Effect of Reduction of Sink Strength in Developing Seeds on Vein Loading Patterns of Photoassimilate in Source Leaves of Pisum sativum L

The effect of sink strength reduction in developing seeds onvein loading of photoassimilate has been studied in Pisum sativumL. The sink strength was manipulated by means of the ‘openseed coat technique’. Sink strength of the operated ovuleswas controlled by the osmolality of a substitute medium replacingthe embryo. A high osmolality of the medium (400 mM mannitol)or a low osmolality of the medium (without mannitol) was usedto maintain a high or low sink strength, respectively. To studythe effect of sink strength reduction on vein loading, macro-autoradiographywas used. After applying ¹⁴CO₂ to the source leaf for 10 to20min autoradiographs of plants with different sink strengthshowed differences in distribution of ¹⁴C-photoassimilate overthe mesophyll and the veins. Under low sink strength conditionsvein loading of ¹⁴C-photoassimilate was reduced. After longertime spans (40 to 60 min) no clear differences in vein loadingwere visible in the autoradiographs. However, measurement of¹⁴C in plant parts along the path of transport from source tosink showed a decrease of the rate of export of ¹⁴C from thesource leaf under low sink strength conditions. Apparently,accumulation of ¹⁴C-photoassimilate into the phloem and exporttowards sink regions can be reduced by lowering the sink strength.A signal must have been transferred from sink all the way tothe source regions. The mechanism of such a signal is discussed. Key words: Pisum sativum, phloem loading, photoassimilate transport, seed development, sink-source interactions     

Billingen (Lower Arenig/Lower Ordovician) acritarchs from the East European Platform and their palaeobiogeographic significance

Billingen (Lower Arenig/Lower Ordovician) sediments of the St. Petersburg region, northwest Russia and the Leba area, northern Poland of the East European Craton yield acritarch assemblages, which are largely homogenous though displaying minor compositional differences that probably reflect a gradient from inner to outer shelf environments. Comparison with coeval acritarch microflora from the Yangtze Platform, South China, shows an overall similarity between Baltoscandian and South Chinese phytoplankton. The widespread uniformity in the fossil microphytoplankton may be related to the extensive global 'evae' sea-level transgression, which characterized the Billingen time. This suggests that during the Tremadoc through early Arenig times, acritarch assemblages displayed essentially an undifferentiated cold-water and oceanic character along the whole margin of Perigondwana in the South, as well as on the South Chinese and Baltic platforms, at middle latitudes (Mediterranean oceanic Realm). Despite this overall similarity, however, some typical taxa of the high-latitude Mediterranean Province (Arbusculidium, Coryphidium and Striatotheca) occur in South China, but are absent in Baltica. This discrepancy is explained as caused by differences in climatic and physiographic conditions that prevailed at the two palaeocontinents at this time. The inferred pattern of oceanic circulation during the Lower Ordovician is consistent with the palynological evidence of a prevailing warmer climate in Baltica than in South China, although the two palaeocontinents occupied the same palaeolatitudinal position.     

Evaluation of PAPNET-assisted cervical rescreening

Evaluation of PAPNET-assisted cervical rescreening
We have compared the results of targeted manual rescreening of 1211 randomly selected smears with the results of PAPNET-assisted rescreening of 1613 cervical smears, containing at least 6.3% low-grade squamous intraepithelial lesion (SIL). PAPNET diagnosis and the targeted rescreening diagnosis were compared with the initial report, issued on the corresponding smear. Reproducibility scores for inadequacy, presence of endocervical and endometrial cells, specific infections and squamous cell abnormalities were determined. The reproducibility scores for the diagnosis of inadequate smears and specific infections were lower with the PAPNET-assisted rescreening. The detection of squamous cell abnormalities was excellent for both methods (>0.95), with a higher detection rate for false-negative smears with the PAPNET testing system.     

A polypharyngeal marine flatworm (Platyhelminthes, Proseriata, Archimonocelididae) from eastern Australia

Archimonocelis medusa sp. nov. is described from eastern Australia. The species is characterized by numerous (15–25) pharynges, as well as by details of sclerotized organs and karyotype. It is the first polypharyngeal marine flatworm known, and the first record of polypharyngy outside the Tricladida. Polypharyngy is interpreted as a disruption of the processes of pharyngeal induction and inhibition during development. Its possible adaptiveness is discussed.     

Interspecific host discrimination and competition in Apoanagyrus (Epidinocarsis) lopezi and A.(E.)diversicornis, parasitoids of the cassava mealybug Phenacoccus manihoti

Abstract.

• 1 Choice experiments on interspecific host discrimination in A.lopezi and A. diversicornis were carried out on discs of cassava leaf containing four hosts (P.manihoti) that had been parasitized by the other species and four unparasitized hosts.
• 2 A.lopezi accepted both host types equally for oviposition, whereas A.diversicornis accepted fewer hosts that had been parasitized by A.lopezi than unparasitized ones. A.diversicornis is therefore capable of interspecific host discrimination, but such a capability was not demonstrated for A.lopezi.
• 3 Survival probability in singly parasitized hosts was 0.85 for both parasitoid species. When the time interval between ovipositions was 2 h or less, survival in multiparasitized hosts was 0.68 for A.lopezi and 0.17 for A.diversicornis, irrespective of priority. Increasing A.lopezi priority to 24±2h did not increase A.lopezi survival. A.diversicornis survival, however, increased to 0.43 when A.diversicornis was given 24 ± 2 h priority. A.diversicornis eggs took 19 h longer than A.lopezi eggs to hatch. This could explain the difference in competitive abilities in multiparasitized hosts.
• 4 The observed difference in host selection behaviour between A.lopezi and A.diversicornis is in accordance with the different benefits of multiparasitism: A.lopezi gains more than A.diversicornis because of its superior within-host competitive abilities.
• 5 Neither species avoided multiparasitism completely. The low survival probability of A.diversicornis in multiparasitized hosts may partly explain its failure to establish when introduced into Africa as part of a biological control programme of P.manihoti.

     

SENSORY ANALYSIS IN MARKETING PRACTICE: COMPARISON AND INTEGRATION

Sensory analysis has traditionally played a prominent role in quality control for food products. More and more principles from sensory analysis are also applied in the area of food product development, bringing sensory analysis more closely into the domain of marketing. Unfortunately, in practice integration between sensory and marketing practices is far from optimal. Differences in basic orientations between sensory and marketing are a major source contributing to this defective cooperation.
Sensory analysis has traditionally been product oriented with an emphasis on internal validity of the test results. Implicitly or explicitly this approach emphasizes the relationships between sensory evaluation and characteristics of the product. Marketing, on the other hand, stresses the external validity of test results: the extent to which test results can be generalized to market behavior. Emphasis on external validity requires an approach to sensory analysis that is fundamentally different from current sensory practice in terms of type of respondents, type of stimuli, scaling procedures adopted and test circumstances.
Closer integration between the product and consumer oriented approach to sensory analysis may contribute to the success of product development in the food industry. The literature suggests several factors that may contribute to a more fruitful cooperation between the two approaches to sensory analysis. The company's senior management plays a central role in the achievement of this integration by providing an infrastructure (in terms of personnel, organizational structure and financial resources) that paves the way for closer cooperation.     

Sterilization by Means of Hydrochloric Acid Vapour

As heat sterilization of glass bottles often results in breakage and of most plastic containers in deformation, we investigated a rapid low-temperature sterilization method as an alternative. Vapour evolving from hydrochloric acid was chosen because it does not leave toxic residues which might contaminate food packed in treated containers. Vapour evolving from 0.25 ml of 31% (w/w) hydrochloric acid reduced the number of viable spores of aerobic and anaerobic bacteria in bottles (300 ml) by a factor of at least 2500 and that from 0.01 ml of 37% (w/w) hydrochloric acid reduced the number of mould spores by a factor of over 40 000 within 5 min at 20°C.