Ascorbic acid (AA) turnover, and levels of RNA and protein were determined during germination ofCicer arietinum cv. Chafa under-(i) normal watering; (ii) water stress of six days; and (iii) revival upto next stage of seedling growth after water stress. Water stress lowered significantly AA, ascorbigen, ascorbic acid-macromolecule complex, RNA and protein content in embryo axis while a reverse trend was seen after revival. In the cotyledon, AA, RNA and protein contents were higher during water stress. However on revival only AA and protein contents decreased, whereas the RNA content showed further enhancement. It is suggested that increased synthesis of AA in the cotyledon during water stress may trigger enhanced synthesis of RNA and consequently of enzymic proteins, thus bringing about rapid mobilization of reserve materials during revival.

It has been shown that intensive elongation of wheat coleoptile sections is correlated with indoleacetic acid-1-¹⁴C metabolism. In tissues actively growing the disappearance of indoleacetic acid-1-¹⁴C and formation of conjugates and metabolites (indoleacetamide, indoleacetyl-β-D-glucose, indoleacetyl aspartic acid) is twice as high as in sections where growth has been stopped by physical constraint (plaster) or in tissue which did not elongate by an unknown reason.

Results of the investigation of four isolates of the sour cherry necrotic ringspot virus are presented in this paper. The isolates used caused characteristic symptoms on woody indicators "Bing", "Montmorency", F 12/1, and on peach seedlings. The virus was transmitted mechanically to some herbaceous species:Antirrhinum majus, Cucumis sativus, Cucurbita maxima, Chenopodium quinoa Crotalaria juncea, Momordica balsamina, Petunia hybrida andLeonorus sibiricus. The attempts to transmit the virus mechanically to further 23 herbaceous species were unsuccessful. The thermal inactivation point of the virus lies between 46 and 58°C and the dilution end-point between 10^-1 and 10^-2. The virus is stable in vitro at room temperature for more than one day. Individual virus isolates gave a positive immunological reaction with the Fulton's "G" antiserum.

During the 24 hours' washing of¹⁴C MNU and¹⁴C MMS-treated seeds the amount of DNA 7-methylguanine as well as the total alkylation of DNA, RNA and proteins in cells of the embryo was enhanced. The drying of shortly washed¹⁴C MNU-treated seeds to 30% and 15% water content led to, a similar increase of alkylation. In accordance with the changes in the biological damage, the amount of single strand breaks and/or alkali labile sites in DNA dropped down during a 19 h washing period of MNU-treated seeds but changed only slightly in MMS-treated and 19 hours washed seeds. The drying of 0.5 or 18 h resp. 19 h washed seeds treated either with MNU or MMS to 15 per cent water content increased the amount of single strand breaks and/or alkali labile sites in DNA.

Sixteen early, medium late, and late homozygote lines ofArabidopsis thaliana, obtained from three natural populations, were crossed with a common check variety S 96. The speed of development was expressed by the value log (x+y), wherex stands for the number of days after which flower primordia appear, andy for the number of leaves in the rosette. The experiments were caried out under conditions which emphasized the differences in the speed of development. We assessed the degree of dominancy, heritability on the basis of F₁ and F₂ variance, and analyzed F₂ distributions. It was established that some of the investigated lines differ from the variety S 96 in one pair of dominant genes or genes with incomplete dominancy for late flowering, other in two pairs of genes with complementary effects, and that the variety S 96 probably also contains other alleles causing late flowering inhibited by some type of epistasis. Even though the most important part is always played by one or two pairs of genes with high dfficiency, genes with lower efficiency often take part in the process; in some lines the genes with high efficiency could not be established.

Cells mechanically isolated from homogenized leaves ofC. sepium dividein vitro. The rate of cell division is strongly influenced by temperature with the optimum between 31 and 34 °C. The rate of cell division increases proportionally with a rise in temperature up to 31 °C and is accompanied by a reduction in the length of the preparatory phase of the division. A supraoptimal temperature (40 °C) inhibits or stops the cell division which can be restored provided that the cells are transferred to 31 °C. If the preparatory phase to the commencement of cell division is accomplished at 17 °C the cells then exposed to 31 °C divide more rapidly than if they are exposed directly to 31 °C.

Two strains of tobacco tissue cultures were investigated cytogenetically, their morphogenetic potency was revealed and the plant regenerates were analyzed. Strain I with less pronounced deficiency of nuclei was more capable to differentiation and organogenesis than the heterogenous strain II. The morphological variability of vegetative and reproductive organs of plant regenerates was described. The variations were characterized by high level of aberations during meiosis and unstable aneuploidy.

Under the conditions applied in our laboratory 4 1/2 days old plants ofChenopodium rubrum require 2-3 photoperiodic cycles for maximal flowering response, whereas 2 1/2 days old plants are able to flower after having obtained a single inductive cycle. The period length of the free-running rhythm of flowering observed in 2 1/2 days old plants after a single transfer from light to darkness is 30h and the first peak of flowering occurs at about hour 12 in darkness. When a cycle consisting of 16h darkness and 8h light or of 8h darkness and 8h light precedes the long dark period the rhythm is rephased. Rephasing is greater when the light commenced to act on the positive slope of the first peak of the free running rhythm than when it impinged on the negative slope. With an 8h interruption of darkness by light rhythm phase is controlled by the light-on, as well as by the light-off signal. Feeding 0.4 M glucose during the long period of darkness enhanced the amplitude of the flowering response and, moreover, substituted for one photoperiodic cycle.

Biological activity of humic acid, hymatomelanic acid, lignofulvic acid, and fulvic acids isolated from peat, from spruce wood decomposed by the fungusFomes marginatus(Fr.) Gillet, and from spruce wood decomposed by the fungusPoria cinerascensBres. was tested on cress seedlings (Lepidium sativum L.). The results evaluated by the analysis of variance indicate that humus acids show a high degree of affinity in their biological activity which is a condition for the applicability of the decomposition of wood by fungi as a model of the humus formation. Humic and hymatomelanic acids, products of an advanced step of humification, have a predominantly stimulatory effect especially on the hypocotyl. Lignofulvic acids and fulvic acids exert a rather inhibitory effect with the root being more affected.

Tubular structures showing honeycomb-like appearance in cross sections were found in mycoplasma invaded sievetube cells of abnormal sprouts of apple trees infected with the proliferation disease. The nature of tubular structures is unknown. There is a striking similarity (or identity) with the tubular structures described formerly in HEp-2 cells which were established from human carcinoma of the larynx.

Additional three plant species were found to be natural hosts of a necrotic TMV. strain,Silene inflata SM.,Melandrium albumGarcke andAtriplex nitensSchkuhr.

Light induces the formation of pycnidia inPhomopsis mali. The induction caused by light can be conserved in darkness. The size and quantity of pycnidia vary with the illuminance. Under low and high illuminances physiologically different pycnidia appear.Phomopsis mali cultivated in darkness in the presence of other microorganisms (fungi or bacteria) can fructify and produces pycnidia similar to those formed under low illuminance and in natural conditions. Our experiments indicate the presence of a pycnogenesis-inducing substance that can exists in different forms and induces the formation of the different pycnidia.

The water potential (Ψ _w ) and the water saturation deficit (δW_sat) in leaves of different insertion levels of potted kale plants were simultaneously measured. In non-wilting plantsδW_sat gradually decreased andΨ _w slightly increased from the upper to the lower leaves. During the wilting of the plants induced by decreasing of soil moistureΨw practically decreased paralelly in all the leaves but the same decrease ofΨ _w was connected with the lowest increase ofδW_sat in upper leaves and the highest increase ofδW_sat in lower leaves. Not only the values ofΨ _w andδW_sat but also their relationship varied considerably with the leaf insertion levels.

Taking into consideration simultaneous infection of tomato leaves withCladosporium fulvumCooke and TMV, the fungus infection inhibits the TMV reproduction. This inhibition occurs in the plant irrespective of the sequence of pathogen inoculation and reaches even 70 per cent. The fungus spores applied to the TMV purificate inhibit the TMV infection, as well.

Healthy and mosaic infected leaves ofL. nudicaulis have been cultivated onMS and modifiedMS media (MC). Profuse growth and differentiation of tissue have been obtained onMS medium in diseased tissues as compared to the modified medium. It has been found on bioassay that although there is no difference between the concentration of the virus in tissue culture and glasshouse material yet the incubation period of the virus is decreased in tissue cultures.

Formation of stems both in callus tissue isolated from hypocotyl and in apical meristems culture of carnation plants (Dianthus caryophyllus L. ev. "Grenadin white, yellow, scarlet red, dark red and pink") was evokedin vitro using chemically defined medium. The rooted stems were transferred into pots and cultivated under natural conditions.

The development of excised flax embryos of different age was followed in nutrient media with different osmotic values. Sucrose media with the osmotic value 4.0 bar. (5%) sucrose were the most suitable for the cultivation of excised 7 and 14 days old flax embryos. Nutrient media with the osmotic potential 1.7 bar (2% sucrose) were optimal for 28 days old embryos. The most convenient osmotic potential for optimal root growth was 4.0 bar and for hypocotyls and stems 1.7 bar. High osmotic value of the cultivation media prevented the germination of the embryos and lower osmotic value promoted the germination. Mannitol, when compared with sucrose, inhibited the development and germination of the embryos. Different abnormalities often occurred on the media with mannitol. Agar media were superior to liquid media for the cultivation of explanted embryos.

The paper describes isolation and partial characterization of the tissue culture of the common spruce (Picea excelsaLink). The tissue culture was grown on the medium ofHarvey (1967) modified by increasing the concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) to l mg l^-1 and by omitting the tyrosine. By selective 10-month subculturing the tissue culture was obtained possessing relatively stable properties and giving good yields of biomass. The tissue of the callus was of yellowish colour, compact and homogenous. The obtained tissue culture was characterized by its growth curve and by following the O₂ consumption during the growth.

Indole-3-acetic acid (IAA-1¹⁴C, IAA-2¹⁴C) and gamma-aminobutyric acid labelled with¹⁴C were applied in lanoline to the surface of intact seeds or inserted into seeds of growing apple fruitlets or to the cut surface of the pericarp. Their translocation in trees was checked by means of autoradiography or by a low background Geiger-Müller counter. Auxin applied to the top of intact seeds, or inserted into the seeds was translocated and distributed within the pericarp, spur tissues and shoots below. The translocation of gamma-aminobutyric acid from seeds suggests that the capacity of apple seeds for extensive interchange with the surrounding tissues of the fruit and the spur is more general than suspected. A much poorer or no translocation to the spur was found when radioactive compounds were applied to the cut surface of the pericarp, while the seeds were left untouched. The results suggest two mechanisms of metabolite translocation in the apple fruit: two-directional for seeds and one-directional for the pericarp.

The photosynthetic rate in leaf discs (P_LD) ofPrunus laurocerasus L. plants taken up from leaves of various ages was measured under constant temperature (20±0.5°C) CO₂ concentration in air (0.03%) complete water saturation and irradiance (71 W m² PhAR). TheP_LD is the highest in mature leaves of the current year. The extent of depression in the second and further years depends on the degree of habitat shading. In a slightly shaded habitat (60 to 73% daily sum of photosynthetically active radiation-PhAR) it decreases by almost 50% in the second year. In a deeply shaded habitat (22.5-28.2% daily sum PhAR) the depression amounts to 31.7% in the second year in the third and fourth years to 61.7 and 73.2% respectively.

Growth of primary (cv. Wisconsin 38) and long-term (cv. Virginia Bright Italia) tissue cultures obtained fromNicotiana tabacum L. pith was affected by exposure to a single dose of gamma-radiation ranging from 1 to 150 krad. The inhibitory effect was proportional to the applied dose. Changes in the degree of inhibition during the subculture interval were ascertained by quantitative evaluation of the growth response. Primary cultures proved to be several times more radiosensitive than long-term cultures, the capacity to recover from radiation damage of the cultures participating in the resulting manifestation of the effect. The possible reasons for these differences are discussed.

The substrate specificity of apple seeds phenol oxidases was investigated in polyacrylamide gel electropherograms. The nonspecifico-diphenol oxidases were distinguished as well as fractions showing the specificity for some structural elements of substrate molecule. The role of particular oxidases in phloridzin transformations in apple seed was discussed.

The flow of the nutrient solution stimulates significantly the growth of maize plants and enhances the absorption of nitrogen, potassium, and phosphorus. Especially the content of phosphorus in the shoots and in the roots is significantly increased, but its incorporation into organic compounds is considerably decreased. The plants grown, in flowing nutrient solutions have an altered distribution of iron with a higher amount of it remaining in the roots. In the shoots there is an increase in the P/Fe ratio, the ratio between ions changes in all parts of the plants in disfavour of N, K, and Fe, the production of dry matter is higher and the synthesis of chlorophyll is inhibited.