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.

"Euonymus mosaic virus", purified from cucumber cotyledons by the differential and density-gradient centrifugation, shows typical nucleoprotein absorption spectrum. Electron microscopy reveals isometric virus particles of about 37 nm diameter. No reaction of purified "Euonymus mosaic virus" was observed with antisera against a raspberry ringspot virus, tobacco ringspot virus, cherry leaf roll virus, strawberry latent ringspot virus, tomato ringspot virus, elm mosaic virus, arabis mosaic virus, tomato bushy stunt virus and watermelon mosaic virus.

The content of naturally occurring free substances with cytokinin activity was investigated in growing apices of apple shoots during the vegetative period. In the end of May one substance with cytokinin activity was found. During the first period of growth activity we found three such substances with more hydrophobic behaviour and in the culmination of the second period of growth activity we found other three or four substances displaying on the chromatogram more hydrophylic behaviour.

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.

Endogenous growth substances were estimated byAvena coleoptile test in hypocotyls of cuttings ofPhaseolus vulgaris which were treated with Umbelliferone, a coumarin which has been found to have a stimulating effect on rooting. A similar growth promoting zone which corresponded chromatographically to indole-3-acetic acid, was found in both treated and control cuttings. A growth-inhibiting zone detected in control extracts was absent in UM treated cuttings. The results are discussed in relation to Umbelliferone effect on rooting stimulation.

The effect of Zn²⁺ ions (in the form of ZnCl₂) in the ceoncentration 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). In the "long-term" experiment zine ions influenced the seedlings during eight days of germination, whereas in the "short-term" experiment zinc ions acted only 72 h on seven days old intact seedlings. The biosynthesis of indole glucosinolates has been followed by the incorporation of³⁵S from Na₂³⁵SO₄ into both glucosinolates in experiments with, hypocotyl segments of the rape seedlings.
Zinc ions at chronic "long-term" application increased the glucobrassicin and neoglucobrassicin level in the seedlings. The neoglucobrassicin content especially was increased. A "short-term" application of zinc ions increased the level of both glucosinolates at higher and lower concentrations, whereas medium concentrations (10^-4 and 10^-5 M) lowered their level.
Zn²⁺ ions lowered absorption of³⁵SO₄^-2 ions by hypocotyl segments and simultaneously lowered the incorporation of³⁵S into glucobrassicin. On the contrary, the incorporation of³⁵S into neoglucobrassicin and proteins was stimulated.
Zinc ions do exhibit a specific effect on neoglucobrassicin biosynthesis, on membrane permeability as against sulphate ions and on the incorporation of sulphur into proteins.

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 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 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.

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.

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.

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.