Doctoral Degrees (Soil, Crop and Climate Sciences)

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Browsing Doctoral Degrees (Soil, Crop and Climate Sciences) by Subject "Bio-stimulatory properties"

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    Bio-stimulatory properties of a Lupinus albus L. seed suspension
    (University of the Free State, 2005-05) Van der Watt, Elmarie; Pretorius, J. C.; Van der Westhuizen, A. J.
    English: The sustainable increase in crop yields on available land, in light of an ever growing world population, remains an issue of importance for agronomists and plant physiologists alike. With this in mind, the underlying study was aimed at investigating the bio-stimulatory properties of a Lupinus albus L. seed suspension (SS) as well as its potential to be applied as a natural plant growth regulator in the horticultural and agricultural industries. Preliminary bio-tests, including the respiration rate of monoculture yeast cells, seed germination and seedling growth, strongly indicated that the rather crude seed suspension possessed the ability to manipulate these aspects when applied exogenously. SS significantly increased the respiration rate of monoculture yeast cells and, although it did not have a significant effect on seed germination, stimulated seedling growth in terms of coleoptile and root length in a number of crops at an optimal concentration of 5 mg L-1. Subsequently, the effect of SS on the yields of a variety of vegetable crops, flowers and cash crops was tested under field conditions at a concentration of 5 mg L-1. This concentration proved to be optimal for most vegetables, flowers, maize and wheat as either flower formation or yield of different crops were significantly enhanced. The most significant yield increases, after a foliar spray treatment with SS at an early growth stage, was observed in beetroot, lettuce and carrots under drip irrigation by increasing the yield with 9.3, 20.0 and 24.3 ton ha-1 respectively. This supplied the rationale for activity directed isolation and purification of the active bio-stimulatory compounds involved using standard chromatography techniques. By means of NMR spectroscopy and mass spectrometry the active compound was identified as a triglyceride, glycerol trilinoleate, and its structural formula elucidated. It was concluded from this study that the development of a natural product with growth regulating and yield enhancing properties should be considered strongly from a commercial perspective.