Correspondenz

Ohne Zusammenfassung     

Versuche zum Herbizideinsatz in gesäten Kohlarten

In den Jahren 1987 bis 1989 wurden die Auswirkungen und Effekte eines kombinierten Befalls des Winterweizens mit Sitobion avenae (Fabr.) und Puccinia recondita Rob.ex Desm. f.sp.tritici Erikss. untersucht. Dabei wurde das Verhalten der Schaderregerpopulationen und die Einflußnahme auf das Ertragsgeschehen bei separatem und simultanem Befall erfaßt. Während bei starkem Befall der oberen Blattetagen mit P.recondita eine Förderung der Aphidenpopulation an den Ähren der befallenen Pflanzen registriert werden konnte, war bei schwachem Braunrostbefall keine Einflußnahme auf die Blattläuse nachweisbar. Durch das kombinierte Auftreten beider Schaderreger kann es zu Reduktionen bei der Kornmasse/Ähre und bei der Tausendkornmasse kommen, die größer sind, als die Summe der Verluste bei Einzelbefall. Ähren stark braunrostbefallener Winterweizenpflanzen wurden zeitiger von S.avenae angeflogen und schneller besiedelt als diese von gesunden Kontrollpflanzen. Als Ursache für die Förderung der Populationsentwicklung von S.avenae werden durch P.recondita induzierte Veränderungen im Angebot an freien Aminosäuren in der Wirtspflanze diskutiert.     

A Non-Synonymous HMGA2 Variant Decreases Height in Shetland Ponies and Other Small Horses

The identification of quantitative trait loci (QTL) such as height and their underlying causative variants is still challenging and often requires large sample sizes. In humans hundreds of loci with small effects control the heritable portion of height variability. In domestic animals, typically only a few loci with comparatively large effects explain a major fraction of the heritability. We investigated height at withers in Shetland ponies and mapped a QTL to ECA 6 by genome-wide association (GWAS) using a small cohort of only 48 animals and the Illumina equine SNP70 BeadChip. Fine-mapping revealed a shared haplotype block of 793 kb in small Shetland ponies. The HMGA2 gene, known to be associated with height in horses and many other species, was located in the associated haplotype. After closing a gap in the equine reference genome we identified a non-synonymous variant in the first exon of HMGA2 in small Shetland ponies. The variant was predicted to affect the functionally important first AT-hook DNA binding domain of the HMGA2 protein (c.83G>A; p.G28E). We assessed the functional impact and found impaired DNA binding of a peptide with the mutant sequence in an electrophoretic mobility shift assay. This suggests that the HMGA2 variant also affects DNA binding in vivo and thus leads to reduced growth and a smaller stature in Shetland ponies. The identified HMGA2 variant also segregates in several other pony breeds but was not found in regular-sized horse breeds. We therefore conclude that we identified a quantitative trait nucleotide for height in horses.     

Trace feature map: a model of episodic associative memory

An approach to episodic associative memory is presented, which has several desirable properties as a human memory model. The design is based on topological feature map representation of data. An ordinary feature map is a classifier, mapping an input vector onto a topologically meaningful location on the map. A trace feature map, in addition, creates a memory trace on that location. The traces can be stored episodically in a single presentation, and retrieved with a partial cue. Nearby traces overlap, which results in plausible memory interference behavior. Performance degrades gracefully as the memory is overloaded. More recent traces are easier to recall as are traces that are unique in the memory.This research was supported in part by an ITA Foundation grant and by fellowships from the Academy of Finland, the Emil Aaltonen Foundation and the Foundation for the Advancement of Technology (Finland) when the author was at UCLA     

Reazioni delle piante di Ricinus communis a incisioni sperimentali

Summary

The author has produced wounds in the stem of Ricinus communis, studing the regeneration and cicatrization processes.

The rapidity of the surface cicatrization is in relation with the water loss of the waunded cells.

Both in the stems woumded let free and in those in which an extra tissue has been introduced, the cicatrization processes tacke place. They only take place with different velocity. The healing process lead to the reconstruction of the cortical and the conducting tissues.

The whole reconstruction of the stele may occur, when the flow of the assimilated stuffs is slowed. Sothat it is probable that the regeneration depends more upon the tissue nutrition tham on a specifical properti of the tissues.