Derek T. Cooke

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It has been shown that N-, P- and S-deficiencies result in major reductions of root hydraulic conductivity (Lpr) which may lead to lowered stomatal conductance, but the relationship between the two conductance changes is not understood. In a variety of species, Lpr decreases in the early stages of NO3-, H2PO4(2-) and SO4(2-) deprivation. These effects can(More)
Plasma membranes have been isolated and purified from two species of fungi, Penicillium cyclopium and Ustilago maydis, using a two-phase aqueous polymer technique. The membranes were characterised using marker enzyme assays (e.g., vanadate-sensitive (Mg(2+)-K+)-ATPase and glucan synthetase II) and lipid composition (sterol enrichment, increased(More)
Oat and rye plants were treated with either tetcyclacis (an experimental plant growth regulator), nuarimol (a fungicide) or gamma-ketotriazole (an experimental herbicide). These treatments reduced shoot growth and changed the lipid composition of the shoot plasma membranes. In oat, both tetcyclacis and nuarimol treatments increased plasma membrane(More)
A study was made of alignment abnormalities and bone deformities in Saudis with osteoarthritis (SOA). Data from standardized radiography of hips and knees were: hip-knee-ankle angle (HKA), condylar-hip angle (CH), tibial plateau-ankle angle (PA), and joint surface (condylar-plateau) angle (CP). Females dominated the <50 years SOA subgroup (1.8:1), having(More)
Accumulation of 14alpha-methylated sterols or delta8-sterols in Ustilago maydis affected three aspects of the plasma membrane H+-ATPase. Proton transport was reduced in delta8-sterol-accumulating samples, due to an altered H+/ATP stoichiometry. ATP hydrolytic activity was increased, but no direct correlation with the extent or type of abnormal sterol(More)
Symbiosomes were obtained from mature pea (Pisum sativum cv. Argona) root nodules infected with Rhizobium leguminosarum strain (biov. viciae 3841) and purified using an aqueous polymer two-phase system (APS). The APS consists of a mixture of polymers, usually dextran T500 and poly(ethylene glycol) 3350, prepared as aqueous solutions on a weight per weight(More)
Ca2+ transport has been measured across plasma membrane vesicles isolated from cells of Ustilago maydis. This transport was found to be ATP- (or to a lesser extent GTP) and Mg(2+)-dependent. Inconsistent release of Ca2+ from intact vesicles was obtained using the calcium ionophore A23187. However, Ca2+ was released by Triton X-100 in a(More)
A simple, automated colorimetric method for determining oxalic acid in plant material is based on the quantitative reduction in colour of a zirconium/3,4-dihydroxyazobenzene-2'-carboxylic.acid complex by microgram quantities of oxaIic acid. I t is suitable for use over a wide range of oxalic acid concentrations. Interference from phosphate, sulphate, citric(More)
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