Non-invasive image analysis evaluation of growth during plant micropropagation

Microcomputerized video image analysis was adapted for rapid, objective, and non-intrusive quantification of shoot growth and development for plants growing in vitro. Custom-developed staging arrangements were essential to insure accurate viewing and representation of the plants in each of three standard culture vessels. Shoot length measurements from digitized culture images were strongly correlated with length measured manually ex vitro. Image analysis weighted density measurements of proliferating microcultures (even with irregular growth habits) provided a reliable indicator of shoot culture fresh weight. Non-destructive time course evaluations of growth rate and quality were demonstrated.Abbreviations FW fresh weight - WD weighted density     

Limited chloroplast gene transfer via recombination overcomes plastomegenome incompatibility between Nicotiana tabacum and Solanum tuberosum

Green cybrids with a new nucleus-chloroplast combination cannot be selected after protoplast fusion in the intersubfamilial Nicotiana-Solanum combination. As an approach to overcome the supposed plastomegenome incompatibility, a partial plastome transfer by genetic recombination has been considered. After fusions of protoplasts of a light-sensitive Nicotiana tabacum (tobacco) plastome mutant and lethally irradiated protoplasts of wild-type Solanum tuberosum (potato), a single green colony was recovered among 2.5×10⁴ colonies. The regenerated plants had tobacco-like (although abnormal) morphology, but were normally green, and sensitive to tentoxin, demonstrating chloroplast markers of the potato parent. Restriction enzyme analysis of the chloroplast DNA (cpDNA) revealed recombinant, nonparental patterns. A comparison with physical maps of the parental cpDNA demonstrated the presence of a considerable part of the potato plastome flanked by tobacco-specific regions. This potacco plastome proved to be stable in backcross and backfusion experiments, and normally functional in the presence solely of N. tabacum nucleus.     

Relationships among recent models for insect population dynamics with variable rates of development

A classification scheme for those population models which allow variation in development rates is proposed, based on two ways of modifying standard age-structured models. The resulting classes of models are termed development index models and sojourn time models. General formulations for the two classes of models are developed from two basic balance equations, and numerous specific models from the literature are shown to fit into the scheme. Concepts from competing risks theory are shown to be important in understanding the interplay between mortality and maturation. Relationships among the classes are investigated both for the most general forms of the models and for the simpler forms often used. The scheme can provide guidance in developing appropriate insect population models for specific modelling situations.Contribution 3878871     

Prey location by Oechalia schellembergii

A total of 548 spiders (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) from three sand dune grassland sites were tested serologically for feeding on the grasshoppers, Chorthippus brunneus (Thunberg) and Myrmeleotettix maculatus (Thunberg). Lycosidae were the most commonly tested species and gave the greatest proportion of positive tests. Laboratory observations suggest that predation in the field was predominantly on first instar grasshoppers.

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Résumé Afin d'améliorer la connaissance de l'importance des prédateurs dans la biologie des populations de criquets (Orthoptères; Acrididae), les araignées de trois pelouses sur dunes de sable ont été examinées sérologiquement pour estimer leur consommation des populations sympatriques de Chorthippus brunneus Thunberg et Myrmeleotettix maculatus Thunberg. Au total, 548 araignées (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) ont été récoltées à la main ou par piège pendant la période d'éclosion des ufs de criquets. Les Lycosidae ont été le plus fréquemment observées (90,5% de toutes les récoltes) et ont donné la plus forte proportion d'individus positifs (jusqu'à 32,3%). Les expériences d'alimentation en laboratoire suggèrent que, dans la nature, les Lycosidae sont les plus actives contre les criquets du premier stade.

     

Value of a control decision rule for leek moth infestations in leek

Fourteen commercial leek fields with first and second generation Leek moth, Acrolepiopsis assectella Z., (LM) injury were sampled during 1986 in The Netherlands. For both generations, plant injury was more prevalent in the perimeter of the field than in interior portions. A sequential sampling program for use in making treatment decisions for LM was developed. An economic analysis of the value of sampling information derived from the sequential sampling program was performed. The parameters used for the analysis were crop yield and value, expected level of LM infestation, potential loss of value due to LM infestation, effectiveness of insecticide application, and cost of sampling. Due mainly to the high value of the crop and low cost of treatment, analysis indicates that there is little difference between a sampling-based management plan and prophylactic application of insecticides in terms of pest control costs. Additionally, such a sampling-based management plan is relatively insensitive to changes in the parameters used in the model. Thus, development of a threshold linked to a sampling procedure will not reduce pest control costs. Use of the sampling-based management plan will also not significantly increase pest control costs and will likely result in reduced insecticide use compared with a prophylactic treatment program.

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Zusammenfassung In den Niederlanden wurde 1986 der durch den Befall der ersten und zweiten Generation der Lauchmotte (Acrolepiosis assectella Z.) verursachte Schaden auf 14 kommerziell genutzten Porreefeldern ermittelt. Für beide Generationen wurde an den Feldrändern ein deutlich höherer Befall als in dem inneren Bereich eines Feldes festgestellt. Zur Bekämpfung der Lauchmotte wurde als Entscheidungsmodell ein sequentielles Probenahmeverfahren entwickelt. Der Informationsgehalt der sequentiellen Befallserhebung wurde einer ökonomischen Bewertung unterzogen. Hierbei wurden folgende Parameter zugrunde gelegt: Erntemenge und Ertrag, erwarteter Befallsgrad sowie hierdurch verursachter möglicher Ertragsverlust, Wirkungsgrad einer Insektizidbehandlung und Kosten der Stichprobennahme. Die Analyse der einzelnen Parameter ergab nur eine geringe Kostendifferenz zwischen einer gezielten Bekämpfung nach sequentieller Probenahme und prophylaktischen Insektizidspritzungen, bedingt durch den hohen Wert der Kultur und die niedrigen Kosten einer Bekämpfung. Darüber hinaus its das Verfahren einer gezielten Lauchmottenbekämpfung gegeüber Veränderungen der obengenannten Parameter relativ unempfindlich. Deshalb wird die Entwicklung eines Schwellenwertes der mit Probenahmeverfahren verbunden ist die Bekämpfungskosten nicht reduzieren. Die anwendung der Probenahmeplans würde Bekämpfungskosten auch nicht erhöhen und würde wahrscheinlich Insecktizidverbrauch reduzieren im Vergleich zu einen prophylaktischen Behandlungsprogramm.

     

Test of Phenice's technique for determining sex from the os pubis

Pubic bone morphology was examined to test the accuracy of Phenice's visual method for determining sex from the os pubis. Twelve participants scored 50 pubic bones from individuals of known sex aged 52-92 years. The sample is of modern males and females, all presumed whites. An accuracy of approximately 83% in determining sex was recorded, compared to 95% reported by Phenice. This accuracy difference may reflect different age distributions of the two samples. Through replication of test results on two series of 25 specimens, the technique was found to be reliable. Previous experiences in human osteological analysis was shown to have no effect on accuracy in this test, confirming Phenice's assertion that the technique does not require extensive experience to yield accurate results. Results suggest that there is a moderate negative correlation between accuracy in determining the sex of an individual and that individual's age.     

Size variation in Brachionus plicatilis resting eggs

The effect of temperature and salinity on resting egg size of two Brachionus plicatilis (Rotifers) clones was investigated. Clones were selected according to their different behaviour in laying resting eggs: one clone ejects them, whereas they remain inside the females body in the other clone. The difference in resting eggs size between the two clones is noticeable, although the difference is not as great as that between female body size. An important temperature-salinity interaction on resting egg size has been observed. The general inverse relationship between size and temperature is only true at lower temperatures. At high temperatures size varies around the mean although could be greater than at intermediate temperatures. This is more evident at the intermediate salinity tested which is considered to be the closest to the optimum in our experiments. This pattern of variation suggests that mean size is bigger than expected, in relation to temperature and salinity, when these factors have values close to the extremes of their range, normally found in nature, and to which adaptative mechanisms can evolve. Size is bigger at the salinity — temperature low - low and high - high combinations which are the most commonly found in the temperate environments.     

Distinction between light-mediated and light-independent variations in phytoplankton production rates

An array of factors simultaneously controls phytoplankton photosynthesis and hence the primary production process. Because their relative importance shifts both with depth and with season, the significance of individual factors cannot be resolved by in situ incubations, even if all relevant environmental and biotic variables are measured.Here a procedure is described by which in addition to in situ measurements, photosynthesis is simultaneously assessed in identical subsamples under constant temperature (10 °C) and light (0.66 mol m^–2 h^–1 PAR conditions, in vitro). By calculating photosynthesis per unit of chlorophyll, effects of shifting biomass on photosynthesis can be eliminated but seasonal variations of light-saturated photosynthesis generated by temperature, and vertical changes of light-requirements (e.g. by light-shade adaptation) remain obscure. Quotients of in situ photosynthetic rates divided by in vitro rates allow the quantification of light-mediated changes. Provided that photosynthesis measured in vitro is light-saturated, quotients in situ: in vitro rates should never exceed unity. They are a measure for the degree of light-limitation. In vitro rates normalized to chlorophyll give information on temporal changes caused by variations in photosynthetic capacity. In Lake Constance, mean cell size appears to control light-saturated assimilation numbers.     

Effect of Moniliformis moniliformis density on distribution within the definitive host population (Rattus norvegicus)

The population dynamics of Moniliformis moniliformis was studied in ‘free-ranging’ laboratory rats, Rattus norvegicus, presented with different relative density levels of M. moniliformis in cockroaches, Periplaneta americana. Changes in selected population parameters of the negative binomial distribution were evaluated as indicators of changes in aggregation. A significant increase in the degree of aggregation of parasites occurred as a result of the increase in relative density of infective stages available to the rats. This increase in aggregation was due to the increase in over-dispersion that occurred in female rats only. The degree of aggregation in females was found to be significantly higher than that in males at both treatment levels. The best indicators of the degree of aggregation were found to be the ratio of the variance to the relative density and the ratio of the log-variance to log-relative density. Changes in k were not correlated with changes in over-dispersion or the relative density.