The analyses for the content of endogenous gibberollins and auxins in leaves and adjacent stem internodia of intactBryophyllum crenatum plants revealed that the level of gibberellins increases in tho direction from the apex to the stem base, whereas in the case of auxins the trend in the increase is tho reverse. This corresponds to the results of morphological experiments, according to which the apical stem part appears as affected by phytohormones of an inhibitory character, the basal part as affected by stimulatory ones.

CO₂ absorption (PAT) and transpiration (E) rates, and leaf diffusion resistance (r_i) were individually studied in all leaves of tobacco plants (Nicotiana tabacum L. cv. Wisconsin 38) before flowering. Differences between old, middle age and young leaves were in all characteristics studied and found statistically significant. In all three leaf age groups E was closely correlated to r_i. No similar correlation was discovered between P_N and r_i. The highest ratiosP _N /E in young and middle age leaves indicate that the increase of the internal resistance to photosynthesis with leaf age was more rapid than that of r_i.

In this report, B₉ treatment had no effect on the growing of rosette biennialScrophularia vernalis L.; it inhibited or slowed stem elongation. Applications of GA₃ to B₉ treated plants produced a significant increase of stem elongation, in relation to GA₃ treated plants. Plants treated with only GA3 failed to flower; otherwise, the flowering of vernalized plants was not altered by GA₃. Thus, B₉ effect on flowering was tested by using GA₃. B₉ by itself induced flowering, it increased inflorescence formation in vernalized plants without altering stem growth pattern in the most of cases. The induction or the stimulation of flowering brought about by B₉ was not reversed by GA₃; we may thus hypothesize that flowering by B₉ oannot be traced back to gibberellin biosynthesis.

In contradiction to Paulet's (1965) data, we found that kinetin/IAA strongly affected organogenesis in callus tissue derived from the stem ofNicotiana glauca Grah. plants both in primary expiants and in subcultured calli. The effect of these substances was higher in the subcultured calli derived from mycoplasma-infected plants. Evidence of the absence of the infectious agent in de novo-formed plants in subcultured calli was given by grafting and by the electron micrograph.

Alcohol dehydrogenase was prepared from 2-day germinating maize and 3-day germinating broad-bean seeds by ammonium sulphate fractionation of sodium phosphate extracts, chromatography onDEAE cellulose and Sephadex G-200. The activity of the broad beanADH amounted to182 800 units per mg protein, that of maizeADH 79 000 units per mg protein. Besides oxidation of a series of alcohols at pH optimum in the alkaline region and with KM equalling 10-2M, alcohol dehydrogenases isolated from both plants catalyze the reduction of acetaldehyde, n-propanal, n-butanal, isobutanal and crotonal at pH optimum in the neutral region with KM equalling 10-3M. The inhibition studies using fatty acids and chloride ions revealed that the oxidation of alcohols is inhibited competitively by both types of inhibitors, with inhibition constants of 10-2M and 10-1M, respectively. The inhibition in the presence of acetaldehyde is non-competitive since the inhibitors do not compete with acetaldehyde and do not form an enzyme-NADH-inhibitor complex, yet they obviously react with the enzyme-NAD product only, thus giving rise to an enzyme-NAD-inhibitor complex. These differences in the behaviour of inhibitors may be interpreted in the sense that the binding sites of ethanol and acetaldehyde as substrates for broad bean and maize alcohol dehydrogenases are non equivalent. The nonequivalency discussed in the text.

Changes in the transpiration rate of intact spring barley plants, cv. "Slovensky dunajsky trh", were studied separately in the light and in the dark under controlled temperature and illumination, after the infection withErysiphe graminis DC, during an 8 day period of the development of the fungus. In the first stage of pathogenesis, the fungus diminishes water output from the host plants in the light. An opposite phenomenon can be observed in the dark; water output from infected plants in the dark increases sharply mainly in the stage of advanced fructification. Thus, the fungus considerably diminishes the ratio of water output from the host plants in the light to that in the dark.

The changes of kernel nitrogen (N), phosphorus (P) and dry weight (DW) were determined during the time period from 10 days after anthesis till maturity in three spring barley strains. The plants were cultivated under field conditions in Gatersleben (German D.R.) and Kroměříž (Czechoslovakia). The course of N, P and DW changes was described by Richard's comprehensive growth function dW/dt = aW^m + bW, where W is the amount of N, P or dry matter per kernel, a, b, m are coefficients. The integral of this function was used and several parameters calculated. There was a remarkable synchrony between N or P and total dry matter accumulation in the kernels. Thus, the N or P concentration per unit kernel dry weight was relatively constant during the investigated period and with few exceptions corresponded to 80% to 100% of the final value. However, considerable differences between strains, years or places of cultivation were found.

In two branched plants ofImpatiens balsamina with intact apex and leaves floral buds are induced only in the branch which is either exposed to 8-h (inductive) photoperiods or receives GA₃ treatment if maintained under 24-h (non-inductive) photoperiods. GA₃ induces floral buds on the treated branch even if the leaves on that branch are removed, showing that while leaves are essential for photoperception, these are not neoessary for GA₃ to cause induction. The effect of the inductive photoperiods or GA₃ treatments to a branch is not transmitted to the other branch which is treated with water and is maintained under non-inductive photoperiods even when the latter is defoliated but is transmitted if the apioal or both the apical and axillary buds on the branch receiving inductive photoperiods or GA₃ treatment are excised. It, therefore, appears that the existence of strong sinks in the form of axillary and apical buds on the treated branch prevents the transmission of photoperiodic as well as GA₃ effects to the other branch in this plant.

This work is a study on the presence of free and bound (mainly proteins) amino acids at the levels of both the individual plants and the producers of a phryganic ecosystem. Therefore the amount of free and bound amino acids (both quantitatively and qualitatively) is determined during two seasons. As far as the producers (green plants) at the ecosystem level are concerned, the amount of free and bound amino acids was determined for both the above ground (stems, leaves) and the below ground (roots) parts during an annual period. On the basis of the above mentioned measurements it was found that, in a year, 17 and 4 g.m~²of bound and free amino acids are produced, respectively. A percentage of about 50% of this quantity remains in the plants, as their annual growth, and the rest returns to the soil because of the litter and root turnover. The model of their flow in the ecosystem was formed considering also data from plant physiology.

Chosen species and cultivars(Nicotiana sanderae, N. glutinosa, N. otophora, N. paniculata, N. sylvestris, N. velutina, N. tabacum cv. Samsun, N. tabacum cv. Samsun - a dihaploid line, and an amphidiploid N.sylvestris x N tomentosiformis) were treated with adequate concentration of n-buthylmethane sulphonate. The anthers of M₁ plants were cultured on the medium of NITSCH 1969 plus 0.1 mg IAA/1. Special attention was paid to quantitative characteristics of androgenesis. Androgenesis occurred more often in the treated variants. The conclusions have been confirmed of a heterosis effect of adequate chemomutagen concentration at the diploid level (an increase in the number of androgenic anthers in the treated variants, and a decrease in the mean number of haploids per androgenic anther) in the broad range of the material. We have recorded a high androgenic ability in the amphidiploidN. sylvestris x N. tomentosiformis, and androgenesis inN. velutina for the first time.

The growth of callus tissue cultures and the infectivity of twenty fiveSolanum laciniatum Ait. plants and of sixteenNicotiana tabacum L. cv. Samsun plants were investigated. The plants were obtained from callus tissue cultures derived from stem pieces of the respective plants infected with a mycoplasma-like organism (MLO) evoking potato witches' broom. The tissues were cultivated on synthetic nutrient medium with kinetin and IAA. Allde novo obtainedS. laciniatum plants were healthy. On the contrary twelve of the sixteen reconstituted tobacco plants showed MLO presence.
Summarizing these and previous results, the authors suppose that the most important factor influencing MLO persistence in callus tissues cultivated on the applied nutrient medium may be the callus growth rate and the organogenesis set. Both these conditions are determined by the metabolism of the investigated plant species.

In comparison with primary leaves of French bean plants grown under a photon flux density of 100 μeinstein m-2 s-1 (LP), leaves grown under 400 μeinstein m-2 s-1 (HP) were thicker (contained 82 to 104% more dry matter per blade area), had 44 to 48% higher stomatal frequency, 18 to 26% more chlorophyll (a + b) per leaf area unit and 31 to 42% less chlorophyll (a + b) per dry matter unit, 41% higher photosynthetic and 38% higher transpiration rates at light saturation, 33% higher stomatal conductance and 40% higher Photosystem 2 (H2O → K3[Fe(CN)6]) activity of isolated chloroplasts. There were no significant differences in the Photosystem 1 (TMPD/Ascorbate → MV) activity per unit amount of chlorophyll. Higher growth irradiance increased the ratio of frequencies of stomata in the upper/lower epidermes.

Water potential of roots was measured by thermocouple psyohometers in a series of two or more plants ofCynodon dactylon (L.)Pers. interconnected by overground stolons and thus forming one s.c. polycormon. Root water potential was lowest (most negative) in the oldest "mother" plant and increased in younger individua to highest walues in the youngest "doughter" plants. This gradient of root water potential was found although the "mother" plants continued to be watered while watering all daughter plants had been stopped one week before the water potential was measured. Thus the whole polycormon consisting of a series of interconnected individua behaves as one hydrodynamic system where all individual root systems act as if being parts of one sole root system.

The distribution of endogenous gibberellin-like substances in individual organs ofZea mays L., cv. CE 250, plants was investigated during the transition from the vegetative to the generative phase of development. The gradient of the content of gibberellin-like substances and photosynthetic activity in leaf segments was followed in different parts of the Jeaves, as well as the changes in the content of gibberellin-like substances in leaf segments during an exposure in the light and in the dark. The gradient of the content of endogenous gibberellin-liko substances in the leaves, in the stem and in the spike is interpreted in terms of possible relationship of these compounds to the regulation of sink - source.

Spraying of CCC (500 ppm) on wheat cv. Kalyan Sona-227 averted the adverse effect of soil moisture stress at the anthesis phase, by maintaining a higher level of chlorophyll, nucleic acids and protein content and acidity of the tissues. Treated plants after recovery from moisture stress yield even more than the untreated plants.

Conditions for the mechanical transmission of some woody viruses to herbaceous hosts were studied. Viruses from naturally-infected spindle tree (Euonymus europaea) and maple (Acer pseudoplatanus) leaves were mechanically transmitted by the homogenate prepared by using charcoal and celite to beans (Phaseolus vulqaris cv. Kocovska and Perlicka). The transmission of Euonymus mosaic virus and maple leaf perforation by nucleic acids prepared from naturally infected woody plants was also successful.

Zn²⁺ ions slightly enhance at low concentrations (0.01 μg ml^-1) the activity of tryptophan synthase obtained from the shoots of 14-day-old pea seedlings (Pisum sativum L.). On the contrary, high concentrations of Zn²⁺ (10 μg ml^-l) exert an inhibitory effect. The direct Zn²⁺ activation of tryptophan synthase, establishedin vitro with a partially purified enzyme preparation, is relatively low and obviously is not decisive from the point of view of tryptophan biosynthesis of the enzyme and thus they are participating in thein vivo experiments.

Two plants which were sectorial chimeras in the two tested characters,i.e. in the length of stomata and their frequency, were found among the 17 individuals regenerated from the stem pith of the same marrow stem kale plant. The chimeral character was also expressed in the size and variability of pollen grains and in the number of colpae in their exine. The different ploidy of sectors (2n, 4n) was confirmed cytologically.

The rate of RNA synthesis in shoot apices of the short-day (SD) plantChenopodium rubrum was compared in three successive dark periods required for flowering.³²P label was used for fractionation of RNA on slabs of polyacrylamide gels on mioroscopic slides. Incorporation of³²P and³H-uridine into apices was followed using histoautoradiography under identical conditions for oomparison. The lowest rate of synthesis was found on the seoond day of induction. A slight increase was usually observed in the third dark period, possibly linked with the first anatomical and/or morphological changes whioh have appeared due to mduction. Most of the label was found in ribosomal BNA in this case. After the plants wero transferred from light to darkness RNA synthesis in the shoot apex decreased within three hours. There was good agreement between results obtained by eleotrophoresis and by histoautoradiography. All previous observations which have been obtained using cytophotometry and histoautoradiography were confirmed.
The rate of synthesis of BNA in shoot apices is paralleled by that in primordial leavea. The marked rise of RNA synthesis during the inductive period, found in some planta requiring only single inductive cycle, was not established inChenopodium. A different pattern of RNA synthesis between plants flowering after one and after several dark periods, is suggested in discussion.

The influence of photoperiodic induction on the incorporation of uridine-³H into the shoot apices ofChenopodium rubrum was studied using the technique of autoradiography. No increase in uridine incorporation was detected either during induction lasting three days or immediately after its termination. Pyroninophylia likewise did not rise. However, changes in uridine incorporation related to morphogenetic activity during leaf formation and later during differentiation of inflorescences were well marked. The distribution of label in the nucleus immediately after three inductive cycles shows the ratio of extranucleolar to nucleolar incorporation to be higher in non-induced control plants than in induced ones.
Data from literature pointing to an activation of RNA synthesis during transition to flowering are discussed and compared with other systems where ontogenetic changes are accompanied by marked changes in RNA synthesis. It is assumed that the activation of RNA synthesis after induction is connected mainly with the activation of growth. However, inChenopodium rubrum photoperiodic induction proceeds together with limited growth and without activation of RNA synthesis.

Phosphorus oxytriamide PO(NH₂)₃ was proved chromatographically in the exudate of decapitatedPhaseolus vulgaris plants. This fact verified the presumption that covalent compounds of phosphorus and nitrogen enter roots without previous hydrolysis.

An electrophoretically homogeneous lactate dehydrogenase was isolated from soybean seedlings, the specific activity of which was approximately 1800 times higher than the crude extract. From the dependence of the rate of reaction catalyzed by lactate dehydrogenase on substrate concentration, Michaelis constants and Hill coefficients were determined for four natural substrates,i.e. lactate, pyruvate, NAD and NADH. The enzyme from soy-bean plants is non-competitively inhibited by oxalate and mesoxalate,i.e. by the compounds analogous to the substrate. At pyruvate concentrations above 0.8 mM, the rate of reaction catalyzed by lactate dehydrogenase from soy-bean plants decreases, fructose diphosphate and ATP function as inhibitors as well. The inhibition by ATP is pH dependent, which seems to be of importance for the regulation of enzyme activityin vivo.

Alcohol dehydrogenase was isolated both from monocotyledons and dicotyledons, some of them with proteins (bean, pea), others with lipids (rape, sunflower) and still others with sugars (rice) as reserve substances. Molecular weights of the isolated dehydrogenases ranged from 53 000 to 80 000. Plant alcohol dehydrogenases (ADH) catalyze the oxidation of ethanol as well as the reduction of acetaldehyde. pH optimum for the oxidation is in the alkaline region, for the reduction it is near neutrality. The Michaelis constants for ethanol oxidation are, with the exception of rice, higher than those for reduction of acetaldehyde. The specificity of plant ADH toward alcohols is relatively broad and only quantitatively different in the individual plants. Inhibitors of the ADH's studied are oximes, amides and intermediates of sugar metabolism, such as malate, acetate or succinate. The degree of inhibition brought about by the inhibitors studied differs from plant to plant but the inhibition type is the same.

Studies performed on winter rape plants(Brassica nnpus var.oleifera, cv. 'Gór-czański') revealed that cold treatment affected the cell membranes and led to the temporary increase in electrolytic leakage from a tissue. This was followed by the marked decrease of the electrolytic leakage in the course of hardening. Changes in membrane properties were accompanied by the promotion of soluble protein accumulation. Inhibition of protein accumulation by the cycloheximide treatment brought about wilting of plants under cold conditions. Possible role of soluble protein in protection of cells against secondary water stress caused by the coldinduced changes in membrane properties is suggested. Cold-induced changes in the electrophoretic pattern of soluble protein are described and discussed.

According to plant age at induction and rate of initial growth ABA leads either to stimulation or inhibition of growth and flowering in youngChenopodium rubrum plants. This differential effect is linked with the morphogenetic potential of the plants at the time of ABA application. Different modes of germination and cultivation of the plants prior to floral induction affect growth and photoperiodic sensitivity of the plants which may also explain differences in the effect of ABA.

Both CCC and cold (5°C) treatment gave rise to an increased content of the water-soluble proteins in leaf tissue of the winter rape, irrespective of the day length. This effect was accompanied by a decrease of the insoluble nitrogen compounds content, mainly under theLD (the 16 hour day). The applied retardant also stimulated the consumption of the structural compounds induced by low temperature.
Low temperature treatment hardened plants more distinctly than the CCC application. The frost hardening effect of CCC andSD (the 8 hour day) was manifested only at 20°C and it disappeared at 5°C.
Changes in frost hardiness were not correlated with the changes in the reducing sugar content and in the reducing ability of the studied tissue. The coincident effect of CCC and cold on the reducing sugar content was observed underSD conditions.

Some diagnostic methods devised for the demonstration of the presence of plum pox virus in plum (Prunus domestica L.) and apricot (Armeniaca vulgarisLam.) leaves were examined. The method of radial diffusion in agar can be recommended as the simplest and the least time consuming method which can be used during the entire vegetation period. In order to obtain antisera, some preparation methods of PPV antigen were verified. The best preparation method was a modification of Van Oosten's method in which HEPES buffer pH 6.7 was used for the homogenization-of leaves from infectedNicotiana clevelandiiGray plants and for the solution of sediments after ultracentrifugation. In this way, antigens with titre up to 1: 2048 and during the immunization of rabbit antisera with titre 1: 512 to 1: 1024 were obtained. After the saturation of antisera according to Uyemoto, the titre of the antisera was 1: 64 to 1: 256. Antisera were used for agar preparation in transparent plastic boxes. 0.2 to 1 g portions of leaf material were homogenized with 0.05 M Tris-HCl buffer pH 7.2, 3% pyrrolidine and 1 % polyvinylpyrrolidone in the ratio of 1: 3 for the determination of PPV in plum and apricot leaves.

Uridine incorporation into the shoot apex of the short-day plantChenopodium rubrum was investigated during a 16 h period of darkness and the following transfer to light. Uridine incorporation during this single inductive cycle was compared to incorporation under non-inductive conditions of continuous light. After transfer of the plants from light to darkness RNA synthesis was reduced to about half after the first two hours. This occurred not only when the plants were precultivated in continuous light but also after an interruption of the dark period by light for 31/2 h. The low level of uridine incorporation was maintained for the whole duration of the dark period. Incorporation regained its initial level after exposure of the plants to light irrespective of the duration of the preceding dark period. After this immediate rise of uridine incorporation in plants transferred from darkness to light a slight temporary decrease was observed in light. In darkness the decrease of incorporation into the nucleoli was still more marked than the reduction of overall incorporation. After the termination of the dark period incorporation into the nucleolus rose slowly and extranucleolar incorporation was relatively enhanced during the first 10 h of light in induced plants. The fluctuations of RNA synthesis observed in the shoot apex during photoperiodic treatment may be regarded as a necessary condition for the transition from the vegetative to the reproductive state.

Two soluble protein fractions were found to increase under cold treatment in winter rape plants. They were the proteins of low molecular weight, impoverished in proline and methionine residues and localized in the citosol subcellular fractions. They seem to be linked in "situ" with the hydrophobic compounds of cytoplasm. Owing to those properties, they seem to be more resistant against salt-induced aggregation which may occur at freezing or at A01GP096.

The content of endogenous auxins was examined in apical buds ofChenopodium rubrum plants induced by a photoperiodic cycle of 16h darkness and 8h light followed by a dark period of various duration so as to correspond with either maximal or minimal flowering response in the endogenous rhythm in capacity to flower initiated by the photoperiodic treatment. Apical buds of potentially generative plants contained less auxins than apical buds of plants which remained in the vegetative state. Apical buds from plants treated with kinetin (1. 10^-3 M) and therefore remaining in the vegetative state showed an auxin level comparable to that of untreated plants exhibiting minimal flowering response irrespective of the duration of the second dark period. Plants cultivated on a sucrose solution (0.6 M) during the second dark period became generative even at the normal minimum of flowering. The auxin content of the apical buds was low, similarly as in untreated plants induced for a period leading to maximal flowering response. On the other hand, apical buds from plants grown on sucrose solution during a dark period leading to the manifestation of maximal flowering response showed a relatively high auxin content comparable to that found in untreated plants which had obtained a more extended induction by three photoperiodic cycles. The results are discussed with respect to the possible role of endogenous auxins in the regulation of the changes in growth correlations occurring in the shoot apex during photoperiodic induction and in the expression of the competence to flower.