Abstract
In vitro and in vivo bio-stimulatory activity of a Lupinus albus cv. Bethuana white Seed Suspension (SS) was previously documented using vegetable crops. This was repeated for two grain crops, maize and wheat, in an attempt to provide a rationale forthe isolation and identification of the active compound(s) involved. In all cases, besides negative controls, the response to treatment with SS was compared to that of a commercial bio-stimulant, ComCat®. At an optimum concentration of 5 mg â„“-1 SS significantly enhanced seedling growth and yield in both crops. Subsequently, activity directed liquid-liquid extraction of ground L. albus seed resulted in an ethyl acetate extract containing most of the bio-stimulatory activity. Two in vitro bio-assay procedures were employed to appraise the in vitro bio-stimulatory properties of semi-purified fractions as well as pure compounds contained in it. The highly active ethyl acetate extract was fractionated further by means of adsorption column chromatography resulting in eighty five fractions that were combined into twelve on the basis of similarities in thin layer chromatography profiles. Four of these fractions showed significant bio-stimulatory activity and were pooled. From this one compound was isolated, purified and identified as glyceryl trilinoleate by means of nuclear magnetic resonance spectroscopy. Key words: Lupinus albus, seed suspension, field trials, yield, NMR spectroscopy, glyceryl trilinoleate.
Highlights
In light of a sharp increase in world population predicted for the future, and the resulting uncertainty towards food security, a need exists to increase crop yields on available arable land (Heidhues, 2001)
As the manufacturers of ComCat® claimed a 0.5 mg l-1 concentration to be optimal for bio-stimulation of crop plants and the minimum stimulatory concentration (MSC) of SS was found to be 5.0 mg l-1 with both bio-assay procedures, only these concentrations were applied in the extended screening program with different seedlings
According to the study of Schnabl et al (2001), extractable amounts of plant growth regulating compounds are associated with the plant families Fabaceae and Caryophyllaceae
Summary
In light of a sharp increase in world population predicted for the future, and the resulting uncertainty towards food security, a need exists to increase crop yields on available arable land (Heidhues, 2001). Due to consumer resistance towards the extended use of synthetic chemicals in an attempt to reach this goal, a rationale for natural product research, especially environmentally friendly natural bio-stimulants that have the potential to improve crop yields, exists This is not a new concept as plant extracts containing growth promoting substances have been of interest to the agricultural research community since the early seventies in terms of the role they could play in addressing future food security issues (Blum et al, 1992; Suzuki et al, 2002). The main objectives of the underlying study were to establish: 1) whether seedlings of grain crops (wheat and maize) respond in vitro to foliar treatment with SS in terms of growth, 2) and in vivo in terms of yield over one growing season in an attempt to provide a rationale for, 3) the isolation and identification of the active bio-stimulatory compound(s) contained in L. albus cv Bethuana White seeds. Other advantages of ComCat® include improved crop quality (Prusakova et al, 1999) and the induction of resistance towards fungal pathogen infection in potato (Schnabl et al, 2001)
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