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.

The virus origin of a Czechoslovak isolate of potato witches' broom disease is discounted: electron micrographs of ultrathin section of phloem tissues from plants infected with potato witches' broom disease demonstratedMycoplasma-like bodies, spherical or elongated showing binary fission and fragmentation. The minute corpuscles have a diameter of about 50-60 nm, the largest bodies of 1000 nm. The width of elongated filamentous structures is about 200 nm, most oval bodies have a diameter of 250 nm. A weak tetracycline treatment of diseased plants causes a delay of symptom development; a strong dose of tetracycline (applied by means of the wick method into the stem) inhibits symptom appearance completely. Tetracycline produces a phytotoxic effect inhibiting the growth of tomato plants and causing (at higher concentrations) necrosis and death of these plants. There is a note in the paper dealing with the term "mycoplasma". The word mycoplasma in the sense ofEriksson (1897) or ofMereschkowsky (1910) does not correspond to the genus nameMycoplasma Nowak (1929).

A study has been made of the level of naturally-occurring growth substances and inhibitors in acid-soluble fraction of peach leaves and shoots using paper chromatography and bioassay methods.
The content of substances which stimulate growth ofAvena coleoptile sections calculated on a fresh weight basis can be expressed by a one-peak curve with a maximum at 10 a.m. The shoots were higher in growth substances than leaves in all periods of time examined. The extract contained two substances which significantly stimulated the growth of coleoptile (accelerator-2 and-3). High inhibition was found in the area of inhibitor-β and to a lesser extent in the area of inhibitor-α. The changes in the concentration of inhibitors were different in leaves and shoots.

The main epicotyledonary axis inPisum sativum exhibits a very fluctuating either left- or right-handed deflexion of its first-order laterals, but the biserial buds on the laterals of various further order reveal in this respect certain regularities according to their position on the seedling, their deflexion being very often adaxial in the vicinity of cotyledons, however, in more distant and therefore later produced laterals, as a rule, abaxial. The integrant characteristics of these relationships may become clear from their experimental shift with the aid of exogenous auxin increasing inhibitions as well as of triiodobenzoic acid blocking the transport of endogenous auxin participant also in these embryonic-growth correlations.

Vascular inter-relationships between axillary bud, axillant leaf and axis have been studied in fives pecies of theSolanaceae, Lycopersion lycopersicum (L. )Karsten,Cestrum nocturnum L.,Cestrum diurnum L.,Withania somnifera (L.)Dunal, andDatura innoxia Mill. The phyllotaxy is alternate and the node is unilacunar with one or more leaf trace strands. The bud traces arise either from the trace of the subtending leaf or of the strands flanking the leaf gap. The vascular relationship between the bud, axillant leaf and main axis is discussed.

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.

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.

Electrophoreograms of protein extracts from leaves of the variety Lord Lambourne, detached at the flowering period toward the end of April, differed quantitatively from electrophoreograms of protein extracts from leaves detached from shoots at the end of May and June. Electrophoreograms of protein extracts of leaves from juvenile seedlings, detached at the end of May and June, did not differ from electrophoreograms of protein extracts of leaves from shoots of the variety Lord Lambourne detached at the same period. Electrophoretic pattern of protein fractions and the fractions of non-specific esterase from leaves differed from the corresponding electrophoretic pattern of flowers quantitatively and in some areas even qualitatively; the pattern of acid phosphatase differed quantitatively. The results obtained are discussed in relation to organogenesis.

Grains ofTriticum monococcum L. var.sofianum Körn. were treated with 0.1mm, 0.2mm and 0.3mm solutions of N-nitroso-N-methylurea (MNH), with 0.03m solution of buthylmethane sulphonate (BMS) and with X-rays in doses of 5 000r and 10 000r. The germination and development of individual colors of chlorophyl mutants were observed by the system developed byLamprecht (1960). All the mutants induced were classified according to their color changes into three main categories-homogenous unicolor, homogenous multicolor and heterogenous multicolor. In the last type the colors of individual leaves of the same plant varied. Anthocyanin mutations "albina" and "albino-transvirgata" sometimes coincided with the chlorophyll mutations. Some chlorophyll mutations showing complicated groups of colors appeared which were beyond the scale of classification by ordinary systems. The largest proportion in the spectrum of chlorophyll mutations, induced by MNH and X-rays was occupied by mutations of thealbina type. The broadest mutation spectrum in our experiments was induced by the application of 0.3mm MNH. The doses of X-rays used induced relatively higher numbers ofalbina-type chlorophyll mutations than MNH and BMS. In our experiments we succeeded in inducing on medium size samples ofTriticum monococcum L. var.sofianum Körn not only almost all types of chlorophyll mutations, induced byFujii (1960, 1962) andMatsumura (1960), but in addition also a great number of other even more complicated chlorophyll mutations, which have never been previously described inTriticum monococcum. L.

Chromatographic separation of an extract of organic acids on a Dowex-l column in the formiate cycle was used to study the content of several organic acids in pea plants, cultivated either in light or in darkness. Concentration changes of the individual acids in the course of growth indicate that the citrate cycle is blocked in the cotyledons of plants grown in light in the period around the 15th day of growth, probably at the site of succinic dehydrogenase (succinic and lactic acids accumulate and the content of citric and malic acids is exhausted). There is no inhibition in the cotyledons of etiolated plants. In vegetative organs, the concentration of the majority of the acids studied is lower than in cotyledons, probably because synthetic processes prevail over degradation processes in these organs. It seems that other processes besides the citrate cycle participate in malate synthesis in pea plants.

Internal symptoms in epidermal cells of tobacco rattle virus infected tobacco were investigated. Ring-, elipsoid- and spindle-shaped inclusions were found in the period between the fourth and thirtieth day after inoculation of Samsun seedlings.

Purification and preservation of potato virus X from leaf sap of tobacco plants before lyophilization was carried out by two methods: 1) precipitation by polyethylene glycol and ultracentifugation, and 2) precipitation by ammonium sulphate, chromatography on Sephadex G-50 and ultracentrifugation. The first method is preferable to the second because the final preparation contains more virus antigen. Both preparations were strongly infectious and maintained antigenic properties after lyophilization.
To achieve a more gentle course of lyophilization of virus preparations, addition of urotropine and dextran T-10 to the virus suspension, purified by the precipitation by polyethylene glycol-6000, was examined. Addition of urotropine was proved unsatisfactory, because only antigenic properties were maintained after lyophilization while the infectivity disappeared. But we can recommend addition of dextran T-10 up to a concentration of 6% to the preparation of virus antigen before lyophilization. The course of lyophilization is much rapider, the lyophilized product can be very easily dissolved in water and is not hygroscopic. The product is strongly infectious and gives the serological precipitation reaction in a dilution four times that of X virus antigen lyophilized without addition of dextran T-10.

Flower initiation induced by three inductive photoperiods inChenopodium rubrum L. was fully inhibited by treating the shoot apex with a 5 μl drop of 1×10^-5 m 5-fluorodeoxyuridine (FDU). This inhibition may be reversed by thymidine applied simultaneously with or after FDU treatment at any time during photoperiodic induction. One day after the end of induction the inhibition caused by FDU is irreparable even by increasing thymidine concentrations. It is concluded that photoperiodic floral induction may take place inChenopodium even if DNA synthesis is suppressed.

The effects of constant soil moisture levels of 90, 60 and 40% of the maximum capillary capacity, applied beginning from the planting of the germinated kernels, on the dynamics of the foliage development of maize was studied in relation to ontogenical changes in leaf area of individual leaves. There were two maxima in the growth of total leaf area (characterized by leaf area duration and loaf area relative growth rate) unrelated to the soil mositure. The first maximum which was less marked, appeared in the phase of 5-8 leaves, the second and main increase being observed before flowering in the phase of 10-12 leaves. The effects of continued decrease in soil moisture were a correspondingly progressive reduction in leaf area and delayed development of the whole plants. Plants with 60% soil moisture attained the same leaf area as those with 90% but only after the end of the vegetative phase. The greatest differences in rate of development between watering treatments appeared at the time of greatest increase in leaf area of control plants. Continued decrease in soil moisture markedly affected the development of the leaves at different insertion levels (especially in elder leaves). Clear-cut prolongation of ontogenesis took place under dry conditions. In conditions of higher soil moisture growth was rather limited or stopped after reaching a certain maximum.

The mutual relationship between the water potential and water saturation deficit (w.s.d.) was studied on samples of leaf tissue of fodder cabage. Definite values of water potential were obtained by long-term exposure of plant material to an atmosphere with definite constant pressure of water vapour. The resulting w.s.d. values were determined gravimetrically.
Water saturation deficit varies indirectly with the water potential. This dependence was linear for values of water potential from -4.4 to -43.9 atm.
Since the stabilization of equilibrum of water potential between the leaf tissue and surrounding atmosphere was very slow the relationship between water potential and w.s.d. was influenced by the size of samples and by the length of exposure. Therefore this method was more suitable for relative than for absolute measurement.

In the years 1963-1965 the content of proline, asparagine, glutamic and γ-aminobutyric acids in young apple (Malus cultivars) shoots was studied. Two groups of apple varieties differing in frost resistance were included into experiments: the Yellow Transparent and Oberländer Himbeerapfel varieties as frost-resistant ones and-the Ontario and Reinette du Canada varieties as sensitive to frost. In the course of experiment γ-aminobutyric acid showed a relatively balanced level but glutamic acid, asparagine and especially proline were found in greater amount in the frost-resistant varieties. According to the results of this experiment the amount of proline-along with many other factors-can be considered as one of the indicators of the length of winter dormancy and also of the frost resistance of apple-trees at the beginning of the winter period.

Fractions of acid phosphate (orthophosphoric monoester phosphohydrolase, EC 3.1.3.2) were studied in extracts of segments from three growth zones of broad bean roots by means of electrophoresis in acrylamide gel. The azocoupling reaction with α-naphtyl phosphate was used for detection. The phosphatase activity was investigated in the range of pH 3.6-7.2. Altogether nine fractions moving towards the anode were revealed. Some fractions differed slightly in their pH optimum. The presence of Mg⁺⁺ in the incubation medium resulted in the activation of two fractions, Mn⁺⁺ showed activation of three fractions and inhibition of the rest of the fractions; the presence of Zn⁺⁺ resulted in a slight inhibition of all fractions. Between electrophoreograms of extracts of segments from the division zone and electrophoreograms of extracts of segments from the enlargement zone and from the maturation zone considerable quantitative differences were found with one fraction; proportions of the other fractions were approximately identical in electrophoreograms of all three growth zones. The response to the presence of Mg⁺⁺, Mn⁺⁺ and Zn⁺⁺ in the incubation medium as well as the pH optima of the individual fractions were identical for all three growth zones.

Fractions of non-specific esterase were studied in homogenates ofVicia faba L. root tips using disc electrophoresis in acrylamide gel. With α-naphthyl acetate, 7 bands were revealed in electrophoreograms, whereas only 5 bands appeared with naphthol AS acetate; the position of bands detected with naphthol AS acetate corresponds to 5 of 7 bands which appear when using α-naphthyl acetate. If incubated with α-naphthyl acetate, 1 band is totally blocked by the inhibitor E 600, whereas the other bands are weakened slightly and-more or less- proportionally, similarly, as if incubated with naphthol AS acetate. No bands appear after detection with α-naphthyl caprylate and with α-naphthyl myristate. Electrophoreograms developed with α-naphthyl propionate differ both from those treated with α-naphthyl acetate and from those treated with α-naphthyl butyrate. Remarkable, but only quantitative differences were revealed when comparing electrophoreograms from division, enlargement and maturation zones, detected with either α-naphthyl acetate, or α-naphthyl propionate. The non-specific esterase fractions revealed by disc electrophoresis are correlated with protein fractions distinguished in the same material by the same technique using xylene brilliant cyanine G staining and with fractions of the same enzyme found in sections of the same object treated histochemically.

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.

A simple modification of a laboratory gravimetric technique for the study of transpiration of intact plants is described, by which the process can be followed continually. The plants are grown in light vessels on a light "keramzite" or other suitable medium, either alone or in combination with agar gel. The mineral component provides for the necessary cultivation properties of the medium, whereas agar gel ensures steady and undisturbed water relations in longer experiments.
The calculation of the transpiration intensity per unite of time is described. For reliable results the number of samples must be lange chough, so that the coefficient of variation does exceed 10 per cent. The determination of the transpiration is sufficiently exact even without a correction for changes in dry solids, the absolute increments in dry solids during the time interval studied being of a smaller order of magnitude than the values of transpiration. The results are expressed per fresh weight of the transpiring unite, by which an undisturbed transpiration study of a longer duration is rendered possible and the effects on the plant are excluded.

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.

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 present paper deals with the epidermal structure and ontogeny of stomata in vegetative and floral organs ofHybanthus enneaspermus. The epidermal cells are either polygonal or elongated with straight, sinuous or arched thick anticlinal walls. The surface of the cuticle shows parallel striations radiating from the guard cells or hair bases. Unicellular and uniseriate bicellular trichomes with verrucose margins have been observed on all organs. The mature stomata are anisocytic, paracytic, anomocytic and transitional between anisocytic and paracytic. The ontogeny of anisocytic and paracytic stomata is syndetocheilic or mesogenous, anomocytic is haplocheilic or perigenous, while that of the transitional type is mesoperigenous. Four types of stomata have been observed on all the vegetative and floral organs and their ontogeny from organ to organ of this plant is constant. Stoma with a single guard cell is the result of disintegration of one of the guard cells before or after pore formation. Contiguous stomata are also occasionally noticed.

An expressive effect of temperature on water saturation deficit determined by "leaf-disc extrapolation method" was found. This error may reach about 15 to 40% of measured value with the temperature gradient of 10° between tissuein situ and under conditions of W.S.D. determination.

Bei 14 Winterweizensorten wurde im Zeitabschnitt Winter-Frühling der Zellsaftbrechungsindex gemessen. Die höchsten Werte wurden bei einigen frostresistenten, die niedrigsten Werte bei nichtresistenten Sorten gefunden, der Zellsaftbrechungsindex war aber nicht in allen Fällen der Frostresistenz proportional. Mit Rücksicht auf Stoffwechselvorgänge der osmotisch aktiven Stoffe, die deren Menge und Verhältnis bestimmen, sind Saisson- sowie Tagesveränderungen im Laufe von Winter und Frühling nicht nur von der Temperatur und Feuchtigkeit der Umgebung abhängig. Der Zellsaftbrechungsindex unterliegt verschiedenen Veränderungen in Beziehung zu Pflanzenernährung in verschiedenen Wachstumsphasen bei Sorten mit verschiedenem biologischen Charakter und unter verschiedenen pedologischen und klimatischen Bedindungen. Stickstoffdüngung erhöht den Zellsaftbrechungsindex bei vielen Sorten, hauptsächlich gm Winter.

The rate of growth of 5 species of white-rot fungi on an agar medium with additions of humus acids was used for assessing the ability of these fungi to utilize humus acids as a sole source of nutrition. Differences in the effect of the various fractions of humus acids and their concentrations, as well as in the reaction of the fungi tested were observed. During the growth, loss of colour of agar media with humus acids was observed. Activity of lacease in the discoloured areas was highest.

Three techniques of the test-tube fertilization by means of an artificial pollen tube culture are described. The essentials for each individual method are:
1. Transfer of pollen tubes from the sugar solution onto the placentae in the test tube.
2. Placing the placentae with ovules onto pollen tube culture.
3. Precultivation of pollen tubes on small cellophane squares placed on the surface of a semi-liquid medium and transfer of cellophane squares along with the pollen culture to the solid medium, over which finally the placentae with ovules are placed.
By means of all the three techniques viable seeds were obtained in vitro. In an artificial medium pollen tubes are able to maintain their fertilizing ability even after the 24 hours cultivation, i.e. at the time after the formation of the gametes.

Using hydroponic cultures, the effect of high concentrations (10^-3 m) of 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the root medium on the water balance of 8-9 week old plants ofPisum sativum L. and of 9-10 week-old plants ofSinapis alba L. was studied. The water balance was determined in the light and in the dark gravimetrically by measuring the intensity of water uptake and transpiration in plants cultivated by the method of root bridges according to Werner. MCPA present in the root medium in illuminated plants decreased rapidly the intensity of both the uptake and the loss components of the water balance. In permanent darkness, MCPA brought about an increase in the intensity of uptake of water and of transpiration. Simultaneous determination of water uptake and transpiration showed that the intensity of transpiration remained higher than the intensity of water uptake. This indicates that in the presence of MCPA in the root medium the relationship between the uptake and the loss components of water balance is not quantitatively equal, enboth in the light and in the dark. The existing disproportion results in the formation of a passive water balance of plants.

In order to interpret the mechanism of elongation growth of the hypocotyl with radicle in the first stages of germination of the pea seed (Pisum sativum L.) a cybernetic model utilizing feed-back as a mechanism of correcting the wrong direction of growth was proposed (Spurný 1966, 1967). In the present study, the effect of amputation of the root tip as the control centre on the trajectory of the growing radicle was investigated. The results have shown that the hypocotyl grows, elongates-the rate of growth being slightly lower than that of the standard, but that no spiral oscillations at all are executed by the organ after amputation of the root tip. This finding appears to confirm the applicability of the proposed cybernetic model, for amputation of the root tip means that not only the control block is eliminated, but also that the channel of feed-back impulses to zone of elongation is interrupted.

The filamentous green algae investigated (Hormidium sp. strainHindák 1963/21,Ulothrix sp. strainHindák 1964/2,Uronema gigas Visch. strainVischer/Bloom. 174,Uronema sp. strainHindák 1963/25 andStigeoclonium sp. strainHindák 1964/1), contain similar amounts of proteins, lipids, cellulose and ash as the hitherto used production strains of the generaChlorella andScenedesmus. The digestibility of proteins in vitro is about one-third higher in the filamentous algae than in the employed referenceScenedesmus quadricauda strainGreifswald/15, used in Czechoslovakia as a model production strain. The heats of combustion of the filamentous algae are relatively lower (5519-5923 cal/g dry weight) than in the reference strain (6145 cal/g dry weight).
From the point of view of application of filamentous green algae to mass cultivation their advantages over the presently employed chlorococcal algae (Chlorella, Scenedesmus) consist in a pronouncedly greater digestibility of their proteins without special technological treatment of the material obtained and a greater production of biomass.