The new growth promoter, N(2-acyl-l,3-indane dione) triethylammonium iodide (L-TEAI) enhanced the elongation of the seedlings of cluster bean (Cyamopsis tetragonoloba (L.) Taub, belonging to familyPapilionaceae). When the two growth regulators, L-TEAI and cycocel were applied together, the cycocel induced inhibition of radicle elongation was reversed, but it failed to reverse the inhibition of hypocotyl elongation.

The course of androgenesisin vitro was investigated with anther cultures of two chlorophyll mutants of Nicotiana tabacum. A different sensitivity to the hormonal composition of the medium was revealed between the cultures White Seedling and Sulfur; the stimulatory effect of kinetin on the frequency of androgenesis was observed only in White Seedling cultures. In addition to green plants, "aurea" (mutation Sulfur) or "albino" (mutation White Seedling) phenotypes also differentiated in both cultures. The possible causes of variability in the participation of green and mutant forms are discussed.

Ultrathin sections were prepared from the tissues of lettuce leaves with mosaic-like symptoms and thickened nervature which were studied by means of electron microscopy. Intracellular inclusions surrounded by a membrane were found in the cytoplasm of parenchym cells of the investigated lettuce leaves(Lactuca saliva L. provar.capitata L. nid.jaggeriHelm., cv. Pražan). Crystals with a distinctly apparent hexagonal lattice could be observed in the inclusions. No crystal containing inclusions were found in the tissues from the leaves without mosaic-like symptoms and in those from thickened nervature.

Changes in the transpiration rate of intact spring barley plants, cv. "Slovensky dunajsky trh", were studied separately in the light and in the dark under controlled temperature and illumination, after the infection withErysiphe graminis DC, during an 8 day period of the development of the fungus. In the first stage of pathogenesis, the fungus diminishes water output from the host plants in the light. An opposite phenomenon can be observed in the dark; water output from infected plants in the dark increases sharply mainly in the stage of advanced fructification. Thus, the fungus considerably diminishes the ratio of water output from the host plants in the light to that in the dark.

In water soaked barley seeds the respiration rate (QO₂) at 25 °C is about 100 times higher at 30% than at 20% water content. The treatment of seeds with mutagenic methyl methanesulphonate led to the depression of the respiration rate in dependence on the applied mutagenic dose. Seed storage at 30% water content resulted in a recovery from the inhibition of seed respiration caused by methyl methanesulphonate. In contrast, at 20% seed water content the respiration rate either slightly decreased or remained unchanged in the course of storage. The results are discussed in relation to the previously described changes in the yield of induced mutagenic effects in barley seeds treated with monofunctional alkylating agents and stored at 30% and 20% seed water content.

Ethylene was collected in methanol solution of mercuric acetate and the addition compound formed was then separated by means of paper chromatography. The spot area and colour intensity after detection were determined using a densitometer. The amount of collected ethylene was calculated from a calibration curve.
The ethylene liberated from plant samples was collected during one or two days. During this period the amputation of the whole plant organs did not influence ethylene production. Changes in ethylene production were found after segmentation of the tissue or after the treatment with auxin and Co²⁺ ions.
The above-ground parts of investigated herbs released 0.3 to 3.5 μl of ethylene per kg fresh weight per hour. The leaves of investigated trees released 1 to 20 μl of ethylene per kg f.w. per hour. The rate of the production of ethylene seems to be specific for a given species.

Unmetabolized nitrite occurs in 3 cm long apical segments of primary pea roots(Pisum sativum L., cv. Raman), isolated from 6 d old seedlings, grown under aseptic conditions for 10 h in nutrient solutions containing 0.1 to 2 mM nitrite concentration, its amount being dependent on the concentration in the nutrient solution. With increasing amount of nitrite in the roots, the ratio between NAD⁺-GDH₁ and NAD⁺-GDH₂ isoenzymes is changed without influencing significantly the total NAD⁺-GDH activity. After 48 h cultivation unmetabolized nitrite occurred in the roots only in small amounts and the ratio of activities of these isoenzymes was not affected significantly. NADP⁺-GDH activity, detected in the gels at the same site as NAD⁺-GDH₁, was depressed by increasing nitrite concentrations.

The experiments showed that after gamma irradiation as well as after irradiation by secondary cosmic rays (hard component)Equisetum arvense spores produce in the first developmental phases prothalia at a changed rate,i.e. in favour of the females. This effect being specific for radiation cannot be produced by heat, pressure or changes of electric and magnetic field (i.e. factors appearing in higher sea levels with a stronger intensity of cosmic rays). It will be possible to apply the sensitivity of the mentioned method for investigating the problems of testing cosmic ray variations. The possibility of its application in spontaneous variability research is not less important.

Fusarium solani (76%),Phyllosticta phaseolina (12%) andAspergillus flavus (10%) were isolated from bean(Phaseolus vulgaris) seeds showing lesions. Out of these the first two caused 30 per cent and 20 per cent seed rotting respectively after artificial seed inoculations. When inoculum was added into the soil before sowing the seed, 35 per cent and 10 per cent pre-emergence rot ocurred and there was 35 per cent and 15 per cent post-emergence blight when soil with healthy seedlings was inoculated withF. solani andP. phaseolina respectively.F. solani caused similar lesions on bean seeds when inoculated after an injury.F. oxysporum was isolated from the roots of dried bean plants showing necrosis.

The dependence of ethylene production and respiration rate on the concentration of gibberellin (GA) applied in water emulsion of lanoline to young fruits was studied in Yellow transparent apples. Ethylene production and respiration rate were slightly increased by GA treatment. The increased level was maintained throughout the entire ripening period, which was also apparent from the total amount of both released gases. A gas-chromatographic method, using a flame ionization detector for simultaneous determination of ethylene and CO₂ in the atmosphere of experimental biological containers, is described in this paper. CO₂ is hydrogenated to methan on Ni - ThO₂ catalyst by hydrogen which is used as carrier gas. The gases pass the hydrogenating reactor after the separation in the Chromatographic column before entering the detector.

The cytokinin activity of a group of derivatives of N-n-butyl-N'-arylthiourea and their effect on the uptake of amino acids and the accumulation of total nitrogen in seven-day barley seedlings have been investigated. It was established that N-n-butyl-N"-2,4-dinitrophenyl-thiosemicarbazide, N-n-butyl-N'-o-,m- andp-chlorophonylthioureas, N-n-butyl-N'-3,4-dichlorophenylthiourea and N-n-butyl-N'-2-methyl-4-ehlorophenylthiourea possess a high activity with respect to the retardation of the chlorophyll breakdown. Substances with a high cytokinin activity cause an increase in the amount of total nitrogen and amino acids, mainly of glutamic acid, aspartic acid and serine in the roots and loaves of seven-day barley seedlings.

Metabolism of dry mungbean seeds(Phaseolus aureus) was compared with that of 3 h imbibed ones. Respiration rates sharply increased upon imbibition which was accompanied by large water uptake. Storage protein was degraded resulting in the rise in soluble nitrogen. RNA and water soluble protein content increased but DNA declined. It is suggested that some of the soluble nitrogen pools are diverted to RNA formation which in turn produce enzyme protein. In mungbean seeds imbibition of water thus triggers a series of metabolic changes within 3 h with the respiratory energy as the driving force.

A study was made on certain problems connected with the application of methods of stigmatal and placental pollinationin vitro in the snapdragon.
Germinable pollen without microbial contamination could be obtained only from the flowers which were left, after surface sterilization, on the stem till the dehiscence of anthers. The germination of pollen, and especially the growth of pollen tubes was better in a 0.3 M lactose solution with 10^-3 per cent H₃BO₃ than in usual sucrose media.
The seedsin vitro could be obtained only after normal pollination and the successive artificial cultivation of the entire pistil (the method of stigmatal pollinationin vitro). The seeds did not differ either in their morphology or in their size from those developed under natural conditions, they were viable and without dormancy.
Though the pollinated pistils were cultivated in the medium without growth substances, callus formation from uncovered ovules and placenta was observed in some cases. A dependence was revealed of the proliferation on pollination and on the cultivar employed.
When using the method of placental pollinationin vitro we failed to obtain seeds. The main difficulty in the use of this method seems to consist in the fact that pollen tubes are not capable of growing from the surface of ovules and placenta into the micropyle.

The relationship between the water potential (Ψ_w) and the water saturation deficit (Δ W_sat) in kale and maize leaf tissue was measured during dehydration and resaturation either of leavesin situ or of cut leaves. The curves relating Ψ_w toΔW_sat were similar in all variants, but at the same values ofΔ W_sat corresponding values of Ψ_w were always lower in leavesin situ than in cut leaves and during dehydration than during resaturation.

The first information concerning the cytogenetic efficiency of thermal neutrons in lentil are presented in this paper. The range of cytologically effective dosages of thermal neutrons in lentil was determined. This determination enables us to compare the efficiency with the mutagenic effect of thermal neutrons and with their effect on the growth and development of plants of M₁ generation. These effects were already evaluated in previous communications.
Thermal neutron irradiation significantly affected all the characters studied. A linear dependence of the effect on the dose of the neutron radiation was found for most of the analyzed characters. From a sample of scored cells, whose nuclei were in the anaphase or early telophase, 9.0 to 72.0% of them had chromosomal bridges and fragments after irradiation with dosages from 3.3×10¹¹ n cm^-2 to 4.5×10¹² n cm^-2. The highest number of rearrangements per one cell reached 2.16 after irradiation with 4.25×10¹² n cm^-2 while the lowest dosage used, 3.3×10¹¹ n cm^-2, induced 0.17 of chromosomal rearrangements per one cell. Irradiation with thermal neutrons is capable of inducing a large number of very complicated chromosome rearragements.

The effects of several growth and trophic substances on bud and root neoformation on leaf fragments ofBegonia rex were studied in precisely defined environmental conditions. IAA, depending on the type of treatment, had different effects. In aseptic cultures, a notable stimulation of bud formation was observed at certain concentrations. However, non aseptic treatments of IAA had no visible effects except at very high concentrations.(10^-3 M) where bud formation was totally inhibited and root formation was favored. NAA, at 10^-6 M and 10^-5 M strongly stimulated root formation and inhibited shoot formation. All the cytokinins used stimulated bud formation and inhibited partially or totally root formation. Gibberellic acid inhibited bud and root formation. Glucose and sucrose clearly stimulated bud and root formation and sucrose, when applied simultaneously with other growth substances, modified the effects of these substances alone. The most favorable environmental conditions were at 24°C in a 24 h photoperiod but other temperatures (17 to 27°C) and photoperiods (9 or 16 h) did not prevent neoformation.

Virus particles (approximately 73 nm in diam.) usually showing an inner capside (45 nm in diam.) and similar to diplornaviruses, esp. reoviruses, were found in some cells of enations inAvena sativa andArrhenatherum elatius leaves infected with the oat sterile dwarf disease (OSDD). (The same virus particles were described by the authors in 1966 in the leafhopper vector.)
Mycoplasma-like microorganisms found in1969 in the OSDD leafhopper vector were absent in OSDD infected plants. Tetracycline did not affect symptom development in plants and did not alter the infectivity of the vector.
Therefore, OSDD is apparently of virus origin; mycoplasmas-like bodies found formerly in the OSDD vector are probably not involved in OSDD etiology.

Studying the influence of the pH of 10% NaCl solutions used for the extraction of RNA and DNA on the yield of both nucleic acids, the maxima of pH were found at which both types of nucleic acids pass into extracts better than at neutral pH and do not remain in residues of the experimental material.The perchloric acid extraction temperature was also studied for obtaining the hydrolysate of nucleic acids from the trichloroacetic acid precipitate of sodium chloride extracts differing by 5 °C within the range of 35 °C to 90 °C and it was found that in this wide range almost the same amount of RNA is extracted by the method used. However, at a lower temperature, some DNA remained in the extracted residue of the trichloroacetic acid precipitate of sodium chloride extracts.

The meioses of four sterile species in the genusAllium which develop bulblets in the inflorescences instead of seeds were compared, namelyAllium sativum, A. cepa var.viviparum, A. carinatum, andA. oleraceum. The most important of them,A. sativum, is an ancient cultivated plant and its vegetative reproduction prevents it from more rapid evolution such as is known in generatively propagated cultivated plants.A. sativum shows fully normal meiosis. After the disintegration of the tetrads, however, the blockade of 1. pm takes place. The cause of the blockade has not yet been cleared up. Removing of bulblets appeared as having no influence on the development of microgones. It is assumed that there may be a viral phenomenon causing a disease of the tapetum without disturbing other functions. InA. cepa var.viviparum there was observed a heavy aberration disturbance in the meiosis, which had already been signalled by the mitosis. On this ground 1. pm does not occur and sterility is fully justified. The aberration disturbance does not seem to spoil the vegetative development but on the contrary to give it a vigorous character.A. carinatum andA. oleraceum are triploid and tetraploid forms; in the meiosis they form various configurations-univalents, bivalents, trivalents, and quadrivalents. The following irregular chromosome distribution results in the coming into existence of variously valuable gametes. 1. pm takes place. There is a theoretical possibility of generative reproduction (after the extirpation of bulblets).

The present studies of the LDH isoenzymes have been made as a part of our studies on the respiration systems of the roots ofVicia faba. All the root zones had 5 LDH isoenzymes and 2 antibands, but there were differences in their relative quantity. Cathodic isoenzymes (LDH₅, LDH₄) prevailed in the meristematic zone, whereas the anodic ones (LDH₁) prevailed in the others. The different enzyme activity in individual zones is probably connected with the transition of the anaerobic metabolism in the meristem to the aerobic one in the differentiating parts of the root.

The character of endogenous growth substances was investigated in developing buds, young fruits and mature walnut leaves. The relatively high content of auxins and gibberellin-like substances was found by means of bioassays in the youngest primordia of vegetative buds. The level of auxins drops in the further course of primordia transformation into the staminate catkins. The development of leaf-buds is characterized by the accumulation of inhibitory activity as revealed by theAvena bioassay, whereas the data obtained from the lettuce bioassay indicate a pronounced stimulation. The onset of terminal bud development is also accompanied by inhibitions and it is only with pistillate flower differentiation that the temporary rise in auxin level is observed. An inhibitory activity was found in these extracts using lettuce bioassay. There is a relatively high auxin level in young fruits, mature leaves and resting buds during the mid-summer period whereas the accumulation of clearcut inhibitions is signalled by the results of lettuce bioassay.
The regulatory role of growth substances in differentiation may be better understood during the second year as many leaf-abnormities appear only with the outgrowing of the bud. Abnormal catkins differ in the number of florets and stamens and some even bear pistillate flowers. Fruit development is liable to deviations in the early stages of differentiation. Abnormal fruits enable us to elucidate many structural peculiarities.

The analysis of diurnal oscillatory movements of tobacco leaves was used in the diagnosis of viral infection of plants. The oscillatory helices circumscribed by a growing leaf of a healthy plant were regular, but some deviations, particularly in the transition points, were recorded.
In order to make clear the cause of these irregularities of trajectory, the course of elongation of leaf petiole and blade in relation to localization and shift of zones of elongation during ontogenesis was analysed. The present analysis is similar to that described by the author's earlier experiments with pea roots. Oscillatory curves circumscribed by petiole, projected on a horizontal plane, were compared with curves circumscribed by the blade tip. The analysis of the leaves of different ages enabled us to study this process in dependence on growth rate. It was confirmed that oscillations are a result of elongation; the extent of oscillations is quantitatively dependent on the growth rate. An analysis of the zones of growth showed that in petiole the active meristems are localized near to its base while in the leaf lamina they move gradually during the ontogenesis from the apical to the basal part of the leaf blade. Active meristems of young rapidly growing leaves are localized approximately in the middle of the blade while those of old leaves were found in close proximity to the base of the lamina. The growth rate of petiole can be expressed in hundreds of mm per hour (4.8×10^-2 mm h^-1); half of this value was recorded for its apical part. The growth rate of leaf blade was found approximately ten times higher (3.2×10^-1 mm h^-1).
The oscillatory movements of growing leaf consists of two integrate components: of oscillations originating in the base of the petiole and of oscillations of leaf blade the centrum of which is localized in the basal third of the blade.
The arrangement of the experiments did not enable us to determine to what extent the phototropic response of leaf blade participates in leaf movements. The movements of leaves of an intact plant are evidently affected by rhythmic stem oscillations. Stem is an integral part of a system which participates in the transfer of information in plants.

A study was made concerning the effect of the analogues of nucleic acid components upon the seed set inPapaver somniferum L. For the experiments flowers one day after anthesis were used, as the pollination taking place at this flower age had previously been found to be most efficient for the seed set. The solutions of analogues in a 10 per cent sucrose were applied by injecting them into the ovaries three hours prior to pollination. Damage to the ovary by the injection reduces the seed set by about two thirds.
In comparison with control flowers, into which only a sucrose solution was injected, 5-bromouracil at a concentration of 5.2×10^-4 M increases the seed set by about 70 per cent. Uracil brings about the same degree of promotion. The same concentration of 5-bromodeoxyuridine has no significant effect on the seed set. When applied simultaneously with uracil it suppresses its stimulating effect completely. The equimolar mixture of uracil and bromouracil did not cause any significant increase in the number of seeds in the capsules, either.

In barley embryos, treated with N-methyl (¹⁴C)-N-nitrosourea, the alkylation of nucleic acids was much higher than that of proteins and lipids. At a concentration inhibiting the growth of M₁ seedlings to 50%, 0.27% of DNA-guanine was methylated to N-7-methylguanine. In barley DNA, alkylatedin vitro, the presence of 3-methyladenine and 0-6-methylguanine was chromatographically detected.

Auxins (NAA, IAA) inhibited the seed germination of lettuce cv. Cabbage. The auxin-indueed inhibition of seed germination could be overcome if 2-chlorethanephosphonic acid (CEPA, ethrel) or kinetin was added simultaneously. Thus ethylene can also modulate the action of endogenous inhibitors in seed germination.

By comparing maize plants cultivated in standing nutrient solution with those from solutions flowing at different flow rates it has been established that absorption of nitrogen, potassium and especially of phosphorus was increased owing to the flow. There was likewise a relative rise in the distribution of nutrients to the overground parts of the plants. The content expressed per unit dry matter was increased only in the case of phosphorus; with nitrogen and potassium it was slightly lower than in the standing solution. Increasing amounts of iron were required under the conditions of flowing nutrient solutions to prevent chlorosis of the plants. The production of dry matter,NAR andRGR was also increased because of the flow. The flow considerably changed the habitus of the primary roots of the maize plants. The roots were longer, thinner and on the whole they contained relatively less dry matter (RWR). The lengthening of the roots is explained as a response to stimulation by the solution flow-the rheotropism.

Growth measurements on individual polycormones ofScirpus lacustris L. cultivated in hydroponic sand cultures from single rhizome cuttings enabled us to analyse the process of offshoot formation. The time interval in the growth of individual subsequent shoots of one polycormone (plastochron), the final length of the shoot and the number of shoots formed during the growth period are suitable parameters for describing the rhythm of offshoot formation. The interdependence of these parameters and the effect of cutting or shading of individual shoots characterize the translocation of assimilates produced by individual shoots, and their use for the growth of subsequent shoots.

The author compares the activity of ¶-fluorophenylalanine and the effect of a medium without nitrogen on the morphogenesis of hyphae of Achlya ambisexualis ♀. A hyperramification often corresponds to a mode of prelethal development and is observed in the same conditions as an asexual multiplication.