Assessment of two biotypes of Solanum ptycanthum that differ in resistance levels to imazamox

Glasshouse and laboratory experiments were conducted on acetolactate synthase (ALS) homozygous resistant Solanum ptycanthum biotypes from Illinois (IL‐R) and Indiana (IN‐R), and homozygous susceptible biotypes from Illinois (IL‐S) and Indiana (IN‐S). Genetic similarity of biotypes was assessed by random amplified polymorphic DNA (RAPD) markers, which determined that the Illinois biotypes are more similar to each other than to the IN‐R biotype. ALS enzyme activity from the IL‐R and IN‐R biotypes had I₅₀ values of 362 and 352 μM imazamox respectively. Dose–response experiments using three‐ to four‐leaf‐stage plants of the IL‐R and IN‐R biotypes had GR₅₀ values of 242 and 69 g ae ha⁻¹ imazamox respectively. Whole‐plant and ALS enzyme results are different than previously reported values in the literature, which was attributed in the current study to the original IN‐R population having individuals that were segregating for ALS resistance. Metabolism studies showed no difference in percentage [¹⁴C]imazamox remaining between the IL‐R and IN‐R biotypes up to 72 h after treatment. The IL‐S biotype metabolised [¹⁴C]imazamox approximately two times faster than the IL‐R and IN‐R biotypes and this trait was heritable. Response of F₃ plants containing homozygous ALS‐resistant alleles from the IL‐R biotype in a genetic background of 50% Illinois and 50% Indiana biotypes suggests that genetic factors other than an altered target site or metabolism may also contribute to the magnitude of resistance at the whole‐plant level in resistant biotypes.     

MOVEMENT PATTERNS OF RIVERINE LITTER

Aspects of litter movement were looked at in a variety of ways. River bank clearances provided valuable information on litter accumulation and movement, showing a distinctive correlation between flood events and litter movement. Introduction of litter outside of channel deposition (diffuse sources) were limited in the study area in South Wales, UK. A rise in litter deposition occurred for some time after flood events, with the main accumulation occurring in the mid-bank zone. As only some litter types have an increased input during flood events e.g. sewage-derived material from combined sewer outfalls (CSO), accumulation of other litter types, e.g. plastic sheeting could be due to their distribution throughout the catchment. A positive correlation between litter stranding and vegetation was found. During high flows, (75.59 cumecs) litter is removed from sites with little restraining vegetation and deposited where stranding potential is high. Smaller items such as feminine hygiene products were more susceptible to stranding than larger plastic sheeting.     

Dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.)

The dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.) was assessed by feeding diets supplemented with graded levels of DL-methionine (9, 12, 15, 18, 21, and 24 g kg⁻¹dietary protein) for 16 weeks at 12°C. All diets contained 400 g kg⁻¹ protein, 170 g kg⁻¹ lipid, 66 g kg⁻¹ ash and an estimated 17.5 MJ digestible energy (DE) kg⁻¹. When live-weight gain was examined using quadratic regression, the estimate of methionine requirement for optimal growth was 17.6 g kg⁻¹ of dietary protein (DP) or 7 g kg⁻¹ of the diet. Requirements estimated on the basis of carcass protein and energy gains were 18.8 and 17.9 g kg⁻¹ DP, respectively. Plasma methionine concentrations and ocular focal length variability measurements did not provide a sensitive measure of requirement, because each responded in a linear fashion to increasing dietary methionine levels. Based on the prevalence of cataracts, the methionine level required to prevent lens pathology (26.7 g kg⁻¹ DP) appears to be higher than that required for maximum growth.     

Photoperiod and temperature effects on growth and development of Emex australis and E. spinosa

The effects of temperature and photoperiod on Emex australis and E. spinosa were studied in a pot experiment. E. spinosa was more precocious than E. australis in terms of earlier flowering, runner and seed formation under conditions similar to those of daylength and mean daily temperatures in the field and it produced three times more seeds. Optimum day/night temperatures for both species, however, were between 15/10 and 20/15°C. Both the lowest (10/5°C) and highest (30/25°C) temperatures tested delayed flowering and there was a terminal necrosis of runners at high temperatures. Flowering in both species also was generally hastened and seed production greater at the longest photoperiod (16 h) compared with the shortest (8 h). The results are discussed in terms of the distribution of E. australis, the similar environmental requirements of both species and the possible encroachment of the less desirable E. spinosa, which is as yet more restricted in distribution in Australia, into areas already colonised by E. australis.     

Variation in Chrysanthemoides monilifera (Compositae) in eastern Australia

Populations of Chrysanthemoides monilifera ssp. monilifera and C. monilifera ssp. rotundata were sampled over their ranges on mainland eastern Australia, and the extent of geographic variation in some morphological characters determined, Both subspecies were morphologically relatively homogeneous over the populations sampled and no obvious patterns of phenotypic variation within them were detected. The subspecies were readily distinguished from each other and no intermediate forms were observed. However there was more phenotypic variation in ssp. monilifera than in ssp. rotundata. The subspecies have ranges in Australia broadly corresponding to their climatic ranges in South Africa, and ssp. monilifera occurs over a wider climatic range in Australia than ssp. rotundata. Further work on genotypic variation within the species is needed. Variation chez Chrysanthemoides monilifera (Compositae) en Australie orientale Des populations de Chrysanthemoides monilifera spp. monilifera et C. monilifera spp rotundata ont été prélevées dans leur site en Australie de l'Est et l'étendue de la variation géographique pour quelques caractères morphologiques déterminée. Les deux sous-espèces étaient relativement homogènes pour les populations collectées et aucun exemple évident de variation phénotypique au sein d'entre elles n'a été mis en évidence. En revanche, les deux sous-espèces étaient bien distinctes entre elles et aucune forme intermédiaire n'a été observée. Cependant, il y avait plus de variabilité phénotypique chez spp. monilifera que chez ssp. rotundata. Les sous-espèces ont une répartition en Australie en relation avec leur répartition climatique en Afrique du Sud et ssp. monilifera est présente sur une plus large aire climatique en Australie que ssp. rotundata. Des travaux supplémentaires sur la variabilité génétique intra espèce s'avèrent nécessaires. Variabilität von Chrysanthemoides monilifera (Compositae) in Ost-Australien Die geographische Variabilität der Unterarten monilifera und rotundata von Chrysanthemoides monilifera wurde an Pflanzen, die in ihren Verbreitungsgebieten in Ost-Australien gesammelt worden waren, an einigen morphologischen Eigenschaften bestimmt. Beide Unterarten waren morphologisch recht einheitlich, wenn auch die ssp. monilifera eine grössere phänotypische Variabilität hatte. Die Unterarten liessen sich einfach unterscheiden, und es wurden keine intermediären Formen beobachtet. Die Verbreitung der Unterarten in Australien entspricht weitgehend ihren klimatischen Arealen in Südafrika, so dass die ssp. monilifera in Australien einen klimatisch weiteren Bereich besiedelt als ssp. rotunda. Die Art muss eingehender genotypisch untersucht werden.