Determination of styrene content in Gorgonzola PDO cheese by headspace solid phase micro-extraction (HS-SPME) and gas-chromatography mass-spectrometry (GC-MS)

Control of the composition of products that are intended for use as packaging material is essential, particularly when these products come into direct contact with food. It is well known that plastics are not inert and that their residual monomers, starting substances, and additives are able to migrate into the food they contact. Among plastics, styrene is a common compound found in many plastic containers that can also be produced by the oxidation of Penicillium roqueforti used in gorgonzola Protected Denomination of Origin cheese manufacturing. Therefore, solid-phase microextraction combined with gas chromatography/mass spectrometry was applied in the present work to determine the styrene content in packaged and unpackaged gorgonzola cheese samples to understand styrene migration phenomena from plastic containers.

     

Chaetotaxy of cercariae of Opisthioglyphe ranae (Fr?lich, 1791) (Trematoda: Plagiorchidae)

A detailed observation of the sensory apparatus of Opisthioglyphe ranae (Fr?lich, 1791) cercariae was carried out. The species was determined on the basis of an experimental study of the life cycle and morphology of sporocysts, cercariae, metacercariae, and adults. In contrast to other species of the family Plagiorchidae, no papillae were present in the positions CId1, CId2, CII0, CII3 and CII4. Papillae with markedly ventral situation on the postacetabular zone were found very rarely. Some of the cercariae possessed ventral papillae variously distributed in the preacetabular zone. A comparative analysis of the chaetotaxy revealed that the cercaria studied by us was very similar to Cercaria 4 of Richard, 1971, with the exception of the number of acetabular papillae and some groups of ventral papillae. Compared to the cercaria of O. ranae studied by Dobrovolskiy (1965). AID papillae and a part of ventral papillae were distributed differently. The chaetotaxy was identical with that of experimentally obtained cercariae of O. ranae from L. stagnalis and of cercariae of the same species obtained from Bulgaria.     

Comparative morphology of Phytophthora species on rubber

Eighty-nine Phytophthora isolates from rubber throughout the world were examined critically. Five species were distinguished: P. palmivora morphological form I (MF1), P. meadii, P. botryosa, P. citricola, P. citrophthora and one currently designated P. palmivora (MF4). P. citrophthora is reported for the first time from rubber in the Ivory Coast and Indonesia, and mating types are given.     

Assessment of competition between crops and weeds

A two-species model was used to summarize results of four experiments with two component mixtures of barley (Hordeum vulgare L.), peas (Pisum sativum L.), Chenopodium album L. and Sinapis alba L. grown in pots in greenhouses. The results, covering a wide range of plant densities both in mixtures and pure stands, showed that the model was not always able to describe the relationship between the yield of a species and the densities of itself and its companion species. The deviations from the model were in all instances greatest for the least competitive species. The model that quantifies competition and niche differentiation appeared to be too general because competition between species was not independent of the wide plant density ranges used here. The results are discussed in relation to possible improvements of the model and an analogy between the principles of assessing crop weed competition and the assessment of the relative potency of herbicides in bioassay studies is put forward.     

Apical dominance in the shoot and its possible rôle in the survival of Paspalum distichum L.

Summary. When sequential single-node shoot segments (third to fifteenth node, counting from the apex) of the perennial grass weed Paspalum distichum L. were buried in soil, new shoot growth was significantly correlated with initial segment length. Growth from the youngest segment (third), which was about 2 cm long, was only half as great as that from segments 8 to 15, which were initially 2–3·5 times longer. When 14-node shoot segments were buried in soil, the apical bud exerted a dominating influence on shoot emergence and new shoot growth of axillary buds. The degree of suppression increased gradually up to node 8 and then decreased as the distance from the apex increased. A similar result was obtained in these shoot segments following decapitation. However, the degrees and patterns of apical and bud dominance varied in shoots collected during different seasons and also in shoots with different node numbers, node position, cutting and chilling treatments. A possible role of apical and bud dominance in P. distichum in keeping aerial shocks in reserve under adverse conditions, thus providing a survival mechanism for this weed, is discussed.     

The significance of VA-Mycorrhiza to future arable farming in the Netherlands

Present conditions of high inputs and narrow rotations render the importance of vesicular-arbuscular mycorrhiza (VAM) in arable farming in the Netherlands rather low. Changes expected in the near future under the influence of economic pressures and environmental problems may change this situation. This is discussed in the light of some such expected changes in Dutch arable farming.     

The chemical control of the lesser date moth,Batrachedra amydraula meyr., and residue levels of organophosphate insecticides in dates

Larvae of the lesser date moth (Batrachedra amydraula Meyr.) cause damage to dates in Iraq. A formulation based on a mixture of equal parts of wheat flour and pollen grains and containing either chlorpyrifos, fenitrothion or pirimiphos-methyl (all at 5 mg kg^?l) was dusted (5 g formulation bunch^?1) onto female clusters of dates at the time of pollination. Numbers of larvae, yield of dates and insecticide residues were monitored over a three-month period. Results showed that, by this technique, all three insecticides were effective in controlling the pest but that fenitrothion and chlorpyrifos were better than pirimiphos-methyl.     

Inhibition of germination of sporangia of Peronospora hyoscyami by cation deprivation: the effects of substrate and chelating agents

Germination of sporangia of Peronospora hyoscyami de Bary (tobacco blue mould) was affected by the germination substrate. Washed sporangia germinated freely in water on glass slides, but failed to germinate on agarose. Germination was reduced on detached tobacco leaves, being lower on cv. Hicks Q46 than on cv. ZZ100. Inhibition of germination by agarose was reversed by the addition to the inoculum of an extract obtained by centrifuging a suspension of non-living, powdered torula yeast Candida utilis (Hennenberg) Lodder & van Rij. Yeast extract also improved germination in vivo. The siderophore rhodotorulic acid, the chelating agents ferric and sodium citrate, and riboflavin combined with calcium and magnesium salts, also stimulated germination of sporangia on agarose. The chelating agent ethylenediaminetetraacetic acid (EDTA) inhibited germination on glass slides. Inhibition by EDTA was partially reversed by the addition of ferric salts. The inhibition of germination by agarose and stimulation by additives may have been due to effects on the availability of cations to sporangia of P. hyoscyami. The reduction in germination on tobacco leaves may have involved a similar mechanism.