The effect of phosphorus deficiency on acid phosphatase activity in the apical, middle and basal parts of the root of maize plants was followed. The supernatant obtained by centrifuging the homogenate of plant tissue at 1500 ×g was further centrifuged at 18 000 ×g, the sediment being marked as fraction II and the supernatant as fraction III. The results obtained document the fact that acid phosphatase activity of the two fractions of all analyzed root segments was higher in plants cultured in nutrient medium without phosphate than in those containing phosphorus in nutrient medium. In most cases this difference was significant to highly significant. The results of experiments proved unambiguously a higher enzymatic activity in all root segments in fraction III than in fraction II. In fraction III the highest acid phosphatase activity was found in the apical part, in fraction II in the basal part of the root.

The clone SJ ofSpirodela polyrhiza (L.) Schleiden forms turions under various nutritive conditions. As compared to 1500 μmol 1^-1 phosphate (P+), growth and frond yield of mixotropic cultures decreased, when 60 μol 1^-1 phosphate (P-) were available. By contrast, P-conditions increased the number, individual size, dry matter content, and total turion yield (mg turions per ml of the nutrient medium) of P-turions as compared to P+ ones. Germination behaviour of P-turions is characterized by fairly low zero levels in the controls, and by low heterogeneity in individual size as well as in the response patterns concerning the influence of light and/or phytoactive substances. P-turions from youngSpirodela cultures are extremely dormant. However, they undergo an after-ripening process if kept inside ageing cultures.

The overall washing out of ions, especially⁸⁶Rb⁺ (as the tracer for K⁺), from hypocotyl segments of pumpkin (Cucurbita pepo L.) into distilled water or a CaCl₂ solution was studied, during plasmolysis with a saccharose solution and during deplasmolysis. Compartimental analysis was used to evaluate the⁸⁶Rb⁺ washing out kinetics. During plasmolysis, the washing out of⁸⁶Rb⁺ increases, due to two processes whose half-times are lower than those during washing out into the CaCl₂ solution. During deplasmolysis, the permeability of plasmalemma and tonoplast is substantially descreased, leading to washing out of most⁸⁶Rb⁺ from the cells. Plasmolysis differs from a mere decrease in the turgor pressure in the fact that after exchange for a hypotonic solution the membranes are irreversibly damaged.
The aim of this work was to monitor the changes in the cell membrane permeability due to a change in the water potential of the cells, especially during plasmolysis and deplasmolysis.

In standardMurashige-Skoog medium, particularly at pH higher than 5.0 and after heat sterilization, there is a tendency for turbidity or a sediment to appear, and for the acidity to increase by 0.2 to 0.5 degrees pH. The sediment is an amorphous precipitate of ferric phosphate and partly also of ferrous phosphate. In a stock iron solution prepared by chelation of ferrous sulphate with an equimolar quantity of the complexone Na₂EDTA. up to 10% free Fe^II ions could be detected. By titration of a concentrated complexon solution it was found that in the presence of an excess of Na₂EDTA (at the approximate molar ratio Fe^II: Na₂EDTA 1: 2) chelation of this free iron takes place to such an extent that its concentration falls to as little as 0.1%. Media with iron stabilized in this way are quite clear and maintain the adjusted pH for up to several weeks. The heat sterilization, too, does not lead to any precipitation or to a shift in pH within the broad range of adjusted values pH 4.8 - 6.0.
We also attempted to increase the relatively low buffering capacity of Murashige-Skoog medium. The addition of sodium citrate (1.25 mmol 1^-1) and particularly of citrate-phosphate buffer (at a final concentration of 1.97 mmol citric acid and 6.07 mmol dibasic sodium phosphate per litre of medium) to the Murashige-Skoog medium considerably increased its buffering capacity, so that at the end of the subculture interval of tobacco cell suspensions the adjusted acidity changed only slightly (pH 5.40 ± 0.15). A thorough evaluation of the growth parameters of tobacco batch cultures (cell counts, vital staining, kinetics of DNA and protein synthesis) failed to reveal any negative effect either of additional chelation or of the buffering components.

The mature nodules ofLens esculenta Moench. contained higher levels of indolyl acetic acid (IAA), cytokinins (CK), gibberellic acid (GA)-like substances and more active in nitrogenase (N₂-ase) activity than young or old ones. Synthesis of IAA and its metabolism was found to be controlled by tryptophan (tryp) and phenol metabolism, respectively, in nodules of different ages. An abscisic acid (ABA)-like substance being a 'late growth phase' hormone, was highest in old nodules.
IAA and CK were highest in winter when N₂-ase activity was also highest but then GA and ABA were low. The IAA metabolic pattern of both roots and nodules was regulated by phenols. The hormones hardly changed seasonally in the roots and showed higher activities of IAA oxidase, MeOx reductase, peroxidase and polyphenol oxidase than nodules.
The nodular anabolic changes are more pronounced in winter as lentil is a winter crop. The size of nodules at a particular age was the same in different seasons, even though their hormone content varied with the season showing that the nodular hormones were not solely utilized for nodule development and growth.

The bean first internode bioassay ofMeudt andBennett (Physiol. Plant.44: 422-428, 1978) is based on the curvature of bean internode sections after unilateral application of test material near to their base. The test was also used for estimation of biological activity of brassinosteroids which enhance the effect of auxin. Sensitivity of the assay to both IAA and 24-epibrassinolide was increased 1000 and 100 times, respectively, when internode sections were incubated in morphologically inversed position. Under these conditions test material was applied to the young auxin-sensitive morphologically apical internode tissues and auxin was basipetally translocated to the zone of curvature. Using this bioassay as little as 10 fmol of IAA and 1 pmol of 24-epibrassinolide can be estimated.

Flower initiation takes place during a rise of peroxidase activity following a peak of minimum activity which marked the completion of the flowering inductive phase. Since basic isoperoxidases underwent an inverse variation of activity in the course of successive inductive and initiative phases, it was hypothesized that the induction of flowering led to a temporary peak of maximum auxin level in the leaves. Our analyses and available literature data support the view. They also show the different capacity of non-induced and induced material to respond to external auxin application. Since some aspects of the physiological state characterizing induced plants can be simultaneously obtained in all plant parts as a result of rapid interorgan communication, the classical florigen theory is seriously challenged.

The mechanisms by which exogenously applied plant growth regulators act to express those genes that are selectively involved in cell and tissue differentiation are not at all well comprehended. However, the ontogenetic sequences of events that enable receptor or target cells to be activated and to undergo dedifferentiation and redifferentiation, can often be followed experimentally and can lead to a better understanding of the causal relations and control mechanisms in coordinated cell growth and development.
Cytokinins, applied either in an agar medium or as high-concentration, short-duration pulses to expiants or as high-concentration, intermittent sprays to intact plants, induce switches in the normal developmental pattern of cells of certain explanted tissues. Examples of cells that are particularly receptive are the subsidiary cells of stomatal complexes and the differentiating cells of very young presumptive leaf primordia, that is before the latter have become irreversibly determined as leaves.

A description is presented of a simplified procedure for the serological diagnosis of plant viruses which utilizes the high sensitivity of the latex test. Small pieces of the plant examined are soaked in a drop of water, buffer, or directly in the sensibilized antiserum. Following the reaction with the antiserum the virus is evidenced by visual evaluation of the presence of agglutination. The procedure is applicable for routine serological diagnosis; it demonstrates even small virus concentrations and is as reliable as the normal procedure of the latex test. Using this simplified procedure the following viruses were demonstrated in various host plants: X-, Y-, S-, and M-virus of potato, the carnation mottle virus, and the tomato bushy stunt virus.

Several examples of transmission of rapid signals within plants are described. Most of these signals may be inhibited by pretreating plants with LiCl, with inhibitors of ionic permeability, or with substances interfering with Ca²⁺. Accordingly, they are dependent on ionic changes. LiCl also prevents or delays the onset of flowering in long-day plants. In addition isolated organs or tissues most often do not react to an external stimulus as do similar organs or tissues within an intact plant. All these facts lead to the conclusion that plants are highly integrated organisms. Any change in the ionic equilibrium occurring in one part of these organisms has rapid consequences in other parts. This hypothesis may be applied to the floral process: after perception of the appropriate environmental conditions, the leaves modify the orientation of meristem differentiation by promoting the redistribution of ions (especially Ca²⁺, which has a "second messenger" function).

Occurrence and operation of sucrose synthetic system in randomly selected callus cultures such as persimmon, soybean and poplar cultures were examined by¹⁴C-tracer analysis and determining enzyme activities involved in sucrose metabolism. All the enzymes examined were present and¹⁴C-glueose was transformed into¹⁴C-sucrose in every callus. Sucrose synthetic capacity appears to be widely distributed in cultured plant tissues.

The present paper deals with the hormonal regulation of reproductive development,i.e. flowering and sex manifestation. Representation of hormonal regulation of flowering is based on the concept of florigen as a two-component, complementary system of flowering hormones, which consists of gibberellins and anthesins. Data are presented on the effect of extracts of gibberellin- and anthesin-type substances from the leaves of flowering and vegetatively growing plants under non-inductive conditions of day length. Experiments with flowering of plants under the influence of graftings serve as a basis for considering the question about the common nature of one of the florigen components - anthesins, for various plant species.
The mechanism controlling tuberization in both intact and grafted plants is based on the participation of all the components of the hormonal system and constitutes one of the most vivid manifestations of integration of all the organs in the whole organism.

The influence of different organs on flowering of photoperiod- or temperature-dependent plants and of neutral plants is described. Special attention is given to the influence of roots which generally inhibit flowering. High or low temperatures applied to the roots ofChenopodium polyspermum, a quantitative short day plant, induce flowering. Vernalizing treatment of roots ofCichorium intybus suppresses the inhibition of flowering arising from the tissues immediately underlying the terminal bud. Other plants such as coniferous trees can flower more intensively if the growth of their roots is reduced. After a short presentation of the very complex situation concerning the regulation of floweringvia the presently known hormones, the methodological limitations of our understanding of the precise hormone mechanism of flowering will be discussed. One example of an immunologica 1 approach to localize endogenous hormones inside tissues is given, using abscisic acid.

The inhibitor of microsomal monooxygenase activities 9-hydroxyellipticine markedly inhibited the frequency of embryonic and chlorophyll mutations induced by the metabolism-requiring mutagen dimethylnitrosamine (DMN) in a higher plantArabidopsis thaliana, but had no effect on the frequency of mutations induced by the direct-acting mutagen N-methyl-N-nitrosourea (MNU). The presence of thiol containing compounds thiourea and cysteine before and during DMN or MNU treatment resulted in a decline of mutation frequency as compared to treatment with either nitroso compound alone. In contrast, the mutagenicity of DMN and. MNU was not altered in the presence of two other thiol compounds, thiouracil and glutathion and by six naturally occurring phenolic acids: ellagic. vanillic, cinnamic, coumaric, caffeic and ferulic acids.

The current status of our knowledge of auxin effects on floral induction is summarized. The most general effect is inhibition, although the concentration of synthetic auxins added to. plants tends to be too high for us to be certain that the inhibitory effects are truly physiological. Studies of endogenous levels of auxin have focused almost entirely on IAA-like bioassay activity. Chemical identifications of endogenous IAA are needed and feasible. In addition, a search for-other auxins involved in vegetative to floral transitions, their chemical identification, and measurement of their changing levels in the plant are urgently needed.

A possible involvement of the alternative oxidase pathway in proton translocation was investigated. Net H⁺ efflux- and elongation-rates were simultaneously and continuously measured by means of a pH-stat and an angular position transducer. Disulfiram, an inhibitor of the alternative path, reduces the IAA- and Fusicoccin-induced as well as endogenous proton secretion and growth. Fusicoccin-induced H⁺ secretion is very sensitive to reduced oxygen concentration values far apart from the K_m of cytochrome oxidase. The sensitivity of non stimulated proton secretion to reduction of oxygen concentration depends on the age of plant material. It is proposed that more than one system is responsible for proton translocation across the plasmalemma. One of them has a high sensitivity to reduced oxygen concentration which is within the same range of the high K_m value of the alternative oxidase.

Experiments were conducted (a) to identify optimum media pH for nitrate uptake by intact corn (Zed ways L. cv. XL-81) plants grown under solution culture conditions, (b) to understand the effect of media pH on growth, nitrate uptake, water use and nitrogen accumulation. pH was maintained using carboxy cation exchange resin IRC-50. Plantswere grown in 15mM NO₃-N per litre and nitrate depleted from nutrient solution over a period of time was measured. Dry matter accumulation by the plants decreased progressively with increased pH. However, the decrease was significant only at pH 7.0 and 8.0. Data on water use showed results similar to dry matter accumulation. Correlation coefficients (r values) among nitrate uptake, dry matter production, water use, nitrate -N accumulation and reduced -N accumulation was observed to be high (above 0.99). All effects of media pH are significant only at pH range 7.0 to 8.0. Despite adequate supply of iron, the plants at pH 7.0 and 8.0 showed symptoms of iron deficiency. Thus, iron and possibly micro-nutrient deficiency could have resulted in poor plant growth. These experimental results indicate optimum pH range for nitrate uptake is 4.0-6.0. Plant growth and dry matter accumulation were directly affected by media pH. The differences in nitrate uptake, water use and total nitrogen accumulation appeared to have resulted as a consequence of differential dry matter production. Whether these differences are due to altered metabolic uptake characteristics of the loots is not known.

The fluctuation of free IAA under 16 h dark period in shoots (receptor organs of photoperiodic induction) and roots of the short-day plant (SDP)Chenopodium rubrum and in shoots of the long-day plant (LDP)Chenopodium murale is very similar. The data reflect the general adjustment of auxin level to day-length rather than changes due to floral induction. However, the shift in phasing of the circadian rhythm of flowering was accompanied by a change in the position of the' troughs' of free IAA levels indicating a possible relationship between the two processes. Periods of higher sensitivity to application of IAA (3. 10^-4M) inhibitory to flowering have been observed both during the endogenous rhythm of flowering in the SDPC. rubrum and during induction by days of continuous illumination in the LDPC. murale. There exist common traits in the response of LDP and of SDPChenopodium to auxin treatment. Aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, counteracted some flowering inhibitory effects of IAA when applied simultaneously with it. This suggests that auxin effects in modifying flowering might in fact be due to ethylene.

Bacteria of the speciesPseudomonas putida andPseudomonas fluorescens isolated from the rhizosphere of maize and bean plants produce indol-3-ylacetic acid and some other auxins when grown in suspension cultures. IAM and ILA were also found besides IAA and its degradation product IAH by means of HPLC and MS methods. This finding indicates the involvement of two different metabolic pathways in IAA synthesis in bacteria. The amounts found varied between 1.6 and 3.3 μg IAA per ml of media which corresponded to 100-200 μg per gram of bacterial dry mass. The effect of IAA production by rhizosphere bacteria on IAA level in the plant is discussed.

Leaf expiants from vegetative plants of the short-day plantStreptocarpus nobilis (C. B. Clarke) developed flower budsin vitro when cultured in 8 h photoperiods. Tn non-inductive photoperiods only vegetative buds were formed.In vitro photoinduction was demonstrated by giving the expiants short-day (SD) cycles and then transferring them to non-inductive photoperiods for expression of flowering. On medium containing 6-benzylaminopurine (BAP) organogenesis was initiated during the photoinductive treatments. Photoinduction of leaf tissue without adventitious bud development was obtained on medium without BAP. The photoinductive state of the leaf tissue was fairly stable, being expressed after 2-3 weeks in non-inductive photoperiods when adventitious buds were formed. The quantitativein vitro flowering response to the endogenous floral stimuli, resulting from photoinduction, could provide the basis of a bioassay for presumptive flower inducing chemicals.

The effect of silymarin complex on various types of expiants differing in their nutrition requirements was investigated. The growth of tumorous periwinkle (Catharanthus roseus [L.] G. Don) callus tissue was still identical with the control tissue at the silymarin concentration of 35 mg in 1000 ml of the nutrient medium. However, this silymarin concentration totally inhibited the growth of habituated periwinkle callus tissue; in the presence of 10 mg of silymarin, the growth of this tissue was similar to that of the corresponding tissue grown without silymarin. The growth of tobacco callus tissue (D-strain) requiring for its growth kinetin was reduced by 46.2% at the concentration 10 mg of silymarin in 1000 ml of nutrient medium, but its dry weight was increased by 21% in comparison with the control. Silymarin was most effective on the growth of callus derived from tobacco (Nicotiana glauca Grah:) stem pieces; callogenesis was observed in control tissue in 89.5% cases while in the presence of silymarin (10 mg) only in 48.6%. The primary callus growth was strongly inhibited, too (by 89.9%). The organogenesis onset was never observed on tobacco stem pieces cultured on a nutrient medium with kinetin and IAA in the presence of silymarin. When all types of expiants were transferred from the medium with silymarin on control medium, normal growth appeared very soon and the differences between the experimental and control expiants were smoothed out during two months. These results indicate that the observed changes might be due to the blocking of membrane system permeability leading to an insufficient supply of cells with nutrients and growth substances.

Plants were regenerated from mesophyll protoplasts of axenically growing plants of four dihaploid clones and five tetraploid cultivars ofSolanum tuberosum L. andSolanum phureja Juz. etBuk.

In the above-ground part of 12 different spring barley genotypes the phenomena were studied as follows: nitrate reductase (NR) activity, nitrate nitrogen (nN)-, ammonium nitrogen (aN)-, total nitrogen (tN)-, and soluble sugars (sS)-concentration, physiological yielding characteristics, their variability and relations during vegetation (field experiments). Significant genotypical differences in NR activity were not ascertained until in the shooting and especially in anthesis and milk ripeness. Of the parameters observed nN- and tN-concentration showed the greatest and the smallest genotypical differences during vegetation, respectively. Variability of the seasonal mean values was as follows [%]: NR activity -12.9; nN-conc. -43.7; aN-conc.-14.3; tN-conc. -7.9; sS-conc. -15.6 and dry weight of 1 plant -19.7. NR activity was in a positive correlation with nN- and tN-concentration and in a negative one with sS-eoncentration except for the period of anthesis. Similar negative correlations were noted between concentrations of sS and nN and between those of sS and tN. A positive and most significant relation was found also between N-translocation from vegetative matter to corn, N-harvest index, grain harvest index, further between grain yield, N-harvest index and grain harvest index. The results are discussed with regard to development of genotypical differences in these parameters and to possibilities of their use as selection characteristics.