A simultaneous azocoupling reaction used for in situ localization of non-specific esterase may be applied even for quantitative in vitro measurements. The developed standard procedure was verified with regard to substrate concentration, inhibitory effect of diazonium salt, incubation time, stability of resulting dye, relation between the amount of dye and the amount of material. On HW medium, non-specific esterase activity increases considerably both in phloem and xylem explants from Daucus carota L. taproot. The increase of enzyme is higher and appears earlier than the increase of fresh weight and dry matter, especially in the explants of phloem.

Some methods were studied which use hot 10% NaCl solution for the extraction of both RNA and DNA from pollen. The raw salt extracts were precipitated with perchloric acid, trichloroacetic acid or ethanol and purified according to the described methods. The nucleic acid hydrolysates were obtained in several ways. In all the samples spectra in the UV-region were measured and the nucleic acid contents were determined according to the absorbance at 260 nm. In order to ascertain the extent of contaminants, the contents of phosphorus, saccharides and proteins were determined. It was found that by the methods studied it is possible to remove some impurities from extracts, but that the extractions of nucleic acids from pollen are not quite quantitative. A part of nucleic acids remained unextracted after the salt extraction in pollen, but it was possible to obtain it only by an additional extraction with 1 N perchloric acid at 75°C.

When cytokinin 6-(γ,γ-dimethylallylamino)-purine-8-¹⁴C was injected into the side root of a one-year-old apple graft, variety Cox's Orange Pippin, it was mainly transported acropetally, but a certain part of the radioactivity was also transported basipetally into the root below the place of injection. 6 days after application of the labelled cytokinin most of the radioactivity was detected in the xylem, 20-30 cm above the place of application. An appreciable quantity of radioactivity was transported toward the apical part of the plant as far as 100 cm from the point of application. Special analysis showed that 6 days after exposition about half of the remaining radioactivity was present in 6-(γ,γ-dimethylallylamino)-purine-8-C¹⁴ and the rest went to the other metabolites. The cytokinin was transported acropetally mainly in the transpiration stream.

Actual heterogeneity of indicators of water balance was studied on tissue segments from leaves ofBrassica oleracea L. v.acephala andNicotiana tabacum L. under controlled conditions. Maximal values of transpiration rate, water absorption rate, water transport rate and low values of WSD at the same time were observed at an initial WSD of 0% in segments from middle leaves and at an initial WSD of 20% mostly in segments from upper leaves. Although the properties of leaf tissue itself were probably the basic factors determining the actual heterogeneity of indicators of water balance, without connection with all other factors (e. g. various microclimates, supply of water) heterogeneity did not appear to a full degree.

In rooting poplar shoot cuttings of identical morphogenetic characteristics at the same time, the author succeeded to evoke differences in the radial arrangement of the vascular system by different environment influences. More favourable rooting conditions in the green-house, when comparing with the less favourable field conditions, caused root formation with a higher number of alternating xylem and phloem poles. The representants observed (I 214,Populus deltoides var.monilifera, P. pyramidalis) did not react in the same way on the different onvironment. The hybrid I 214 was the most sensible.
It was also possible to induce differences by indoleacetic acid (IAA) exogenous application. Not only the number of the roots formed increased in a highly significant manner in the cuttings influenced by IAA, but also the number of poles in the radial vascular bundles of the induced roots was higher in a highly significant way.
From the results given above it can be deduced that external conditions affecting activation of dormant root primordia in poplars influence also the pattern of vascular tissue differentiation in formed roots.

When cytokinin 6-(γ,γ-dimethylallylamino)-purine-8-¹⁴C was injected into the side root of a one-year-old apple graft, variety Cox's Orange Pippin, it was mainly transported acropetally, but a certain part of the radioactivity was also transported basipetally into the root below the place of injection. 6 days after application of the labelled cytokinin most of the radioactivity was detected in the xylem, 20-30 cm above the place of application. An appreciable quantity of radioactivity was transported toward the apical part of the plant as far as 100 cm from the point of application. Special analysis showed that 6 days after exposition about half of the remaining radioactivity was present in 6-(γ,γ-dimethylallylamino)-purine-8-C¹⁴ and the rest went to the other metabolites. The cytokinin was transported acropetally mainly in the transpiration stream.

The formation of the protein complex during barley grain maturation is characterized by unequal synthesis of different protein fractions. In ten day-old grain the dominating protein is glutelin, followed by albumin and globulin. The content of prolamin is at this stage negligible. Particularly after the eighteenth day of maturation intensive synthesis of prolamins begins, which continues during the entire maturing period in almost the same ratio as total N accumulation in the grain. From the twenty-fourth day the amount of prolamins exceeds that of glutelins, and at full maturity 50% of the proteins are prolamins. The glutelin content increases absolutely, but relatively it decreases from 41 to 26%.
The amino acid composition of flour from total grain as well as the amino acid composition of the individual proteins is significantly changed during maturation. Generally the changes are manifested in an increasing content of Glu and Pro and a decreasing content of Asp, Ala and Lys. These changes seem to occur as a result of an increasing representation of prolamin, which is characterized by large content of Glu and Pro and low content of Asp, Ala and Lys compared with other protein fractions.

Red clover mottle virus isolated in Czechoslovakia was studied in relation to its reaction to varying temperature on primary French bean leaves (Phaseolus vulgaris L.) on which it forms local necrotic lesions. The plants were kept 24 or 48 h before, or 24 or 48 h after inoculation at the temperatures 23, 25, 27, 30, 33 and 36° C. After such exposures the French beans were kept at a constant temperature of 25° C. The lesions were counted at various intervals. In the experiment the optimal temperature for the maximum number of lesions seems to be 36 °C 48 h before inoculation. The temperature above 25° C applied 24 h after inoculation seems to have a decreasing effect upon the number of lesions formed by RCMV on primary leaves of French beans and the lesions appeared several hours later, especially at 30, 33 and 36° C. The temperatures 27, 30 and 33° C applied 48 h after inoculation have a further decreasing effect on the number of lesions. The temperature of 36° C applied 48 h after inoculation has an inactivating effect upon RCMV inoculated on French bean leaves and no lesions appeared 5 days after inoculation.

Callus tissues were derived from the stem of healthy tomato plants (Lycopersicum esculentumMill. ev. Průhonické) and of plants infected with potato witches' broom-a disease caused by mycoplasma. Callus cultures were established on modified fully synthetic media described byMorel (1948) and byMurashige andSkoog (1962). Callus cultures obtained from diseased plants were grown and subcultured on both media, growth in primary isolates from healthy plants took place on the Murashige and Skoog medium only. Growth of callus tissue derived from diseased plants was more vigorous even after several subcultivations in comparison with callus tissues isolated from healthy plants. Variations in the morphology in these callus cultures were not noted. Callus cells of diseased plants varied in size; they were about 50% larger than those from healthy ones. Implantation of primary and subcultivated callus tissues into tomato stems of healthy plants did not show any symptoms of infection on test plants.

For three consecutive years the content of natural stimulators and inhibitors was observed in leaves and shoots of peach trees. Research was directed to the question of development of flower buds.
The substances under study were isolated from the acidic fraction of ether extracts by means of paper chromatography and their concentration was determined by biological test. The activities of substances which either stimulate or inhibit the growth of oat coleoptiles, were added up. The curve expressing the content of stimulators in shoots in relation to the fresh weight showed its maximum in the period of full growth of shoots (15 June-15 July according to the fluctuating vegetative conditions) and it showed a decreasing tendency at the end of the season. The decline of the curve showing the content of inhibitors is of similar direction but less steep. The trend of substances under study is the same in leaves as in shoots, but their quantity is lower. Stimulation and inhibition effects in individual sampling intervals were added up to make a common curve which seems to express the combined action of stimulators and inhibitors in the plant, which determines its growth pattern.

We have found in a number of plants (lentil, lupine, bean, barley, oats, rye, wheat, cucumber, melon, flax, sunflower and rape) that varying amounts of ethanol are formed under natural anaerobiosis and, that in later growth periods these plants continue to react to anaerobiosis by formation of ethanol. When the testa has opened in germinating plants or, when plants are transferred from the anaerobic atmosphere to air, ethanol disappears.
Plants contain alcohol dehydrogenases, the activity of which depends on the alcohol concentration in their tissue; the maximum concentration is reached during natural anaerobiosis, rising in the course of further growth when the plants are kept in a nitrogen atmosphere.
Alcohol dehydrogenases of the plants studied are localised in the soluble cell fraction notsedimenting at 120 000 g, their pH optimum is in the weakly alkaline region and their Michaelis constants are equal in order of magnitude (10^-5m). They are all inhibited in the same way by Zn²⁺, Cu²⁺, Hg²⁺, B₄O₇^2- ions, p-chloromercuric benzoate, iodoacetate, EDTA and phenantroline, which may be considered as evidence of the presence of -SH groups. The specific activity of alcohol dehydrogenase preparations is higher in plants grown in light than in plants grown in the dark.
The specific activity of plant alcohol dehydrogenases can be increased by precipitation with ammonium sulphate by at most one order of magnitude, while all the activity is lost by this purification process in the case of cereals.
The following isoenzyme composition of ADH was found by means of electrophoresis on polyacrylamide: the enzyme from poas and sunflower, for example, is composed of three, that from wheat and oats six, the enzyme from maize and barley of five isoenzymes.

The effect of abscisic acid (ABA), gibberellin A₄₊₇ and benzyladenine on germination of apple embryos which had been stratified for different periods of time was investigated.
The growth stimulators accelerated the germination of non-stratified embryos or those stratified for a short time. After a longer period of stratification, the effect of growth stimulators was visible only when germination of the embryos was artificially inhibited by simultaneous application of synthetic ABA.
The sensitivity of stratified apple embryos to the exogenous ABA diminished with the number of hours elapsed between the imbibiting by the embryos of the water or gibberellin and the application of the ABA.
This was similar to the change in the sensitivity of apple embryos during stratification due to the increasing concentrations of ABA.

The effect of the herbicides MCPA and simazine on some physiological processes in bindweed was studied. An enhanced respiration rate in roots was demonstrated when MCPA was added to the nutrient solution, and when the plants were later transferred to a solution without any herbicide. When overground parts of plants were treated with the herbicide their respiration rate was found to proceed at a higher rate than in controls. the opposite situation being found to prevail in roots. In this experimental variant the content of glycides and of nitrogen in the overground parts was found to be reduced. It seems probable that the glycides were consumed due to the more intensive respiration caused by the presence of MCPA.
In experiments with simazine a lower respiration rate as compared with the controls was demonstrated in the majority of cases, independent of the means of application of the herbicide. When simazine was applied to roots and the plants were transferred to a solution without the herbicide, the overground parts were found to contain less glycides than the controls. In roots the opposite was true; after 7 days of the experiment no difference between the treated and untreated plants was observed. The nitrogen content was rather variable in this experiment. The reduced respiration rate after simazine treatment may be explained by a lack of respiration substrates resulting from an impairment of photosynthetic assimilation.

The effect of GA₃ on the initiation and the development of epiphyllous buds inBryophyllum tubiflorum exposed to different photoperiods was studied. It was observed that although the bud primordia were initiated under both photoperiods, they developed as epiphyllous buds only under theLD condition. GA₃ did not affect the magnitude of bud development underSD and inhibited it under theLD condition.

The present report is focused on the study of participation of exogenous DNA in the process of postirradiation reparation of meristematic cells ofVicia faba primary roots. It is aimed at comparison of the positive reparative effect of isologous DNA with postirradiation action of heterologous DNA in its native, thermally denatured and DNAase-degraded forms, or DNA degraded by ultrasound, and with the effect of other biologically important macromolecules (RNA, histone, heparin, and dextran sulphate). For this purpose, the roots ofVicia faba irradiated by 150 r exposure were cultivated in solutions containing the above substances for an appropriate time interval. In squash slides both mitotic activity of the investigated cell population and frequency of postmetaphase chromosomal aberrations induced by radiation were evaluated. It was shown that a stimulation of cell division and reparation of chromosome damages were supported exclusively by isologous DNA. On the contrary, exogenously applied heterologous DNA increased postirradiation frequency of aberrations; maintenance of native structure of applied DNA was an essential condition for the above effect. Other macromolecules investigated on the course of postirradiation reparation ofVicia faba meristematic cells were without effect.

Kind of substrate utilized by the respiration of mustard seedlings (Sinapis alba L.) was determined on the basis of found RQ values of control plants. This led to the study of the effect of 4-phenethylpyridine on relationships between lipase, lipoxidase, glycerolkinase and O₂ consumption: Enzyme activities and O₂ consumption rose from the second to the fifth day. According to these results, 4-phenethylpyridine increases degradation of storage fats in the beginning phase of fat catabolism, bringing about advantageous conditions for their metabolic utilization in plant, like in the case of saccharide metabolism.

Values of the water saturation deficit (WSD) for hydroactive stomatal movements of kale leaves were estimated using the method of transpiration curve analysis.
Stomata of young leaves started closing at WSD values of 5 to 6 per cent and were completely closed at 18 to 20 per cent WSD. During maturation and ageing of leaves these WSD values increased to 12.5 and 18 to 23 per cent respectively. Thus the stomatal reaction is more sensitive to changes in WSD in adult leaves than in young ones. After maturation is attained both values decrease. In apparently withering leaves the individual phases of transpiration curves can barely be distinguished, probably for the reason that even under optimal conditions their stomata remain half-closed and at high WSD values an incomplete closing of the aperture occurs. The injured cuticle of withering leaves affects the shape of the transpiration curve as well.

The present report is focused on the study of participation of exogenous DNA in the process of postirradiation reparation of meristematic cells ofVicia faba primary roots. It is aimed at comparison of the positive reparative effect of isologous DNA with postirradiation action of heterologous DNA in its native, thermally denatured and DNAase-degraded forms, or DNA degraded by ultrasound, and with the effect of other biologically important macromolecules (RNA, histone, heparin, and dextran sulphate). For this purpose, the roots ofVicia faba irradiated by 150 r exposure were cultivated in solutions containing the above substances for an appropriate time interval. In squash slides both mitotic activity of the investigated cell population and frequency of postmetaphase chromosomal aberrations induced by radiation were evaluated. It was shown that a stimulation of cell division and reparation of chromosome damages were supported exclusively by isologous DNA. On the contrary, exogenously applied heterologous DNA increased postirradiation frequency of aberrations; maintenance of native structure of applied DNA was an essential condition for the above effect. Other macromolecules investigated on the course of postirradiation reparation ofVicia faba meristematic cells were without effect.

Physiological effects of volatile substances released by the overground as well as by the underground organs of higher plants were studied. The activity of the volatile substances was tested both when these substances were allowed to act directly in the air and when they were dissolved in water in the form of solutions. Plants which do not contain essential oils or which are not rich in them as well as those abounding in essential oils and other volatiles were used in the experiments. The physiological activity of the volatile substances was tested on rye seedlings.
The overground as well as underground mature organs of the tested plants were found to release volatile substances causing, when acting directly, in the majority of cases an inhibition of the growth in length and of the formation of dry matter in rye seedlings. A pronounced inhibition of the growth of rye seedlings was brought about especially by the volatile substances of "aromatic" plants such as common dill, wild thyme, yarrow milfoil, garden thyme, marjoram, etc. The volatile substances released by the organs of "non-aromatic" plants like sugar-beet, common sunflower, quackgrass, etc., were found to bring about a significant inhibition of the growth of rye seedlings, too.
The volatile substances released by the plant organs were found to be altogether absorbable in water and physiologically active also in the form of water solutions. With the exception of volatile substances from hemp and quackgrass leaves, which brought about a mild stimulation of the dry matter formation in rye seedlings, inhibitory effects of these solutions were found to prevail in all cases. Most effective were the solutions of the volatiles from some of the "aromatic plants".
An assay for olefines in the atmosphere of the experimental vessels demonstrated that in almost all cases ethylene is being released by the plant organs.

Changes in the variability of quantitative characters (number of fertile stems, length of the stem and of the spike, number of spikelets in the spike, number of seeds in the spike and in the spikelet) in M₂ induced with 0.1 mM, 0.2 mM and 0.3 mM N-nitroso-N-methylurea (MNH) and with 5000r and 10 000 r of X-rays inTriticum monococcum L. var.sofianumKörn. were evaluated. The mean of the populations remained practically unchanged by the mutagens whereas the variability increased considerably with increasing concentration or dose. Changes in the variability were more pronounced in the values for the first stem than in the values for the first three stems. When changes in the population mean were found (with some of the most elevated concentrations and doses), these changes were shown to be mostly due to a repetition of the cultivation, whereas the changes in the variability were mostly due to the action of the mutagens. In all experimental populations, mutations in quantitative characters were successfully induced.

Some biochemical properties ofTrigonella foenum-groecum infected withPeronospora trifoliorum have been investigated. Qualitative changes were observed in lipids, coumarins, amino acids and indole compounds only. A quantitative study of the phosphate content was also carried out. Neutral lipids did not show any significant changes. In addition to the fourteen phospholipid bands, the infected leaves contained a new band corresponding in R_f to phosphatidic acid or polyglycerophosphate. Seven coumarins were present in both the extracts. In addition 3-hydroxy coumarin, 5-hydroxy-4-methylcoumarin and 7-hydroxy-4-methyl-coumarin were detected in infected leaves. Higher levels of indole acetic acid and three of its derivatives were observed due to infection. Infection altered the free amino acid content. Tryptophan appeared and the total phosphate content increased. Increase in phenols and indoles suggest a higher respiratory rate whereas a higher content of inorganic phosphate suggests uncoupling of phosphorylation from respiration.

The shoot apex or fruitlets of Jonathan apple trees grafted on M IX rootstock and grown in pots in a greenhouse were exposed to¹⁴CO₂ in an assimilation chamber. The translocation of¹⁴C-labelled assimilates from treated organs to other parts of the plant was studied.
It was found that a very small amount of¹⁴C-labelled compounds was translocated from the shoot apex and very young fruitlets to the shoot stem. Preliminary chromatographic studies show that the chemical composition of the labelled substances detected below assimilation chamber differs profoundly from that of those remaining in the supplied leaves. The results support the view that there exists a translocation of some substances, possibly regulators from the sink to the donor.

Antonovka seedlings were obtained from the embryos soaked in abscisic acid (ABA) alone, gibberellin A₄₊₇, benzyladenine or the mixtures of these regulators. The inhibitory effect of ABA on the growth of the seedlings was of temporary duration. The height of the 12 week-old seedlings was dependent only on the degree of seed after-ripening and not on the ABA treatment.
The growth stimulators studied were unable to overcome the inhibitory effect of ABA observed in the early stages of seedling growth. The growth stimulators did not substitute, for cold treatment of apple seeds which is the only treatment so far known to overcome the dwarf conditions of the seedlings obtained from non-after-ripened embryos. ABA greatly suppressed the early stages of apple seedling growth (up to 6 weeks) during which they resembled physiological dwarfs.
The highest concentrations of ABA (2.0 μg ml^-1) greatly modified the root system of the seedlings, and produced a larger percentage of seedlings with unbranched roots.

Isozyme patterns and specific activity of ribonuclease (ribonucleate pyridinenucleotido-2'-transferase, E. C. 2.7.7.16) were followed in the extracts of segments from three growth zones of the root and in extracts of young and senescent leaves ofVicia faba L. Electrophoreograms of extracts from all three investigated root zones were identical, in the electrophoreograms of extracts from senescent leaves however one new ribonuclease occurred which could not be detected in the electrophoreograms of extracts from young leaves. Extracts from senescent leaves had higher specific activity of ribonuclease than extracts from young leaves. Extracts from the enlargement zone of the root and those from the maturation zone had a three times higher specific activity of RNase than extracts from the division zone.

The character of endogenous regulators in walnut buds was followed by means of bioassays in the course of vegetation. It was ascertained that a rise in the level of gibberellin-like substances precedes the sprouting of buds. The origination of new buds in the axil of young leaves is accompanied by a fall in the level of auxins, by a low gibberellin content and by the presence of inhibitors. In this situation the primordia of staminate catkins are diferentiated in the basal buds. The vegetative buds which are formed in the axils of further leaves, stop developing because of the accumulating inhibitors. Towards the close of vegetation the primordia of pistillate flowers originate in terminal buds and their differentiation is accompanied by a substantial rise in the level of auxin-like substances, while some of the inhibitors keep asserting themselves. On the basis of these findings we have tested the possibility of affecting the differentiation of staminate primordia and of vegetative buds by the exogenous application of selected regulators. Spraying young leaves with IAA and MH solutions will increase the number of vegetative buds in the twigs. A later spray of other twigs by TIBA and GA₃ solutions will increase the number of staminate buds.

The light regime effect on the growth rate variability of clones of one chlorococcal alga strain growing on the surface of a solid medium was studied from the point of view of the clone selections manifesting the desired grade of this complex character. Several combinations of light regimes used for the cultivation of coenobia treated by UV-light and untreated control on two types of solid media proved the significance of manifestation degree changes of this character due to the given light conditions. The sizes of the alga colonies after a certain growth time on the surface of solid medium were evaluated statistically and the values obtained indicated the degree of growth rate manifested by the clones of a given population. The x and s_x values of their growth rate variability were considered as the indicators facilitating the choice of selec-tion type and screening level. This paper is a partial contribution to the solution of the problems concerning the primary selection of alga clones on the surface of solid media.

Algae were cultivated in nutrient solutions containing nitrates or ammonium salts as the nitrogen source. We measured the culture density in the case of autotrophic and mixotrophic cultivation at different pH values, in the presence of nitrate also at different concentrations and in the absence of molybdenum. The dry weight and amount of nitrogen in the cells under these conditions were determined.
According to results obtained we conclude thatChlorella, in contrast toScenedesmus, prefers ammonia as the nitrogen source in the first growth period, later both prefer nitrogen from nitrates. Nitrogen from ammonium salts has a positive effect only during short-time cultivation. If glucose was used as a mixotrophic energy source (or perhaps H-donor), the unsuitability of ammonia as a nitrogen source was more marked. We suppose that the lower growth intensity of older cultures (i.e., after seven days) in ammonia medium is the result of the use of endogenous energy sources.
Both algae have adaptive systems making it possible to use nitrate nitrogen even in the absence of molybdate.

1. The transfer of immature embryos from maternal plants to artificial media influenced the radial arrangement of vascular bundles in developing root primordia. The variability in the number of poles of the prospective protoxylem and protophloem, observed as a rule during embryogenesis under natural conditions, could not be suppressed even under the conditions ofin vitro cultivation. The possibility is admitted that when using agar medium the nutrient supply need not necessarily be equivalent for all embryos.
2. Using excised embryos of various ages the period of delimination of the vascular system in the root primordium was determined. It is relatively short and occurs in the first half of embryogenesis. The results obtained revealed no relationship between vascular system arrangement in root primordium and mature grain and mature embryo size.
3. Maize ear represents a type of inflorescence of which the apical part is delayed in development. Histogenically this uneven development becomes evident with the formation of a significantly lower mean number of poles in root primordia from the grains originating from the apical region of the cob. This is further evidence of the adaptibility of the vascular system development to environmental conditions.
4. As further causes of the variability in pole number those differences are considered which occur during sex cell formation, pollination and fertilization.

Studies with gamma rays, fast neutrons, and EMS treatments in rice showed higher frequency of M₁ chlorophyll chimeras in the EMS treatments, a correlation between the frequencies of M₁ chlorophyll chimeras and M₂ chlorophyll mutants, and a higher M₂ mutation frequency in the progeny of chimerical M₁ plants compared to those of normal-looking plants.

The meiosis of two mutants ofBrassica oleracea var.capitata was analysed which have been isolated after gamma irradiation and hybridization.
1. Univalents appear in different frequencies in the pollen mother cells of both these mutants attributed to a genetically conditioned reduction of the chiasmata frequency resulting in manifold irregularities in the later stages of microsporogenesis. The number of microspores per PMC varies between 1 and 8, the chromosome number of the microspores between 6 and 12. As a consequence of these meiotic disturbances a strong reduction of the fertility of male and female germ cells occurs.
2. In principle, both mutants show the same meiotic behaviour, but the irregularities appear in a stronger degree in mutant 45 as compared with mutant 47. They are obviously caused by the same mutated gene which shows differences in its manifestation in the two mutants due to their different genotypic constitution.
3. The mutant gene belongs to the group of desynaptic genes controlling the process of chiasmata formation. The degree of desynapsis caused by this gene is very weak as compared with ds-genes of other species.