The effect of CO₂ on the plasmatic structure of root-hairs of wheat and barley and the epidermal cells of onion was observed. The results were evaluated on living material with the aid of phase contrast. The root-hairs of barley and the epidermis of onion react to short exposure to an atmosphere of CO₂ by a cessation in the flow of plasma, a lengthening of the mitochondria and a rounding of the plastids.
When the influence of CO₂ lasts longer, it causes fragmentation of the mitochondria. In this phase the cells recover most quickly from the shock caused by their exposure to CO₂. When the plant is under the influence of CO₂ for too long a time, the effect is lethal. The root-hairs of wheat, which have mainly granulated mitochondria, reacted after only 40 minutes in CO₂ by a rolling-up of all the plasmatic particles.
This observation agrees with the results obtained on permanent preparations in the former work and leads to the conjecture, that by fragmentation of the mitochondria, the cell adapts itself to inhibited respiratory conditions.

1. The differences in the dynamics of the origin and further development of the water saturation deficit (WSD) in leaves of different age from 100- to 120-day-old plants of fodder cabbage and rape were investigated.
2. WSD in leaves of different age detached from plants and wilting without water supply develops most quickly in young and most slowly in old leaves. This is in basic agreement with differences in transpiration rate.
3. When entire plants are cut off, leaves of different age wilt at the same rate. In the later phases of wilting, (i.e. at a WSD value of over 20 to 30%) slightly higher WSD values were found in old leaves.
4. During slow wilting of plantsin situ, induced by decreasing soil moisture, a definite preference of young leaves in water supply was determined commencing from medium WSD values, i.e. on an average from 8 to 20%. During total lack of water in the plant, old and adult leaves wilt markedly and die off; the WSD of young leaves remains for a long time at comparatively low values.
5. In the observed preference of young leaves, the translocation of water to young leaves from the wilting older leaves takes a part.

After the application of a fractionated X-ray dose toArabidopsis thaliana L. (Heynh.) plants, chlorine type mutations (simple recessive -cc- as compared with the normal type -CC-) characterised by changed proportions of chlorophyll colouring matter as well as a decreased leaf area, retarded development in the initial phase and a substantially longer vegetative cycle, make themselves apparent. In the course of future generations, however, these characteristics change in the direction of normal types and stabilise in the sixth generation. A genetical and cytological evaluation of this manifestation showed that this mutation is connected with lesser number of plastids in the assimilative tissues. This number remains standard in all generations of the chlorine type, but on the other hand, the size of the plastids increases.

The intensity of photosynthesis and the content of chlorophyll were estimated in disks cut out from different areas of fodder cabbage leaves (var. Coulet de Flandre). The content of chlorophyll per unit area was higher in the apical than in the basal part and in the central than in the peripheral part of the leaf. No significant differences were observed in the intensity of photosynthesis in samples removed from different parts of the leaf. The intensity of photosynthesis is not directly proportional to the dry weight of the sample although the dry weight per unit area is considerably higher in the apical than in the basal part of the leaf area.

The localization of the non-specific esterase was studied by azo- coupling methods (α nyphtyl acetate or naphtol AS acetate + fast blue RR) in the root tip of the broad bean Vicia faba L. on transverse sections at different distances from the apex. With AS acetate both on frozen sections of material fixed with Baker's calcium-formol and on sections of paraffin-embedded objects, fixed with modified Wolman's acidified alcohol a positive reaction was observed in central cylinder. Different localization was observed on Baker-fixed frozen and on Wolman-fixed paraffin embedded material with a acetate. On Wolman-fixed material an intensive staining appeared in root cap and within phloem poles of central cylinder, whereas on Baker-fixed objects the inner layers of primary core were the most intensively active. Thus, our previous results have been proved and further developed.

Blätter von Nicotiana tabacum var. Xanthi-nc, die mit Gurkenmosaikvirus (CMV) systemisch infiziert worden waren, wurden mit TabakmosaikvirusPurifikat (TMV) beimpft. Beim Vergleich mit den Kontrollpflanzen wurde unter dem Einfluss von CMV eine Herabsetzung der Susceptibilität für TMV beobachtet: Die Anzahl der Läsionen sank um 64-83%; die Läsionen wuchsen langsamer und die TMV-Konzentration lag bei ihnen (im Vergleich mit der Kontrolle nach einer sechstägigen TMV-Reproduktion) um 72-90% tiefer. Interferenzerscheinungen sind nicht beobachtet worden bei einem Zeitabstand von nur sieben Tagen zwischen den Infektionen beider Viren, wurden aber bei einem Zeitintervall zwischen den Inokulierungen mit beiden Viren von 19, 34, 40 und 68 Tagen beobachtet. Die Blattgewebe von N. tabacum

Seeds of apple and pear trees were found to contain 0-5-0-7% tryptophane expressed per dry weight. The hydrolyzate of the seeds contained tryptophane demonstrable microbiologically. Exogenous tryptophane applied to apple-tree shoots toward the end of the vegetation season gives rise to a new compound. Its R_F in isopropanol : ammonia : water (10 : 1 : 1) was found to be 0.08, in butanol : acetic acid : water (4:1:5) 0.25.

Wenn wir eine Keimwurzel der Puffbohne (Vicia faba L.) mehreremale nacheinander chloralisieren, entsteht in der Aussenschicht des Pleroms und in der Innenschicht des Periblems eine grosse Anzahl polyploider Zellen, die ein unregelmässiges Mosaik bilden, aus welchem ein transversales Meristem mixoploider Seitenwurzeln entsteht. An der Entstehung einer jeden von ihnen beteiligen sich durchschnittlich ungefähr dreissig Zellen und als Folge ihrer Tätigkeit durch-laufen die Wurzel neben diploiden noch einige polyploide Stränge oder Sektoren. Die Initialen der Seitenwurzeln können zweiseitig wie ein Kambium wirksam sein oder einseitig Zellen nur für die Wurzelhaube oder nur für die eigentliche Wurzel abteilen. An der Anlage von Seitenwurzeln können sich in chloralisierten Hauptwurzeln mehrere Zellschichten beteiligen. Im Laufe der Entwicklung mixoploider Wurzeln kann manche Schichte von Initialen durch eine benachbarte Schichte ersetzt werden, wodurch der weitere Verlauf des einen oder anderen Stranges oder Sektors im Wurzelscheitel eingestellt werden kann. Diploides und mixoploides Gewebe kann sich im Wurzelquerschnitt sehr unregelmässig verteilt äussern. Dennoch können mixoploide Wurzeln eine im ganzen normale äussere Form besitzen; die Unregelmässigkeiten entstehen durch die Ausschaltung polyploider Rippen aus der weiteren Entwicklung der Wurzel oder bei eutelischen und amorphen Stämmen. In Wurzeln, in denen polyploide Zellen in der Minderzahl sind, wirken sie als fremde Elemente und werden auf verschiedene Weise aus der weiteren Entwicklung des Scheitels ausgeschlossen. In den Wurzeln geht eine Art Selbstreinigung vor sich, die zu ihrer Diploidisierung führen kann; es ist aber wahrscheinlich, dass in den Scheiteln, die sich grösstenteils aus polyploiden Zellen zusammensetzen, ein umgekehrter Vorgang vor sich gehen kann, der zu ihrer völligen Polyploidisierung führt.

In the course of seven years, mutual compatibility relations in 16 Sweet Cherry cultivars, grown in Czechoslovakia were investigated. Successful pollinations were evaluated according to the percentage of fully ripe fruits. The results obtained are summarized in Table l.The fertility as well as the pollinating ability of the individual cultivars are recorded in Table 2.
It was found that the cultivar Emperor Francis, cultivated in this country, differs from the variety of the same name grown in Western Europe, belonging to another incompatibility group and thus being also of another genotype. It must therefore be designated as Emperor Francis B. It is incompatible with Bigarreau Noir de Winkler, belonging to incompatibility group II (genotype S¹S³).
All remaining cultivars investigated are mutually compatible. Therefore, when larger plantings of these cultivars are to be established, only the time of flowering should be considered.
Further, the conditions are discussed which may cause repeated incompatibility in one direction only. The probable cause lies in flower biology (i.e. the age of blossoms of maternal plant) not in genotypic constitution.

Für eine Unterscheidung vonAgrobacterium tumefaciens undAgrobacterium rhizogenes sind drei geeignete Differenzialpflanzen gefunden worden.
1. Bryophyllum diagremontiana reagiert auf Agrobacterium tumefaciens mit der Bildung von Tumoren 32 Tage nach der Beimpfung und durch eine Stimulierung des Wuchses der Würzelchen am Rande der Tumoren (nach 52 Tagen). Bei Bryophyllum tubiflorum beträgt die Inkubationsfrist der Tumoren und der Würzelchen 30 Tage. Solanum laciniatum weist eine Inkubationsfrist für Tumoren von 15 Tagen auf, aber es kommt zu keiner Stimulierung des Würzeichenwachstums.
2. Nach einer Inokulierung mit Agrobacterium rhizogenes weisen alle drei Pflanzenarten gleiche Kennzeichen auf; Stimulierung der Würzelchen; aber die Inkubationsfrist ist verschieden (36-52 Tage), doch kommt es zu keiner Tumorbildung mehr.
3. Nach der Inokulierung mit einer Mischung von Agrobacterium tumefaciens und Agrobacterium rhizogenes bildeten sich bei Bryophyllum diagremontiana an der Impfstelle kleinere Tumoren, als bei ausschliesslicher Verwendung des Stammes Agrobacterium tumefaciens; Die Würzelchen durchwuchsen jedoch unmittelbar den Tumor. Bei Bryophyllum tubiflorum und Solanum laciniatum stimuliert die angegebene Mischung nur das Wachstum von Tumoren, die kleiner sind, als die von Agrobacterum tumefaciens hervorgerufenen und eine körnige Oberfläche haben; zu einer Stimulierung eines Würzeichenwachstums kommt es nicht.
4. Pflanzen von Bryophyllum diagremontiana wurden dekapitiert und die Schnittfläche mit Agrobacterium tumefaciens beimpft. So kam es zu einer starken Tumorbildung und zur Inhibierung des Wachstums der Achsenknospen des obersten Internodiums sowie zu seiner auffälligen Verdickung. Nach einer Inokulierung mit Agrobacterium rhizogenes kam es weder zu einer Würzelchen- noch zu einer Tumorbildung, das dekapitierte Internodium blieb am Leben, während es bei den Kontrollpflanzen eintrocknete. Nach einer Beimpfung mit einer Mischung beider Bakterien blieben die Tumoren kleiner und waren manchmal mit Würzelchen versehen, aber zu einer Verdickung des Internodiums kam es nicht.

The intensity of respiration and of photosynthesis were investigated simultaneously in sugar-beet leaves not detached from the plant. Several hours before the experiment the leaves had assimilated radioactive¹⁴CO2 whereafter they were placed into a normal leaf chamber for continuous gasometric estimation of the intensity of photosynthesis, according to the changes in the concentration of carbon dioxide in the passing air. At the same time, the specific activity of C0₂ was measured in the air that had passed through the assimilation chamber. From the values of the specific activity of CO₂ produced by the leaf in the dark the intensity of respiration in mg. CO₂ can be calculated.
It was found that sugar-beet leaves produce radioactive carbon dioxide when illuminated, both on the first and the second day after assimilation of labelled CO₂. During the considerable over-heating of leaves in the chamber when the gasometric method did not reveal anything but respiration a high production of¹⁴CO₂ could be observed radiometrically, corresponding to a higher respiration intensity. The authors explain this fact by the assumption that photosynthetic assimilation of carbon dioxide takes place simultaneously with respiration but the passive CO₂ balance in the gas exchange results in increased respiration, which actually represents the difference between the intensity of full photosynthesis and that of full respiration.
The production of carbon dioxide by whole sugar-beet leaves under illumination is no exceptional phenomenon under normal nutritional conditions.

Practical directions and examples are given for the use of quantitative ring precipitation to determine the intensity of cross reactions. The ability of this method to reproduce objectively the intensity of an antigen-antibody reacting system under various concentrations was verified. A comparison was made between Boyden's method of "complete curves" and the quantitative ring precipitation method.
The advantage of using quantitative ring precipitation is the saving of antiserum (0.05 ml. is sufficient for one determination), the smaller demand on working time and a noticeably reduced sensitivity to non-specific factors.
Quantitative ring precipitation (QRP) is a suitable method for quantitative experiments in immunochemistry and for purposes of comparative serology.

The growth of pollen tubes evokes changes in the level of free amino-acids in the style. This has been demonstrated in the cases of alanine, valine, leucine-isoleucine, serine, threonine, γ-aminobutyric acid, asparagine, glutamic acid and proline. These changes take place mainly in the parts of the style where the pollen tubes are present.
The most marked changes are an increase in the level of γ-aminobutyric acid and alanine and a decrease in glutamic acid. The intensity of these processes is much greater following compatible pollination than in the case of incompatible autogamy. On the assumption that the main course of γ-aminobutyric acid and alanine katabolism takes place by transamination with α-ketoglutaric acid, the basic nature of the above changes is explained as being due to a relative deficiency of the latter acid.
Alongside a reduction in the level of sugars an accumulation of asparagine takes place in pollinated styles. The rise in its level is considerably more rapid in cross-pollinated than in self-pollinated styles. If accumulation of asparagine is a result of more intensive consumption of proteins during respiration when there is a scarcity of sugars, it follows from the above results as from previous work (TUPý 1961), that pollen tubes use substrates from the style tissues for respiration and that this process is limited in the case of incompatible inhibition.
At the time when the pollen tubes are growing through the styles, the levels of γ-aminobutyric acid and alanine are already rising in the ovaries of pollinated flowers. This increase is quantitatively in direct ratio to the rate of pollen tube growth, which depends on the compatible or incompatible character of the pollination.

1. Photoperiodic experiments with the effect of short day during vernalization of winter wheat under field conditions have shown that the short day enhances development if applied during vernalization. Short day applied after vernalization prolonged the development.
2. At low intensity artificial illumination and under optimal vernalization temperatures vernalization proceeds the faster the longer the illumination. On increasing illumination intensity differences between the effect of short and long day are obliterated. Vernalization in the dark takes place only if saccharides are added.
3. It is assumed that even in green plants the accumulation of a certain amount of ergastic material, particularly saccharides, represents one of the conditions of vernalization. This accumulation may be achieved by longer illumination (under conditions of vernalization temperature and low illumination intensity), i.e. by a direct photosynthetic effect, or else by short day (under field conditions) causing a specific, photoperiodically controlled growth reaction which inhibits growth. When vernalization proceeds in the dark saccharides must be supplied.

If the flowers for experiment were separated from the plants one day before pollination and incubated in water at a temperature of 25° C, pollen tube growth in the pistils made itself apparent during the following three days in the glucose and fructose level. On the first day after pollination the amount of these sugars in the apical style parts was higher in non-pollinated flowers, while on the other hand, in most cases it was lower in the basal sections and ovaries than in the corresponding parts of pollinated flowers. During the next two days there was a greater loss of both carbohydrates where pollination, particularly allogamy, occurred, so that after the third day the glucose and fructose level was highest in the non-pollinated pistils and lowest after compatible pollination. This decrease was most pronounced in the ovaries even though the compatible tubes had not yet penetrated into them. In experiments in which the flowers were left on plants cultivated under field conditions, a decrease in the glucose and fructose content of their pistils had not occurred even 80 hours after compatible pollination.
From these facts the following conclusions can be drawn: The growth of the tubes through the styles causes an increased inflow of carbohydrates into the whole pistils. Both compatible and incompatible tubes use sugars from the style tissue. Both these phenomena are more intense after allogamy than in the case of incompatible autogamy. In view of the fact that compatible tubes grew normally through the styles even with a lowered glucose and fructose level, an absolute rise in the content of these sugars in the pistils is not necessary for tube growth.
The proportion of glucose/fructose in pollinated styles changes in favour of glucose. The value of this quotient rises both in the apical and basal style parts mainly, however, after compatible pollination. This phenomena is in agreement with the previous hypothesis (TUPý 1959, 1960), according to which, in the respiratory process, pollen tubes consume mainly sucrose and from this, primarily its fructofuranose component.

Proof is given in this paper that dwarfing of wheat, which occurs in several regions of Czechoslovakia, is a virus infection. The virus was transmitted by means of naturally infected imagos of the leaf-hopperPsammotettix alienus DAHLB. to spring wheat and spring barley. It was also found that it is transmissible to a high degree by larvae grown from eggs which are then artificially infected at the source of infection. An attempt to transmit the virus by means of the aphidsBhopalosiphon oxycanthae (SCHRANK.) andSitobium granarium (KIRBY) MORDV. was negative. Nor was it possible to transmit it by soil, wheat grains or by mechanical inoculation with sap from diseased plants.
The Russian mosaic virus of winter wheat would seem, in view of its vector, to be the most closely related to the wheat dwarf virus. It differs, however as regards the symptoms produced on the host cereals, by having a different vector and by the absence of inclusions in the cytoplasm of infected plants. These facts indicate that we are probably dealing with a new virus, which has not previously been described.

In der vorliegenden Arbeit ist eine einfache Methode beschrieben, mit deren Hilfe es möglich ist, die kritische Bodenfeuchtigkeit ganz objektiv zu bestimmen, bei der die Pflanzen absterben und zwar im Gegensatz zur Bestimmung des Welkungspunktes, die durch subjektive Fehler belastet ist.
Versuche an Sonnenblumen, Bohnen, Mais, Weizen, Buchweizen, Gräsern, Waldholzbäumen und verschiedenen Arten und Abarten des Zuchtweizens zeigten, dass die Bodenfeuchtigkeit, bei der die Pflanzen absterben, bei den verschiedenen Arten und Abarten verschieden ist. Ferner sind andere Arbeiten des Autors zitiert (Stojanov 1955, 1957b, und 1958) in denen er zeigte, dass diese kritische Feuchtigkeit sich nicht nur mit der Dichte der Bestände von Monokulturen, mit der Zusammensetzung der Bestände von Mischkulturen, sondern auch weiter sowohl unter dem Einfluss verschiedener chemischer Stoffe, als auch ihrer Konzentration änder.
Die Werte der Bodenfeuchtigkeit, beider die Pflanzen absterben, bzw. die Punkte des dauernden Welkens sind nicht nur für das Überleben von Pflanzen in der Zeit der Trockenheit wichtig, sondern beeinflussen wahrscheinlich die Ernte auch in Fällen, in denen diese Bodenfeuchtigkeitswerte nicht erreicht werden. Das ergibt sich aus den Untersuchungen vonMaximov undkomiserko, welche zeigten, dass das Pflanzenwachstum vom Abstand (von der Differenz) der Bodenfeuchtigkeit vom Punkte des unzugänglichen Wasser des Bodens abhängig ist.

In a hybridisation experiment, the hereditary fixation of mutations of a branched form of rye, characterized by an enlargēd number of blossoms and inflorescence parts, was studied. It was found that the hereditary fixation of this form was monomerily recessive with respect to the rye sort Dobřenická trsnatá, the spike formation being normal. It was also shown that neither particularly good nor particularly bad soil conditions had any effect on the split ratio of 3 : 1 in the F₂ generation. The mutation form studied was stable within a very wide interval of soil and climatic conditions. We are probably dealing here with a stable disturbance in the morphogenetic process resulting in spike formation.

Antagonism of three saprophytes to the pathogen,Rhizoctonia solani was studied in plate cultures under different conditions of temperature, pH, and nutrition. The antagonistsTrichoderma viride andChaetomium cochlioides were found more effective in the inhibition of the growth ofR. solani at temperatures 25 and 20° and this conforms to their growth-temperature relationship.T. viride was found more effective in acid media as reported by others, whereas other antagonists and especiallyC. cochlioides was more effective in the alkaline medium. Hence the suggestion is made that soil amendments increasing the activity ofC. cochlioides might be a good control measure against the pathogen in alkaline soils.
The most interesting result of the investigation is that, contrary to the previous reports,R. solani appeared to be more cellulolytic thanT. viride andC. cochlioides and this result was unaffected by the use of NH₄C1 as N-source.

The author investigated in the course of two years the osmotic pressure of 70 trees of 7 apple tree sorts, 5 of these bearing fruit periodically and 2 every year. At the beginning of the experiment, one half of the trees were without fruit and the other half with fruit-set. The experiment was carried out on 10-12-year-old trees (stock M II, M IX and M IV) in the NW apple-growing region of Bohemia (Střčžovice, Těchobuzice). Three or four times during every vegetation season leaves of brachyblasts of fruit-bearing and resting apple trees were removed and the osmotic pressure of their cell sap as well as its electric conductivity were measured. Once in every season, terminal buds of brachyblasts usually giving rise to flower buds were removed and treated identically as the leaves.
It follows from the data obtained that growing fruits bring about a decrease in osmotic pressure of leaves of apple trees by 2-6 atmospheres, depending on the amount of fruit-set and on the season. This decrease depends very little on weather and differences in osmotic pressure of the cell sap of fruit-bearing and resting apple trees are highly significant in July. The cell sap osmotic pressure in buds is decreased less - by 1-2 atmospheres. A significant positive correlation between the value of osmotic pressure and flöwer-bud formation of the sort Boskopská červená was demonstrated. In sorts bearing fruit annually, no such correlation, could be observed.