4-phenethylpyridin favours pentose cycle in glycide degradation inSinapis alba seedlings. The influence of the tested compound on following enzymes: hexokinases, saccharase, phosphorylase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase and phosphoglucoisomerase was studied. In roots of treated seedlings a substantial increase of pentose cycle enzymes was found together with the corresponding increase in glycide content. The increased activity of phosphoglucomutase may be explained by the chromatographically detected presence of stachyose in the seeds which as the source of galactose enables the formation of glucose-1-phosphatase.

Water potentials of leaves from well-watered plants were measured. There were species-specific differences in both the total and the osmotic potentials of pea (Pisum sativum), tradescantia (Tradescantia versicolor), rose (Rosa hybrida), bitter lemon (Citrus aurantium) and olive (Olea europaea). With tradescantia the potential measured after the destruction of turgor by freezing was less negative than before, a result which suggests that the value obtained is not identical with the real osmotic potential of the leaf. detached leaves of all species showed less negative water potential readings, and those of pea even a less negative osmotic potential, when cut into five pieces than when measured intact. Application of vaseline to the cut surface of the leaves reduced this effect with rose and olive, though not with tradescantia and pea. Measurements were also made of the water potentials of comparable leaves of tradescantia and bitter lemon, attached to and detached from their plants; when bitter lemon leaves were detached and watered through their petioles which protruded outside the thermocouple chamber, their potential became considerably less negative than when the same leaves had been attached to well watered plants. However, similar leaves whose cut petioles were introduced into the thermocouple chamber registered an even less negative potential.
The results are consistent with the hypothesis that when a leaf is cut off a plant, and even more so when it is cut into sections, the water previously held by matrix forces becomes available to dilute the "spilled" cell sap and to be absorbed by adjacent cells and thereby to increase their turgor and render the net water potential of the leaf less negative. Similarly, the apparent negative turgor of the succulent, tradescantia leaves is likely to be due to dilution of the osmotic component by cell wall water. The discrepancies between the readings of attached and detached leaves indicate a considerable whole-plant matrix component, and the results as a whole suglest that thermocouple psychrometer readings carried out on detached and even more on cut-up leaves may be artifacts and that it is desirable to determine water potentials on leaves attached to their plants.
The work was supported by a Government of Israel Fellowship and was conducted at the Department of Pomology and Viticulture, Faculty of Agriculture of the Hebrew University of Jerusalem, Rehovot, Israel.

When studying the determination of nucleic acids in pollen based on extraction with hot 10% NaCl, further factors influencing the results were observed. Prolongation of the homogenization from 3 to 5 or 7 min caused considerable loss of DNA in extracts. On using trichloracetic acid to precipitate nucleic acids from the NaCl extracts, higher final values for the sum of nucleic acids were obtained than by precipitating with perchloric acid.

Experiments were aimed at checking whether the non-stratified apple embryos are sensitive to growth factors and light. The effect of growth regulators on light sensitivity was also studied. The stimulating or inhibiting effect of GA3, benzyladenine and IAA or coumarin on the dynamics of apple embryo germination was demonstrated. Seasonal fluctuations of the effect of the growth factors were noted. The stimulating effect of light on the germination of non-stratified apple embryos was demonstrated. This effect is independent of season and seems to be independent of the effects of growth regulators.

Our paper describes some morphological peculiarities ofMycoplasma bodies located in vascular bundles ofNicotiana glaucaGrah. and tomato infected with potato witches' broom disease. The influence of postfixation on the density of bodies and possible development of artifacts was studied in particular. It was found that bodies of adjoining cells may have a different shape. Also elementary bodies, approximately of uniform diameter, may occur in masses in close proximity to the cells containing "adult"Mycoplasma bodies. Deformed large bodies giving in a certain position the impression of "vacuolization" are evidently degenerated saucershaped forms. In addition toMycoplasma some other bodies with different inner structure were observed in the same cells.

The intact seeds ofPsoralea corylifolia which are actieually one-seeded fruit, presents a unique problem of dormancy. Germinability of these dormant seeds is not enhanced as a result of a number of treatments: 1) Dry-storage of 44 months under moderate conditions of the laboratory. 2) Periodic germination in different months of the year. 3) Immersion in ethylalcohol (70% and 100%), hydrogen-peroxide, nitric acid, acetone, ether solvent and hydrochloric acid. 4) Removal of pericarp.
Four distinct methods have also been evolved which effectively overcome the dormancy of the seeds: 1) Mechanical puncturing of seedcoverings. 2) Sulphuric acid treatment. 3) High temperature treatment. 4) Weathering of seeds.
Germination-behaviour of the latter 4 lots of seeds is compared and ecological significance of the reported dormancy mechanism is discussed.

The dynamics of the germination and formation of lateral roots under constant conditions were studied in pea Pisum sativum L., cv. Pyram. Various parameters of the above processes were evaluated statistically. The time at which the germination proceeds at the maximum rate was found to be 24.9 h from the start of the imbibition of seeds. The standard deviation of the germination time of an individual seed from the time corresponding to the maximum of germinated seeds was found to be 4.0 h. The formation of the lateral root primordia took place at 54.2 ± 2.9 h. At 73.5 ± 5.5 h from the beginning of the experiment, laterals on the surfaces of primary roots of seedlings became apparent. Differential curves of the distribution of the above processes were plotted graphically. The data obtained are valid for the given conditions and given experimental procedure. The methods described can be used in studies of primary root branching in various plant species.

The influence of GA and CCC on endogenous estrogens content in beans was investigated. The experiments were conducted in two variants analysing the amounts of estrogens 12, 24, 48, 96 h after application, and in the specific stages of plant development. The lack of influence of GA and the lowering of estrogens content under the influence of CCC was observed.

Apical buds ofChenopodium rubrum from plants treated with CCC contain more endogenous auxins than buds from control plants, the level of these compounds increasing with the application of rising concentrations of the retardant. An especially marked increase was observed in the level of substance "X" which on chromatographic separation runs in the zone of tryptamine or its derivative. Since it has been shown in previous experiments that the inhibitory effect of CCC on flowering ofChenopodium rubrum may be reversed by indole-3-acetic acid (IAA) it is believed that the increase in auxins after application of CCC does not concern biologically active substances immediately available to the plant. It seems more likely that inactive precursors are involved which cannot be converted to the active substance in the presence of CCC, possibly due to blocking of the pertinent enzyme. If we assume that the wheat coleoptile used in the auxin bioassay in our experiments contains the pertinent enzyme it might convert the inactive precursors to active substances and, therefore, exhibit a growth stimulation even though the substances concerned would not necessarily be active in the buds from which they were extracted.

The addition of boric acid or calcium, or both boric acid and calcium to the warm water in which the styles were treated led to a further enhancement of pollen tube growth in otherwise incompatible styles.
It was established that developing pollen tubes ofOenothera organesis obtain sugar from the stylar tissue through which they grow. The rate of this utilization of endogenous sugar was stimulated by the addition of boric acid.
It was further established that with increased pollen tube development there was reduction in callose plugs as well as in content of endogenous stylar sugar.

Growth correlations in leaves ofBryophyllum may be recognized by the development of marginal shoots varying in their particular lamina regions, the correlative inhibition increasing from the top to the base. Cytokinins extend their promoting action inB. crenatum leaves farther in the apical than in the basal direction. In the uppermost leaves ofB. daigremontianum they evoke the development of marginal shoots with flowers in the apical and of vegetative shoots in the basal region. Less suitable for this research are auxins, gibberellins, and triiodobenzoic acid which are unable to stimulate the development of marginal shoots on leaves grown out under short days if not supplemented by cytokinins. Only TIBA induces under long days formation of adventitious shoots directly from the lamina surface on leaves developed below the terminal ring fasciation exhibiting at free ends of connate leaves normal marginal shoots. Under short days a complete reduction of lateral teeth takes place inB. verticillatum both on the extremity of ring fasciation and on the uppermost leaves, the marginal shoots being formed under the subsequent long days only in the angles between the ring fasciation parts. Furthermore the correlative inhibition of the leaf causes anisophylly in marginal shoots in the same way as that of axillaries inBryophyllum.

The influence of decrease of water absorption rate on the transpiration rate and the development of water saturation deficit (WSD) was studied on the leaf segments of kale. Solutions of polyethyleneglycol (0-25m, 0-50m, O-75m and 1-00m) and mannitol (0-50m) were used as osmotic agents.
The rate of water absorption decreased to zero when the concentration of polyethyleneglycol was 0-25m. At a concentration higher than 0-50m, water from the tissue diluted the external solution. The transpiration rate of samples affected by polyethyleneglycol or mannitol was only a little lower than that of control samples. WSD was noticeably increased only in the absorbing part of segment; in the adjoining, transporting part of segment WSD was practically the same in all variants. WSD in the transpiring part was slightly increased only in some cases. Due to decrease of osmotic potential of the external solution also the gradient of water potential changed. In the case of absorption from pure water, water potential gradually decreased from the absorbing to the transpiring part. Under the influence of polyethyleneglycol or mannitol solution the highest water potential was in the transporting part and from this point water potential decreased to both opposite sides.

Embryogenesis occurred in carrot root callus (Daucus carota L.) cultivated on simple synthetic medium containing IAA and 2,4-D. Embryoid development continued also during successive years when the tissue was cultivated on the same nutrient medium without those substances. Sometimes production of plants with atypical leaves was also observed. In those plants development of adventive embryoids occurred repeatedly. Result of this work confirmed reports about the organogenic potentiality of this species and about its sensitivity to some chemical substances.

A study was performed on the influence of obligate parasitesErysiphe graminis Dc. andPuccinia hordeiOtt4 on peroxidase activity in barley leaves, namely in both susceptible and resistant varieties. Attention was also paid to peroxidase activity in a susceptible wheat variety infected withPuccinia striiformisWest.
The following results were obtained:
In leaves of wheat and harley plants an enzyme was revealed which oxidized pyrocatechol and guajacol only in the presence of hydrogen peroxide. This enzyme can be inactivated by heating and strongly inhibited by cyanide. Evidently peroxidase is concerned.
Peroxidase in susceptible varieties of wheat and barley is markedly activated after infection with parasites mentioned above, this activation reaching maximum at the periode of parasite sporulation. On the other hand the barley varieties resistant toE. graminis andP. hordei, exhibit only a slight or no increase in peroxidase activity at this period. Thus we come to the conclusion that peroxidase does not probably appear to be the cause of the resistance of these varieties. It seems that in tissues attacked by obligate-parasites the intensity of its activation can be a result of the infection intensity.

Positive linear correlation between the resistance to water transport in liquid phase and water saturation deficit (w.s.d.) in the tissue ofBrassica oleracea andNicotiana tabacum leaves was observed. At the same values of w.s.d. corresponding values of the resistance to water transport were higher when dehydration of the leaf tissue occurred during the experiment and lower when water balance was in equilibrium or resaturation of the leaf tissue occurred.

The intensity of water uptake by halves of splitroot cuttings fromColeus blumeiBenth was measured by potometrical method. Inhibition of the water uptake induced by application of high concentrations of sodium salts of α-naftylacetic acid (NAA) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the treated half of the root induced an increase of water uptake by the other half. The compensation is not complete. If only one half of the root treated by synthetic auxin was allowed to take up water, MCPA appeared to induce a smaller degree of reversibility than NAA.

CCC (2-chloroethyl)trimethylammonium chloride applied to plants ofChenopodium rubrum during floral induction led to an increase in the level of endogenous cytokinins in the apical buds. Application of gibberellic acid or indole-3-acetic acid at concentrations reversing the effect of CCC reduced the level of cytokinins. After simultaneous treatment with both CCC and one of the growth substances this reduction was less pronounced. From the comparison bf the present results, as well as of those published in previous papers it follows that in apical buds ofChenopodium rubrum there exists a mutual interaction between gibberellins and cytokinins. Under certain conditions both these groups of hormones may substitute for each other in flowering. IAA seems to affect flowering by regulating the level of both gibberellins and cytokinins.

The methyl-ester of 2-chloro-9-hydroxyfluorenole-9-carboxylic acid (Chlorflurenol-Methyl =CFM) enhances the elongation of intact plants ofColeus blumei and induces leaf curvatures and an anormalous abscission of the youngest leaves. In long-time-experiments (3-4 month), CFM induces increased outgrowth of the axillary buds including leaf deformations and abscission of organs on the originating shoots. CFM stimulates the adventitious root formation of cuttings fromHelianthus, Phaseolus, andColeus. It is shown inColeus cuttings that an inhibition of root formation precedes the stimulation of root formation. Gibberellic acid does not influence any one of CFM-induced effects. Therefore morphactins are not GA₃-antagonists. TIBA qualitatively causes the same effects as CFM. Therefore it is possible that the mechanisms of actions of both substances are similar.

Maize mosaic and stunt, occurring to a considerable degree under Cuban field conditions, was determined as a virus disease, transmissible by the corn planthopperPeregrinus maidis Ashm. Negative results were obtained in the experiments in which aphidsRhopalosiphum maidis Fitch, served as vectors or when transmission was realized mechanically using the sap of infected plants. The incubation period in the infected plants fluctuated between 15 and 27 days. Besides maize, the virus disease could be transmitted also to sorghum(Sorghum vulgare Pees.) and to weed plants of the grassRottboellia exaltata L. It follows from the results that the disease concerned is identical with virus stripe, described in 1927 in Cuba by Stahl as corn stripe (raya del maiz).
Under field conditions the disease spread fluctuated in average from 3.4 to 46 per cent of inflected plants. Plant communities concentrated on larger areas which received good agro technique and chemical protection against pests exhibited lower infection for the most part The most suitable time for the determination of spread and infection intensity under field conditions is that shortly before and during flowering of maize.

The transamination activity in five or seven days-old poppy seedlings (Papaver somniferum L. cv "Váhovecký") germinated in darkness or light was studied. The changes in L-phenylalanine:-(E.C.2.6.1.5), aspartic acid:-(E.C.2.6.1.1), and L-ornithine: α-oxoglutarate transaminase (E.C. 2.6.1.13) were followed and correlated with duration and conditions of cultivation.

The effect of phosphorus deficiency on anthocyanin content in tomato plants was studied from the point of view of pathological anthocyanin formation. Phosphorus deficiency resulted in an evident increase of anthocyanin content in all experiments, independently of the tomato variety and of the cultivation conditions. The anthocyanin amount was five times higher on the average and the differences were statistically significant. The average growth inhibition of tomato plants under phosphorus deficiency was 18%. Accumulation of anthocyanins is limited by the temperature; anthocyanins are not synthesized at temperatures above 30°. The results of the experimental variant with enhanced phosphorus concentration in nutrient solution were not uniform. In some experiments a decrease of anthocyanins accompanied by slight growth stimulation was observed, in others an increase associated with growth inhibition. It seems that cultivation conditions, especially the light intensity, play an important role in these experimental variants.

Populations of theChloretta vulgaris Beijeb. strain Česnokov "V" clones (progenies of single cells) grown up from cells treated by chemical mutagens were cultivated on the surface of solid media. The differentiation of growth types according to their growth rates in the populations originating from the same sample of cells but growing under different conditions was compared. The strain studied exhibited much greater growth rate variability on the complete medium than on the minimal one. Short time changes of light regime during the cultivation for the purpose of inducing reparation processes in the mutagen damaged cells did not manifest themselves significantly in the composition of resulting clonal populations. The possibility of selection of growth types under conditions studied was considered.

The effect of phenolic substances isolated earlier from cabbage, maize and pea on L-tryptophan-3-¹⁴C (L-Try-¹⁴C) metabolism in those plants was investigated. For the sake of comparison the effect of diethyldithiocarbamate (DIECA) on cabbage was also observed. A phenolic substance of unknown structure isolated from cabbage was utilised in a 0.5 mg/ml concentration, p-coumaric acid (PCA) from maize in 0.7 mg/ml concentration and quercetinglucosyl-coumarate (QGC) found in pea in 8 mg/ml concentration were used. The chosen concentrations were on the limit of their inhibitory effect on the growth of the respective plant apical segments. The effect of DIECA was investigated at 0.1 mg/ml concentration. Using non-labelled L-Try as substrate (5×10^-3m) biological tests have shown that QGC and DIECA have a weaker but distinct effect on the increase in auxin level (+17% and +15%, respectively). All phenolic compounds, as well as DIECA increase the intake of L-Try-¹⁴C from the incubation solutions. Phenolic substances decrease the conversion of L-Try-¹⁴C to its metabolites. The changes were studied after a 20 hour period of L-Try-¹⁴C metabolism. On chromatograms changes in the proportion of L-Try-¹⁴C metabolites took place, especially in the areas of substances of complex character from which IAA splits off easily,i.e. in the areas of 3-indolylacetylglucose and 3-indolylacetamide. The radioactivity of these areas is generally decreased (e.g. the decrease of radioactivity in the 3-indolylacetylglucose area under the influence of the phenolic substance ofBrassica plants is -7,4%, under the influence of PCA in maize it is -8.9% and under the influence of QGC in pea it is -17.1%). DIECA also decreased the radioactivity of this zone, by -10,5%. In cabbage a large part of L-Try-¹⁴C was transformed to glucobrassicin; its biosynthesis increases in the presence of the phenolic substance of cabbage by +3%, in the presence of DIECA by +27%. The results are discussed in a working hypothesis based on the key formation of IAA, accompanied by its oxidation and detoxication.

Using electrophoresis in acrylamide gel, fractions of peroxidase, indoleacetic acid oxidase, and o-diphenol oxidase were investigated in extracts from three growth zones ofVicia faba L. roots. Three peroxidase fractions (zones) moving towards the anode were revealed as well as four peroxidase fractions (zones) migrating towards the cathode. Three peroxidase fractions showed detectable indoleacetic acid oxidase activity. The o-diphenol oxidase activity was revealed in all peroxidase fractions moving towards the anode, in those moving towards the cathode the o-diphenol oxidase activity differred according to the substrate used. One fraction with both peroxidase and o-diphenol oxidase activity occurred only in electrophoreograms of extracts from the maturation zone; in this fraction no indoleacetic acid oxidase activity was demonstrable.

Maize caryopses were exposed in moist, sterile sand to temperatures of 24°, 10° and 6°. The amino acid content of embryo, endosperm and pericarp tissues of kernels and amino acid occurence in sand eluates was analysed by paper chromatography.
The lower the temperature to which the seeds were exposed and the greater the delay in start of germination, the greater were the amounts of amino acids exosmosed from the kernel to the surrounding media. The exudation of aspartic acid, proline, alanine, γ-aminobutyric and glutamic acids was especially high.
The time-course of amino acid content in various kernel parts proves that cold does not check the enzymic hydrolysis of reserve nitrogen compounds. There is, however, an inhibition of translocation and use of amino acids in the embryo. Therefore, amino acids diffuse out from the caryopse into the media. Although mainly the peripheral parts of endosperm take part in exosmose, participation of the embryo in the exudation of certain amino acids (proline) can be supposed as well.
In cold resistance of emerging maize kernels the remarkable interaction of microorganisms is causally related to the high amino acid exosmose found in these experiments. The mechanism of amino acid exosmose and its relationship to cold resistance are discussed in detail.

The rate of carbon dioxide evolution, respiration quotient, and the rate of liberation of heat were determined on the 3rd day of germination of wheat seeds. The seeds were germinated with pure water (control) or they were transferred for a 5-hour period to a solution of dinitrophenol, sodium arsenate, sodium phosphate or indole-3-acetic acid. The heat liberated was compared with the total energy released in respiratory processes of the seedlings, calculated from the gas exchange measurements. The amount of heat liberated for 1mm of carbon dioxide evolved and for 1mm of oxygen absorbed was definitely changed in the presence of the compounds used. However, the ratio of heat liberated to the total energy released in respiration of the seedlings changed only slightly.

The seeds, seed covers and leaves, taken after 17, 27, 37, and 47 days after tagging of flowers of soybean, were analysed quantitatively for their contents of different phosphorus fractions. Total phosphorus content increased in seed cover and leaves, there was a gradual decrease during ripening. All the phosphorus fractions i.e. acid soluble-P, lipid-P, nucleic acid-P, and protein-P were found to increase with maturity in seeds whereas in case of seed covers the content of acid soluble-P, nucleic acid-P and protein-P decreased but a marked increase was observed in lipid-P. In leaves during ripening, all the phosphorus fractions decreased except protein-P which was found to be almost constant. In lipid-P an increase was observed during later stages of maturity.

Beet yellows virus was transmitted by wingless aphidsMyzus persicae (Sulz.) after 16 hrs acquisition feeding on leaves covered with a Parafilm M membrane. Effectiveness of the virus transmission was decreased approximately to half of the original value by acquisition of the virus through the membrane. No virus was transmitted to healthy beet seedlings after 6 or 16 hrs continuous feeding on a concentrated suspension of the purified virus or on crude juice extracted from an infected plant (suspensions contained 15% of sucrose).

The paper deals with the effect of mineral nutrition on the content of free flavonoid glycosides (phloridzin, hyperine) free and bound C₆-C₁ aldehydes (vanillin, syringic aldehyde) in the woody parts of apple shoots of the variety 'Antonovka' and on the content of products oxidized by nitrobenzene (vanillin, syringic aldehyde) in connection with the lignification of cell walls.
It was established that the biosynthesis of phenolic compounds is retarded under the influenco of nitrogenous fertilizer while the biosynthesis of proteins is activated, intensifying growth. Contrary to nitric fertilizer, phosphoric with potassic fertilizers promote formation of phenolic compounds and suppress protein synthesis and growth; at the same time phenylalanine is included in the biosynthesis of lignin, but not in the biosynthesis of proteins.