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.

"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.