We studied the significance of actual accessibility of ions for presence of α-amylase in roots and cotyledons of young pumpkin plants. We considered α-amylases to be-in agreement with published data-amylolytic enzymes which lose their activity after being dialysed against EDTA or a dilute solution of hydrochloric acid and which can be reactivated by addition of Ca²⁺. N connection with activity and Ca²⁺ nutrition appeared in cotyledons; it did, however, in roots: Ca-deficient plants revealed after preparation either completely inactive enzymes or enzymes with slight activity. It was, however, possible to reactivate them by addition of Ca²⁺ during preparation.
So, using polyacrylamide disc electrophoresis we present evidence for the appearence of amylase with typical characteristics for α-amylases of other sources. Its relative mobility was the same for isolates from both roots and cotyledons. Its biosynthesis was not dependent upon metal which is associated with enzyme. No conclusion can be drawn as to whether Ca-deficient α-amylases are activein vivo; therefore it was impossible to judge whether α-amylase activity is subject to feed-back regulation.

The effect of phenols and simple phenolic glycosides on the activity of IAA-oxidase isolated from gherkin seedlings was studied in experimentsin vitro. Phenol stimulated the enzyme system activity, eugenol and quinol were proven as inhibitors. Simple phenolic glycosides (arbutin, gein and phenol glucoside) influenced IAA-oxidase activity only if β-glycosidase was present: rree phenols released from their bound form increased or decreased the IAA level. The potential fegulatory effect of simple phenolic glycosides on the IAA level in plants has been discussed; this effect is thought to be mediated by free phenols and by influence on the IAA-oxidase system.

The present paper deals with the possibility of using growth regulators for the physiological emasculation of rye flowers and utilizes our knowledge of the higher sensibility of stamens to the auxin level. By means of bioassays it has been found that a relatively low content of auxins and a definite level of gibberellins and inhibitors are characteristic for normal rye spikes at the time of stamen differentiation. The higher level of auxins and expressive inhibitions occur in the later course of pistil differentiation.
Two sprayings of plants with mixed solutions of MH and NAA and two further sprayings with a solution of NAA only before the stamen differentiation change slightly the natural character of endogenous regulators in spikes and cause the destruction of mother pollen cells in anthers and the sterility of anthers in the majority of rye florets. The anthers in the basis of spikes sometimes contain pollen grains after treatment, but their fertility is substantially lowered because the spray evidently disturbed the accumulation of reserve substances in pollen grains. The development of pistil was not affected by the exogenous application of growth regulators. Normal kernels arose in the majority of flowers after supplementary pollination. Some accidental effects of exogenous application of growth regulators, as for example reduced stem growth and disorder of lodicule function were lowered to a great extent by adding GA_S to the last two sprayings of NAA.

The effect of phenolic substances isolated earlier from cabbage, maize and pea on L-tryptophan-3-¹⁴G (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-coumarie acid (PCA) from maize in 0.7 mg/ml concentration and quercetin-glucosyl-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^-3 M) 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-indolylaeetamide. 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.

Separate selection indices were constructed for various combinations of selective characters, in which together with components of economic yield also four separate subcharacters, yield prerequisites were used, namely: flag leaf area, length of the flag leaf, angle of the second leaf (from the top) and length of plant at heading time. Maximum genetic advance in weight of grains per plant (yield) from selections may be expected in selection indices in which three economic yield components together with flag leaf area or angle of the second leaf were used.
When as criteria for selection the flag leaf area together with yield components were used, selection indices with six different sets of economic weights for yield and weight of one grain were also computed. For the ratio of economic values 1∶1, the total expected advance was the highest, but separate advance in yield was approximately only 57% in comparing with selection made according to yield as complex character. For the ratio of economic values 1∶0.03 to 1∶0 the expected genetic advances in yield were about 22 and 24 per cent higher in comparing with selections according to yield. It may be expected that yield improvment will not be acquired by means of a great number of small, inferior grains.

Seedlings of horse chestnut (Aesculus hippocastanum L.) originating from two different localities were cut into several parts in which the tin content was estimated. When expressed per dry weight unit the vegetative parts of plants contain about 9 μg Sn per g dry weight, its content in apical parts of stem and root being still higher. This gives evidence of good mobility of tin in the plant.

Decreased accumulation of elements, particularly of nitrogen, had in dense stand a negative influence on the plants, in spite of the supply of fresh solution and the control of the concentration of nutrients in the pots. The fresh weight and the dry matter of one plant were reduced substantially with rising stand density (from 5 to 10, 20, 40 and 80 plants per 450 sq. cm); the RGR value, the relative absorption rate I_M, the content of all tested elements calculated per one plant, the chlorophyll content in the overground parts of one plant, and the distribution index decrease. Qualitatively the same influence is caused by deficiency of nutrients. Plant dying and self-thinning of the culture occurred in denser stand in the course of cultivation. The root-weight ratio rose with stand densification, particularly at the end of the experiment. The net assimilation rate (NAR) related to chlorophyll dropped with stand density; NAR at density "80" rose slightly from the 22nd day of cultivation and did so at further lower densities. Almost all NAR values lie over the control value at the last measurement. The chlorophyll content in mg g^-1 dry matter of the overground parts rose with stand density to density "40" (41% more than at density "5"); afterwards it dropped. The accumulation (in mg g^-1 d.m.) of phosphorus ions was higher in the plants from dense cultures compared with density "5", particularly in the roots. The accumulation of potassium was near to the control value ("5"), while that of nitrogen was lower. The utilization quotients of phosphorus and potassium in denser stands were the same or negligibly lower than at density "5". They were a little higher in nitrogen than in the controls. Also the ratio RGR/I_M was a little higher than in denser stands. The root-weight ratio, the accumulation of elements in mg g^-1 d.m., the chlorophyll content in mg g^-1 d.m., NAR_ch, the utilization quotient, and the ratio RGR/I_M differed qualitatively by the densification of the culture (with complete mineral nutrition) from the influence of element deficiency (at the same stand density).

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).

Intensity of transpiration, intensity of water absorption, water saturation deficit (w.s.d.) in different parts of samples and rate of water transport was investigated in samples from leaf tissue of fodder cabbage and banana-tree.
In all experiments (at initial w.s.d. 0% and 20%, in samples from upper, middle and lower leaves of fodder cabbage and from leaves of banana-tree) a distinct gradient of w.s.d. in the direction of transport of water was determined, therefore the limiting factor in the water balance was rate of water transport and not rate of water absorption.
The lowest amount of water was always transported within transpiring part of sample. When the initial w.s.d. was 0% not only the water transported by tissue from the environment, but also the water of the leaf tissue itself took part in water lost by transpiration and therefore water stress originated in the whole sample. At an initial w.s.d. of 20%, the rate of water absorption was higher than the rate of water transport and therefore the increase of w.s.d. in the transpiring part of the sample was accompanied by a simultaneous decrease of w.s.d. in the transporting part.
An increase in the value of w.s.d. in leaf tissue proportionally increased the resistance of water transport in the liquid phase (on the average from 1.7 . 10³ to 6.7 . 10³ atm min cm² g^-1) and also in the gaseous phase (on the average from 2.7 . 10^-2 to 14.0 . 10^-2 min cm^-1).
It was proved that insufficient rate of water transport can be responsible for the origin of water stress. At the same time the rate of water transport was influenced by the value of the w.s.d. since every change of w.s.d. in leaf tissue not only the gradient of water potential changed but also the resistance to water transport.

A new porometer operable in field conditions was used to study air passage capacity of maize(Zea mays) leaves in relation to light intensity, temperature and ferilization. In addition to light intensity, temperature was found to affect stomatal movement in a significant manner.