Direct mechanism in solar nuclear reactions

A short overview of the direct reaction mechanism and the models used for the analysis of such processes is given. Nuclear reactions proceeding through the direct mechanism and involved in solar hydrogen burning are discussed. The significance of these nuclear reactions with respect to the solar neutrino problem is investigated.Comment: 17 pages, LaTeX, 5 figures available upon request to [email protected], IK/TUW-Preprint 940440

Some remarks ob triploid grapevines

Research Not

Opening of flowers and time of anthesis in grapevines, Vitis vinifera L.

During two years, opening of flowers in Vitis vinifera, cvs Muller-Thurgau and Blauer Spatburgunder was investigated. At average weather conditions flowers opened in periods of about 24 h. Opening started about 5:00, reached a maximum between 7:00 and 9:00 and was finished at about 12:00. Within an inflorescence, opening of flowers reached a maximum on the 5th or 6th d and was finished after 7 d, i.e. 7 periods. The diurnal rhythm was probably regulated by the photoperiod. To a certain extent the length of periods depended on temperature. High temperatures caused an advanced rhythm and a decreased length of period and vice versa. At the time of opening, anthers in all flowers had already dehisced. About 16-18% of the flowers of cv. Blauer Spätburgunder and 60-63% of cv. Muller-Thurgau proved to be pollinated before opening and growth of pollen tubes had already started. The two cultivars were partially cleistogamous. From corresponding data of this trait in both years a genetic basis for the two cultivars can be concluded. From the length of pollen tubes and the temperature during their growth, the time of anthesis was calculated. Within 24 h, anthesis probably followed two periods: the first period, 5:30-10:30 with a maximum between 6:00 and 8:00, included most of the flowers; the second period was observed between 16:30 and 1.30 with a maximum between 18:00 and 1:00.Das Aufblühen der Blüten and der Zeitpunkt der Anthese bei Reben, Vitis vinifera L.Das Aufblühen der Blüten der Vitis vinifera-Sorten Müller-Thurgau and Blauer Spätburgunder wurde in zwei Jahren untersucht. Bei mittleren Witterungsbedingungen öffneten sich die Blüten in Perioden von ca. 24 h. Das Öffnen begann um 5 :00, erreichte zwischen 7:00 and 9:00 ein Maximum and war gegen 12 :00 beendet. In den einzelnen Infloreszenzen erreichte das Aufblühen am 5.-6. Tag sein Maximum and war nach 7 Tagen, d. h. nach 7 Blühperioden, beendet. Der diurnale Rhythmus wird wahrscheinlich durch die Photoperiode reguliert. Die Länge der Perioden hing zum Teil von der Temperatur ab. Hohe Temperaturen nach Ende einer Blühperiode beschleunigen den Blührhythmus and führen zu einer Verkürzung der nachfolgenden Periode; niedrige Temperaturen wirkten in umgekehrter Weise.Zum Zeitpunkt des Aufblühens waren die Antheren in allen Blüten bereits dehisziert . Mikroskopische Untersuchungen ergaben, dass 16-18 % aller Blüten von Blauer Spätburgunder und 60-63 % derBlüten von Müller-Thurgau schon vor dem Öffnen bestaubt waren und das Wachstum der Pollenschläuche bereits begonnen hatte. Die beiden Sorten sind also partiell kleistogam. Die übereinstimmenden Werte für die Sorten in beiden Jahren lassen eine genetische Abhängigkeit vermuten. Aus der Länge der Pollenschläuche beim Aufblühen und der Temperatur während ihres Wachstums konnte der Zeitpunkt des Beginns des Wachstums und daraus der Zeitpunkt der Anthese errechnet werden. Innerhalb von 24 h läuft die Anthese wahrscheinlich in zwei Perioden ab . Während der ersten Periode, von 5:30 bis 10:30 mit einem Maximum zwischen 6:00 und 8:00, fand die Anthese vermutlich in den meisten Blüten statt. Die zweite Periode, von 16:30 bis 1:30, hatte ihr Maximum zwischen 18:00 and 1:00.

Evaluation of resistance to grapevine powdery mildew (Uncinula necator [Schw.] Burr., anamorph Oidium tuckeri Berk.) in accessions of Vitis species

119 accessions, including species from America and Asia, various hybrids and breeding stocks, were tested for resistance to powdery mildew (Uncinula necator) by a leaf disc test. Vitis candicans, V. munsoniana, V. piasezkii and V. rotundifolia were found to be resistant with a rating of up to 1.4 in all accessions (1-no infection, 9-very strong infection). V. munsoniana and V. rotundifolia showed extremely high resistance and may be excellent material for breeding programs. However, the accessions of V. candicans and V. pinsezkii should be preferred for breeding of powdery mildew resistant grapevine Varieties because of the corresponding chromosome number. The surprisingly high number of 10 species included resistant as well as susceptible accessions. V. doaniana and V. tiliaefolia, probably V. palmata and most of the accessions of V. shuttleworthii may be characterized as moderately resistant. V. cordifolia, V. lanata, V. rupestris and some accessions of V. vulpina and cultivars of V. vinifera proved to be highly susceptible.

Evaluation of downy mildew resistance in various accessions of wild Vitis species

107 accessions of 21 species from America and East Asia were investigated for resistance to downy mildew, Plasmopara viticola, by the leaf disc test. The species, Vitis rotundifolia, munsoniana and yenshanensis showed resistance in all accessions investigated (rating 1.0). Vitis cinerea, palmata and shuttleworthii can be rated as moderate resistant (rating 1.1 - 1.9). In V. candicans, doaniana, piasezkii, riparia, rubra and tiliifolia resistant as well as susceptible accessions were observed. In V. acerifolia, aestivalis, amurensis, champinii lanata, rupestris, solonis, vinifera and vulpina all accessions showed susceptibility to the fungus, the rating varied from 1.1 to 7.2

Elimination of grapevine leafroll associated virus type I in Vitis vinifera cv. Lemberger

Research Not

Resistance to transmission of grapevine fanleaf virus by Xiphinema index in some Vitis species and hybrids

Many vineyards in Germany are infested by nematodes which can transmit virus diseases. Breeding of rootstocks resistant to nematode feeding and virus transmission is an important way to control these virus diseases. A method has been developed for testing breeding stocks for these characteristics with regard to grapevine fanleaf virus (GFV) and its vector Xiphinema index. The plants to be tested were first grown together in a single pot with both GFV-infected plants of Vitis cv. Siegfried and plants of the same cultivar which were virus negative according to an ELISA test: 2 months after planting, the pots were inoculated with about 50 nematodes. In a second experiment, single healthy plants of different hybrids and species were potted and inoculated with about 200 nematodes carrying GFV. After 3-10 months, roots were inspected visually for swellings and galls and tested for the presence of GFV by ELISA. In all cases, the previously healthy cv. Siegfried showed symptoms of feeding on the roots and these roots showed a positive reaction to the ELISA test. After 6 months, GFV could also be detected by ELISA in the basal parts of the stems. The reaction of the test plants was dependent on their genotype. A high susceptibility to feeding by the nematodes and high percentage of transmission to GFV was displayed by American species and interspecific hybrid rootstocks. One of the V. vinifera x V. rotundifolia hybrids showed no visual symptoms of nematode feeding and no virus transmission 9 months after inoculation

Alpha Clustering and the stellar nucleosynthesis of carbon

The astrophysical S--factor and reaction rates for the triple--alpha process are calculated in the direct--capture model. It is shown that the stellar carbon production is extremely sensitive to small variations in the N--N interaction.Comment: 2 pages LaTe

Ploidiechimären bei europäischen Vitis vinifera-Sorten

An drei bisher als tetraploid bezeichneten Klonen der Sorten Portugieser, Riesling und Scheurebe und deren diploiden Ausgangsformen wurde die Zellgröße und das Kernvolumen der Epidermis der Beeren während der Reife untersucht. Bei der Sorte Portugieser wurde auch der Längen/Breiten-Index der Epidermiszellen der Beeren und die Zellgröße der Epidermis der Samenschalen untersucht. In den meisten Fällen waren die Differenzen zwischen den Epidermiszellen der di- und tetraploiden Klone nicht signifikant. Die Epidermis der tetraploiden Klone dürfte also diploid sein.Durch Untersuchungen der Chromosomenzahl an Wurzelspitzen und in der Meiose, durch Messungen der Durchmesser der Pollenkörner und durch Untersuchungen der Nachkommenschaften konnte eindeutig nachgewiesen werden, daß die subepidermalen Zellen der tetraploiden Klone tetraploid sind. Somit können die betreffenden Klone als Ploidiechimären mit diploider Epidermis und tetraploiden subepiclermalen Schichten bezeichnet werden.Ploidychimeras in European Vitis vinifera cultivarsIn three clones of the cv. Portugieser, Riesling and Scheurebe, hitherto called tetraploid, and the diploid strains from which they have originated, the cell size and the volumes of the nuclei of the surface layer of the berries during the course of ripening were investigated. In the cv. Portugieser the length/width index of the surface layer cells of the berry and the size of the surface layer cells of the seed coat were also investigated. In most cases no significant differences have been observed between the cells of the surface layer of the diploid and tetraploid strains. The surface layer of the tetraploid strains should therefore be diploid. By counting the chromosome number in the root tips and in the meiosis, by measuring the diameter of the pollen grains and by investigating the offspring it could be shown that the inner layers of the so-called tetraploid strains are really tetraploid. It can, therefore, be concluded that the tetraploid strains of the mentioned cultivars are ploidychimeras with a diploid surface layer and tetraploid inner layers