The selective allelopathic interaction of a pasture-forest intercropping in Taiwan

Summary An allelopathic interaction of a pasture-forest intercropping system was evaluated by experiments conducted in field and by laboratory assays. A study site was situated in the farm of Hoshe Forestry Experiment Station at Nantou County, Taiwan. After deforestation of Chinese fir (Cunninghamia lanceolata), a split plot design of 4 treatments, namely litter removed, litter removed and kikuyu grass (Pennisetum clandestinum) planted, litter left, and litter left and grass planted, was composed. Field meaurements showed that the fir litter left on the ground did not significantly inhibit the growth of weeds, kikuyu grass, and fir seedlings in the first four months following deforestation, while kikuyu grass significantly suppressed the growth of weeds longer than four months but did not reduce growth of fir seedlings. The aqueous extracts of fresh fir leaves, fir litter, and kikuyu leaves were bioassayed by using lettuce and rice seeds and stolon cuttings ofBrachiaria mutica. Bioassays showed that fresh fir leaves produced significant phytotoxicity while fir litter and kikuyu grass gave limited toxicity. Nine phytotoxic phenolics and many unidentified flavonoids were found in the leaf and litter of Chinese fir and kikuyu leaves. A good correlation between the degree of phytotoxicity and phytotoxins was obtained, indicating an allelopathy was involved. This finding suggests that allelopathy may contribute benefits in the intercropping system to reduce the need for herbicides and to lessen the labor cost for weed control. Paper No. 304 of the Scientific Journal Series of the Institute of Botany, Academia Sinica, Taipei, Taiwan, Republic of China. This study was supported in part by grants of Academia Sinica, Taipei, and Council of Agriculture, Executive Yuan of the Republic of China.     

Aflatoxin-producing potential of Aspergillus flavus strains isolated from Spanish poultry feeds

A total of 126 fungal strains belonging to the Aspergillus flavus group isolated from commercial poultry mixed feeds were studied. One hundred and twenty-five were identified as A. flavus and one as A. parasiticus. Forty nine strains (39%) produced aflatoxins on a crushed moist wheat medium (28 °C/10 days), whereas only sixteen (13%) showed specific fluorescence on Aflatoxin-Producing Ability Medium. In both media, mainly aflatoxins B₁ and B₂ were detected, the average concentration of aflatoxins being 4294+/–1083 g/kg in crushed moist wheat medium, and 877+/–257 g/kg in Aflatoxin-Producing Ability Medium.     

Promotion of flowering in the Pinaceae by gibberellins

Significant male and female flowering (cone bud production) by girdled branches of 6-year-old Douglas fir (Pseudotsuga menziesii (Mirb. Franco) seedlings was promoted by applications (mid-April to June) of 1.6 or 3.2 mg per branch (in total) of certain non-polar gibberellins (GA's). Girdling alone was ineffective. When tested alone, a mixture of GA_4/7 was most effective. GA₉ less so, while GA₅ and the more polar GA₃ were essentially ineffective. For female cone buds GA_4/7+ GA₉ were synergistically effective, but for male cone buds GA_4/7 alone was best. The auxin naphthaleneacetic acid (NAA) was not tested alone, but at low dosage (0.175 mg/branch in total) NAA enhanced the flowering efficacy of GA's for both sexes; at a high dosage (0.875 mg/branch in total) male cone bud production was further enhanced, but only at the expense of females. For female flowering the best treatment (90% frequency of flowering 6.8 cone buds/branch), was GA_4/7+ GA₉+ low NAA; for male flowering, it was GA_4/7+ high NAA (30% frequency and 4.2 cone buds/branch. Frequency of flowering for controls was 18% and 0%, average number of cone buds/branch was 0.9 and 0, for females and males, respectively. The successful treatments did not affect promordia initiation, rather they caused the differentiation of previously initiated, but undetermined, lateral primordia into cone and latent buds at the expense of vegetative bud differentiation. The lack of success reported by earlier workers in promoting flowering in Pinaceae species by GA's appears to be the unfortunate result of selecting GA₃ for initial testing. The practical implications of this early and enhanced flowering by non-polar GA's seedlings of a commercially important conifer are discussed in relation to accelerating the processes of tree improvement.     

Somatic embryogenesis from seed explants of Abies alba

Megagametophytes of Abies alba containing the immature embryos were dissected from the seed coats and divided by longitudinal and transverse sections. They were placed with the cut surface down on modified Schenk & Hildebrandt medium containing 50 mgl^-1 myo-inositol and 2% sucrose, supplemented with 1 mgl^-1 N⁶-benzyladenine (BAP). An embryogenic type of callus proliferated after one month of culture. Closer examination revealed the presence of structures resembling early stages of embryogenesis as well as of single elongated, vacuolated cells and clusters of cells with dense cytoplasm. Under appropriate conditions, some of the somatic embryos elongated and formed cotyledons.     

Eighteen polymorphic microsatellite markers for the highly endangered Spanish imperial eagle (Aquila adalberti) and related species

Here we describe the development of 18 polymorphic microsatellite markers for the endangered Spanish imperial eagle (Aquila adalberti). Microsatellites were tested in five other raptor species. These markers were revealed as good molecular tools for genetic population studies, individual identification and parentage assessment in Spanish imperial eagle and closely related species.     

Purification and properties of glutamine synthetase from Douglas fir roots

Glutamine synthetase (GS. EC 6.3.1.2) was purified to apparent electrophoretic homogeneity from roots of Pseudotsuga menziesii (Mirb) Franco by a three-step procedure involving diethylaminoethyl (DEAE)-Trisacryl chromatography, affinity chromatography on Matrex Gel Red A. and preparative polyacrylamide gel electrophoresis. The enzyme was purified 40-fold with a 16% recovery. The native enzyme had a molecular mass of 460 ± 5 kDa as estimated by gel filtration, interpolation of the Ferguson plots and non-denaturing gradient-PAGE. It was composed of two different subunits of 54 and 64 kDa. Affinity constants for glutamate (Glu), glutamine (Gln), ATP and ADP were 2.6, 10.5, 0.5 and 0.083 m M . respectively. The enzyme exhibited a negative cooperativity for ammonium (Hill number of 0.7) with two K_m values which were 11 and 75 μ M in the presence of ammonium concentrations lower and higher than 1.3 m M , respectively. Glycine and ADP appeared as potential inhibitors of the GS activity. The optimum pH values were 7.2 and 7.6 for the transferase and the biosynthetic assays, respectively. The enzyme lost 30% of its activity within 25 days of storage at 4°C. The optimum temperatures of activity were 40°C and 45°C for the transferase and bio-synthetic activities, respectively.     

Leaf phloem alterations in two provenances ofAbies alba Miller (silver fir) during ageing

The phenomenon of premature needle senescence in two Italian provenances of silver fir was studied as part of a more general research project on decliningAbies alba. The two provenances showed a different degree of sensitivity to atmospheric pollutants. Comparative observations on 1-, 3-, 5-, 7- and 9-year-old needles from both provenances highlighted a faster loss of function in the phloem of needles from the Vallombrosa provenance. This fact appears to be related more to a loss of function in the cambium, than to a different rate of degeneration of sieve cells. This phenomenon may help explain why needles of the Vallombrosa provenance tend to be shed sooner than those of the Serra San Bruno provenance.     

Unequal excess mortality during the Spanish Flu pandemic in the Netherlands

A century after the Spanish Flu, the COVID-19 pandemic has brought renewed attention to socioeconomic and occupational differences in mortality in the earlier pandemic. The magnitude of these differences and the pathways between occupation and increased mortality remain unclear, however. In this paper, we explore the relation between occupational characteristics and excess mortality among men during the Spanish Flu pandemic in the Netherlands. By creating a new occupational coding for exposure to disease at work, we separate social status and occupational conditions for viral transmission. We use a new data set based on men’s death certificates to calculate excess mortality rates by region, age group, and occupational group. Using OLS regression models, we estimate whether social position, regular interaction in the workplace, and working in an enclosed space affected excess mortality among men in the Netherlands in the autumn of 1918. We find some evidence that men with occupations that featured high levels of social contact had higher mortality in this period. Above all, however, we find a strong socioeconomic gradient to excess mortality among men during the Spanish Flu pandemic, even after accounting for exposure in the workplace.