A gasometric method was developed for measuring water deficit in leaves. For a leaf at full turgor the amount of water penetrating into the tissue after removing the air from intercellular spaces by means of a vacuum pump, is equal in volume to the gas removed from the intercellular spaces. In a leaf with a water deficit the amount of the infiltrating water is greater than the removed gas volume by the amount egual to the water deficit. Determination of the volumes of the gas removed and penetrating water enables water deficit, if any, to be calculated. Comparative measurements carried out on five plant species confirmed the correctness of the method suggested. Reduction of the measuring time allowed to eliminate completely the sources of errors associated with the growth of tissue and loss of dry weight during respiration.

Identification trials were carried out to determine what virus causes a mosaic disease of sweet peas in Czechoslovakia. The found properties of the identified sweet pea mosaic virus, the character of its transmission and its host range prove that sweet peas in Czechoslovakia are attacked by common pea mosaic virus (CPMV). Some insignificant differences in properties between our virus isolate and CPMV were observed in the course of the determination of properties of our virus isolate on various host plants. The possible existence of more strains of CPMV is discussed. The transmission of sweet pea mosaic to the plants ofPhaseolus vulgaris L. was negative. For this reason bean yellow mosaic virus (BYMV) was eliminated as a possible pathogen of our virus isolate. At the same time the indicator plantsChenopodium giganteum Don. andChenopodium guinoa Willd. with eight developed leaves were established to be most suitable for the determination of the properties of the isolate by the half-leaf test. The transmission of the virus isolate by seeds was not proved.

Im Wasserextrakt der zerriebenen BlattläuseBrachycaudus napelli Schrk. befinden sich phytotoxische Stoffe, die durch einen biologischen Tomatensprosstest untersucht werden können.
Bei Erwärmung der Aphidenextrakte von 125°C sowie bei zweistündiger Erwärmung der getrockneten Rückstände bei 105°C blieb die Phytotoxizität von denselben unverändert erhalten.
Die phytotoxischen Stoffe sind aus dem Aphidenhomogenat sehr gut mit Wasser, gut mit Äthanol und Azeton, dagegen gar nicht mit Diäthyläther, Benzol und Chloroform bei Zimmer-temperatur extrahierbar.
Durch Dialyse wurde aus dem Blattlausextrakt eine kleinmolekulare Fraktion abgetrennt, welche an Testtomaten Blattnekrosen hervorrief. Die andere, im Dialysierschlauch zurückgehaltene höhermolekulare Fraktion, rief bei den Testpflanzen Welkeerscheinungen hervor, die mehr auf eine mechanische Verstopfung der Leitgefässe der behandelten Pflanzen hindeuteten.
Entwickeltes Extraktionsverfahren: thermolabile Stoffe wurden durch Erhitzen, lipoide Stoffe durch Ätherextraktion und höhermolekulare Stoffe durch eine Dialysemembran von den Aphidenhomogenaten entfernt und phytotoxische Stoffe in grob gereinigter Form mittels Wasser- und Azetonextraktion gewonnen.

The content of the carbohydrates glucose, fructose and sucrose was determined in spring barley anthers at different stages of maturity. During maturation the sucrose content of the anthers increased markedly. The following 17 free amino acids were detected in anthers of different stages of maturity: aspartic acid, glutamic acid, serine, alanine, arginine, leucine, isoleucine, lysine, α-aminobutyric acid, glutamine, proline, tyrosine, phenylalanine, valine, threonine, cystine and glycine. Quantitative analysis was only carried out in amino acids present in higher concentrations in the analysed samples. These were: aspartic acid, glutamic acid, α-aminobutyric acid, proline, serine, valine and glutamine, and a mixture of amino acids (leucine, isoleucine, valine and phenylalanine). The total content of free amino acids increased with increasing maturity of the anthers. However, not all amino acids followed contributed to this increase, but only proline, glutamic acid, aspartic acid and glutamine. A small difference was found in the variety Gopal in which the aspartic acid content did not increase significantly, but the content of the mixture of amino acids and serine did. With the exception of green anthers of the variety Firlbecks Union, proline was present in the highest concentration in all samples analysed.

The effect of temperature on the number of lesions and the time of their appearance was studied by inoculating French bean leaves (Phaseolus vulgaris L. cv. Perlička) with lucerne mosaic virus either 24 or 48 h before or, 24 or 48 h after they were exposed to various temperatures. The temperatures tested were 23, 25, 27, 30, 33 and 36° C.
Before and after such exposures the plants were kept in a constant temperature of 25° C. By increasing the temperature before inoculation the number of lesions increased in comparison with the control. The optimal temperature for the maximum number of lesions is between 27° and 30° C. There is no significant difference between those experiments when the exposure time was 24 h or 48 h before inoculation. The same temperatures applied for 24 or 48 h after inoculation have a decreasing effect upon the number of lesions formed by LMV on French bean leaves. The decrease is 30 to 75%. In this case the first necrotic local lesions appeared 42 h after inoculation when exposed to higher temperatures above 27° C for 24 h, and 60 h after inoculation when exposed to these temperatures for 48 h. The shape of lesions varied a little in both cases as the pictures show.

In Wurzelhomogenaten aus Keimlingen der Modellpflanze Sinapis alba L., die durch Pyridinderivate in der Konzentration 5×10^-4 M beeinflusst worden waren, wurden Aktivitätsänderungen der Glucose-6-phosphat-Dehydrogenase gefunden: Phenäthylpyridine (IA, B, C) und trans-Styrylpyridine (IIA, B, C) steigern die Enzymaktivitätin vivo, in vitro führen sie jedoch zu einer deutlichen Hemmung. Der dritte Strukturtyp, Pyridylphenazetylene (IIIA, B, C), istin vivo zwar unwirksam, doch in denin vitro Versuchen war er noch wirksamer als die beiden vorher genannten Typen. Es ist wahrscheinlich, dass die Ursache der Enzymaktivitätssteigerung in der Steigerung der NADP-Biosynthese liegt. Die Erhöhung dieses Koenzyms kann den Kohlenhydrateabbau zu Gunsten des oxydativen Mechanismus, des Pentosecyclus, zur Folge haben.

The callus tissue derived from tobacco pith and subcultured for 5^1/2 years on a solid synthetic modium revealed considerable differences in cell division activity depending on the age of the subculture and diurnal rhythm. The callus cells exhibited different level of ploidy among which an aneuploid condition nearer to diploid (2n=30-50) predominated. Chromosomal bridges and other structural rearrangements (lagging chromosomes, fragments) were observed in ana-and telophase.

The Euonymus Mosaic Virus was isolated fromEuonymus europaea. The virus was transmitted by sap to cucumber and other test plants, by seeds orAphis euonymi F., and it was soilborne, too. The sap from cucumbers lost its infectivity after 10 minutes at 80°C and after 35 days at 20-22°C. It is probably a new virus so far not described. The investigations of this problem are not finished, yet.

Immediate response of water uptake by intact plants ofPisum sativum L. to the introduction of high concentrations of α-naphtaleneacetic acid (NAA), β-indoleacetic acid (IAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), coumarin was determined by a series of potometric measurements. Growth substances were present in the root medium in two concentrations: 10^-3 m and 10^-2 m; the concentration of coumarin was 5. 10^-4 m and that of EDTA was 10^-3 m.
The response of water uptake to the application of the growth substances and coumarin was always negative. EDTA did not affect immediately the intensity of water uptake. The inhibition of water uptake brought about by the growth substances takes place immediately. Coumarin causes slow, progressively increasing inhibition of water uptake. A coincidence was found as to the time course of the changes in the water uptake intensity in the presence of high concentrations of growth substances and coumarin in the root medium with the time course of changes of transpiration intensity, found under analogous conditions by Allerup (1964). This may be considered as another justification for the hypothesis, according to which the rapid changes of transpiration intensity in the presence of high concentrations of growth substances in the root medium are caused by rapid changes of the intensity of water uptake.

L'aire d'écoulement du latex a été déterminée sur le tronc de l'Hevea brasiliensis à l'aide de Rb⁸⁶ inoculé avant la saignée à diverses distances de l'encoche. Une telle détermination peut être effectuée par une extrapolation non linéaire des courbes de drainage ou par une formule mathématique. Dans ce dernier cas, il suffit de connaître la quantité totale de latex écoulée depuis le début jusqu'au moment de l'apparition du latex radioactif provenant d'un point d'inoculation.
Les courbes d'écoulement du latex radioactif ayant plusieures maxima, correspondant aux divers points d'inoculation de Rb⁸⁶, peuvent être utilisées pour calculer les quantités relatives de latex écoulées de ces points. Dans ce but, on doit déterminer la radioactivité du latex aux points d'inoculation du Rb⁸⁶ dans l'écorce avant la saignée et réconstruir le parcour des courbes d'écoulement du latex radioactif pour les inoculations individuelles. Les quantités de latex déterminées de cette façon, provenant de diverses distances de l'encoche, se trouvent en bon accord avec les contractions de l'écorce aux mêmes endroits.
On a déterminé à l'aide de Rb⁸⁶ la forme de la partie principale de l'aire d'écoulement et on a comparé sa longeur à celle de l'aire de déplacement, délimitée par la contraction de l'écorce et par le déficit en latex dans l'écorce. La longeur de l'aire de déplacement a été trouvée deux fois et demie plus grande que celle de l'aire d'écoulement. La quantité totale de latex écoulé correspond à 80 % de la quantité mis en mouvement dans l'écorce lors de la saignée.

The present work is a study of the frequency of polyvalents in autotetraploid kohlrabi, cabbage and their intervarietal hybrids. Polyvalents were stated in the final phases of heterotypic prophasis, usually in diakinesis.
In none of both varieties any significant relationship between frequency of polyvalents and fertility expressed by mean number of seeds per siliqua was found, while in intervarietal hybrids some correlation was observed between mentioned characters. This leads to the conclusion that the frequency of polyvalents is not always a measure of the degree of fertility in auto-polyploids.
Autotetraploid intervarietal hybrids were characterized by marked prelevance of bivalents, by a considerable percentage of well-developed pollen grains and by high correlation between frequency of polyvalents and fertility. These characters are typical rather for amphidiploids.

The time course of fertilization in barley is described and the observations compared with those of older authors. The triple fusion is terminated in spite of its late onset always before syngamy. Whereas the time period reported for the so-called preparatory phase of fertilization and for the division of the primary endospernal nucleus is similarly reported by many authors, there are difference of as much as 8 hours in various report on the beginning of the division of the zygote (beginning of the prophase 13-21 hours after fertilization). In the present material, the zygote began to divide latest.
The transient reserve substance representing an energy store for fertilization in barley was found to be starch. Barley belongs to the species in whcih starch is formed in the pollen grain and the pollen tube itself. When the content of the pollen tube is released, part of it arrives in the embryo sac. A mature embryo sac contains many starch grains near the nucleus of the oosphere and the polar nuclei. Gradual hydrolysis of this starch is related to the more rapid triple fusion and the slower syngamy.

The chlorophyll mutation rate on a large number of plants after the dose rates 0.004-16.800 R/day during the whole vegetation cycle was examined. The mutation frequency increases as early as after the dose rate 4 mR/day. The dose rate of approximately 8 mR/day is necessary to double the mutation frequency.

Dispersing of splits of NaCl and KCl during the drying process has been found using labelled²⁴Na and⁴²K preparations. This bursting effect can cause some misinterpretations in biological experiments with plant material.

The effects of low doses of two mutagens (UV-light and ethyl methansulphonate) on the growth of algae on a solid minimal (anorganic) medium were studied. It was supposed that low doses of mutagens will be more suitable for the induction of growth mutations.
The UV-light had an inhibitory effect in the whole range of the applied doses on the growth of colonies of algae from the cells inoculated on the solid medium immediately after irradiation.
Ethyl methansulphonate produced growth stimulation if applied in the lowest doses. The growth was inhibited in a further range of doses and then there appeared the range of lethal doses.
The growth responses to the influence of these mutagens were different in all the three algal species used and to the previous cultivation conditions before their exposure to the mutagens. It is certain that most of these growth responses are only modifications.
The influence of ethyl methansulphonate differed according to the method of application. If it affected the algae for a long time (it means if they were inoculated directly on the solid medium containing mutagens), or, if the algae were exposed to its influence immediately before their inoculation on the solid medium, the growth responses of colonies were quite different.
Growth responses with the single studied strains differed quantitatively only.

The paper deals with the resaturation of water saturation deficit in fourStipa species tested under various ecological conditions. Attention is paid to the relations between the saturation and oversaturation types of curves, on the one hand, and soil moisture on the other. The oversaturation type appears in plants well supplied with soil moisture. The explanation of this phenomenon is discussed.

Irradiation with visible light reduced the mutagenic activity of 1-methyl-1-nitrosourea (MNH) and 1-methyl-3-nitro-1-nitrosoguanidine (MNG) solutions during their application onArabidopsis thaliana seeds for 24 hours. The antimutagenic effect of light was stronger with MNG than with MNH and in solutions buffered to pH 5 than in aqueous solutions. The decrease of activity of both the mutagens corresponded with the rate and degree of their photolysis. In the paper are presented the curves for the dependence of the decomposition of both substances and the formation of nitrous acid on pH and temperature of the solutions, amount of seeds.

Using paper chromatography and conventional methods of isolation, natural growth inhibitors were isolated from green leaves of different plants (Brassica oleracea, Zea mays, Pisum sativum andSalix rubra). All isolated inhibitors were found to be phenolic compounds and the chemical structure of most of them was determined; only the final structure of theBrassica inhibitor has not yet been ascertained. 500 mg of natural inhibitor ofPisum sativum was isolated from 1500 g of leaves and was identified as quercetin-glucosil-p-coumarate (QGC), described earlier byFuruya, Galston andStowe (1961). The structure of the natural inhibitor ofZea mays (4 mg from 100 g of leaves) was identical with p-coumaric acid and the chemical nature of the plant growth inhibitor fromSalix rubra (700 mg from 1,5 kg of leaves and young bark) was that of 2-chalconaringenin-glucoside or isosalipurposide, described earlier byCharaux andRabaté (1931) andHarborne (1966). All isolated substances had inhibiting properties in the straight growth test of wheat coleoptile sections and decreased the growth of isolated stem sections prepared from plants-donors of inhibitors. Thus, maximum growth inhibition (LG max) was attained, if wheat coleoptile sections were incubated with:Brassica inhibitor in the concentration of 0.5 mg/ml, withPisum inhibitor (QGC) in the concentration of 16 mg/ml, withZea inhibitor (p-coumaric acid)-0.35 mg/ml and with Salix inhibitor (isosalipurposide) in the concentration of 0.5 mg/ml. In small concentrations no mentioned substances were able to enhance the growth as actively as indolic auxins (on 250-300%); only slight growth activation in biotests was sometimes observed for low concentrations. Inhibition in p-coumaric acid was much more active in a free form than in the bound form as an acyl-rest of QGC. As a rule, the wheat coleoptile test was much more sensitive (3-5 times) to the plant growth inhibitors, than tests prepared from tissue and organs of plants-donors. The retardation activity of plant growth inhibitors is not correlated with their molecular weight. Dormin (or±abscissin II) was also tested on wheat coleoptile sections. In neither of the applied concentrations (10-0.05 μg/l range) was dormin able to depress straight growth of wheat coleoptile sections, but even in a 1.7 μg/l concentration it inhibited the IAA-activated growth of sections. However, additional experiments showed that dormin in higher concentrations (40 μg/l and more was able even to depress endogenous straight growth of wheat coleoptise sections. The differences between the properties of natural phenolic growth inhibitors and dormin were discussed.

In estimating the water-holding power and thus also their drought resistance, the portion of curvature as shown by the desiccation curves (transpiration, loss curves) appears most suitable in which the water-binding forces within a plant body feature a steep and characteristic rise. Since this portion of the curving stage coincides, in the majority of cases, also with the linear stage for the desiccation curves as described byCetl, this author's method of establishing drought resistance of plants (Cetl, 1953, 1957) may be applied to good advantage also to the woody species seedlings. For particularly urgent instances serving the purpose of orientation a modification of this method has been suggested, as follows: following cutting off the seedling the output of water is weighed at these intervals only: 0, 60, 120, and 240 minutes; as the criterion for drought sistance the resulting value for the rate of water output (v) is taken as measured between the interval of 60 and 120 minutes. When a detailed analysis is made it is advisable to consider the v value measured for the interval between 0 and 60 minutes and for that between 120 and 240 minutes. Moreover, it is likewise advisable to maintain the soil with experimental seedlings at the level of optimum moisture (60 to 80 per cent maximum capillary water capacity), for some 18 to 22 hours prior to the seedling's abscission.

6-azauracil (AU) and 2-thiouracil (TU) were applied to the short-day plants Pharbitis Nil and Chenopodium rubrum and to the long-day plants Hyoscyamus niger, Lolium temulentum and Triticum aestivum cv. Chlumecká 12 at different times before, during or at the end of floral induction. In wheat the effect of 5-bromouracil, 5-iodouracil and 2-thio-6-azauracil was also tested.With the exception of bromouracil, which slightly stimulated flowering in wheat, all analogues either strongly inhibited or completely blocked flowering when applied in appropriate concentrations a short time prior to induction or at its beginning. Treatments given a longer time before induction or after its termination was less effective. Inhibition of flowering was always associated with damage to the vegetative growth. The effect of TU was reversed by uracil and that of AU by uridine, if these compounds were applied simultaneously with the analogue at a concentration exceeding at least 5 times that of the analogue. Reversal also applied to vegetative growth. Simultaneous application of gibberellin and analogues did not remove the inhibition.

The effect of 2-thiouracil on vegetative growth and floral differentiation was investigated inChenopodium rubrum plants grown in water cultures. Between the low concentrations of the agent, stimulating vegetative growth and floral differentiation, and those inhibiting both these processes, a narrow concentration range was found (1.10^-5 m to 2.10^-5 m), where growth was inhibited selectively. At a concentration of 1.10^-4 m a selective inhibition of development was found when 2-thiouracil was applied at the beginning of photoperiodic induction. Inhibition of development was strong regardless of whether 2-thiouracil was applied before, during or closely after 4 days of photoperiodic induction; the degree of growth inhibition, however, changed in dependence on photoperiodic induction. The strongest relative inhibition of development, calculated as a ratio between development and growth, was observed always at the beginning of photoperiodic induction.
Investigation of plant growth as well as the anatomical and autoradiographic study after the application of 2-thiouracil indicate that the inhibition becomes evident at the end of 4 days of application by an overall growth inhibition and a decrease of mitotic activity. Reversal by uracil was possible after simultaneous application of 2-thiouracil. The nature of the selective inhibition is discussed and two possible interpretations of the data obtained are analyzed: a) different response of growth processes in apices and young vegetative organs respectively with regard to different participation of cell division and elongation, b) specific inhibition of floral differentiation.

In young pumpkin plants, the phosphorus was found not to be affected substantially by potassium deficiency whereas the deficiency of calcium has marked effects. Potassium distribution is not affected substantially by either phosphorus or calcium deficiency.
In short-term experiments, the presence of calcium affects markedly the total uptake of potassium but the potassium distribution remains unaltered. The stimulation of potassium uptake is far more pronounced in plants pre-cultivated in a complete nutrient solution than in those pre-cultivated in a calcium-deficient one; this is apparently due to profound metabolic changes taking place in plants grown without calcium.
The reserves of phosphorus and potassium stored in the cotyledons are easily mobilized and translocated so that they can be used for growth in early stages of development; the appearance of pathological symptoms of phosphorus or potassium deficiency is thus prevented.

Using moving boundary electrophoresis in a veronal buffer, pH 8.5, of 0.05 ionic strength and at 4.3 mA, we succeeded in separating the inhibitor, which was obtained by fractionation on a Sephadex G-50 column, into four components. The two most substantial components represent 25% and 65% respectively from the separated proteins as a whole. The heterogeneity of the inhibitor was proved by analytical ultracentrifugation, too. The ionex chromatography was applied for the quantitative separation of the inhibitor. We used ionex chromatography on DEAE Cellulose the concentration gradient being 0-1m NaCl in a 0.01m phosphate buffer, pH 7.3, and on DEAE Sephadex A-50 using the same concentration gradient in a phosphate buffer, of 0.1 ionic strength and pH 7.3. In both cases four components were obtained. The most substantial component, representing 65% of the whole analysed material, was eluted at the concentration 0.15-0.3m NaCl, and was electrophoretically homogenous and showed the most effective inhibitory ability.

The lignine content and mechanical rigidity of siliquae ofBrassica napus L. ssp.oleifera f.biennis, cv. Třebíčská were studied. Experimental plants were harvested in five consecutive periods and developmental stages of siliquae were determined on the basis of the weight of 1000 seeds. During the development of siliquae a gradual accumulation of lignine takes place; the content reached its maximum in certain developmental phases and then decreased. The mechanical rigidity of siliquae had a similar tendency. There were statistically significant differences in both properties studied within individual developmental phases. A highly significant positive correlation was found between lignine content and mechanical consistency.

The induced meiotic abnormalities as a result of sprayingVicia faba plants with aqueous saturated solutions of podophyllin and 8-hydroxyquinoline were studied. The 2 drugs induced the same types of abnormalities including lagging chromosomes, stickiness, and bridges. The main difference between the 2 agents was the induction of polyploid P.M.Cs. by 8-hydroxyquinoline.

Development of the shoot apex up to floral differentiation was investigated in the short-day plantChenopodium rubrum. The changes occurring in the apex from energence until full opening of the cotyledons (Figs 1-4), development during photoperiodic induction (Figs. 5-8), as well as the resulting floral differentiation (Figs. 9-10) are described. It was aimed at excluding the influence of plastochron changes on the interpretation of ontogeny of the shoot apex. For that reason two planes of longitudinal sections and two plastochron stages were compared.
In young plants zonation does not become fully evident prior to floral differentiation. The anatomical structure of the shoot apex does not change substantially during the first two inductive cycles which proved to be obligatory under the given experimental conditions. The changes occurring during two further inductive cycles correspond to the total activation of the meristems as manifested by the growth and branching of the apex preceeding floral differentiation proper.

The presence of potassium humate (commercial sample of Humussäure Riedel-de Haën A. G., Seelze-Hannover) in distilled water led to an increase in the content of alanine, aspartic and glutamic acid in the overground parts of wheat plants as compared with the content of these substances in control plants grown in distilled water. In plants cultivated on nutrient solutions a higher level of alanine and glutamic acid and a considerably lower level of amides was found than in plants grown in distilled water and in water with humate. Generally the content of amino acids was higher in the overground parts than in the roots after a cultivation period of one week as well as of 14 day. In the overground parts of 1 days old plants the level of aspartic acid, asparagine and alanine was found to be higher and that of glutamine lower than in seven days old plants. In the roots of the examined plants a decrease of the amino acid content accurred almost in all cases after a cultivation period of 14 days as compared to one of 7 days.

In der meristematischen Zone, Streckungszone und in der Zone der beendeten Zellstreckung der Wurzeln vonVicia faba L. cv. Chlumecká, wurde festgestellt, dass 8×10^-2 m NaF und 10^-3 m Monojodessigsäure den Q_{O 2} in der Streckungszone und der Zone mit beendeten Zellstreckung am meisten und in der meristematischen Zone am wenigsten hemmen. Bei der Applikation des Malonats in der Konzentration 5×10^-2 m sind die Unterschiede zwischen den einzelnen Zonen statistisch nicht gesichert, der RQ wird jedoch erhöht, besonders im Meristem. Von den angewendeten DNP Konzentrationen wirkt die Konzentration 10^-5 m auf den Q_{O 2} und Q_{CO 2} stimulierend; bei dieser findet die höchste aerobe Gärung im Meristem statt. Bei höheren DNP Konzentrationen wird der Q_{O 2} im Meristem gehemmt, es kommt die höchste Q_{CO 2} Produktion und auch die höchste aerobe Gärung in der Streckungszone vor. Durch 10^-2 m 1-Amino-2-naphtol-4-sulphonsäure werden Q_{O 2}und besonders Q_{CO 2} in der Streckungszone und der RQ im Meristem beschleunigt.
Diese Ergebnisse zeugen für den höchsten Anteil der Glykolyse in der Streckungszone; dies stimmt jedoch mit den Versuchen mit dem Verbrauch spezifisch markierter 1-¹⁴C und 6-¹⁴C-Glukose, den gefundenen RQ und dem Vorkommen des Äthanols nicht überein. Diese Diskrepanz zwischen den Ergebnissen verschiedener Methoden wird weiter verfolgt.