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.

Whereas experiments directed towards proving the infectious character of the hop curl disease did not give reliable proof of its virus character (we have not been able to transfer it neither by cuttings nor by graft), but made possible its differentiation from the English nettlehead hop virus disease, the practical experiences and results presented in this paper show that nutritional conditions essentially affect the known variability of the external manifestations of the hop curl disease. Especially such nutrients play a role which with the normal fertilising techniques are not returned to the soil in sufficient quantity. Since the hop curl disease was noticeably inhibited in a nutritional field experiment on application of the salts of some elements, predominantly of B, Mg, Mo, Mn, Ni, I and Zn, it appears possible to apply "symptomatic therapy" of the hop curl disease, which could have wide practical importance for limiting this disease.
In order to supplement the provocation field experiments, comparative investigations of the chemical composition of the leaves from healthy and hop curl diseased plants were carried out. Quantitative analysis of the biogenic elements carried out by the usual methods and by polarography showed a regularly higher content of P, K, Ca and a lower content of Zn in the diseased plants as compared to healthy ones. The differences observed in the content of N, Na, Mg, S, Fe and Cu were not always in the same sense. Chemical analysis was accompanied by parallel spectral analysis of ash. This made it possible to obtain a considerably complete survey of the qualitative and approximately quantitative representation of a whole series of other elements in healthy and diseased plants; however, no characteristic differences were recorded.
Finally the results obtained in the present work are confronted with the findings of other researches, especially from Germany, and discussed.

The metabolism of D-and L-tryptophan-3-¹⁴C (Try-3-¹⁴C) was studied and compared for three different plant species, cabbage, maize and pea. Apical segments of the seedlings were incubated for 6 hours in solutions of L- or D-Try-3-¹⁴C (1.5 μc/ml) with the addition of chloramphenicol (10^-4g/ml) and then allowed to stand for another 20 hours in moist chambers. The methanolic extract of the tissues was analyzed radiochromatographically and by paper electrophoresis in combination with biological tests. Chloramphenicol in a concentration of 10^-4 g/ml had little influence on the growth of the segments, though the antibiotic slightly decreased the uptake of L-Try, it did not prevent the formation of IAA from L-Try. In the segments of cabbage the following metabolites were formed from L-Try-3-¹⁴C (accounting for 52% of the activity of the chromatographically separated extract): glucobrassicin (26.0%), neoglucobrassicin (3.6%), a spot corresponding according to its Rf to 3-indolylacetamide (IAAmide-10.9%), β-glucoside of 3-indolylacetic acid (IAGluc-3.3%) and traces of 3-indolylacetonitrile (IAN), IAA and indole-3-carboxylic acid (total 5%). In maize segments L-Try-3-¹⁴C (53.0%) was transformed to several unidentified hydrophilic substances, one of them possessing auxin activity (total amount 6.9%), IAGlue (9.3%) accompanied by a small amount of tryptamine, a spot corresponding according to its Rf to IAAmide (16.5%), IAA and another unidentified hydrophobic substance (4.1%). In pea segments L-Try-3-¹⁴C (66.7%) gave a zone corresponding according to its Rf to IAAmide (20.0%), a substance similar to IAGluc (10.5%) and also hydrophobic substances (3.1%) containing traces of IAA, which could be demonstrated only by bioassay.
D-Try is metabolised in the three plants by the virtually exclusive formation of malonyltryptophan.

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.

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.

Phosphorus-nitrogen compounds characterized by the direct P-N bond, represented by trimeric and tetrameric phosphorus nitridoamide-[PN(NH₂)₂]_3-4, phosphorus oxytriamide-PO(NH₂)₃ and ammonium diamidophosphate-NH₄PO₂(NH₂)₂, were applied as fertilizers in a vessel experiment with barley and their agrochemical effectiveness was compared with that of ammonium phosphate-(NH₄)₂HPO₄. The results obtained indicate that the above compounds are of nutritive value for plants.

A method for determination of potato X-virus and tobacco mosaic virus in infected tobacco leaves was tested. The leaves are rubbed with isolated antibodies against homologous viruses and after 30 minutes incubation in a humid chamber at room temperature are washed with fresh distilled water 3 times. The leaves are afterwards rubbed with³⁵S-labeled pig gamma globulin against rabbit gamma globulin. The most convenient radioactivity of the labeled pig gamma globulin was 100 (µCi. Leaf discs 5 mm in diameter are punched out after half an hour incubation and their radioactivity is measured on a 27π window methane flow counter. The leaves from healthy plants are treated in the same way. The virus presence is presumed from the differences of radioactivity between healthy and infected leaves. If the mean radioactivity of the discs from healthy leaves equaled 100, the discs from potato X-virus infected leaves showed a moan value of 382.3%. This method can be used for estimation of virus distribution in the plant, and/or tracing its translocation.

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.

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).

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.

A study was performed on the interaction of cucumber mosaic virus (CMV) of potato virus Y (PVY) with tobacco mosaic virus (TMV).
Interference was evaluated using tobacco plantsNicotiana tabacum cv. Java responding to CMV and PVY with a systemic infection and to TMV with local necrotic lesions. The decrease in TMV - induced lesion number gave evidence of a decrease in susceptibility caused by the previous infection with CMV or PVY, the decrease of lesion enlargement demonstrated a decreased TMV reproduction in the plants previously infected with CMV or PVY. The interference concerned was incomplete, as evaluated from reproduction of the challenging TMV and from the decrease in susceptibility of the host to TMV brought about by the first infection with CMV or PVY.

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.

Relationship between roots and shoots ofPimpinella saxifraga L.,Petroselinum hortense Hoffm.,Lactuca sativa L., andBeta vulgaris subsp.esculenta (Salisbury) Gürke var.altissima Roessig was studied in irrigated and non-irrigated plants. It was found that the irrigation water did not influence distinctly the root-shoot ratio of the experimental plants. From the statical point of view, this relationship could be expressed by the following quantitative ratios for irrigated and non-irrigated plants: 3∶1 forPimpinella saxifraga L., 2∶1 forPetroselinum hortense Hoffm., 9∶1 forLactuca sativa L., and 1∶1 for beetroot. From the dynamic point of view it is possible to state that this ratio changes in the course of individual development. With plants cultivated for their aerial parts, it increased with age, while with plants cultivated for their roots, it decreased with age. The irrigation water produced much greater morphological changes (the shape and the surface area) in the root and shoot system of experimental plants.

Stomatal frequency in leaves of plants of Iris hollandica, cultivated under four light intensities, about 12%, 37%, 75% and 100% of natural daylight, was studied. The stomatal frequency decreases with lower light intensities. The gradients of stomatal frequency of successive leaves show an increase up to the third or fourth leaf with a subsequent decrease of values up to the highest leaf. The total number of stomata per leaf is not constant; differences exist in successive leaves of a shoot as well as among the leaves of plants growing under various light intensities. The character of gradients was changed at lower light intensities. The largest reaction to the light intensity appeared in leaves with higher stomatal frequency. The gradients in individual leaves depend on the insertion of the leaf. Both the shape and the slope of these gradients are influenced by the light intensity.

A reduction of stomatal aperture in light was found in leaves of maize after they had been treated with 10"3-5 m phenylmercuric acetate (PMA). Complete closure of the stomata in darkness was prevented, whilst there was total closure in the controls. Higher PMA concentrations had bigger effects. The relative water content (RWC) of barley tissues was slightly reduced 12 hours after treatment with PMA. The transpiration rate observed on PMA-treated barley plants was lower in light and higher in darkness than in untreated plants. Water saturation deficit (WSD) was higher by about 5%, and water holding capacity (WHC) lower (25%) than in untreated plants. The results suggest that the concentration of PMA normally applied as an antitranspirant is unfavourable for healthy growth of maize and barley.

Experiments with youngHordeum sativum andHelianthus annus plants showed that in the excretion of mannitol in the guttation liquid observed byGroenewegen andMills (1960) after uptake by the root system of plants, the osmotic concentration of mannitol in the nutrient medium and the temperature are significant. The beginning of mannitol excretion during guttation is accelerated considerably by the increase of the osmotic concentration of mannitol in the nutrient medium and the rising temperature. The osmotic concentration of mannitol is also important for the duration of mannitol excretion in the guttation liquid after transfer of the plants into a nutrient medium without mannitol. In the presence of mannitol in the nutrient medium water uptake by the root system and growth are inhibited and the tissues of the organs above ground and of the root system are dehydrated. The inhibitory effect of mannitol on the water uptake by the root system is immediate.

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.

A purified potato virus S was prepared using precipitation by the solution of 35% polyethylene glycol 4000 in the presence of an electrolyte. The mixture for precipitation of the potato virus S had to contain 11% polyethylene glycol and 0.25m NaCl. The S virus was extracted by 0.01m phosphate buffer, pH 7.5, from the precipitation separated by centrifugation. One part of the extract was further purified by means of differential centrifugation and the other by means of gel filtration on Sephadex G-100. The ultraviolet absorption measurements of both preparations showed that the differential centrifugation gave a purer preparation than the gel filtration.

Dispersing of splits of NaCl and KCl during the drying process has been found using labelled²⁴Na and⁴²K preparations. This bursting effect can cause some misinterpretations in biological experiments with plant material.

The following work deals with the role of auxin in growth and differentiation processes of isolated shoot tips ofZea mays L. It seems that an optimal auxin concentration is apparently a function of a photoperiod duration. In case of a short day the optimal concentration is approximately 5 mg/l and in case of a long day it represents 1 mg/l. The duration of photoperiod influences even the level of exogenous auxins in explants. The plants exposed to the short photoperiod contain more substances of stimulative character while the ones exposed to the long day possess inhibitive substances. Externally applied auxin takes part in differentiation processes, especially in the formation of female elements in tassel spikelets and in transformation of the tassel primordium in pistillate ear.

The effect of Ca-deficiency on changes in the protein content of cotyledons and roots of germinating pumpkin (Cucurbita pepo L.) plants was studied by means of immunoelectrophoresis. Antiserum against seed proteins gave 11 clear precipitation zones in homological reactions and 7 zones with proteins from cotyledons of 10 day-old plants. Several less mobile zones in the area of start appeared in variant "-Ca". Using antiserum against root proteins of 10 day-old control plants, 8 precipitation zones in the homological reaction and 6 zones (two cathodic zones are missing) in the heterological reaction were obtained. The patterns of proteins from the root and those arising from the protein of seed are both changed under Ca-deficiency.

A water-soluble germination- and growth-inhibitor present in plants of Brassica genus was studied. Aqueous eluates from chromatograms of methanolic extracts of Savoy cabbage, cabbage and Brussels' sprouts leaves, and of Brussels' sprouts roots, inhibited the growth of wheat; the chromatographic behaviour of this inhibitor was similar to that of the thioglycoside glucobrassicin (GLUBR). GLUBRat 10^-3 m, and the supposed product of its enzymatic degradation, 3-indolylacetonitrile (IAN) at 10^-4 m, inhibited the growth of wheat and clover in a similar manner. At lower concentrations, both substances gradually enhanced growth. In contrast to IAN, GLUBR did not appreciably influence the growth of Savoy cabbage. Other products of GLUBR degradation, such as thiocyanate ion and ascorbigen, influenced the growth to a lesser extent and in a different way. At higher concentrations GLUBR and IAN also inhibited the germination of clover seeds. The biological effect of GLUBR is dependent on the presence of the indole nucleus in its molecule; the thioglycoside glucoiberin, which is not of indolic character, does not influence growth. The presence of free myrosinase was shown in intact wheat seedlings. Hence, GLUBR taken in by the germinating plants must undergo enzymatic cleavage. The in vitro activity of myrosinase in wheat and clover was lower than in Savoy cabbage, but the quantity of IAN formed at a pH corresponding to the natural pH was higher in wheat and clover than in Savoy cabbage, where the formation of the growth-inactive ascorbigen prevailed. On the basis of these results the hypothesis was formulated that GLUBR, the indolic complex from the generaBrassica, Raphanus, Cochleria, Nasturtium, Barbarea andSisymbrium, is a representative of a class of potential inhibitors of growth and germination, whose activity can be explained by the liberation of large amounts of growth-affecting substances during their specific enzymatic cleavage.

The interactions between cereals-wheat, barley, rye and oats-in combined cultivation in mixtures of always two species in relation 1:1 in the initial phase of growth were studied. During thirty days' cultivation in pots the growth of the experimental plants in pure cultures and in mixtures and the changes of the nitrate nitrogen content of the soil in the experimental vessels were followed.
The experiments showed that all tested species of cereals interacted with each other during the growth in mixture. The growth changes began soon after sowing, were of a stimulating and inhibiting character and increased during the growth. An exception was the small reaction of oats to rye.
Decrease of the nitrate nitrogen content was determined in the soil of the experimental vessels during the cultivation of the plants. The changes of the nitrate nitrogen in the soil corresponded on the whole with the exception of the last phases of the experiments to the growth intensity of the experimental plants. No essential differences, either in the content or in the rate of the decrease of nitrate nitrogen, were found in the soil of control plants and in the soil of plant mixtures. Small differences which were manifested cannot be considered the primary cause of the mutual relations of cereals. The cause of the mutual relations may be attributed to allelopathic factors.

Samples of the leaf tissue (14cm²) were placed in a plexiglass chamber which consisted of three parts. Water absorbed by the leaf tissue on one side of the sample was transported through the middle part of the sample to the opposite side and was transpirated there. The intensity of transpiration the intensity of water absorption and water saturation deficit (w.s.d.) were determined simultaneously in this tissue by gravimetry. Water balance was studied either in saturated samples of leaf tissue or in tissue where w.s.d. (10%, 20%, 30%, 40%) was established in advance. Although conditions for water absorption in leaf segments were optimal, w.s.d. originated in the saturated leaf tissue under all given external conditions (evaporation from 41.7 to 17.8 mg cm^-2 h^-1). W.s.d. which was established in advance for the most part increased during the experiment and reached even high values (more than 60%). the equilibration was reached only under conditions of low evaporation and initial w.s.d. higher than 20% in young leaves and higher than 30% in adult leaves. A positive correlation between the ratio of the intensity of water absorption to the intensity of transpiration and w.s.d. was found only under conditions of lower evaporation (17.8 and 23.2mg cm^-2h^-1). The maximal values of w.s.d. were limited in this way.
Water balance was studied: 1. in leaf tissue of upper, middle and lower leaves of fodder cabbage, 2. in leaf tissue of middle leaves of young and adult plants of fodder cabbage, 3. in leaf tissue of dicots (fodder cabbage) with different vessel orientation in respect to water transport, 4. in leaf tissue of monocots (banana-tree) with water transport upright to the vessel orientation.
Considerable change of water balance was observed when the water transport was prolonged by two incisions in the middle part of the sample.
Results of all these experiments revealed the possibility of water stress origin even in leaf tissue sufficiently supplied with water.

A new mathematical model, representing the transpiration process during ontogenesis and a circadian transpiration cycle, analysed in detail statistically, was designed using data obtained by the new modification of the gravimetric determination of the transpiration of intact plants. Regression analysis applied to the circadian cycle makes it possible to characterize basis parameters of the intensity and of the extent of this process and may serve as a starting point when studying transpiration methodologically in greater detail.

In the pea test a highly positive response to the treatment with IAA reversed to a negative one or became 5 to 6 times weaker when CCC was applied together with IAA. In cultivating pea seedlings, following their decapitation, for two days in a 0.25 per cent CCC solution and then in water, growth of their cotyledonous axillaries (cotylaries) were inhibited. This inhibitive action of CCC could be made ineffective when the seedlings, following two-days' cultivation in the CCC solution, were grown further in kinetin solutions (0.37-3 mg per 1). Cotylaries of decapitated pea seedlings, when grown in kinetin solutions were inhibited. With kinetin solutions of 6-12 mg/l a strong inhibition also occured in the growth of roots at the apical parts of which spherical swellings were developing.
The CCC supplied to the roots of intact etiolated pea seedlings is translocated acropetally into the stem at a rate of about 5 cm per hour. Decapitation of the plant causes retardation of this transport, yet a coat of 0.00001-1% IAA or kinetin paste produces acceleration of the stream.
Existence of an antagonism between CCC and IAA, demonstrated earlier, was found holding true also for B-9 (N, N-dimethyl-aminesuccinamic acid) and IAA, as the inhibitive action of B-9, 0.06% solution on the growth of lettuce hypocotyls was reduced to a highly significant degree when the plants were supplied with B-9 together with IAA at a concentration of 10 mg/l.

The authors studied the growth intensity, the accumulation and distribution of nitrogen, phosphorus, and potassium in maize and pea plants under conditions of hydroponic culture. They found that RGR dropped by about 50% within 32 days of cultivation. The content (in mg/g dry weight) of nitrogen and potassium in maize, and of nitrogen and phosphorus in peas registered a substantial decrease, while the content of phosphorus in maize and that of potassium in peas exhibited a slight increase and a slight decrease towards the end of the experiments. The relative absorption rates of nitrogen and phosphorus in maize were maximum after 28 days of cultivation, while that of potassium reached a maximum immediately at the beginning; nitrogen and potassium absorption in peas reached maximum values after 28 to 30 days, whereas phosphorus was highest at the beginning. In the course of growth, the ratio of accumulated ions of N:P:K changed; maize accumulated relatively less potassium, and peas more nitrogen and potassium.

A now mathematical model, representing the transpiration process during ontogenesis and a circadian transpiration cycle, analysed in detail statistically, was designed using data obtained by the new modification of the gravimetric determination of the transpiration of intact plants. Regression analysis applied to the circadian cycle makes it possible to characterize basis parameters of the intensity and of the extent of this process and may serve a s a starting point when studying transpiration methodologically in greater detail.

Beet yellows virus (BYV) was mechanically transmitted by sap from sugar-beet plants, infected with BYV, to the plants of Chenopodium quinoa Willd. and of Chenopodium foliosum (Moench) Asch. Mechanical transmission of BYV to the plants of Tetragonia expansa Murr. failed. Infectious material was homogenized in phosphate buffer with veronal and EDTA, pH 7-8. Experimental plants were darkened three days before infection and kept at a temperature of 5°C. Plants of C. quinoa Willd. were decapitated. Back transmissions from C. quinoa Willd. and C. foliosum (Moench) Asch. infected with BYV, to sugar-beet plants were carried out by the aveid Myzus persicae Sulz. These transmissions were positive. Filamentous particles of BYV, of an average length 1275 nm, were found in plants of C. quinoa Willd. and C. Foliosum (Moench) Asch., infected with BYV.

Changes in the nucleic acid (NA) content were studied in roots of young wheat plants cultivated under various nutritive conditions, namely in a nutrient solution, in distilled water and in a solution of sodium humate in distilled water. Changes in the ribosomal ribonucleic acid (RNA) in particular and their connection with growth rate were investigated. The amount of the NA fraction investigated (more than 90 per cent of which is represented by the ribosomal RNA) changed substantially under the cultivation conditions studied. In roots of one plant cultivated in water the content of the NA fraction investigated was at the most about 25 μg and it began to decrease as early as from the second day of cultivation. After 12 days of cultivation it decreased to 15 μg. When cultivated in Na-humate the roots contained at the most 33 μg NA, between the 5th-7th day, followed by an intensive decrease after 12 days, to 17 μg. The content of the fraction investigated in wheat plants cultivated in a nutrient solution was about double the value in comparison to these two cases with the maximal value about 60 μg between the 7th-9th day. After 12 days this amount decreased to 45 μg.
The ratio between the growth rate and the NA content presented positive values only when plants were cultivated in a nutrient solution and in Na-humate until the day when the NA content ceased to increase. In the case of Na-humate this took place on the 6th day and in the case of a nutrient solution on the 9th day. Under conditions favourable for growth (in a nutrient solution and in field conditions) the precultivation of wheat plants in Na-humate resulted in a more intensive growth of roots in comparison with the root growth of plants precultivated in distilled water. In plants precultivated in distilled water for 4 days the growth rate continuously increased under favourable nutrition conditions in contrast to plants transferred from distilled water as late as on the 6th day. Their growth stopped after the transplantation and was restored only after a 2 day lag phase. On the other hand, in plants precultivated in Na-humate the transfer to favourable nutritive conditions resulted in both cases in a short term cessation of growth.