Synthesis and insecticidal activity of lipophilic amides. Part 5: Influence on activity of varying the substituent on nitrogen

Isomerisation or shortening of the 2-methylpropyl group in (2-methylpropyl)-6-phenylhexa-2, 4-dienamide lowers insecticidal activity, as does methylation at nitrogen. Methylation at each carbon atom in turn, and, within limits, in combination, gives compounds with substantial, sometimes increased, activity. Cyclic and olefinic equivalents of the effective alkyl substituents are mostly less active.     

Mortality of sheep exported by sea: evidence of similarity by farm group and of regional differences

OBJECTIVE: To determine whether mortality of sheep exported by sea is similar for sheep from the same farm exported in different years or is associated with the region of origin. DESIGN: Mortalities were monitored in farm groups of sheep exported from the southwest of Western Australia under normal commercial conditions. PROCEDURE: Mortalities were monitored on commercial shipments from 1985 to 1996. For each consignment, the mortality rate was assigned its percentile ranking within the month and year of loading of the ship. A mortality rate was high if its percentile ranking was above a selected cut-off value. Five cut-off values were used in separate analyses. The spatial distribution of farms with high mortality was compared between and within zones of rainfall and length of pasture-growing season. RESULTS: A total of 479 groups of sheep from 405 farms was monitored. Mortality rates ranged from nil to 28.2%. Half of all deaths were from 14.2% of the consignments. There was a significant association (P < 0.05) between the category of mortality (high or low) in the first and second years of monitoring for four of the five cut-off values. The spatial analyses indicated that there were more high-mortality groups, and the average mortality was higher, in the zones of higher rainfall and longer pasture-growing season (P < 0.001). CONCLUSION: Mortality data can be used to identify regions and groups of sheep that are at risk of suffering high death rates when exported by sea.     

Growth form and seasonal variation in leaf gas exchange of Colophospermum mopane savanna trees in northwest Botswana

We investigated differences in physiological and morphological traits between the tall and short forms of mopane (Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard) trees growing near Maun, Botswana on a Kalahari sandveld overlying an impermeable calcrete duricrust. We sought to determine if differences between the two physiognomic types are attributable to the way they exploit available soil water. The tall form, which was located on deeper soil than the short form (5.5 versus 1.6 m), had a lower leaf:fine root biomass ratio (1:20 versus 1:6), but a similar leaf area index (0.9-1.0). Leaf nitrogen concentrations varied between 18 and 27 mg g(-1) and were about 20% higher in the tall form than in the short form. Maximum net assimilation rates (A sat) occurred during the rainy seasons (March-April 2000 and January-February 2001) and were similar in the tall and short forms (15-22 micromol m(-2) s(-1)) before declining to less than 10 micromol m(-2) s(-1) at the end of the rainy season in late April. As the dry season progressed, A sat, soil water content, predawn leaf water potential (Psi pd) and leaf nitrogen concentration declined rapidly. Before leaf abscission, Psi pd was more negative in the short form (-3.4 MPa) than in the tall form (-2.7 MPa) despite the greater availability of soil water beneath the short form trees. This difference appeared attributable to differences in root depth and density between the physiognomic types. Stomatal regulation of water use and carbon assimilation differed between years, with the tall form having a consistently more conservative water-use strategy as the dry season progressed than the short form.