LD2668 .T4 1942 O15 / Master of Science

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The production of azadirachtin and other related limonoids were investigated using plant cell culture systems of Neem (Azadirachta indica). The production of antifeedant compounds in callus lines was monitored by no-choice bioassays with Schistocerca gregaria with instar nymphs. Growth of two callus lines produced from leaves of a Ghanaian neem tree were monitored and the growth patterns displayed the typical lag, stationary and exponential phases. Growth and product formation, as measured by antifeedant bioassays with S.gregaria, showed non-growth associated product formation. Azadirachtin was isolated from callus derived from a Ghanaian neem tree by Prof. E.D. Morgan, University Keele using the standard procedure of solvent partitioning and column chromatography. Biological activity of the partitioning fractions was measured with antifeedant tests. Azadirachtin was identified by chromatography on three independent systems (Supercritical Fluid Chromatography (SFC), High Performance Liquid Chromatography (HPLC) and Thin Layer Chromatography). The yield of azadirachtin was 0.0007% based on dry weight of callus. Neem leaf explants collected from wild neem trees could be successfully surface sterilised by treating with 0.1% HgCl2 for 5 min followed by 10% Bleech (Care Products, Sri Lanka) or NaOCl (Sigma, UK) for 10 min. New callus lines were initiated from leaves collected from wild neem trees by incubating on Maintenance Medium (Kearney et al., 1994) at 25°C in the dark. Fifteen callus lines thus initiated were extracted with ethanol under reflux, quantified and screened for the production of azadirachtin, nimbin and salannin by reversed phase HPLC. There was no correlation between azadirachtin, nimbin and salannin yields of callus lines and those of seeds collected from same neem trees. The genetic variation of callus lines was examined by iso-enzyme electrophoresis using three enzymes, malate dehydrogenase, alcohol dehydrogenase and diaphorase and no variation was observed among the callus lines examined.

Call number: LD2668 .T4 1950 Y4 / Master of Science

Water regulation in drought-resistant eggs of the brown locust Locustana pardalina (Walk.) may be mediated by specialised serosal cells in the hydropyle region. These cells are thought to both supply water to the embryo and to waterproof the egg during very dry periods. The characteristics of hydropyle cells in quiescent eggs were examined at intervals during desiccation at 15-22% RH, and again after rehydration. Embryos were pre-catatreptic and any pre-existing diapause condition had terminated. Egg water contents and the sizes of cells and nuclei decrease with desiccation, and increase after rehydration. Deformable cell and nuclear membranes accommodate size changes. Surface microvilli increase in length with rehydration and cytoplasmic vacuoles become larger, indicating absorption of water. Organelle integrity improves upon rehydration while autophagy remains common. Evidence of the production and secretion of a waterproofing protein substance, while expected, was not found. However, electron dense vesicles present at the apical boundaries suggest that the cells may nonetheless produce some substance in that region. Dehydrated and rehydrated cells show signs of desiccation damage, but this does not affect cell functioning as embryos from rehydrated eggs developed to hatching. The results indicate that, in addition to structural protection, hydropyle cells may have molecular protection against desiccation damage, and may be able to undertake limited repair upon rehydration.

Digitized by Kansas Correctional Industries

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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