Peroxidase activity and isoenzyme pattern were investigated in buds and tubers of Jerusalem artichokes in relation to induction and breaking of dormancy. Peroxidase activity per unit soluble protein is the highest in the dormant stage. Conditions leading to growth,i.e. release of dormancy by the cold, stimulation of axial growth by gibberellic acid or stimulation of radial growth (tuberization) by kinetin, cause rapid loss of total peroxidase activity together with a decrease of intensity of the most cathodic isoperoxidases. Induction of dormancy by AMO-1618 increases peroxidase activity mainly through the same cathodic isoenzymes. The role of the cathodic isoperoxidases is discussed in relation to auxin catabolism and the genesis of oxygenation products inhibitory to plant growth.

The formation of starch in excised 3-days-old pea roots was enhanced up to three fold after cultivation for five days in liquid media containing 3% glucose, microelements, and 10^-6 M kinetin or 10^-7 M naphtaleneacetic acid (NAA). A synergistic effect of kinetin and NAA on starch formation was observed when both hormones were applied simultaneously over a wide range of concentrations.

A technique for studying the water relations of fleshy fruits such as strawberry by measuring the beta ray penetration through the tissue is described. As a source of beta radiation, an active preparation of³²P melted into a capillary glass tube was used. The technique described permits a study of the changes in the water content of fruitsin vivo.

The effect of acute gamma rays (⁶⁰Co; 1 to 10 kR) on the vascular differentiation in stems of seedlings of Capsicum annuum L. long fruited cultivar at 8-loaf stage of development. Prooambium, phloem and xylem of irradiated seedlings showed an early initiation and maturation in terms of distance from the tip. Magnitude of these differences increased with the increasing exposures and time following irradiation. In irradiated seedlings there is a ohange in the developmental sequence of metaphloem and metaxylem when they first appear (in terms of number of leaf primordia). There is also a general increase in the number of procambial cells, sieve elements and vessel elements after irradiation.
The early initiation and maturation of the vascular tissue is correlated with the growth inhibition resulting from cell death and suppression of cell division activity in the shoot apex.

Free and bound gibberellins were estimated in individual leaves of winter wheat using TLC a lettuce hypocotyl bioaasay. Bound gibberellins were extracted from the hydrolyzate of the water remnant after the removal of free gibberellins.
Each leaf exhibits its own dynamics of free and bound gibberellins during its individual ontogeny, the gradual changes tending to be identical in every leaf. In young developing leaves the level of free gibberellins is high and that of bound is low. Further, inhibitors are sometimes present. The free gibberellin level rises with the activisation of growth and vital activity of a given leaf. Towards the end of the life cycle the content of free gibberellins is reduced to its minimum and inhibitory substances appear. The dynamics of bound gibberellins is opposite to that of free ones during ontogeny.

Using four independent late mutants, obtained by treatment of the early cultivar Dijon-G with N-methyl-N-nitrosourea, it was found that their delayed flowering has a monogenic genetic basis, the mutant alleles appearing to be incompletely dominant. All these mutants display a positive reaction to the graded vernalisation; the vernalisation requirement of the individual mutants is, however, both quantitatively and qualitatively different and hence specific for each of the mutant genotypes. lodoacetic acid is found to inhibit the vernalisation of the mutants to some extent only when the duration of the vernalisation is relatively short (20 days). A hypothesis is advanced, assuming a potential existence of a complete genetic apparatus for vernalisation already in the Dijon-G cultivar, where it is, however, blocked by suppressor or epistatic genes.

Using the phenol extraction method and MAK column chromatography the contents of nucleic acids in styles ofNicotiana alata were estimated before and up to 48 h after compatible pollination. As a result of pollination, high-molecular-weight rRNA and DNA registered a significant increase in their content approximating 30% and 16% respectively. The change in sRNA (4-S tRNA and 5-S rRNA) level was very slight and non-significant. In pollen grains there is an unusually high amount of rRNA with respect to the content of other nucleic acids and the rRNA/tRNA ratio approximates 14 : 1. On the other hand, in non-pollinated styles the content of rRNA is only about 6 times higher than that of tRNA. The changes in nucleic acid level found in styles after pollination are at least in a major part the result of the addition of the nucleic acids present in the amount of pollen used for pollination. The high rRNA level relatively to tRNA being generally associated with rapidly growing cells, its significance in pollen may be related to the rapid growth of pollen tubes.

The new growth promoter, N(2-acyl-l,3-indane dione) triethylammonium iodide (L-TEAI) enhanced the elongation of the seedlings of cluster bean (Cyamopsis tetragonoloba (L.) Taub, belonging to familyPapilionaceae). When the two growth regulators, L-TEAI and cycocel were applied together, the cycocel induced inhibition of radicle elongation was reversed, but it failed to reverse the inhibition of hypocotyl elongation.

The course of androgenesisin vitro was investigated with anther cultures of two chlorophyll mutants of Nicotiana tabacum. A different sensitivity to the hormonal composition of the medium was revealed between the cultures White Seedling and Sulfur; the stimulatory effect of kinetin on the frequency of androgenesis was observed only in White Seedling cultures. In addition to green plants, "aurea" (mutation Sulfur) or "albino" (mutation White Seedling) phenotypes also differentiated in both cultures. The possible causes of variability in the participation of green and mutant forms are discussed.

Ultrathin sections were prepared from the tissues of lettuce leaves with mosaic-like symptoms and thickened nervature which were studied by means of electron microscopy. Intracellular inclusions surrounded by a membrane were found in the cytoplasm of parenchym cells of the investigated lettuce leaves(Lactuca saliva L. provar.capitata L. nid.jaggeriHelm., cv. Pražan). Crystals with a distinctly apparent hexagonal lattice could be observed in the inclusions. No crystal containing inclusions were found in the tissues from the leaves without mosaic-like symptoms and in those from thickened nervature.

Changes in the transpiration rate of intact spring barley plants, cv. "Slovensky dunajsky trh", were studied separately in the light and in the dark under controlled temperature and illumination, after the infection withErysiphe graminis DC, during an 8 day period of the development of the fungus. In the first stage of pathogenesis, the fungus diminishes water output from the host plants in the light. An opposite phenomenon can be observed in the dark; water output from infected plants in the dark increases sharply mainly in the stage of advanced fructification. Thus, the fungus considerably diminishes the ratio of water output from the host plants in the light to that in the dark.

In water soaked barley seeds the respiration rate (QO₂) at 25 °C is about 100 times higher at 30% than at 20% water content. The treatment of seeds with mutagenic methyl methanesulphonate led to the depression of the respiration rate in dependence on the applied mutagenic dose. Seed storage at 30% water content resulted in a recovery from the inhibition of seed respiration caused by methyl methanesulphonate. In contrast, at 20% seed water content the respiration rate either slightly decreased or remained unchanged in the course of storage. The results are discussed in relation to the previously described changes in the yield of induced mutagenic effects in barley seeds treated with monofunctional alkylating agents and stored at 30% and 20% seed water content.

Ethylene was collected in methanol solution of mercuric acetate and the addition compound formed was then separated by means of paper chromatography. The spot area and colour intensity after detection were determined using a densitometer. The amount of collected ethylene was calculated from a calibration curve.
The ethylene liberated from plant samples was collected during one or two days. During this period the amputation of the whole plant organs did not influence ethylene production. Changes in ethylene production were found after segmentation of the tissue or after the treatment with auxin and Co²⁺ ions.
The above-ground parts of investigated herbs released 0.3 to 3.5 μl of ethylene per kg fresh weight per hour. The leaves of investigated trees released 1 to 20 μl of ethylene per kg f.w. per hour. The rate of the production of ethylene seems to be specific for a given species.

Unmetabolized nitrite occurs in 3 cm long apical segments of primary pea roots(Pisum sativum L., cv. Raman), isolated from 6 d old seedlings, grown under aseptic conditions for 10 h in nutrient solutions containing 0.1 to 2 mM nitrite concentration, its amount being dependent on the concentration in the nutrient solution. With increasing amount of nitrite in the roots, the ratio between NAD⁺-GDH₁ and NAD⁺-GDH₂ isoenzymes is changed without influencing significantly the total NAD⁺-GDH activity. After 48 h cultivation unmetabolized nitrite occurred in the roots only in small amounts and the ratio of activities of these isoenzymes was not affected significantly. NADP⁺-GDH activity, detected in the gels at the same site as NAD⁺-GDH₁, was depressed by increasing nitrite concentrations.

The experiments showed that after gamma irradiation as well as after irradiation by secondary cosmic rays (hard component)Equisetum arvense spores produce in the first developmental phases prothalia at a changed rate,i.e. in favour of the females. This effect being specific for radiation cannot be produced by heat, pressure or changes of electric and magnetic field (i.e. factors appearing in higher sea levels with a stronger intensity of cosmic rays). It will be possible to apply the sensitivity of the mentioned method for investigating the problems of testing cosmic ray variations. The possibility of its application in spontaneous variability research is not less important.

Growth correlations among lateral shoots of one-year-old apple treesMalusMill., were described. The existence of a mechanism was postulated through which small original differences between buds or young shoots are quickly augmented, thus leading to differentiation of long shoots and short shoots. Existing hypotheses do not seem sufficient for explaining correlative phenomena of this type; a cybernetic approach was therefore applied. Studying growth correlations in terms of cybernetic revealed that previous hypotheses concerning correlations do not contradict each other as often thought, but depict different links in a more general chain of events. A cybernetic model points out the importance of root influences in interaction among shoots. It also shows that synergism between auxin, gibberellin and cytokinin in xylem and phloem differentiation and in starch metabolism is very important for understanding correlations in apple trees.

A phosphatase enzyme hydrolysing NADP⁺ and NADPH to NAD⁺ and NADH was found to be present in extracts ofChlorella pyrenoidosa

The present paper incorporates a detailed study on the distribution of 5-nucleotidase in the germinating pollen grains ofEschscholtzia califomica. The intense activity of this enzyme has been found in the wall of pollen grains and pollen tubes and small positive granules in the lumen of both in the pollen grains and pollen tubes. The presence of this enzyme in the wall is presumably connected with the permeability and transport process and growth regulation of the pollen tubes.

The nucleic acid fractions in cotyledons of young Chenopodium rubrum plants exposed to continuous light, continuous darkness and short (8 h) day, respectively and labelled with³²P 24 h prior to harvesting were studied by means of chromatography on MAK columns. Some parameters of cotyledon growth (dry weight, cotyledon area, occurrence of mitoses) were also investigated.
The changes in the nucleic acid fractions agreed with the dynamics of cotyledon growth. In continuous light the content of all fractions increased. The radioactivity of DNA and s-RNA did not undergo any great changes and only r-RNA increased. The specific activity of r-RNA increased slightly, that of soluble RNA and DNA was reduced. In continuous darkness the content of all the fractions did not undergo any great changes. The radioactivity as well as the specific activity of all fractions decreased. In short day the content of the nucleic acid fractions did not change conspicuously. Only the specific activity of s-RNA increased in a noticeable way while the radioactivity of r-RNA and the specific activity of DNA decreased and this of r-RNA did not change. The changes in nucleic acid metabolism were partially connected with changes in³²P uptake which depended upon light conditions but they were not merely a consequence of this fact. Obviously, there also exists a more direct relationship between nucleic acid synthesis and growth.

Phosphorus oxytriamide PO(NH₂)₃ was proved chromatographically in the exudate of decapitatedPhaseolus vulgaris plants. This fact verified the presumption that covalent compounds of phosphorus and nitrogen enter roots without previous hydrolysis.

Studying relationships between tobacco mosaic virus reproduction, anthocyanin biosynthesis and phosphorus content in cultivation medium, it was found thatMartin's (1958) finding of an indirect proportion between anthocyanin and virus synthesis is valid even under the complicated conditions of pathological anthocyanin formation induced by phosphorus deficiency. A decrease of anthocyanin biosynthesis with simultaneous stimulation of virus reproduction takes place at temperatures below 20°C. Increased anthocyanin biosynthesis accompanied with the inhibition of virus reproduction occurs at temperatures above 20°C. The obtained results suggest that enzyme systems and substrates participating in considerably increased anthocyanin biosynthesis induced by phosphorus deficiency, differ from those taking part in anthocyanin synthesis induced by virus infection.
The enhanced phosphorus content in the cultivation medium does not influence anthocyanin biosynthesis significantly. Nevertheless, a highly significant inhibition of tobacco mosaic virus reproduction takes place at temperatures above 20°C. This inhibition may be in correlation with some other metabolic systems affected probably by the enhanced phosphorus concentration in the nutrient medium.

The photosynthetic production of dry matter of discs cut out from leaves of cucumber plants severely infected withCorynespora melonis was significantly lower than that of discs from healthy plants. The decrease was found in discs from leaves both infected and symptomless. Expected inhibition agent has not been isolated up to now.

Anthers ofLycium halimifolium were grownin vitro at the following stages of development: tetrads, microspores and binucleate pollen grains. Pollen plantlets were obtained only from anthers inoculated at the stage of microspores. The growth of androgenic embryos was very slow. Mature embryos were formed in about 3% of the inoculated anthers. The largest number of embryos obtained from one anther was 4.

The first information concerning the cytogenetic efficiency of thermal neutrons in lentil are presented in this paper. The range of cytologically effective dosages of thermal neutrons in lentil was determined. This determination enables us to compare the efficiency with the mutagenic effect of thermal neutrons and with their effect on the growth and development of plants of M₁ generation. These effects were already evaluated in previous communications.
Thermal neutron irradiation significantly affected all the characters studied. A linear dependence of the effect on the dose of the neutron radiation was found for most of the analyzed characters. From a sample of scored cells, whose nuclei were in the anaphase or early telophase, 9.0 to 72.0% of them had chromosomal bridges and fragments after irradiation with dosages from 3.3×10¹¹ n cm^-2 to 4.5×10¹² n cm^-2. The highest number of rearrangements per one cell reached 2.16 after irradiation with 4.25×10¹² n cm^-2 while the lowest dosage used, 3.3×10¹¹ n cm^-2, induced 0.17 of chromosomal rearrangements per one cell. Irradiation with thermal neutrons is capable of inducing a large number of very complicated chromosome rearragements.

The effects of several growth and trophic substances on bud and root neoformation on leaf fragments ofBegonia rex were studied in precisely defined environmental conditions. IAA, depending on the type of treatment, had different effects. In aseptic cultures, a notable stimulation of bud formation was observed at certain concentrations. However, non aseptic treatments of IAA had no visible effects except at very high concentrations.(10^-3 M) where bud formation was totally inhibited and root formation was favored. NAA, at 10^-6 M and 10^-5 M strongly stimulated root formation and inhibited shoot formation. All the cytokinins used stimulated bud formation and inhibited partially or totally root formation. Gibberellic acid inhibited bud and root formation. Glucose and sucrose clearly stimulated bud and root formation and sucrose, when applied simultaneously with other growth substances, modified the effects of these substances alone. The most favorable environmental conditions were at 24°C in a 24 h photoperiod but other temperatures (17 to 27°C) and photoperiods (9 or 16 h) did not prevent neoformation.

Virus particles (approximately 73 nm in diam.) usually showing an inner capside (45 nm in diam.) and similar to diplornaviruses, esp. reoviruses, were found in some cells of enations inAvena sativa andArrhenatherum elatius leaves infected with the oat sterile dwarf disease (OSDD). (The same virus particles were described by the authors in 1966 in the leafhopper vector.)
Mycoplasma-like microorganisms found in1969 in the OSDD leafhopper vector were absent in OSDD infected plants. Tetracycline did not affect symptom development in plants and did not alter the infectivity of the vector.
Therefore, OSDD is apparently of virus origin; mycoplasmas-like bodies found formerly in the OSDD vector are probably not involved in OSDD etiology.

Studying the influence of the pH of 10% NaCl solutions used for the extraction of RNA and DNA on the yield of both nucleic acids, the maxima of pH were found at which both types of nucleic acids pass into extracts better than at neutral pH and do not remain in residues of the experimental material.The perchloric acid extraction temperature was also studied for obtaining the hydrolysate of nucleic acids from the trichloroacetic acid precipitate of sodium chloride extracts differing by 5 °C within the range of 35 °C to 90 °C and it was found that in this wide range almost the same amount of RNA is extracted by the method used. However, at a lower temperature, some DNA remained in the extracted residue of the trichloroacetic acid precipitate of sodium chloride extracts.

The meioses of four sterile species in the genusAllium which develop bulblets in the inflorescences instead of seeds were compared, namelyAllium sativum, A. cepa var.viviparum, A. carinatum, andA. oleraceum. The most important of them,A. sativum, is an ancient cultivated plant and its vegetative reproduction prevents it from more rapid evolution such as is known in generatively propagated cultivated plants.A. sativum shows fully normal meiosis. After the disintegration of the tetrads, however, the blockade of 1. pm takes place. The cause of the blockade has not yet been cleared up. Removing of bulblets appeared as having no influence on the development of microgones. It is assumed that there may be a viral phenomenon causing a disease of the tapetum without disturbing other functions. InA. cepa var.viviparum there was observed a heavy aberration disturbance in the meiosis, which had already been signalled by the mitosis. On this ground 1. pm does not occur and sterility is fully justified. The aberration disturbance does not seem to spoil the vegetative development but on the contrary to give it a vigorous character.A. carinatum andA. oleraceum are triploid and tetraploid forms; in the meiosis they form various configurations-univalents, bivalents, trivalents, and quadrivalents. The following irregular chromosome distribution results in the coming into existence of variously valuable gametes. 1. pm takes place. There is a theoretical possibility of generative reproduction (after the extirpation of bulblets).