Third internodes or whole stems of 7-days old etiolated pea plants were extracted and the content of gibberellin-like substances and inhibitors has been determined. Extracts were found to contain four or five different gibberellin-like substances, some of which are chromatographically similar to GA₃. The content of gibberellins has been high in young internodes and decreased along with the internodes elongation. Brief red light irradiation brings about quantitative changes in gibberellin content, depending also on the length of internodes. The extracts contain acidic and neutral inhibitors which interfere with the response to GA₃. The content of the inhibitors does not seem to be affected by the ageing of internodes or by the light treatment.

An open system has been designed which enables a simple and rapid manual regulation of the CO₂ concentration and absolute humidity in the assimilation chamber according to the actual CO₂ and water vapour exchange rates, respectively. This ensures a constant effective CO₂ concentration and humidity irrespective of the gas exchange of the leaves. The installation is supplemented with an irradiation system providing irradiance at the leaf level up to 3 200 μeinstein m^-2s^-1 (400-700 nm),i. e. ca. 675 W m^-2.

On the roots of the unchilled apple seedlings treated with morphactin many deformed adventitious shoots were formed, whereas when the roots were dipped in the mixture of morphactin and NAA more adventitious roots were produced than when only NAA was used. The growth of these lateral roots was greatly inhibited. Similar interaction of NAA with morphactin in the development of roots was obtained when the chilled seedlings were treated with these growth regulators before the buds developed. The sections of the roots from all the treatments were made and the anatomy studied.

The transpiration rate of intact spring barley plants, cv. Profesor Schiemann resistant to powdery mildew was studied separately in light and in darkness. At the first stage of pathogenesis the fungus temporarily reduced the transpiration rate of the host plants in light (E₁). The transpiration rate in darkness (E_d) was not influenced in this period and only in the period of formation of necrotic spotsE_d in the host plants was somewhat higher than that in the control plants.E₁ of the host plants gradually reached the level of the control plants in this period. The fungus considerably reduced the rationE₁/E_d. The differences in this ratio between infected and control plants increased in the susceptible cultivar but were moderated in the course of necrobiosis.

Six to seven-day-oldNostoc sp. strain 221, I.A.R.I. cultures leach out considerable quantity of urea in the culture medium while only detectable quantity of urea was noticed in algae cells.

The effect of exogenous DNA of syngeneic origin on the course of reparation of meristematic cells ofVicia faba primary roots followed after treatment with monofunctional alkylating agent, ethyl methanesulphonate (EMS), was tested. Time course of alternations in mitotic activity of investigated cellular population and the dynamics of formation of postmetaphase chromosomal aberrations was evaluated. A reparation of damaged cells was significantly supported by syngeneic DNA; its application induced an increased incidence of cellular division already in the early intervals of the repair which was accompanied by concomitant decrease of microscopically detectable rupture in the chromosomes. The study performed on the localization of induced damages occurring in metaphase chromosomes pointed out an increased sensitivity of small chromosomes ofVicia faba to EMS. Similarly, a reparative action of syngeneic DNA was exhibited by significant decrease of aberrations frequency, predominantly in the same chromosomal group. Per cent representation of individual types, not affected by the action of syngeneic DNA, was established by detailed classification of induced aberrations. In both cases, isochromatide breaks were found of greatest predominance.

Spraying the growth retardant (B-9) ranging from 500 to 4000 ppm, on caraway and fennel plants reduced stem height, whereas increased the umbel number per plant. There was a slight increase in seed-yield as well as weight of 1000 seeds of the two umbelliferae plants, induced by B-9. The largest values of volatile oil, crude fat, and carbohydrate in the seeds of the two plants resulted from 4000 ppm B-9. Whereas, the crude protein was not affected by B-9 treatments in both plants.

The specific activity of glucose-6-phosphate dehydrogenase (G-6-PD) in growth zones ofVicia faba roots is increasing with cell maturation and differentiation. Changes in the total activity of G-6-PD are not associated with a change in the number of G-6-PD isoenzymes. Five G-6-PD isoenzymes were found in all root growth zones. Some differences were found in the activity of individual isoenzymes.

The cytological effect of one of the alkaloid of Opium, namely morphine sulphate onAllium cepa root tips from a qualitative and quantitative point of view were studied. It was found that morphine sulphate caused partial effect on spindle formation and also showed a mito-depressive effects particularly after long treatment.

The association between latex RNA and latex production was examined using MAK column chromatography techniques. In young untapped trees the introduction of tapping or the treatment of bark with growth regulators resulted in an increase of RNA level and of rRNA/tRNA ratio in the latex. In regularly tapped trees an increase in rRNA but not in tRNA was brought about by increasing the tapping frequency. Treatment with growth regulators had the same effect but essentially only through the related enhancement of latex export from latex vessels. During latex flow, the highest RNA level was registered in latex fractions originating from the most heavily drained areas of bark. Using³²P labeling, evidence was obtained that the export of latex results in an enhancement of rRNA migration into the inner latex containing space of the vessels. This is considered as the reason of the generally observed association of high RNA level and of high rRNA/tRNA ratio with high latex yield. It is proposed that in controlling the RNA level and RNA proportions in the latex an important role is played by changes in turgor pressure associated with the loss of latex which may influence the export of RNA from the nucleus through related induction of pressure disequilibrium between the nucleoplasm and the latex cytoplasm.

Chimeral plants with variegated leaf blades were obtained by induction of organogenesis in primocultures of leaf explants ofNicotiana tabacum L. cv. Burley 49, chlorophyll mutation White Seedling. Only green plants regenerated from primocultures of explants taken from dark green leaf areas of the chimeras. The possibility of a multicellular initiation of chimera regeneration from tissue cultures is discussed.

The content of carbohydrates and activities of phosphatases onN. tabacum cv. 'Samsun' inoculated with Y-virus were studied. Dynamic manner of the systematic studies allowed to find new immediate connections. The results of this experiments with the results of our previous investigations gived the explanations of the varying content of carbohydrates in the tissues. The investigated time period of 10 day were divided into 2 parts with breaking point arround fourth day. During the first part at the decreased activity of hexokinases and at the increased activity of phosphatases the accumulation of saccharides in tissues was observed. During the second part slightly increased activity of phosphatases could not supply to the very stimulated kinases the sufficient amount of carbohydrates so that the content of saccharides considerably was being reduced untill the rate of the control plants.

The influence of Cu²⁺ ions (in the form of CuCl₂) in the concentration range 10^-3 to 10^-6 M on the content and biosynthesis of indole glucosinolates glucobrassicin and neoglucobrassicin has been studied on etiolated seedlings of rape (Brassica napus var.arvensis(Lam.) Thell.). Ions Cu²⁺ acted on the seedlings either chronically from the beginning of the germination or acutely, during 3 to 72 h, on seven days old seedlings. The biosynthesis of both glucosinolates was followed by the incorporation of³⁵S from Na₂³⁵SO₄ into them in hypocotyl segments from seven days old intact etiolated seedlings. After the entry of small amounts of Cu²⁺ ions into the plants, stimulation of the glucosinolates formation occurs, as was found after three h action of Cu²⁺ ions. After the entry of a greater amount of Cu²⁺ ions into the plant, harmful effects appear, as was found after chronic two days action or after 24 and 48 hours acute action of Cu²⁺ ions. Later further stimulation of glucosinolate formation occurs, probably due to enhanced metabolism during reparation processes, as was manifested after chronic action of Cu²⁺ ions lasting four and eight days. The optimal effect of copper was found mainly in the concentration range 5×10^-4 M to 10^-5 M.
Ions Cu²⁺ in higher concentration increased the uptake of sulphate ions by hypocotyl segments, and in lower concentrations increased the incorporation of³⁵S from³⁵SO₄^2- into the proteins.

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.

Salicylic,p-coumaric, and ferulic acids were detected in the acetone-insoluble cell fraction, presumably protein, extracted from the brown discoloured tissues of rice (Oryza sativa L.) leaves infected withPyricularia oryzaeCav. but not from healthy leaves. It is proposed that these phenolic acids are oxidizedin vivo in blast diseased rice leaves, and forms a protein-quinone complex.

During the histochemical investigation of dehydrogenases in the developing shoot apex of wheat plants it was found that the morphologically similar cells of the peripheral meristem may be differentiated according to the differential activity of alcohol dehydrogenase. While the enzyme was not present or exhibited a very small activity only in the tissue of leaf primordia it was highly active in the cells of bud primordia irrespective of the degree of their development and their differential physiological determination.

Hydroxylamine added to the nutrient medium in sublethal concentrations (0.2 to 1.0 mN) enhanced NADH₂ dependent glutamate dehydrogenase activity in isolated pea roots. The increase in activity depended on proteosynthesis and was lower in the presence of NO₃^- and NH₄⁺ ions. The induction of nitrate reductase and of nitrite reductase was partly inhibited by sublethal hydroxylamine concentrations.

The endogenous auxin-like substances were analyzed in the shoot extracts of young spinach seedlings, exposed to photoperiodic induction. At least eight indole auxins were found. One of them was identified as tryptophan, the other one is most probably IAA. The plants grown in long days had a higher level of ether soluble auxins than the controls in short days. Separate extractions of plants after each of the eight inductive days showed that the auxin content was not constant, but subjected to irregular oscillations. However, parallel oscillations were also found in control plants grown in short days. Staminate plants were found to contain more endogenous auxins than the pistillate ones. It is concluded that the quantitative changes in auxins during the photoperiodic induction are probably not related to flowering, but to some other growth process, common to all plants in that phase of growth. The higher level of auxins in staminate plants may be the cause of their faster elongation before the onset of flowering.

The growth of coleoptile sections ofTriticum and its stimulation by indole-3-acetic acid (IAA) are inhibited by 5-azacytidine added into the cultivation medium. 50 per cent depression of the elongation was observed at 2×10^-3M 5-azacytidine concentration. Thymidine kinase activity in cell-free extracts prepared from coleoptile sections treated with 5-azacytidine, and caleulated per 10 mg of their wet weight, is increased while IAA administration resulted in its depression. The observed changes in thymidine kinase activity can be explained assuming the different uptake of water due to 5-azacytidine and IAA treatment.

The roots ofAllium cepa L. were treated with water solutions of cyanein and griseofulvin for 24 and 48 h respectively, thereafter cultured for 48 h in the medium without the antibiotics, and the reversibility of the inhibition caused by the antibiotics was evaluated. Changes in the mitotic index of meristematic cells were followed in squash preparations of root apices. In addition to the cytologic observations, the differentiation of the primary meristem was followed in longitudinal sections. After the treatment with reversible doses of cyanein and griseofulvin respectively, differences were found in both the effects of the antibiotics during the treatment and the restoration of the inhibited processes after the treatment. In the cells treated with cyanein the restoration of mitotic activity was instantaneous but less intensive and in|complete especially in the case of the 48 h treatment. After the treatment with griseofulvin which temporarily interfered also with the differentiation of the primary meristem, the restoration of the inhibited processes was delayed but intensive after both application times, 48 h after the treatment no symptoms of the preceding inhibition could be observed.

Using the quantitative serological method of double diffusion in agar, the amount of sugar beet yellows virus in the leaves of sugar beet was investigated and the possibility of an accurate serological analysis was examined at certain time periods in the course of vegetation. In sugar beets infected artificially at the beginning of the vegetation period the increase of the titre has a fluctuating course at first. In August, after the intensive growth of plants is over, the virus content maintains on a relatively high degree, increasing further toward the end of vegetation. For a reliable virus analysis the sap can be diluted approximately in the ratio 1/128. The table presented enables one to determine the probable accuracy of the serological analysis at the individual time periods during the vegetation of sugar beet.

The supernatants obtained after the centrifugation of the homogenates of healthy barley leaves and the extracts from the surface of barley roots can enzymatically oxidize exogenously supplied IAA in the presence of Mn²⁺ ions and 2,4-dichlorophenol. On the contrary, IAA oxidation is strongly inhibited or does not occur at all in the supernatants from the leaves infected with powdery mildew (Erysiphe graminis DC.) and in the extracts from the surface of both healthy and diseased leaves. The supernatants from diseased leaves inhibit IAA oxidation proportionally to the amount of the added supernatant. That indicates that natural inhibitors formed in the course of infection are present. In the case of the roots, the enzyme obviously penetrates to the surface of the organ. The presence of the enzyme on the surface of the leaves could not be proved either for its low concentration or owing to the presence of the above-mentioned inhibitors.

Kinetin (KIN) and benzyladenine (BA) stimulate to different extent the germination of apple embryos isolated from dormant seeds or seeds submitted to stratification. KIN is much more active in the replacement of light requirement in apple embryos germination. Both cytokinins decrease the photosensitivity of embryos isolated from the seeds stratified less than one month, but only BA accelerates the appearance of the second photosensitivity maximum, normally occuring on the 70th day of stratification. Both cytokinins stimulate the activity of acid phosphatase between the 30th and 50th day of apple seed stratification. The stimulation between the 50th day and the end of stratification is exerted only by KIN.
These differences allow to discuss the specificity of action of particular cytokinins during the after-ripening and germination of apple embryos.

Starch degradation inNicotiana tabacum cv. Samsun infected with PVY was studied with respect to the formation of Glc-6-P which serves as a starting substrate for glycolysis and pentosephosphate cycle. Enhanced activity of these two metabolic pathways at the time of maximal reproduction of the virus requires an increased content of this substrate which is probably produced mainly by the hexokinases. The results of this paper indicate that Gle-1-P, synthesized during starch degradation, is not the main intermediate enabling an enhanced activity of the pentosephosphate cycle, because despite a high starch content in the tissues only a decreased amylophosphorylase activity was found. However, an appreciable amount of Glc-6-P at the time of maximal reproduction of the virus results from enhanced phosphoglucomutase activity.
As there is not enough Gle-1-P for an enhanced activity of this enzyme due to the lowered activity of amylophosphorylase and because its curve resembles activity curves of the hexokinases (published in the previous paper), this result could be explained by the presence of galactose and by the presence of an enzyme system which would be able to metabolize it to Gle-1-P.Additional index words: Nicotiana tabacum, respiration, glycolysis, pentosephosphate cycle.

The effects of temperature treatments on rice seeds in the early imbibitional phase were studied with respect to changes in germination percentage, seedling growth in terms of root and shoot lengths, water uptake, respiration and hydrolytic enzymes,viz. α-amylase, adenosine triphosphatase (ATPase) and phytase. As compared with the control, the treatment for 30 min at 50 °C caused a variable degree of increase in all these characters and a positive correlation existed between seedling vigour and hydrolase activities. The treatment for 30 min at 60 °C, on the other hand, elicited a retarding influence on these characters. As regards the enzyme activities, the damaging effect of 60 °C could, however, be visualized only after 72 h of germination which was preceded by an enhancement during the early hours.

The growth stimulating effect of 5-bromouracil and uracil on two strains of chlorococcal algae has been found in cell colonies grown from single cells, which were inoculated onto an agar medium. Analyses of the effect recorded in the cell cycles after treatment have revealed that the growth stimulating effect required four, or more, cell cycles to become evident. This has been proved by the number of autospores released from the treated cells and by the length of the lag phase after inoculation. The differences between the control and the treated population in some experiments with 5-bromouracil inChlorella and with uracil inScenedesmus obliquus have been visible by the unaided eye, whereas in some other experiments, they have been proved statistically. Growth stimulation has not been found only in a small number of experiments. The inhibition of growth induced by 5-bromouracil has been recorded in one experiment withScenedesmus quadricauda.