The biological effect of barley root excretions was studied during a 4 to 10 days cultivation period. The effect of root excretions changes according to the cultivation period of barley. It was ascertained by means of a bioassay that growth was either conclusively stimulated or the root excretions did not affect growth of the roots and of the upper part ofNasturtium. No significant inhibitory effect was observed. The effect of the single amino acids and of their mixtures found in the root excretions of barley was quite different. The following amino acids were determined by paper chromatography in root excretions: alanine, asparagine, phenylalanine, glycine, leucine, lysine, serine, tyrosine, glutamic acid and valine plus methionine. During cultivation their total quantity increased from 5.48. 10^-5 up to 1.13. 10^-3 mg per plant. Most of the 20 amino acids observed, displayed in theNasturtium test at a concentration from 0.1 to 1,000 mg/l an inhibitory effect onNasturtium growth. The effect of amino acid mixtures, corresponding qualitatively and quantitatively to the free amino acids in barley root excretions was dependent on their concentration.
Growth regulators of the auxin type were found in culture solutions by chromatographic separation and with bioassay. As it may be seen from the results obtained, there are besides amino acids and indole derivatives other non-identified compounds involved in the effect of barley root excretions.

The application of CCC at concentrations inhibiting flowering ofChenopodium rubrum reduces the level of endogenous gibberellins in the apical buds of the plants. The effect of CCC may be reversed by appropriate concentrations of gibberellin (GA-), indole acetic acid (IAA) or kinetin. Kinetin applied to the apical bud during floral induction reduced the level of endogenous gibberellins similarly as CCC and if both CCC and kinetin were applied simultaneously their action was additive. On the other hand IAA applied under the same conditions increased the level of endogenous gibberellins and after joint application of CCC and IAA their level was the same as in untreated control plants. After application of CCC during floral induction the level of endogenous auxins did not change markedly but an active substance "x" appeared on the chromatograms of indole compounds. This substance was found also after simultaneous application of GA- and CCC but not after joint application of CCC and kinetin. If follows from our results that the same morphological phenomenon (flowering) can take place in plants considerably differing as to their level of endogenous growth substances. The ratio of different growth substances is obviously more important than the actual level of the single substances.

The 0.03-0.06% indole-3-acetic acid (IAA) in lanoline paste smeared on the cut surface of decapitated epicotyl of the pea seedling inhibited the growth of the axillary buds of the cotyledons. 0.03-0.06% solution of (2-Chlorethyl) trimethylammonium chloride (CCC) considerably weakened the inhibitory effect of IAA when applied simultaneously to the roots. In a similar way CCC diminishes even the growth inhibition of intact pea epicotyls caused by 0.06% IAA lanoline paste. 0.03% solution of CCC administered to the roots of the decapitated pea seedlings significantly increased growth of the axillary buds. This effect may play a role in the demonstrated antagonism between the low concentration of CCC and IAA.

Bei 14 Winterweizensorten wurde im Zeitabschnitt Winter-Frühling der Zellsaftbrechungsindex gemessen. Die höchsten Werte wurden bei einigen frostresistenten, die niedrigsten Werte bei nichtresistenten Sorten gefunden, der Zellsaftbrechungsindex war aber nicht in allen Fällen der Frostresistenz proportional. Mit Rücksicht auf Stoffwechselvorgänge der osmotisch aktiven Stoffe, die deren Menge und Verhältnis bestimmen, sind Saisson- sowie Tagesveränderungen im Laufe von Winter und Frühling nicht nur von der Temperatur und Feuchtigkeit der Umgebung abhängig. Der Zellsaftbrechungsindex unterliegt verschiedenen Veränderungen in Beziehung zu Pflanzenernährung in verschiedenen Wachstumsphasen bei Sorten mit verschiedenem biologischen Charakter und unter verschiedenen pedologischen und klimatischen Bedindungen. Stickstoffdüngung erhöht den Zellsaftbrechungsindex bei vielen Sorten, hauptsächlich gm Winter.

The rate of growth of 5 species of white-rot fungi on an agar medium with additions of humus acids was used for assessing the ability of these fungi to utilize humus acids as a sole source of nutrition. Differences in the effect of the various fractions of humus acids and their concentrations, as well as in the reaction of the fungi tested were observed. During the growth, loss of colour of agar media with humus acids was observed. Activity of lacease in the discoloured areas was highest.

Three techniques of the test-tube fertilization by means of an artificial pollen tube culture are described. The essentials for each individual method are:
1. Transfer of pollen tubes from the sugar solution onto the placentae in the test tube.
2. Placing the placentae with ovules onto pollen tube culture.
3. Precultivation of pollen tubes on small cellophane squares placed on the surface of a semi-liquid medium and transfer of cellophane squares along with the pollen culture to the solid medium, over which finally the placentae with ovules are placed.
By means of all the three techniques viable seeds were obtained in vitro. In an artificial medium pollen tubes are able to maintain their fertilizing ability even after the 24 hours cultivation, i.e. at the time after the formation of the gametes.

Using hydroponic cultures, the effect of high concentrations (10^-3 m) of 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the root medium on the water balance of 8-9 week old plants ofPisum sativum L. and of 9-10 week-old plants ofSinapis alba L. was studied. The water balance was determined in the light and in the dark gravimetrically by measuring the intensity of water uptake and transpiration in plants cultivated by the method of root bridges according to Werner. MCPA present in the root medium in illuminated plants decreased rapidly the intensity of both the uptake and the loss components of the water balance. In permanent darkness, MCPA brought about an increase in the intensity of uptake of water and of transpiration. Simultaneous determination of water uptake and transpiration showed that the intensity of transpiration remained higher than the intensity of water uptake. This indicates that in the presence of MCPA in the root medium the relationship between the uptake and the loss components of water balance is not quantitatively equal, enboth in the light and in the dark. The existing disproportion results in the formation of a passive water balance of plants.

A quantitative anatomical study of the stem structure of grasses of various ecological groups: xerophytes, mespohytes, ephemers, hydrophytes and psammophytes (a total of 30 species) was carried out. The proportions of the various tissues in the stem were expressed as a percentage of the cross-sectional area of the stem. Stems of hydrophytes were found to have only small proportion of mechanical (4-8%) and conducting (2-5%) tissues but a large pro. portion of parenchyma (85-93% - primary cortex and basic parenchyma) and air system (38-40% - parenchyma channels or specialized aerenchyma). The stems of xerophytes possess a highly developed sclerenchyma (30-50%) and vessel bundles (6-13%) while the parenchyma is less developed (36-60%). The cells of the stems of hydrophytes are larger than those of xerophytes, but the cell membranes are thinner. The structure of mesophytes is intermediate between that of hydrophytes and xerophytes and the structure of ephemers is very similar to that of mesophytes. Psammophytes differ from xerophytes in having more mesomorphous features.

In order to interpret the mechanism of elongation growth of the hypocotyl with radicle in the first stages of germination of the pea seed (Pisum sativum L.) a cybernetic model utilizing feed-back as a mechanism of correcting the wrong direction of growth was proposed (Spurný 1966, 1967). In the present study, the effect of amputation of the root tip as the control centre on the trajectory of the growing radicle was investigated. The results have shown that the hypocotyl grows, elongates-the rate of growth being slightly lower than that of the standard, but that no spiral oscillations at all are executed by the organ after amputation of the root tip. This finding appears to confirm the applicability of the proposed cybernetic model, for amputation of the root tip means that not only the control block is eliminated, but also that the channel of feed-back impulses to zone of elongation is interrupted.

The filamentous green algae investigated (Hormidium sp. strainHindák 1963/21,Ulothrix sp. strainHindák 1964/2,Uronema gigas Visch. strainVischer/Bloom. 174,Uronema sp. strainHindák 1963/25 andStigeoclonium sp. strainHindák 1964/1), contain similar amounts of proteins, lipids, cellulose and ash as the hitherto used production strains of the generaChlorella andScenedesmus. The digestibility of proteins in vitro is about one-third higher in the filamentous algae than in the employed referenceScenedesmus quadricauda strainGreifswald/15, used in Czechoslovakia as a model production strain. The heats of combustion of the filamentous algae are relatively lower (5519-5923 cal/g dry weight) than in the reference strain (6145 cal/g dry weight).
From the point of view of application of filamentous green algae to mass cultivation their advantages over the presently employed chlorococcal algae (Chlorella, Scenedesmus) consist in a pronouncedly greater digestibility of their proteins without special technological treatment of the material obtained and a greater production of biomass.

In dieser Arbeit wurden die Unterschiede in der Wirksamkeit der β-(3-Pyridyl)-propion-(VIII) und der β-(3-Pyridyl)-acrylsäure (IX) mit Hinsicht auf den Sättigungsgrad der Seitenkette studiert. Beide Säuren hemmen das Wurzel- und Hypokotylenwachstum der Modellpflanze Sinapis alba L. und verursachen eine starke Hemmwirkung der Succinat-Dehydrogenase. Die Säure IX hemmt dieses SDH-System ungefähr um das Zweifache als die Säure VIII. Dagegen bleibt die Aktivität der Cytochromoxydase fast ohne Änderung. Auf Grund der erzielten Resultate wurde die Strukturbedingung der phytotoxischen Aktivität der Modellsubstanzen der Styrylpyridine (Typ I) im folgenden Sinne ausgesprochen: alle Verbindungen mit dieser Struktur hemmen ausser dem Wachstum auch das SDH-System.

Respiratory metabolism of the cultures of algaeChlorella pyrenoidosa (82) andScenedesmus obliquus (125) was investigated. One part of algae were cultivated on a mineral nutrient solution, another two parts on the solution with glucose and on the solution with glucose and yeast decoction. Individual steps of respiratory metabolism-endogenous as well as in the presence of exogenous sugars-were estimated according to the response to the following inhibitors: monoiodacetate, NaF, NaN₃, and 2,4-DNP. In the last two cases, fructose, glucose-6-phosphate and fructose-1,6-diphosphate were applied in parallel for comparison. Na-monoiodacetate was found to inhibit the respiration of both endogenous and exogenous (with glucose) substrates, NaF (concentrations up to 2.5.10^-2 m) stimulated the O₂ uptake. The effect of sodium azide and 2,4-DNP depended in both strains on previous cultivation. On the basis of the results obtained, the presence of particular respiration pathways in the dissimilation of glucose is discussed. The following catabolic processes are to be considered: a) direct oxidation (with both autotrophically cultivated strains and with theChlorella cultivated on glucosecontaining medium), b) the process similar to glycolysis, which, however, does not necessarily involve the enolase (it is not inhibited by NaF) c) pentosephosphate cycle (Chlorella), and d) glycolysis, in which both algae can operate when sugars previously phosphorylated are applied.

Experiments revealed that the synchronized cultures ofScenedesmus quadricauda, strainGreifswald/15, must be kept under continuous illumination throughout the whole growth phase (from the release of daughter coenobia up to the moment when all cells are capable of further reproduction). The length of the light period is among others the function of the suspension density. With regard to these facts a method of synchronization was worked out on the basis of a rhythmical repetition of the calculated light regime, corresponding to the physiological parameters of the synchronized strain under given cultivation conditions. This method enables to maintain synchronized cultures in adequate cycles for any required period, even in sufficiently dense, linearly growing suspensions. It may be applied to any chlorococcal algae; however, if coenobial types are studied, it is necessary to consider special peculiarities, which result from the regular arrangement of the cells in the coenobium.

Potato leafroll virus induces considerable disturbances of phosphorus metabolism in leafroll-infected potato plants. Each variety reacts differently in this respect on the infection, to some extent being dependent on the susceptibility of the respective variety to leafroll and to the season as well. In varieties particularly susceptible to leafroll as in Apta and Sieglinde there is a decrease of total P after infection. On the contrary, varieties showing medium susceptibility such as varieties Tatranka, Rita and Ambra react to leafroll infection with a considerable increase of total P. In the comparatively less susceptible variety Krasava, there is no change in the level of total P after infection. In autumn, however, a slight decrease of total P even in the medium susceptible variety Tatranka, and the less susceptible variety, Krasava, can be found. Our results shed a new light on existing controversies in literature regarding phosphorus content in leafroll-infected potato plants.
When the changes in the contents of various phosphorus fractions in the infected plants are compared we can observe a tendency of lowmolecular fractions to rise. Among the different phosphorus fractions one common feature could be seen, except for the hypersensitive resistant variety Apta, namely, that the acid-soluble organic phosphates in the stems of all varieties examined, were considerably higher than in healthy stems.

The exodermis of ash roots is initiated early in the apical meristem. When fully differentiated, it is composed of alternating "long" and "short" cells measuring approx. 70×25×25 μm and 25×28×25 μm respectively. At a short distance from the apex, the long cells undergo structural and histochemical changes from a "primary" towards a "secondary" stage: an impermeable suberized lamella is formed, cellulose lamellae become impregnated by lignin, and the protoplast dies off. The short cells show a distinctly thickened outer wall ("cap") which is composed exclusively of cellulose, and possess abundant cytoplasm with a large nucleus. In the process of ageing the structure of short cells is not markedly affected. Following the early disintegration of rhizodermis, the exodermis works as the external protective layer of tho fragile end-root. Its long cells fulfil the mechanical protection, the short cells serve as passage cells for solutions and gases, during the whole life-span of the rootlet.

The water loss of leaves of the same level of insertion but of various ages was examined. The results show that the transpiration of youngest leaves is higher than that of the older ones. The oldest leaves which have started yellowing show an increase of transpiration. This is probably related to the premortal changes of the leaf. The differences are probably caused by various physiological states of leaf because the leaf area was not different.

The presence of beet yellows virus (BYV) particles was electron microscopically proved in the roots of sugar beet. Specimens for the electron microscopical examination of root sap were prepared by differential centrifugation. It was proved that, contrary to expectations, examinations in spring showed most virus particles in the basal part of the root. At the same time it was found by experiment that the diagnostical BYV antiserum, for which the antigen was prepared from sugar beet leaves, did not react with a purificate of BYV containing virus particles.

A purified potato virus S was prepared using precipitation by the solution of 35% polyethylene glycol 4000 in the presence of an electrolyte. The mixture for precipitation of the potato virus S had to contain 11% polyethylene glycol and 0.25m NaCl. The S virus was extracted by 0.01m phosphate buffer, pH 7.5, from the precipitation separated by centrifugation. One part of the extract was further purified by means of differential centrifugation and the other by means of gel filtration on Sephadex G-100. The ultraviolet absorption measurements of both preparations showed that the differential centrifugation gave a purer preparation than the gel filtration.

Several methods of NA isolation and estimation were examined in order to determine RNA in the whole root systems of young wheat plants. It was found out that during the hydrolysis of roots with perchloric acid according toOgur andRosen (1950),Spirin (1958) andHeitefuss (1965) a considerable amount of orcine-positive compounds is released which cannot be adequate to the RNA content. Therefore the separate RNA determination in the presence of DNA was excluded even after the NA fractionation by hydrolysis at various temperature and perchloric acid concentration. Besides NA hydrolysates contained a high amount of other compounds absorbing in the UV-region. Compounds interfering with both these methods were present especially in the basal parts of roots.
Using the method ofKern (1960) a nucleoprotein fraction was isolated containing about 75 per cent of the total NA content in the tissue. This fraction consisted of more than 90 per cent RNA combined with proteins, namely the ribosomal RNA. After the hydrolysis it could be estimated spectrophotometrically for the hydrolysate did not contain other compounds absorbing in the UV-region. In the root tips the content of this fraction was high in comparison with the basal parts of roots and it changed with the kind of nutrition.

2,4-D was applied to the roots of diploid and tetraploid corn. After the application the mitotic division in the meristem of root tips was blocked; the mitotic division in differentiated cells of cortex and central cylinder, on the other hand, was provoked. In the cortex of diploid corn (variety České) predominantly tetraploid were found cells with 28 chromosomes and, to a lesser extent, octoploid and diploid ones with 56 and 14 chromosomes respectively. In the cortex of tetraploid corn (variety Bernburger Tetraroggen), most cells were octoploid with 56 chromosomes; the metaphase levels with 112 and 28 chromosomes, e.g. 16-ploid and tetraploid cells, were found less frequently. The relations between the numbers of cells with different polyploidy were similar in both the varieties. The first endoreduplication cycle was different polyploidy were similar in both the varieties. The first endoreduplication cycle was found to occur in the region where the cortex cells finish their elongation. In the central cylinder of the roots of diploid corn most cells were found to be diploid, in tetraploid corn most cells were tetraploid.

The production of pectic enzymes byHelminthosporium atypicum and its morphogenesis on different media were studied. It was observed that the fungus produces pectic enzyme (macerating enzyme) adaptively. Increasing concentrations of glucose had an inhibitory effect on enzyme production. Glucose promotes profuse growth and early sporulation whereas presence of pectin slows down the growth and delays sporulation. Delay in sporulation is the effect of presence of pectin and not of the low pH of the medium. It is also suggested that in the case ofH. atypicum low pH of the medium does not allow the fungus to utilize a carbon source as efficiently as at higher pH.

Versuche, in denen der Einfluss der Phenäthylpyridine (I A, B, C), trans-Styrylpyridine (II A, B, C) und Pyridylphenylazetylene (III A, B, C) auf die Aktivität der Pyrogallolund der Ascorbinsäure-Oxydase in den Wurzeln vonSinapis alba-Keimlingen verfolgt wurde, ergaben folgende Resultate:in vivo wurde die Pyrogallol-Oxydase durch keinen dieser Stoffe beeinflusst, jedochin vitro zeigten die trans-Styrylpyridine und die Pyridylphenylazetylene eine bedeutende Hemmung. Die gefundenen Resultate lassen darauf schliessen, dass es sich wahrscheinlich um eine direkte Inhibition, diein vivo durch Einschaltung dieser Stoffe in den Stoffwechsel teilweise kompensiert wird, handelt. Die Aktivität der Ascorbinsäure-Oxydase war dagegen mächtig gesteigert, besonders in den Versuchenin vivo.

Labelled carbon dioxide was supplied for 22 hrs to a leaf of the leader or to the lateral shoot in two-year-old apple seedlings. The distribution of radioactive assimilates within the plant following this treatment was investigated by using radioautography.
The transport of labelled assimilates from the young leaf of the leader was very meagre and affected only parts of the stem and the leaves situated in the close vicinity of the treated leaf.
The¹⁴C-labelled assimilates from the mature leaf of the leader were transported in a considerable amount to the apex and to the other leaves of the leader. They were also found in an appreciable amount in the stem and the roots, as well as in some lateral shoots.
After supplying¹⁴CO₂ to the lateral shoot remarkable transport of labelled assimilates was observed. Radioactivity was detected in the tip and in the youngest leaves of the leader, as well as in the roots. Their path in the stem was studied by dissecting the plant and examining the cross section from each internode. This method revealed that the assimilates from the treated leaf or shoot were transported downward only on one side of the stem in a helical pattern. The lateral shoots situated on the radioactive side of the stem were also labelled, whereas those situated on the opposite (non-radioactive) side were not labelled.

1. Kinetin at a supra-optimal dose of 1.0 mg/l reduces the growth inhibitory effect of CCC at 5 × 10^-2 M on tobacco callus and increases it on tobacco crown-gall.
2. CCC increases the content of total, acid soluble, protein anti nucleic acid nitrogm in both tissues. Kinetin partially reduces the effects of CCC on nitrogem metabolism in callus tissue, and increases it in crown-gall.
3. It is suggested that (1) CCC affects the synthesis of RNA directing the synthesis of protein, and (2) interaction of kinetin with CCC realizes via the genetic apparatus of the cell.

In this paper we compare the influence of heterologous and isologous DNA on the radiation damage repair of primary root meristematic cells ofVicia faba. Roots, irradiated by exposure of 150 r were cultivated at different time intervals either in tap water, or in a solution of heterologous or isologous DNA. In comparing mitotic activity of meristematic cells it was found that both types of DNA studied enhance the recovery of irradiated cells. The frequency of postmetaphase chromosomal aberrations of irradiated cells was influenced also by post-irradiation action of exogenous DNA. While heterologous DNA exhibited synergical effect with radiation in the sense that it increased the post-irradiation incidence of aberrations in all time intervals studied, isologous DNA had a strong repair effect-the application caused a significant decrease of the percentage of post-metaphase aberrations. Both kinds of DNA caused changes in the relation of chromosome to chromatid aberrations; a higher percentage of chromatid aberrations was registered. The study of the distribution of aberrations between large and small chromosomes ofVicia faba showed that the post-irradiation application of heterologous DNA increases damage of small chromosomes while isologous DNA caused an increased repair ability in this chromosomal group.

Floral differentiation ofChenopodium rubrum is more AD-sensitive than growth of the vegetative organs. With a suitable combination of the manner of application and the concentration of AD used, selective inhibition of flowering can be attained without any effect on growth. The inhibition of flowering was greatest if AD acted during the first two days of photoperiodic induction. With later application its effect on flowering was weaker. RNA synthesized in the first days of photoperiodic induction to a considerable extent ensured its further course.

An investigation was conducted to study the interrelation of free amino acid metabolism and root formation in etiolated pea stem sections as dependent on time and on inhibition of root formation by kinetin and ethionine.
The rise in the level of aspartic acid and increase in the rate of conversion of¹⁴C-labeled glucose to free amino acids were found to be characteristic features of the formation of foci of meristematic cells in pericyclo region. The formation of roots was reflected, in general, much more in the rate of conversion of labeled glucose to free amino acids than in the levels of corresponding amino acids.
The total amount of free amino acids was not significantly changed during incubation of stem sections in a solution of kinetin (5×10^-5 m). A rapid fall in their level was recorded in the next 24 hours. The incorporation of¹⁴C from glucose into a precursor of lignin, phenylalanine, was completely inhibited by kinetin which stimulated simultanously the growth of adjacent buds. Stimulation of secondary xylem formation, which appeared later, was accompanied by the resumption of¹⁴C-incorporation into phenylalanine.
Inhibition of root formation by ethionine resulted in the rapid fall of the level of most amino acids and in a significant decrease in the rate of incorporation of¹⁴C from glucose into amino acids. A decreasing level of ethionine in tissues during cultivation of ethionine-treated stem sections was accompanied by a gradual rise in the individual amino acids and in the rate of conversion of glucose into free amino acids.

Kinetin (10^-4 m) is initially more effective than GA (10^-4M) in reversal of the inhibitory effect of Phosfon D (10^-3m) on the germination of kale seed (Fig. 2 and Fig. 3). Kinetin is about 2.5 times more effective than GA in reversal of the synergistic inhibitory effect of coumatin (100 p.p.m.) plus Phosfon D on germination of kale (Fig. 2 and Fig. 4); initially most effective in this respect is a supraoptimal concentration of kinetin, 5 x 10^-4M, which markedly inhibits germination in the control.
It seems that kinetin, Phosphon D and coumarin act specifically on the process of germination. It is suggested that in the germinating seed of kale Phosfon D and coumarin block alternative metabolic pathways, induced by kinetin.

The Czechoslovak isolate produced symptoms characteristic for viruses belonging to the rattle group. A virus variant comparable to Köhler's "Wintertyp" appeared to be present. Two predominant particle lengths of 90 and 191 nm were found in purified preparations. The virus reacted with Dutch TRV antiserum.

In the experiment with 18 winter varieties the genotypic, phenotypic and environmental correlations were estimated in all combinations between the pairs of 11 quantitative characters.
Both yield of grain with its components and further characters were evaluated, of which flag leaf size and leaf angle of the last but one leaf are of importance for the utilization of light energy and consequently for receiving maximum rates of photosynthesis.
In simple genotypic and phenotypic correlations their different stability with regard to mineral nutrition, eventually to the date of sowing was proved.
In the discussion the limited signification of simple correlation for the statement of complicated processes in plants caused by multiplied associations of characters was pointed out. In the example of yield components of the plant at the application of 60 kg N per hectare it was shown that also further unknown variable factors might participate in the genotypic correlation. It may be concluded that the inclusion of them when constructing the selection indexes will give further foundations for handling yield as a breeding or genetic character, and for the causal analysis of yield formation in wheat.