The elongation of pine seedlings (Pinus silvestris L.) is associated with nutation movements. Trajectories of these growth oscillations were recorded by film technique in horizontal and vertical projection during a three day period of growth. On the basis of these data the parameters of elongation and nutation oscillations,i.e. rate, amplitudes and frequency of oscillations, were calculated and their changes during plant development compared. Oscillation trajectories are circular or elliptic spirals the amplitudes of which are increasing with the age of hypocotyl from 1.5 mm to 7.5 mm. The frequencies of nutations are decreasing during the growth from 0.5 to 0.2 rev. h^-1. On the other hand, the growth rate of hypocotyl increased from values near to 10^-3 mm h^-1 at the beginning of the experiment to 4×10^-1 mm h^-1 recorded at the end of the third day. The zone of nutation curvature was slightly transferred from the middle of the hypocotyl toward the apex and its location has not been identical with that of elongation. This indicates that the system controlling nutation oscillations need not be identical with that controlling direction of elongation. At a certain stage of development behaviour of the decapitated pine hypocotyl is analogical to that of the root without the centre of georeception. A possibility of analogy of the system controlling direction of hypocotyl growth and of the system proposed for geotropical control of root growth is discussed.

The suitability was evaluated of MNNG as a mutagen inducing increased frequencies of mutations in the cell populations of three strains of chlorococcal algae for the purposes of selection. MNNG has proved to be highly toxic to those algae as it produces severe physiological responses of the affected cells. The mutagenic effect of MNNG was relatively small in comparison with the recorded toxic effect. From these results it has been concluded that in reverse to NEU, MNNG can hardly be applied with such good an effect in the mutation breeding of chlorococcal algae that are suitable for mass cultivation.

Barley seeds were treated for 3 h at 25°C with 240 mM ethyl methanesulphonate (EMS), washed for 18 h, treated with various concentrations of unbuffered sodium azide (pH 6.7-7.3) for 3 h at 25°C, re-dried to 30% water content and either sown immediately or stored at 25°C for 12 days and then sown. The synergistic action of sodium azide post-treatment has been demonstrated only for the EMS-induced M₁ germination reduction, while the EMS-induced M₁ sterility and the yield of M₂ chlorophyll mutants were unaffected. The "storage" recovery from EMS-induced mutagenic effects was insensitive to sodium azide post-treatment. The 12 day-seed storage at 25°C brought about an improvement of M₁ germination, M₁ survival, M₁ fertility and a decrease in the amount of M₂ mutants, regardless of whether sodium azide post-treatment was applied or not.

Various quantitative anatomical characteristics were measured in the potato tuber by the using of integration methods. There were found the gradients showing the dependence of the changes on the distance from the surface of the tuber.

Changes in the metabolic pathway linked up directly with respiratory pathways were followed inN. tabacum L. cv. 'Samsun' plants inoculated with potato Y virus. The consumption of oxygen in infected tissues before the occurrence of visible symptoms (up to the sixth day) was lower than in control plants, then it started to rise and the tenth day after inoculation it reached 116% of the control. It was established that two main respiratory chains were involved, from which the glutathion-ascorbate system was responsible for the total respiration rate during the entire period of investigation.
The other respiratory system,i.e. NADPH-glyoxalate-glycolate, is not related directly to the respiration rate, but, it is probably linked up with the changing content of NADPH. The results obtained with catalase and peroxidase show that these enzymes are not directly linked up with changing glycollate oxidase activity but that they cooperate. While at the beginning their activities are mutually compensated, at the later period of enhanced glycollate oxidase activity and increase in the activities of both these enzymes occurs which then remove the originating excessive toxic H₂O₂.

The mutual relationship between the water potential (γ _w ), its components, namely the osmotic potential (γ _s ) and the pressure potential (γ _p ), and the water saturation deficit (ΔW _sat ) were determined in the leaves of different insertion levels. During the water stress development in kale plants induced by decreasing soil moisture theγ _w decreased, parallely in all the leaves but the same decrease ofγ _q was accompanied by the highest decrease of theγ _p , probably due to the accumulation of osmotically active solutes, and the lowest decrease ofγ _p in the upper leaves and with the lowest decrease ofγ _s and the highest decrease ofγ _p in the lower leaves. Also the corresponding values of the ΔW _sat were always lower in the upper than in the middle and lower leaves. Thus the upper leaves wilted at more negative values ofγ _w than the other leaves. On the contrary, during the wilting of the cut off leaves the relationship betweenγ _w and ΔW _sat in the upper, middle and lower leaves was practically the same. The very slightly higher decrease ofγ _s in the upper leaves in comparison with the other leaves was compensated by a lower deerease of theirγ _p .
These changes in the ratios ofγ _w ,γ _s ,γ _p and ΔW _sat with the leaf insertion levels enabled the preference of the upper leaves in retaining the necessary water supply during the wilting of plantsin situ.

Most of the peroxidase activity of strawberry petiole is obtained from ionic treatment and pectinase-cullulase digestion of the cell-walls: two ionically-and three covalently- bound isoperoxidases were separated by starch gel electrophoresis. A technique is described for preparing an active IAA-oxidase extract. Final oxidation products of indoleacetic and indoleacrylic aeids appear to be the most effective IAA-oxidase promoters.

Methyl methanesulphonate (MMS), applied on barley seeds, inhibits the seed respiration and thein vitro activity of cytochrome-oxidase and catalase, whereas doubles the activity of total dehydrogenases and has no influence on the activity of peroxidase.
Storage of MMS-treated seeds for 10 days at 30% seed water content, thus under conditions favouring the recovery from the MMS-induced toxic and genetic effects, resulted in an enhancement of the cytochrome oxidase and catalase activity, which reached or exceeded the activity of the control. The activity of peroxidase, although increasing during storage, did not attain the value of the control and the activity of total dehydrogenases remained two times higher as compared to the control.

The culture filtrates of the rhizosphere fungi of broad bean (Vicia faba L.) and cotton (Gossypium barbadense L.) were analysed for the presence of plant growth substances of auxin and gibberellins nature. Bioassay test and chromatographic analysis indicated that these fungi, each synthesized different auxins in their culture medium. These auxins were indole compounds. Similarly the rhizosphere fungi produced in their culture medium some gibberellins and gibberellin-like substances.

Isoenzyme pattern of peroxidase, polyphenol oxidase and catalase at different intervals during germination and in different plant parts during early development of 'C-306' and 'Hira' cultivars, representing tall and dwarf wheats, respectively were investigated. The number of isoenzymic components of the three enzymes increased progressively with the concomitant increase in the stage of germination. The isoenzymic patterns, in general, were more clear and better developed during the later stages of germination. Different tissues or organs of the wheat plant possessed specific isoenzymic pattern of these enzymes. Differences between cultivars were observed both in the number and relative intensity of the various isoenzymic fractions.

No proportional changes in the photosynthetic rate,P, (measured as the dry weight increments in leaf discs) as related to the specific leaf weight,SLW (i.e. leaf dry weight per unit leaf area) were found because of different variation inP andSLW, respectively, with the age and insertion level of individual sugar beet leaves as well as with the age of the whole plant.

Neither the incubation of the flower scapes of garlic (Allium sativum L.) in tetracycline solution nor the extirpation of the bulblets from the inflorescences led to the development of fertile binuclear pollen. Higher tetracycline concentrations than 125 mg per litre showed a clearly phytotoxic effect. The removal of the bulblets from the inflorescences improved the survival of flowers but it enabled only the initial stages of seed development. The seeds obtained were defective and not able to germinate. The hypothesis on infectious nature of the factors causing sterility in garlic is discussed.

Humus substances synthesis was investigated in the course of birch wood decomposition by a brown-rot fungusPiptoporus betulinus. With progressing decomposition of wood by brown rot the proportion of high molecular weight humic acids is gradually increased at the expense of fulvic acids, the amount of which is proportionally lowered. The high molecular weight humus constituents are not accumulated in wood decomposed by a laccase producing white-rot fungi despite the availability of suitable phenolic substrates; the low molecular weight fraction of fulvic acids is permanently higher than the fraction of humic acids. The function of laccase in lignin degradation and in biosynthesis of humic acids is problematic.

The endodermal cells of the maize roots are linked to each other via plasmodesmata mainly localized at the proximity of the Casparian band on the anticlinal walls. In this part of the walls was noticed the absence of the suberin lamella in the thickening endodermal cells.

Pollination induced dissolution of nucellar cells at the micropylar end forming a passage for pollen tube entry even when the pollen tubes are in the stylar region.

Virus origin of lilac ringspot and chlorotic ringspot of lilac was identified serologically by means of double gel diffusion method. The former of these diseases is due to Arabis mosaic virus, the latter to a mixture of Arabis mosaic virus and cherry leaf roll virus. The occurrence of these viruses has been detected for the first time in Czechoslovakia.

Anomocytic stomata and stomata with single subsidiary cells are commonly observed Sometimes a stoma appears anisocytic. Double cytoplasmic connections between nearby stomata and division of guard cells with persistent or degenerating nuclei are seen in GA. One or more divisions of guard cells, displaced guard cells and single guard cells with or without pore are noticed in SUC. Formation of single guard cells is a common feature in TIBA. Paracytic stomata, one and a half stomata and persistent stomatal initials are seen in SUL. COUM seems to be not inhibitory inCucumis sativus. In COL stomata with unequal guard cells, unequal stomatal cells with thickening in between but without intervening pore, stoma with double pores, persistent stomatal initials which may be solitary or in groups with varying shapes and with one or two nuclei of different shapes are noticed. The growth regulators affect the frequency of stomata, epidermal cells; stomatal index; size of guard and epidermal cells.

The uptake and translocation of³²P applied to nutrient solutions, as influenced by (2-chloroethyl) trimethylammonium chloride (CCC) and 2, 4-dichlorobenzyltributylphosphonium chloride (Phosfon), were investigated in growth chambers. Specific effects depended on the "Retardin", the method of application, and the concentration.
Foliar applications of CCC had no significant effect on³²P uptake 5 h after feeding. At 20 and 80h after feeding, CCC at 100 and at 1 000 mg l^-1 decreased P uptake. With root applications of CCC the same concentrations decreased P uptake as early as 5h after feeding, while the 1 mg l^-1 concentration enhanced P uptake by 40% after 20h. Both the foliar and the root applications of Phosfon influenced P uptake 5h after feeding. With foliar applications the low Phosfon concentration of 0.01 mg l^-1 increased P uptake throughout the experimental period of 80h, but the magnitudes of enhancement declined from 109% at 5h to 63% at 80h. Similarly, the enhancement of P uptake due to the 0.1 mg l^-1 foliar treatment declined from 132% at 5h to 80% at 80h.
100 mg l^-1 CCC enhanced P translocation to the shoot in 5h, with magnitudes of 29% (foliar application) and 64% (root application). At 20 and 80h the stimulations were nullified. The highest concentrations (100 mg l^-1 CCC; 10 mg l^-1 Phosfon) enhanced P translocation 80h after feeding. There were thus general enhancements of P uptake at low concentrations and suppressions at high concentrations, but these effects diminished with time, indicating transitory influences.

Populations ofScenedesmus quadricauda grown in a continuous chemostatic regime and synchronized by light and dark intervals were exposed to continuous illumination. The effect of light on synthetic and reproduction processes during the time of the omitted dark period and in the subsequent cell cycle was studied. In general, the sequence of cellular processes and their mutual coupling remain the same as in the darkened population. Synthetic processes and photosynthetic activity are depressed during the period of protoplast fission also in the light. The synchronizing effect of the dark period in chlorococcal algae consists in reducing the developmental variability in the population. The developmental state of daughter cells at the end of the dark interval varies in the span of two (as a rule) or four (at maximum) genomic cycles, while at the end of the light period this variability comprises up to eight genomic states. The more advanced autospores start the next cycle with a greater lag.

The preparation of antisera against S alleles of homozygous incompatible lines of the marrow-stem kale (Brassica oleracea var.acephala DC.) is described. The antisera obtained reacted specifically with homologous antigens on using the serological method of double diffusion into agar. The results confirmed the specificity of S alleles of incompatible lines of the marrow-stem kale.

A method of enzymatic separation of protoplasts from long-term tissue culture ofNicotiana tabacum L. is described. The efficiency of this method is dependent on conditions of separation and on the portion of meristematic cells in the tissue culture. This portion can be increased by pre-cultivations of the tissue on medium containing suitable concentration of hormones. The knowledge of the micromorphology of the filamentous culture enables us to investigate the course of release of protoplasts from various cell types. A preferential lysis of cell walls was observed between neighbouring cells in filaments and the fusion of their protoplasts was recorded. The preservation of cell walls which are not in a contact with other cells may be a result of the cell wall heterogeneity.

The IAA oxidase activity was studied during the culture of dormant apple embryos. The effect of different factors on this enzyme activity was investigated either by adding them to the reaction mixture or to the culture medium. Phloridzin was found to be the best phenolic cofactor. The development of IAA oxidase activity was stimulated by phloridzin and GA₃. The properties of apple embryos IAA oxidase allow to postulate the presence of two enzyme systems able to oxidize IAA in the material studied. The involvement of peroxidase activity in IAA oxidation was also investigated. The differences in the changes of peroxidase and IAA oxidase activities during the culture of dormant apple embryos do not permit to consider the activity of peroxidases to be identical with that of IAA oxidase.

The relationships between protein- and RNA synthesis and the germination behaviour of lettuce seeds were studied. Protein synthesis starts right at the beginning of imbibition and increases until the radicle protrudes. According to our results the causes for a blocked development of scotodormant lettuce seeds cannot be seen in a generally reduced protein or RNA synthesis.

Metabolic changes in tomato plants infected with potato leafroll virus were followed. The virus was transferred by grafts taken from diseased tomato plants. Sharp changes in the respiration rate and in the activities of the investigated enzymes observed before the concrescence of the graft with the stock are obviously connected with the defence reactions of the plant. In the roots of the experimental plants a nearly complete correspondence of the course ofo-diphenol oxidase and ascorbic acid oxidase activities with the respiration rate occurs. In the shoots the respiratory chain with ascorbic acid oxidase as terminal oxidase is involved, whereas both chains probably take part in the respiration in the roots by which a link with sugar degradation is achieved. The rate of glycolysis and that of pentose phosphate cycle in the roots of experimental plants are nearly identical. The comparison of glucose-6-phosphate dehydrogenase activity with ascorbic acid oxidase activity reveals that both curves show the same course, which indicates the presence and action of a respiratory thain with ascorbic acid oxidase functioning as terminal oxidase.

A new method enabling to localize recessive alleles controling lethal embryonal or chlorophyll mutations in linkage groups has been devised and verified. The information on the linkage was obtained in B₁ in repulsion after the crosses with recessive visible markers representing the individual linkage groups. The distinction of four B₁ genotypes was achieved by means of Müller's embryotest. Altogether eight mutant alleles were localized. The allelesch 2411, ch 4062 andX 3 are carried by the first linkage group, the allelesM 33 andM 25 by the third and the allelech 1378 by the fourth linkage group. The mutant allelesch 42 andM 4-6-18 showed the linkage with the markers of the fifth and the sixth linkage groups simultaneously. The possibilities of further development and use of this method are discussed.