Phosphorus Redistribution in Maize Plants, Zea mays L., in Relation to the Nitrogen Supply

The influence of different nutrition regimes on phosphorus (P) redistribution in maize plants, cv. LG 11, was studied. Nutrient solutions in four combinations of high and low nitrate concentrations and high and low phosphate concentrations were used to grow four different groups of plants. During the development of the plants dry weights and total P contents were measured. It was concluded that P redistribution into reproductive organs was dependent on N supply and was a consequence of N redistribution. The ratio of N and P concentrations was not equal in several parts of the plant, and was not constant during the development. In different parts of a young plant the ratio increased. As soon as redistribution of N and P started the N/P ratio decreased. The minimum N/P ratio of a mature maize plant was about 3 for leaves and 1 or 2 for roots and stems.     

Resistance to triforine: A nonexistent problem?

Permanent resistance to triforine in Cladosporium cucumerinum was obtained after UV irradiation of spore suspensions and selection of resistant strains in the presence of triarimol or triforine. About 50 strains were examined for mycelial growth on malt agar, viability upon routine subculturing, growth and inhibition by triforine in thin-layer chromatographic bioassays, and virulence towards cucumber seedlings. In addition, sporulation and spore germination, as well as effects of ergosterol were investigated in a restricted number of strains. Although all strains differed considerably from each other in these characteristics, they were quite similar in a reduced overall-fitness. These triforine-resistant mutants of C. cucumerinum might, therefore, have a greatly reduced chance of survival in competition with the wild-type strain, as was actually demonstrated for two strains in greenhouse experiments with mixed-inoculations of cucumber seedlings. Such a reduced chance of survival might also explain why under practical conditions development of resistance to triforine has not been observed yet.The triforine-resistant C. cucumerinum strains showed cross-resistance to a number of systemic fungicides known or supposed to inhibit ergosterol biosynthesis, viz. Denmert, fenarimol, imazalil, triadimefon and triarimol. The practical implications and potential hazards of such cross-resistance for the use of already established fungicides are discussed.     

Effects of temperature on growth and development of hybrid Tea-rose seedlings

Hybrid Tea-rose seedlings were grown, from germination to first flowering, at 6 constant temperatures between 10 and 26°C in greenhouses of our phytotron. All seedlings flowered regardless of temperature. When temperature increased, the juvenile period, the number of days to first flowering, the length of the leaved part of the shoot, the length of the flower stalk, the fresh weight of the shoot and of the root decreased; leaf number was not affected.     

Finite Radiocarbon Dates of the Port Talbot Interstadial Deposits in Southern Ontario

Three new finite radiocarbon dates Suggest that (i) the thermnal maximum of the Port Talbot interstadial ocurred prior to 47,000 years before the present and (ii) the interstadial deposits were overridden by a glacial advance approximatels 44,000 years before the present. To facilitate correlaltions with other areas, new rock-stratigraphic names are proposed for the Port Talbot type section.     

A Hypoderma diana (Diptera: Hypodermatidae) infection in a horse

An infection with second-stage larvae of the warble-fly H. diana in a horse is described. The second-stage larvae were incapable of developing into the third stage, because horses are unsuitable hosts and because the infected horse was treated with an insecticide. Since the horse was used for dragging trees in the forests, the infection was likely contracted via contact with H. diana, a normal parasite of roe deer in the Netherlands.     

Inherited congenital extrahepatic portosystemic shunts in Cairn terriers

The pathogenesis of congenital portosystemic shunt (CPSS) in dogs still is incompletely understood. In Irish Wolfhounds and Yorkshire Terriers, CPSS is reported to be hereditary. The aim of this study was to investigate a possible genetic basis and the mode of inheritance of CPSS in Cairn Terriers. Between July 1990 and July 2001, 6-week-old pups of the Dutch Cairn Terrier population were screened by measuring venous ammonia concentrations and in the presence of hyperammonemia by ultrasonography, autopsy, portal vein angiography, or exploratory celiotomy. The same successfully operated female was used 3 times in test matings with an unrelated affected male, her unaffected sire, and an affected offspring. The prevalence of CPSS in the general Cairn Terrier population, the direct progeny of frequently used males, and the offspring of the test matings were tested for significant differences. In total, 6,367 Cairn Terriers were screened; 32 males and 26 females had CPSS. In 3 large family groups, significantly higher prevalences were found compared with the general population (P < .0001, P < .0001, and P < .044). The prevalence of CPSS in the offspring of the test matings was significantly higher (P < .002) than in the general population. No sex predisposition occurred among the affected dogs. The higher prevalence of CPSS in the test matings and the 3 family groups compared with the general population indicates that CPSS in Cairn Terriers is a genetic disease. The inheritance is autosomal and most likely polygenic or monogenic with variable expression.     

Interaction of temperature and light on growth and development of hybrid tea-rose seedlings,with reference to breeding for low-energy requirements

As a basis for a breeding-programme of glasshouse roses adapted to low-energy conditions (low temperature and low light intensity), growth and development of Hybrid Tearose seedlings were studied in 9 controlled environments (16, 20 or 24°C combined with 8, 16 or 24 Wm^?2 for 8 h). The percentage of flowering seedlings increased with increasing light intensity independent of temperature, rapidity of flowering was promoted by increasing both light intensity and temperature, stem length at anthesis was promoted by increasing light intensity but shortened by increasing temperature. The possibility of selecting seedlings, and consequently cultivars, adapted to low-energy conditions was discussed.     

Case report: congenital myoclonus in a German Holstein calf

A female German Holstein calf was not able to stand up after birth. Resting the animal was lying in normal position and could lift its head. Sensory stimuli like auditory or tactile impulses induced myoclonic jerking of the whole body. Afterwards it calmed down quickly. The signs observed correspond to the clinical findings of congenital myoclonus in poll Hereford calves. The pathological examination revealed no indications for changes in organs. The inbreeding coefficient of the calf was 1.56 %. The present type of congenital myoclonus in the calf examined is likely to be genetically determined, even if the point mutation in exon 2 of the glycin receptor alpha 1 gene was not confirmed.     

Independent segregation of two isozyme markers and inter-plant differences in nuclear DNA content in the interspecific backcross (Allium fistulosum L. × A. cepa L.) × A. cepa L.

Summary From backcrosses of three interspecific hybrids (A. fistulosum x A. cepa) with a. cepa 14 diploid and 2 triploid plants were recovered.In this BC1 population introgression of A. fistulosum genetic material into the A. cepa nuclear genome was studied using two isozyme markers: Got-1 and Got-2. Both loci carried two alleles. A. cepa was monomorphic for both markers. A. fistulosum was polymorphic for Got-2. Based on their Got isozyme pattern seven out of the 14 diploid BC1 plants had a recombinant genotype. The loci appeared to be unlinked. Differences were observed in nuclear DNA contents between the diploid BC1 plants, indicating that gametes produced by the interspecific hybrids contained different combinations of chromosomal material from A. cepa and A. fistulosum.Abbreviations Adh alcohol dehydrogenase - Got glutamate oxaloacetate transaminase - Idh isocitrate dehydrogenase - Pgi phosphoglucoisomerase - Pgm phosphoglucomutase