The interaction of endogenous gibberellins in correlation with cotyledons and axillary buds in the pea (Pisum sativum L.)

After the decapitation and amputation of one cotyledon in germinating pea seedlings, the axillary bud of the amputated cotyledon always grows and the growth of the axillary bud of the remaining cotyledon is inhibited. Before morphological differences appear between the axillary bud of the amputated and preserved cotyledon, a higher endogenous gibberellin content can be demonstrated chromatographically in the axillary bud of the amputated cotyledon. This indicates that the increased growth of the axillary bud of the amputated cotyledon is in connection with an earlier increase in the activation of endogenous gibberellins.     

Zur Kenntnis der peritubulären Zone des Dentins

Zusammenfassung Elektronenmikroskopische Replika-Präparate (Methylmethakrylat, Bedampfung mit Chrom-Beryllium) von nativen Schliffflächen von Dentin und mit HNO₃, EDTA, KOH-Glyzerin, Äthylendiamin und Inzineration bei 300° C und 1100° C behandelte Präparate zeigen, daß sich die peritubuläre Zone von dem intertubulären Dentin in der Resistenz gegen die einwirkenden Mittel unterscheidet. Durch Inzineration bei 300° C wird sie nicht angegriffen. Säure, EDTA, KOH-Glyzerin, Äthylendiamin und Inzineration bei 1100° C greifen sie verschieden intensiv an. Die peritubuläre Zone unterscheidet sich dann häufig nicht mehr von der intertubulären Grundsubstanz. Dadurch, daß beim Polieren, bei teilweiser Inzineration und manchmal infolge Extraktion eine Fibrillenstruktur in Erscheinung tritt — wahrscheinlich durch Entfernen der Fibrillen und Darstellung des Mineralgerüstes, welches die Fibrillen einbettet — gewinnen wir einen Einblick in den Aufbau der peritubulären Zone. Anschließend wird der Strukturunterschied der peritubulären Zone dadurch bestimmt, daß die Fibrillen, die das Dentingerüst bilden, sich daselbst in feinere aufspalten, einen anderen Verlauf nehmen und von einer größeren Menge von homogener Kittsubstanz umgeben werden, die infolgedessen intensiver kalzifiziert. Obwohl die peritubuläre Zone der Dentingrundsubstanz angehört und nicht der periphere Anteil des Odontoblastenfortsatzes (Frank 1956) ist, scheint dieser bei ihrer Genese eine besondere Rolle zu spielen.     

Comparison of the effects of radiation and deoxyribonucleic acids on the mitosis in roots ofVicia faba

Differences as well as similarities in the action of ionizing radiation and deoxyribonucleic acids from various sources on mitosis in root cells ofVicia faba were established. The time course of occurrence of aberrations were examined. Whereas in irradiated broad beant the maximum percentage of aberrations was observed immediately after irradiation, the aps plication of non-isologous DNA was followed by maximum aberrations after 8–16 hours. As all the time-intervals studied, an incraasad number of aberrations was found during metaphase-as compared with anaphases, both after irradiation and after application of DNA. A comparison of isologous, homologous and heterologous DNA as inductors of chromosomal aberrations supported our previous findings and showed that the efficiency of DNA depends on the genetic difference between donor and acceptor. During a study of distribution of aberrations between large and small chromosomes of meristematic cells ofVicia faba, at various time-intervals it was obsarved that after irradiation the distribution of aberrations between individual chromosomes is proportional to their total length, whereas the effect of heterologous DNA is mostly in the damage to small chromosomes. It was also found that aftar irradiation mostly chromatid aberrations are formed at shorter time-intervals and only later chromosomal aberrations will appear. On the other hand, heterologous DNA brings about in all time-intervals a predominance of chromatid aberrations.     

Suitable indicators and an altered empirical equation for calculating the CO2 concentration in colorimetric determinations of photosynthetic rate

Cresol red was found to be the most suitable of the six colour pH indicators tested for the colorimetry of CO₂ concentration within the range of 100 to 2000 p.p.m. In the region near pH 8-2 (corresponding approximately to 300 p.p.m. CO₂)this indicator is most suitablein view of its low unit concentration, although somewhat greater differences in absorbancy can be found on changing pH by one unit if an approximately six-fold higher concentration of thymol blue is used. For higher concentrations of CO₂ (pH below 7-5) phenol red is most appropriate. Tropaeolin 000 and aurin (rosolic acid) are not suitable. It is more convenient in spectrophotometry and colorimetry using filters with narrow spectral ranges to apply any of the above indicators in the green-yellow-orange spectral region rather than in blue radiation. When the air to be measured is bubbled through a bicarbonate solution, an equilibrium between the CO₂ concentration in the air and pH value is established in less than 10 min for differences in CO₂ concentration from 100 to 400 p.p.m. Partial pressure of CO₂ and the experimentally established pH value are related by the altered equation: pH =α- 0-934 log P. The values of α at different temperatures were determined.     

Cytological study on wheat (Triticum timopheevi Zhuk.) protoplasts

Protoplasts were obtained from tetraploid wheat (Triticum timopheevi Zhuk.) suspension culture by incubation in solution of 1 % pectinase 500, 1 % driselase and 1 % cellulase and cultivated in Schenk and Hildebrandt medium. Freshly isolated protoplasts contained dense cytoplasm and constricted organellae exhibited negative contrast of their membranes. Together with normal protoplasts huge multinucleate protoplasts were present in the population. 3 h after plating, the cytoplasm showed normal appearance, the negative contrast of membranes was not evident any longer. Cisternae of endoplasmic reticulum and Golgi apparatus were numerous. There were some vesicles and fibres on the protoplast surface. 8 d after plating, many dividing cells were found out and cell clumps arosen in this way were present in the culture. Some of the protoplasts particularly those originally multinucleate ones were upset.