The role of exogenously supplied gibberellin (GA₃) and cytokinin (benzyladenin -BA) in the correlation between the mature leaf and its axillary bud was investigated in one-node segments ofHydrangea. When both leaves were left on the segments, then both GA and BA were able to determine the dominance between axillary buds, that means that the bud treated with the corresponding growth regulator grew more vigorously. When one of the leaves was removed, the bud belonging to the removed leaf grew more vigorously, but GA applied onto the axillary bud belonging to the remaining leaf caused a complete correlation reversal: the bud belonging to the remaining leaf grew more vigorously. On the contrary, the application of BA onto the bud of the remaining leaf resulted in only insignificantly stimulated growth of the bud belonging to this leaf.

The main enzymatic oxidation products of IAA have been tested for biological activity, using as bioassay the straight-growth test ofAvena coleoptile. After being purified by rechromatography, none of these products (including methyleneoxindole) exhibited biological activity within the wide range of concentrations employed; consequently, the results accord with the evidence that IAA is the true hormone of plant growth.

Cytochrome oxidase and ascorbic acid oxidase activities were investigated in rye, wheat, barley and oat plants. The variations in the activity of both enzymes was followed in the course of the initial 28 days of growth, as well as at the phase of milk ripeness, namely in the cytoplasmic and mitochondrial cell fractions of roots, leaves and spikes.
Both enzymes were active in all measurements. Cytochrome oxidase mostly exhibited a higher activity than ascorbio acid oxidase. The activity of the former enzyme was substantially higher in the mitochondrial fraction of leaves, roots and spikes of the four experimental plants in comparison with the cytoplasmic fraction. On the contrary, the ascorbic acid oxidase activity varied in both cell fractions according to the plant species, organ and growth phase.
The variations in the activity of both enzymes exhibited on the whole a course similar to that of the respiration rate. During the first 14 to 21 days of growth the enzyme activities increased up to the maximum. This was thon followed at first by a rapid, later on by a slow decrease. The course of variations in the enzyme activities was, with certain exceptions, alike in all the four plant species investigated.

Changes in respiration, activity of cytochrome oxidase and ascorbic oxidase and in BSMV content were investigated on winter wheat plants cv. 'Kaštická osinatka' after application of growth stimulating and growth inhibiting concentrations of 2,4-D. It has been found that the rate of respiration is almost exclusively dependent on the activity of both these terminal oxidases. Consumption of oxygen was regularly increasing with decreasing herbicide concentration and at concentration 10^-7 M was even higher than the control value. Healthy and BSMV inoculated plants treated with 2,4-D differed in ascorbic oxidase activity while activity of cytochrome oxidase was almost the same. In contrast to healthy plants the BSMV inoculated ones were seriously damaged after 2,4-D application. Plants inoculated with BSMV and treated with 2,4-D contained in contrast to those inoculated and not treated with 2,4-D a higher content of virus (124 to 150 %) which was not proportional to herbicide concentration. These results, which were obtained from experiments with plants grown in nutrient solutions supplemented with 2,4-D, indicate that BSMV inoculation induces metabolic changes which cause a loss of selectivity of 2,4-D.

Callus tissues were derived from the stem of healthy tomato plants (Lycopersicum esculentumMill. ev. Průhonické) and of plants infected with potato witches' broom-a disease caused by mycoplasma. Callus cultures were established on modified fully synthetic media described byMorel (1948) and byMurashige andSkoog (1962). Callus cultures obtained from diseased plants were grown and subcultured on both media, growth in primary isolates from healthy plants took place on the Murashige and Skoog medium only. Growth of callus tissue derived from diseased plants was more vigorous even after several subcultivations in comparison with callus tissues isolated from healthy plants. Variations in the morphology in these callus cultures were not noted. Callus cells of diseased plants varied in size; they were about 50% larger than those from healthy ones. Implantation of primary and subcultivated callus tissues into tomato stems of healthy plants did not show any symptoms of infection on test plants.

The lowering of the cultivation temperature allows one to alter the growth intensity and micromorphology of tobacco cell strains specifically. By a long-term low temperature treatment the effect is deepened, by transferring inocula into normal cultivation temperature it is repaired. Both the growth and morphogenic effects of the low temperature correspond to those of cytokinins, exhibiting even the same strain specificity.

Abscisic acid (ABA) (5 x 10^-4M and 5 x 10^-5M) and gibberellic acid (1 x 10^-4M) was applied to the plumula ofChenopodium plants with partly (one dark period) or completely (three dark periods) fulfilled photoperiodic requirements for flowering. Morphological and cytoogical criteria were used to investigate the time-course of the differentiation of the treated shoot apices. Both substances were ineffective in increasing the mitotic activity of the shoot apex at the suboptimal level of induction. The degree of branching was temporarily stimulated by ABA and GA treatment under these conditions. Moreover, GA caused the elongation of the shoot apex. With the completely induced plants ABA hastened flowering and the rise in branching was observed in all the treatment 48 h following the application of growth substances.

The analysis of diurnal oscillatory movements of tobacco leaves was used in the diagnosis of viral infection of plants. The oscillatory helices circumscribed by a growing leaf of a healthy plant were regular, but some deviations, particularly in the transition points, were recorded.
In order to make clear the cause of these irregularities of trajectory, the course of elongation of leaf petiole and blade in relation to localization and shift of zones of elongation during ontogenesis was analysed. The present analysis is similar to that described by the author's earlier experiments with pea roots. Oscillatory curves circumscribed by petiole, projected on a horizontal plane, were compared with curves circumscribed by the blade tip. The analysis of the leaves of different ages enabled us to study this process in dependence on growth rate. It was confirmed that oscillations are a result of elongation; the extent of oscillations is quantitatively dependent on the growth rate. An analysis of the zones of growth showed that in petiole the active meristems are localized near to its base while in the leaf lamina they move gradually during the ontogenesis from the apical to the basal part of the leaf blade. Active meristems of young rapidly growing leaves are localized approximately in the middle of the blade while those of old leaves were found in close proximity to the base of the lamina. The growth rate of petiole can be expressed in hundreds of mm per hour (4.8×10^-2 mm h^-1); half of this value was recorded for its apical part. The growth rate of leaf blade was found approximately ten times higher (3.2×10^-1 mm h^-1).
The oscillatory movements of growing leaf consists of two integrate components: of oscillations originating in the base of the petiole and of oscillations of leaf blade the centrum of which is localized in the basal third of the blade.
The arrangement of the experiments did not enable us to determine to what extent the phototropic response of leaf blade participates in leaf movements. The movements of leaves of an intact plant are evidently affected by rhythmic stem oscillations. Stem is an integral part of a system which participates in the transfer of information in plants.

The flowering ofSalvia splendensSellow under noninductive short days is promoted by exogenous application of estrogen fraction isolated from flowering sage plants, gibberellin GA₄₊₇ and to some extend N⁶-benzyladenine and estradiol. The most active is the combination of GA₄₊₇ with estrogen fraction. No synergistic action of GA₄₊₇ with N⁶-benzyladenine estradiol was found.

The investigation of the hormonal nature of plant flowering in connection with their photoperiodic reaction has shown that flowering depends on a bicomponental system of hormones, gibberellins regulating stem formation and growth and substances of the anthesin type regulating flower formation. In agreement with the division of the photoperiodic reaction into a leaf and a stem phase the study of the internal factors acting on plant flowering was carried out by means of leaf and stem (apex, bud and callus) models. The results obtained from work with leaf models proved the presence of two groups of hormones of flowering in plants. The data obtained from the application of stem models pointed to the localization of the action of gibberellin and anthesin in different zones of the shoot apices and characterized the potential capacity for flower formation of isolated callus tissue of neutral and photoperiodically sensitive species.

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.

Vicia faba plants cv. 'Erfordia' were treated with single application of CCC at 250 mg l^-1, 7 days before extraction. Such a concentration resulted in a 10.4, 14, 5 and 3.3 fold, respectively, increase in the levels of endogenous IAA, ABA, gibberellins and cytokinins relative to the controls. The results obtained indicate that a single application of CCC at a low concentration was sufficient to enhance the endogenous growth hormones in the treated plants. The results were obtained using GLC analyses for IAA, ABA and cytokinins, and the lettuce hypocotyl and soybean callus bioassay for gibberellins and cytokinins, respectively.

The light regime effect on the growth rate variability of clones of one chlorococcal alga strain growing on the surface of a solid medium was studied from the point of view of the clone selections manifesting the desired grade of this complex character. Several combinations of light regimes used for the cultivation of coenobia treated by UV-light and untreated control on two types of solid media proved the significance of manifestation degree changes of this character due to the given light conditions. The sizes of the alga colonies after a certain growth time on the surface of solid medium were evaluated statistically and the values obtained indicated the degree of growth rate manifested by the clones of a given population. The x and s_x values of their growth rate variability were considered as the indicators facilitating the choice of selec-tion type and screening level. This paper is a partial contribution to the solution of the problems concerning the primary selection of alga clones on the surface of solid media.

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.

In Jerusalem artichoke tuber,in situ RNA synthesis along vegetative cycle shows two maximums. The first one appears during tuberization and installation of dormancy and a growth inhibition is sufficient to bring it about. The second reveals breaking of dormancy and precedes germination.

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.

Indole-3-acetic acid (IAA-1¹⁴C, IAA-2¹⁴C) and gamma-aminobutyric acid labelled with¹⁴C were applied in lanoline to the surface of intact seeds or inserted into seeds of growing apple fruitlets or to the cut surface of the pericarp. Their translocation in trees was checked by means of autoradiography or by a low background Geiger-Müller counter. Auxin applied to the top of intact seeds, or inserted into the seeds was translocated and distributed within the pericarp, spur tissues and shoots below. The translocation of gamma-aminobutyric acid from seeds suggests that the capacity of apple seeds for extensive interchange with the surrounding tissues of the fruit and the spur is more general than suspected. A much poorer or no translocation to the spur was found when radioactive compounds were applied to the cut surface of the pericarp, while the seeds were left untouched. The results suggest two mechanisms of metabolite translocation in the apple fruit: two-directional for seeds and one-directional for the pericarp.

Callus tissue cultures were established from stems of tobacco plants (N. glaucaGrah.) both healthy and mycoplasma (potato witches' broom disease) infected on a modified nutrient medium (with a lower content of mineral salts) according toMurashige andSkoog (1962) in the presence of 2,4-D (1 mg l^-1) as a growth regulator. No differences were observed in the growth and development of both tissues. Organogenesis appeared on a nutrient medium (Petrůet al. 1972) supplemented with kinetin (0.64 mg or 2.56 mg l^-1) and IAA (2 or 4 mg l^-1). Callus derived from mycoplasma diseased plants started to form numerous buds after three months whereas organogenesis in callus from healthy controls appeared only after six months. We suppose that the reason of this difference is the fact that an expressively higher content of 2,4-D was found in the calli from healthy plants in comparison with the corresponding tissue from mycoplasma diseased ones. Reconstituted plants were isolated, rooted and transferred in the soil. The infectivity of these plants was assayed by grafting their stem tips on tomato plants which indicate very reliably and sensitively this mycoplasma disease. 31 reconstituted plants were obtained in the whole from calli isolated from mycoplasma infected plants and all of them were healthy.
It was established that mycoplasma failed in the presence of 2,4-Din vitro. Stem pieces from diseased plants in which mycoplasma presence was proved, lose their infectivity after 4 weeks of cultivation on nutrient medium with this growth regulator. On the contrary 2,4-D which spreads and acts especially through phloem (Smithet al. 1947) does not kill mycoplasmain vivo even in doses evoking strong symptoms of 2,4-D effect on experimental plants.

The relationships between DNA synthesis and germination capacity ofAgrostemma seeds have been studied. Protein synthesis and RNA synthesis are activated at the very beginning of imbibition, whereas DNA synthesis starts in the second part of the imbibition phase.
Agrostemma seeds inhibited by higher temperature (30° C), or aged seeds with a low germination capacity are characterized by a remarkably reduced protein synthesis. DNA synthesis is also reduced. The inhibition of protein-synthesis ofAgrostemma embryos fed with cycloheximid or actinomycin D causes a depression of DNA synthesis. These results indicate that the initiation of DNA synthesis of imbibingAgrostemma seeds depends on the synthesis of special proteins. Abscisic acid inhibits growth as well as DNA synthesis of isolatedAgrostemma embryos. Mitomycin inhibits germination and DNA synthesis to the same extent. Dormant seeds with an undiminished intensity of protein synthesis also show a reduced incorporation of³H-thymidine in DNA. We suggest that DNA synthesis of imbibed seeds, which is a necessary prerequisite for the radicle protrusion, is involved in the mechanism of afterripening of theAgrostemma seeds.

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

Kinetin, coumarin and four growth retardants including Phosfon D (2,4-dichlorobenzyltributylphosphonium chloride), CCC [(2-chloroethyl) trimethylammonium chloride], B-Nine (N-dimethylaminosuccinamic acid) and AMO-1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride) arrested chlorophyll, protein and RNA degradation in the leaf discs of maize kept in darkness; GA₃ was without effect. Coumarin and Phosfon D markedly lowered the level of TCA soluble nitrogen compounds in the tissue; other compounds were inactive in this respect. Puromycin, 4-fluorophenylalanine, actinomycin D, 5-diazouracil and 2-thiouracil also retarded the loss of chlorophyll from the leaf discs of maize; chloramphenicol was without effect on yellowing. The inhibitors of RNA and protein synthesis slightly decreased, increased or had no influence on the chlorophyll preserving effect of coumarin and growth retarding chemicals. 2-Thiouracil markedly decreased the loss of protein content from the discs.
Coumarin and growth retardants inhibited the synthesis of chlorophyll in the leaf tissue of etiolated seedlings of maize.
It is suggested that synthesis of some specific protein(s) is required for senescence in the detached leaf tissue. Synthesis of this protein(s) was possibly arrested by the compounds which were under examination.

A non-specific effect of antiviral factor (AVF) was proved by interference of five different viruses (CMV, PVX, PVY, TMVe, TMV vulgare) with CBRV.
The non-specific AVF originates in non-infected tissues around TMV lesions. Transmitted mechanically to other plants this AVF exhibits the same suppressive effect on multiplication of TMV and CBRV.
The AVF is formed in the non-infected apical part of the leaf which was infected in its basal region. The susceptibility of leaves is decreased even when AVF is added to virus inoculum and applied mechanically on the leaf. The apical part of the leaf the base of which is met with necrotic reaction to TMV, is considerably less susceptible and TMV multiplication in this region is decreased. The necrosis on the leaf base induced by mechanical injury or by cysteine hydrochloride may decrease the susceptibility of the leaf to some extent, but has no effect on multiplication of the virus.
The activity of AVF in healthy apical region of the leaf increases till the fifth to the eighth day after its basal part was infected. The apical region then exhibits lower susceptibility (decrease in number of lesions) and the growth of lesions is decreased. This indicates the virus multiplication being suppressed.

The uptake and translocation of³²P applied to nutrient solutions, as influenced by (2-chloroethyl) trimethylammonium chloride (CCC) and 2, 4-dichlorobenzyltributylphosphonium chloride (Phosfon), were investigated in growth chambers. Specific effects depended on the "Retardin", the method of application, and the concentration.
Foliar applications of CCC had no significant effect on³²P uptake 5 h after feeding. At 20 and 80h after feeding, CCC at 100 and at 1 000 mg l^-1 decreased P uptake. With root applications of CCC the same concentrations decreased P uptake as early as 5h after feeding, while the 1 mg l^-1 concentration enhanced P uptake by 40% after 20h. Both the foliar and the root applications of Phosfon influenced P uptake 5h after feeding. With foliar applications the low Phosfon concentration of 0.01 mg l^-1 increased P uptake throughout the experimental period of 80h, but the magnitudes of enhancement declined from 109% at 5h to 63% at 80h. Similarly, the enhancement of P uptake due to the 0.1 mg l^-1 foliar treatment declined from 132% at 5h to 80% at 80h.
100 mg l^-1 CCC enhanced P translocation to the shoot in 5h, with magnitudes of 29% (foliar application) and 64% (root application). At 20 and 80h the stimulations were nullified. The highest concentrations (100 mg l^-1 CCC; 10 mg l^-1 Phosfon) enhanced P translocation 80h after feeding. There were thus general enhancements of P uptake at low concentrations and suppressions at high concentrations, but these effects diminished with time, indicating transitory influences.

Chemotropic effects exerted by metal cations have been investigated simultaneously with their influence on the increments ofSinapis alba roots cultivated in dark and light. The effects of Na-EDTA and Na-humate and its fractions, as well as the interaction of these substances with cations have also been studied. Chemotropics have been administered in agar-agar to the ends of roots growing on glass plates. Chemotropic and growth effects were exerted by Cu²⁺, Fe²⁺, Fe³⁺ and Ca²⁺ cations. The light strongly changed the effects of all but Cu²⁺ cations. Both Na-EDTA and humante appeared to be active chemotropically and generally abolished the effects of cations, although in some cases Na-EDTA made this influence more intense. Of the humate fractions, only those characterized by the ability to form complex compounds appeared to be active. No correlation has been found between chemotropic effects and the influence on the growth of roots, except for the Cu²⁺ cations, which always caused positive chemotropism and inhibited the growth of roots.

In controlled environment growth chambers, the effects of foliar and root applications of 2-chloroethyltrimethylammonium chloride (CCC) and 2,4-dichlorobenzyltributylphosphonium chloride (Phosfon) on the translocation of³²P fed to leaves, were investigated. When applied to leaves or to root, CCC had no effect on the relative amounts of³²P radioactivity retained by the fed leaf 5, 20 and 80 h after feeding. At 20 and 80 h after feeding, Phosfon concentrations of 0.01 and 0.1mg l^-1 reduced retention of the applied³²P. 80 h after³²P feeding, CCC concentration of 1 mg l^-1 applied as a foliar spray or to the root enhanced the downward movement of³²P. Phosfon at low concentrations, particularly at 0.1 mg l^-1, on the other hand, favoured an upward transport of the applied³²P. Foliar applications of CCC and Phosfon at high concentrations had no significant effect on³²P transport to the root and the shoot below the fed leaf, while root applications of CCC and of Phosfon inhibited downward transport. Root applications generally caused greater alterations in³²P distribution patterns than did foliar applications. On the basis of total active ingredient uptake, Phosfon was more effective than CCC in altering translocation patterns.

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.

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.

Humate (10 mg l^-1) supplemented to streptomycin solutions (0.1 and 1 mM) stimulates growth of germinating wheat and barley grains and of apical cuttings ofCrassula portulacea after 24 h treatment. It does not, however, prevent formation of albinic leaves. Albinism induced by the streptomycin alone and by streptomycin in presence of humate is irreversible and can be removed neither by an iron salt nor by a chelate added to the nutrition solution or applied on the leaves. Cells of plants treated with streptomycin and humate are larger than those of plants treated with the streptomycin alone. The same is true for plastids which in both cases are colourless and much smaller than chloroplasts of control plants. These plastids in a living or a fixed state have reduced ability to uptake stains. The albinic leaves are anatomically similar to chlorotic leaves of virus infected plants.

The importance of various correlative influences on growth and vegetative or floral development of cotyledonary buds inScrofularia argutaSol. is shown. The terminal bud, on the one hand, inhibits growth of cotyledonary buds and, on the other hand, induces their early flowering. The cotyledon stimulates growth of its axillary bud, but has no action on its floral development. Leaves above the cotyledonary node have the same effect as the cotyledon. Finally, roots stimulate vegetative growth of cotyledonary buds and suppress floral expression, but only when apical dominance has been removed at an early stage of development.

Leaf angles, frequency distribution of leaf area inclinations, leaf area index, amount of intercepted radiation, biological, vegetative and grain yields and grain yield proportion of biological yield were determined in maize stands of two population densities, 55 555 plants ha^-1 (S₁), and 80 000 plants ha^-1 (S₂). Also the effect of the artificial change of leaf angle upon these indices was studied. We classified normal maize stand (N) as the interstage between a planophile and a plagiophile type of canopy, that with artificially changed leaf angle (V) as an erectophile type of canopy. The relative interception of the incoming radiation in the variantsV S₁ andV S₂ was lower than in the variantsN S₁ andN S₂. The variantsV in comparison with variants N increased grain yield and biological yield.