Search

Model experiments were carried out with the tomato varieties ‘Moneymaker’ (no resistance genes), ‘Leaf Mould Resister No. 1’ (resistance gene Cf 1), ‘Vetomold’ (resistance gene Cf 2) and ‘V 473’ (resistance genes Cf 1 and Cf 2) and various physiological races ofCladosporium fulvum. Leaking of32P from labelled leaf disks, was obtained on infiltration with high molecular weight excretion products from incompatible races ofC. fulvum but not with those from compatible races. These products were obtained by Sephadex G-25 gel filtration of culture filtrates. The observations are in line with our hypothesis that the gene-for-gene relation existing between tomato andC. fulvum is based on interaction of specific fungal excretion products with specific receptors in the host which may be located in the cell membrane. The presence of these fungal compounds is supposed to be controlled by four avirulence genes (A1, A2, A3 and A4) and that of the receptors by the four resistance genes (Cf 1, Cf 2, Cf 3 and Cf 4). Results obtained from experiments with tomatoes Cf 1, Cf 2 and Cf 1 Cf 2 suggest that leakage followed by the hypersensitivity reaction occurs whenC. fulvum races possessing a specific avirulence allele penetrate into a host carrying the corresponding resistance allele. It is not yet clear why growth ofC. fulvum is stopped when leakage of the host tissue resulting in the hypersensitive reaction takes place. No compound toxic toC. fulvum is present or is formed in homogenates of tomato leaves. Modelproeven werden uitgevoerd met de tomatenvarieteiten ‘Moneymaker’ (geen resistentiegenen), ‘Leaf Mould Resister No. 1’ (resistentiegen Cf 1), ‘Vetomold’ (resistentiegen Cf 2), ‘V 473’ (resistentiegen Cf 1 en Cf 2) en verschillende fysiologischen rassen vanCladosporium fulvum. Bladponsjes van radioactief gemerkte bladeren (gemerkt met32P) werden geinfiltreerd en geincubeerd met cultuurfiltraatfracties (fractionering over Sephadex G-25) vanC.fluvum. Waargenomen werd dat ponsjes, behandeld met cultuurfiltraat van een niet compatibeleC.fulvum, een grotere uitlek van radioactief gemerkt materiaal te zien gaven dan in de, gevallen waarin een compatibele schimmel werd gebruikt. Deze waarnemingen stemden overeen met onze hypothese dat de gen-om-gen relatie die bestaat tussen tomaten enC.fulvum, gebaseerd, is op een interactie van specifieke schimmelprodukten met specifieke receptoren in de plantencellen, mogelijk in de membranen. De produktie van de specifieke stoffen door de schimmel zou worden bepaald door vier avirulentiegenen (A1, A2, A3 en A4), en de aanwezigheid van de specifieke receptoren in de plantencel door de vier resistentiegenen Cf 1, Cf 2, Cf 3 en Cf 4. De waarnemingen, verkregen uit de proeven met de tomaten Cf 1, Cf 2 en Cf 1 Cf 2, doen vermoeden dat de uitlek een gevolg is van een overgevoeligheidsreactie die optreedt, indien een fysio vanC.fulvum, dat een specifiek avirulentie allel bezit, een gastheer binnendringt die beschikt over een bijpassend resistentie allel. Het is tot nu toe niet duidelijk waarom de groei vanC.fulvum stopt indien, uitlek op gaat treden als gevolg van de overgevoeligheidsreactie. In homogenaten van tomatenbladeren werd geen stof gevonden die de groei vanC.fulvum remt.

Using 227 Th sources obtained by evaporation of the activity onto A1 foils, α-γ coincidences and α-γ directional correlations have been measured employing Ge(Li) and silicon surface-barrier detectors. A decoupling experiment using a superconductive magnet of 1.5 Tesla has been carried out to investigate the attenuation of the α-γ directional correlations due to extranuclear effects. Of the about 100 γ-rays observed (20 of them for the first time), all but 6 have been placed in a decay scheme. The directional correlation data have led to several new spin assignments and to the confirmation of earlier tentative assignments. The relative α-particle intensities and the α-γ directional correlation results show that the L = 2 intensities in the favoured α-decay to the different levels of the 3 2 + [631] band are uncommonly weak, indicating a limitation to the applicability of the Nilsson model at low excitation energy.

The extracellular soluble proteins of 15 different isolates comprising 9 different physiological races ofCladosporium fulvum were harvested from 3 to 4 weeks old shake cultures. The culture filtrates were purified by gel filtration over Sephadex G-25 and the Vo-fractions were freeze-dried. These preparations were submitted to disc gel electrophoresis on polyacrylamide gels at pH 9.5 at circa 4°C.

n/a

A digital model was developed based on conservation of mass, energy and momentum. The equations were supplemented by suitabe correlations for slip factor, two-phase friction multiplier and subcooled boiling parameter. The CSMP program of IBM was used for the solution. The purpose of the model was to support a number of experiments performed to study the phase relationship between void fraction and inlet flow rate in a natural circulation boiling water channel, and the effect of a sine-shaped heat flux on the stability of the system. The qualitative effects were represented very well and the quantitative agreement with experimental results was promising.

The use of polyvinyl acetate as a stationary phase in thin-layer chromatography has been investigated using the derivatives of some organic compounds as the test substances. The phase gives very rigid layers and can be used for the separation of derivatives of homologous series as well as for the separation of derivatives of other types of organic compounds.

Void fraction and inlet flowrate in a natural circulation boiling water loop have been analysed in terms of their relative dependence. Power spectra were calculated by means of a special-purpose analogue computer. The independent variables were channel power and inlet subcooling. Increasing power beyond certain values generated spontaneous hydraulic oscillations. The experiments covered both stable and unstable behaviour of the system. The amplitude of the signals indicated an obvious transition between both regions, but the relative phases did not change. No rapid change of phase between any two signals was observed. Knowledge of the phase offered the possibility of calculating void propagation velocities. The results affirmed the physical inconsistency of a boiling boundary.

This woody legume, originally native to Mexico but now naturalized in Arizona, Florida and Texas, has been extensively used in Indonesia for soil erosion control and should be similarly employed in our Southern States.

(1969). The Effect Of Dissolved Gas on Cavitation In Horizontal Pipe-Lines. Journal of Hydraulic Research: Vol. 7, No. 3, pp. 301-314.

1. For two flocks of 48 and 40 hens, consisting of the F1 of Rhode Island Red males and White Leghorn females, peck-order, aggressiveness and egg production were determined. Flock I was built up step by step by continually adding a group of 8 hens to the hens already present in the testing pen. Flock II was brought into the testing pen as a whole at once. 2. The peek-order of the hens of flock I was clearly correlated with the date they had been put into the testing pen. The earlier the hens came into the testing pen, the higher their ranks. When the flock was rebuilt so that the groups were brought into the pen in reversed order, this correlation between peck-order and date of introduction into the pen was found again. 3. In flocks I and II a clear correlation between peck-order and aggressiveness existed, higher rank being correlated with stronger aggressiveness. 4. The peck-order, settled in flock I must have been determined for an important part by environmental factors, which can be summed up as “familiarity with the environment”. The peck-order of flock II must on the contrary have been mainly dependent on the physical and behavioural characteristics of the individual hens, because the environmental factors were equal here for all hens from the beginning. The hens were all brought into the testing pen together. 5. In flock I a clear correlation existed between peck-order and egg production. Hens with a higher rank laid more eggs and produced a higher total egg weight. The same correlation exists between aggressiveness and egg production. A stronger aggression is correlated with a higher egg production. 6. The correlation between peck-order and aggression on the one hand and the egg production on the other hand runs through the feeding possibilities. The less aggressive hens get less food, because they are regularly chased from the food trough by the more aggressive hens. This shortage of food leads to a decreased egg production. 7. For flock II no clear correlation could be shown between peck-order and aggressiveness on the one hand and the egg production on the other hand. It is probable that the egg production of this flock started during the experiment and, therefore, was not yet properly stabilized.

Experiments were carried out with the tomato varieties Vetomold (resistance gene Cf2), V 121 (resistance gene Cf 3), Purdue 135 (resistance gene Cf 4), Vagabond (resistance genes Cf 2 and Cf 4) and various physiological races of Cladosporium fulvum . Leakage of 32 P-labelled compounds from tomato leaf disks was greater after infiltration with high molecular weight products of incompatible than of compatible races of C. fulvum. These fungal products were separated from low molecular weight material by Sephadex G-25 gel filtration of culture filtrates. It is suggested that toxic products from the incompatible fungus cause specific membrane damage followed by a leakage of host cell components. The observations support our hypothesis that the gene-for-gene relation between tomato and C. fulvum is based on interaction of specific fungal products with specific receptors in the host plasma membrane, leading to a hypersensitive reaction. The production of these fungal compounds is thought to be controlled by four avirulence genes (A 1 , A 2 , A 3 and A 4 ) and that of the receptors by four genes for resistance (Cf 1, Cf 2, Cf 3 and Cf 4).

An experimental study of incipient hydrodynamic instability in a vertical boiling channel. Attempted definition of a standard reference for incipient instability, based on auto-correlations and power/density curves. Establishment of instability characteristics by voids fraction detectors measuring impedance at various levels. Occurrence of instability depending on pressure and subcooling at the channel intake. Flow patterns in a boiling water loop at atmospheric conditions., Dans ce rapport sont présentés les résultats d'une étude expérimentale de l'apparition des instabilités hydrodynamiques dans un canal à ébullition vertical. Un effort a été fait pour décrire une norme pour l'apparition des instabilités utilisant des auto-corrélations et des courbes de puissance-densité. Le caractère des instabilités a été étudié par des détecteurs de la fraction de vide posés à différentes hauteurs mesurant l'impédance. L'apparition des instabilités est présentée en fonction de la pression et du sous-refroidissement à l'entrée du canal. Des configurations d'écoulement observées dans une boucle de l'eau bouillante atmosphérique sont montrées., Spigt C. L., Dijkman F. J. M., Bogaardt M. Les phénomènes accompagnant le début de l’instabilité de l’écoulement dans les canaux verticaux bouillants. In: Les instabilités en hydraulique et en mécanique des fluides. Compte rendu des huitièmes journées de l'hydraulique. Lille, 8-10 juin 1964. Tome 2, 1965.

Blossoms fromii several varieties of orchids fade prematurely when their pollinia are removed or disturbed (2,3,7), and also if the flowers are gassed with ethylene (8, 9, 10), pollinated (3, /7), or treated with an auxin (3, 7). During natural Ifading as well as that induced by removal of the pollinia, ethylene is evolved (2, 3, 9, 10), andtherefore it has ibeen inferred that the gas is the catusative agent. Ethylene evolution also is stimlulated Nvllen plant tissuies are exposed to auXin ( 1, 4), andl wve now )resent evidence that this response is the basis for flower fading1 indtuced by pollination or an,xin application. Blossoms from ['undo Petanboeran or Van(la Rose .M1arie were iplaced wvitlh their cut ends in a beaker of water, and( sealed nudtler a 200 nlm bell jar having a ground glass base anid a side arm closed with a rubber vaccine cap. Otlher flowers svere pollinated, emilasculated (pollinia removed), self-pollinated, or treated with 5 mnm IAA in lanolin or 0.1 mm carboxyl lajbeled '-C-IAA in 0.8 % agar (specific activity 8 mc/mmole) applied to the stigmas, and then the flowers were sealed under a bell jar. Air samples, removed with a hlypodernmic syringe, were analyzed by gas chromatography to determine the ethylene content (4), anid at least every 10 hours the chambers were completely aerated. Ethylene evolution by isolated sepals and petals, columns or lips was measured by incubating each tissue in a 50 ml flask fitted with a vaccine cap. and sampling the air in the flask at hourly intervals. Cutting the floral parts induced a wound response, lasting about 1 hour, during whichi time 1.5 mkdJ of ethylene per gram of cut control tissue 'was produced. Treated cut tissue was only considered to produce ethylene if the total evolution exceeded this value, and if the extra evolution contintued at a nearlv constant rate for at least 4 hours. Intact blossoms were also placed in desiccators and gassed for 3 to 24 hours with 10 ppnm ethylene. In suich cases the flowNers were aerated f'or at least 1 hour 'before ethy;lenle production was measured in order to remiove any ethylene contained within the tissue. The sipread of 1AC-IAA from the stigmas of the flower was determined by excising the 'floral parts from representative blossomiis after 3, 6, and 24 hours and dividing these into pieces as illustrated in figure 3. Each piece was ground with ethanol on a planchet, dried, and counted w ith a 21 % efficient gas flow counter. When blossoms of V. Rose Marie were emasculated, ethylene evolution began after a 10 hour lag period (fig 1), and fading became obvious after an additional. 8 to 12 hours. A similar time course of ethvlene production and fadintg hias been reported for V. Miss Agnes Joaquitin blossoms after renoval of tlieir pollinia (2). whereas F. Petarnioeran, a semiterete of heav\ texture, fades after a considerablv longer lag(fig 2). That remiioval of the pollinia per se is not responsible for floral fading is indicated bv experiments with Phalcanopsis Pamiiala (7) which have showun that disturbance of the connection between the rostelluii (tthe structure supporting the pollinia) and the upper surface of the sticky disk with which it is in intimate contact, suffices to induce the response. There is no indication that this tvpe of fading ,in.volves a release or production of auxin, for it does not result in swelling of the column whereas both auxin application and pollination bring about such an effect. Self ,pollination induces ethylene formation within 1 hour in V. Rose Marie, and flower fading within 8 to 10 bhours (ifig 1). A simil.ar time course was observed with V. Petamboerant even when the flower was pollinated with its own pollinia intact (fig 2). This response was duplicated by applying enough IAA (5 mm) in lanolin paste to fill the stigmatic cavity (figo2), and exactlv the same result was obtained using 0.1 bM '*C-IAA in 0.8 % agar. Other cases .n which the fading response caused by pollination is stimulated by auxin have been reported (3, 7), and led to the suggestion that the large quantity df auxin contained in the pollen is responsible for the pollination effect (7). As auxin stimulates ethylene evolution in these blossoms and other plant tissues within an hour, an(d since ethylene causes floral fading, it is logical to conclude that this is the mlechanismll involved. Auxin induced ethylene formation must also influence the growvth of the column for within 2 hours after application of pollinia or auxin this structure