We describe an enzymatic method for rapid, precise measurement of serum triglycerides with use of sample:reagent ratios as large as 1:200. Hydrolysis of triglycerides is catalyzed by lipase to produce glycerol and free fatty acids. The glycerol generated is then phosphorylated by adenosine 5'-triphosphate in the presence of glycerol kinase. Oxidation of the resulting glycerol 3-phosphate to produce hydrogen peroxide is catalyzed by L-alpha-glycerophosphate oxidase. An intense red chromogen is produced by the peroxidase-catalyzed coupling of 4-aminoantipyrene and sodium 2-hydroxy-3,5-dichlorobenzenesulfonate with hydrogen peroxide. This sensitive chromogen system not only permits use of unusually small sample volumes, it also facilitates a linear response to serum triglyceride concentrations up to at least 10 g/L while displaying good Ringbom (measure of accuracy) characteristics.

SummaryThe production of root axes and the growth of the root system are reported for a commercially grown crop of Maris Huntsman winter wheat. Soil cores were extracted on 17 occasions during the growing season permitting a detailed study of root length and root dry weight with depth and time.Production of seminal root axes was complete by the beginning of March when all plants possessed six (occasionally seven) axes which persisted throughout the life of the crop. Nodal axes were produced continuously from mid-February until late May and finally numbered approximately 20 stem nodal axes per main stem. Total root dry weight increased exponentially until the beginning of April and then almost linearly to reach a maximum of 105 g root/m2 field in mid-June (anthesis). After anthesis, total root dry weight decreased but root growth continued below 80 cm. From April onwards, approximately 65% of the total root dry weight was in the 0–30 cm layer.

SUMMARYMaris Huntsman winter wheat was sown on 30 October 1974 and grown under typical farming conditions. Between sowing and harvest (5 August 1975), the crop was sampled on 23 occasions and dried samples of individual plant components were analysed for Na, K, Ca, Mg, P, S and N composition.The concentration of nutrients within the whole plant generally decreased throughout growth but different parts of the plant varied in their behaviour. Uptake of all nutrients ceased at, or shortly after, anthesis in mid-June while dry-matter accumulation continued slowly for a further 2–3 weeks and almost stopped 4 weeks before harvest. The major period of nutrient uptake occurred between mid-April and mid June coincident with the period of rapid shoot growth. Large amounts of potassium and sulphur (almost 50% of the plant's anthesis content) and lesser amounts of calcium (15%) were lost from the plant after anthesis and efflux from the roots into the soil appeared to be the most likely pathway of removal.Accumulation of nutrients in the ear occurred throughout grain-filling by translocation from other parts of the plant, particularly the leaves and stems: the effects of this redistribution on the production of dry matter after anthesis are discussed.

SummaryVolumetric soil water content and soil water potential were measured beneath a winter wheat crop during the 1975 growing season. Almost no rain fell between mid-May and mid-July and the soil dried continuously until the potential was less than – 20 bars to a depth of 80 cm. Evaporation was separated from drainage by denning an ‘effective rooting depth’ at which the hydraulic gradient was zero.Rates of water uptake per unit length of root (inflow) were calculated for the whole soil profile and for individual soil layers. Generally, inflow decreased throughout the period of measurement from a maximum of 2·5 × 10–3 to a minimum of 0·66 × 10–3 ml water/cm root/day. Values in individual layers were frequently higher than the mean inflow and the importance of a few deep roots in taking up water during a dry season is emphasized. A similar correlation between inflow and soil water potential was found to apply for the 0–30 cm and 30–60 cm layers during the period of continual soil drying. This relationship represents the maximum inflow measured at a given soil water potential; actual inflow at any particular time depends upon the interrelationship of atmospheric demand, soil water potential and the distribution of root length in the soil.

The authors regret the following errors: Page 102, Appendix Table 1, lines 13, 15, 17, 20 and 22 of the Table should be amended as follows: