation water (0.5 mmho/cm to 8.0 mmho/cm). At low salinity levels (0 .5 mmho/cm) dry matter production and the number of pods per pot were increased with the addition of nitrogen in the irrigation water (at the rate of 112 kg N/ha). The application of banded fertilizer phosphorus helped beans overcome the effects of saline conditions and water stress and resulted in increased yield. The application of liquid 10-34-0 fertilizer produced a statistically significant increase in all yield parameters at every level of salinity, and every irrigation frequency studied. Nitrogen fixation was found to decrease as irrigation water salinity increased. The application of 0-50-40 as a fertilizer band treatment increased nitrogen fixation in t he presence of added nitrogen, due probably to the presence of potassium.

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Water uptake by a single root of an onion plant (Allium cepa) was measured potentially before, during and following exposure of shoots to an external electric field (EEF). The field strength used was 9kV/m DC and AC (60-Hz) brought about a statistically significant increase (44-71%) in water uptake if the shoot chamber was at almost 100% humidity.

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