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.

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.

Metabolites of indolepyruvic acid and indolelactic acid were investigated using 2 systems: a bacterial (pea stem homogenates containing the epiphytic bacteria) and a plant system (pea stem sections under sterile conditions). The products of spontaneous indolepyruvic acid decomposition in aqueous solution and during chromatography were investigated, too.
Biological indolepyruvic acid conversion yields, besides those substance amounts which occur spontaneously, indoleacetic acid, indoleethanol (tryptophol) and (only in the sterile plant system) indoleacetaldehyde. An inhibitor extract from pea stems decreases the indoleacetic acid and increases the indoleethanol and indoleacetaldehyde gain.
Indolelactic acid is not metabolized in the sterile plant sections. Indolelactic acid oxidation by the bacteria-containing homogenate yields indolepyruvic acid and is inhibited by the inhibitor extract.

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.

A study was performed on the effect of various concentrations of IAA, 2,3,6-triiodobenzoic acid, and maleic hydrazide, supplied to Richter's nutrient solution, on growth of pea plants in water cultures. After a 18-day cultivation growth was evaluated and in the plants gathered the content of total N, P, K, and Ca was estimated.
Growth of experimental plants (as evaluated from fresh and dry weight) was affected by all three regulators in dependence on the concentration used. It was stimulated by lower concentrations and inhibited by higher, the production of both fresh and dry weight of the root system being stimulated by all IAA concentrations used.
The ratio of root dry weight to that of the entire plant was markedly increased after application of IAA and 2,3,5-triiodobenzoic acid, whereas when applying maleic hydrazide it was only slightly increased in comparison with control.
Stimulation or inhibition of growth induced by IAA treatment was accompanied by an accordingly increased or decreased accumulation of N, P, K, and Ca. Thus their utilization did not change in comparison with control. On the other hand, both inhibitory and stimulatory effects of 2,3,5-triiodobenzoic acid and maleic hydrazide on growth were associated with a relatively lower accumulation of the elements in question, resulting in an increased utilization.
The distribution index of N, P, K, and Ca decreased with increasing concentrations of IAA, 2,3,5-triiodobenzoic acid and maleic hydrazide. Only the highest 2,3,5-triiodobenzoic acid and maleic hydrazide concentrations used brought about a more marked increase in the distribution index of potassium, simultaneously with a marked decrease in the distribution index of calcium.

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.

When comparing conductivity in 5 mm long segments from the basis of the primary seminal root with that in segments from adventitious roots of the first to fifth node it was revealed that the conductivity is not a general function of the transection area. The conductivity determined experimentally is minimal in the primary seminal root and gradually increases in the adventitious roots. However, when calculating per area unit, roots of the first coleoptile node appear the most efficient, with roots of the second and third node the values gradually decrease, and conductivity in roots of the fourth and fifth node approximately equals that of the primary seminal roots.
The conductivity is not a function of the conducting area. The conducting capacity of tissues which do not function directly as conductors is substantially lower; however, they cannot be neglected in evaluating the conductivity because of their high percentual occurence. The total conductivity in the individual root types is influenced by the ratio of the participation of water-conducting and non-conducting tissues.

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 authors succeeded in demonstrating accumulation of tyrosine and p-coumaric acid in three day-old roots of maize (Zea mays L.) fed with L-phenylalanine and einnamie acid. Phenylpyruvic acid applied under the same conditions gave rise to phenylalanine, indicating the presence of the corresponding transferase activity. Even simultaneous application of inhibitors of transaminase activity - hydroxylamine and isonicotinic acid hydrazide - did not result in the formation of p-hydroxyphenylpyruvic acid.

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.

Changes in soluble sugar content in individual parts (embryo, endosperm and pericarp) of maize caryopses exposed to the influence of 24°, 10° and 6° were studied. At the same time the eluates from sand in which the seeds were planted and exposed for various periods were analysed by paper chromatography.
It was found that the lower was the temperature of exposure the greater were the amounts of sucrose, glucose, raffinose and other sugars diffused from the caryopses into the medium before the start of germination. The exosmose course and the changes in sugar content in kernel tissues proved that the hydrolysis of storage polysaccharides is not inhibited by low temperatures but that under such conditions the use of products of hydrolysis for the growth of the embryo is inhibited.
It is concluded that not only surface parts of endosperm but also the embryo participates in exosmose. The relatively high sugar exosmose found from seeds germinated at low temperatures explains the well-known interaction of pathogenic and parasitic microorganism in cold resistance during emergence.

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.

The root cap develops out of the cells of the caliptrodermatogen. The root apex belongs to the first of Haberlandt's histogen types. The velamen usually consists of three layers of cells, and develops out of the protoderm by periclinal divisions. Funnel-shaped cells later divide tangentially into two cells, and in one of these cells a fibrous body develops. Two to four thick-walled cells alternate, usually with one passage cell in the exodermis. The cortex proper consists of approximately ten to twelve layers of parenchymatic cells in the mature root. There are eight to sixteen xylem poles alternating with the same number of phloem poles in the central cylinder.
In the roots ofDendrobium cunninghamii I observed two types of mycorrhizal infection, which can be classified as transitive types between ptyophagus and tolypophagus mycorrhizae. In my opinion, a state of balanced symbiosis exists between the fungus and the plant; a part of the time the plant acts as a parasite on the fungus.

Evidence for the effect of sterols on plant mycoplasma is presented. Two essential sterolsi.e. cholesterol and stigmasterol were applied in the following way: grafts from tomato plants infected with potato witches'broom, wedge-shaped at the base were dusted on the cut surfaces with the corresponding sterol in the amount of 4 mg to one graft, inserted in freshly cut wedges of stock plants and firmly tightened with rubber tubes. Both sterols stimulated growth of diseased grafts and delayed symptom manifestation. The stimulation was more evident with stigmasterol and the delay in symptom manifestation and intensity was more distinct with cholesterol. Supplying tomato plants with sterols externally probably enables additional multiplication of mycoplasma in already infected grafts, and the plants need not provide the grafts with essential metabolites which they themselves need for the development of reproductive organs. Stigmasterol, a metabolite peculiar to the tomato plant, is probably more rapidly consumed than cholesterol which may remain in the plant as a metabolic pool of sterols for mycoplasma propagation.

Tryptophan, tryptamine, or indolepyruvic acid were applied to 2 systems: a bacterial (pea stem sections containing the epiphytic bacteria) and a plant system (pea stem sections under sterile conditions).
In the plant system, the production of indoleacetic acid and indoleethanol (tryptophol) from each applied indole derivative is clearly reduced by the aldehyde reagents bisulfite and dimedon, respectively. Indoleacetaldehyde is chromatographically detected after alkaline liberation from its bisulfite addition product.
In the bacterial system, the production of indoleacetic acid and indoleethanol is likewise reduced by bisulfite and dimedon. However, after tryptophan or tryptamine application, we could not detect indoleacetaldehyde in the described way.
In one case only, namely tryptamine application to the bacterial system, indoleethanol production (contrary to indoleacetic acid production) is scarcely reduced by the aldehyde reagents. This indicates a bacterial pathway tryptamine → indoleethanol which bypasses indoleacetaldehyde.