Effects of 2,3,5-triiodobenzoic acid (TIBA) and age of etiolated pea epicotyl segments on the indol-3-ylacetic acid (IAA) stimulated transport of¹⁴C-abscisic acid (ABA) was studied. In spite of a slight decrease of IAA transport after the application of TIBA, the IAA stimulation of¹⁴C-ABA transport did not change. In segments excised from epicotyls of different age,³H-IAA transport was identical and the induction of prolongation growth by IAA in segments from the upper part of the epicotyl was observed. The IAA ap{ie226-01}ation to the growing segments was connected with intensive attraction of¹⁴C-ABA to the site {ie226-02}AA application, while the application of IAA to the older segments was growth ineffective ana no stimulation of¹⁴C-ABA transport by IAA was observed.

The influence of growth regulators (GA and IAA) on the genetic effects of sodium azide was studied. Treatments with growth regulators were administered either prior to or after the mutagen. Post-treatments were found to be more effective against mutagen-induced plant growth injury and gave a slightly higher frequency of mutations. M₁ spike sterility however showed a rise following treatments with growth regulators.

The specificity of IAA-binding site from the wheat shoots was investigated in an attempt to confirm its receptor function. Several monofluoro-, monochloro-, dichloro- and monobromo-substituted indol-3-ylacetic acids were allowed to displace¹⁴C-IAA from the binding site. Displacement abilities of these halogenated IAAs were closely related to there activities in wheat coleoptile straight growth biotest. This finding indirectly confirms thephysiological significance of this binding site.

Inhibition of root growth was observed inChenopodium rubrum under photoperiodic conditions inducing flowering. That this inhibition is mediated by the cotyledons was shown directly by the effect of their excision, which changes the responsiveness of the roots to photoperiodic treatment. On the other hand, decapitation did not lead to such an effect. Some evidence is put forward suggesting that changes in IAA may be involved in these correlations. The existence of two different mechanisms of photoperiodic action in flowering and in root growth is proposed to explain these differences.

The changes in the levels of growth regulating substances using the wheat coleoptile straight growth test were determined in the leaves of vernalized (flowering) and non-vernalized (non-flowering) plants of sugar-beet, cv. Poly-AG-Poland at two stages; the end of vernalization treatment (210 days from planting) and full-flowering stage. IAA was detected only in the extracts of the leaves of non-vernalized plants after210 days from planting. No inhibitory activity was detected, except in the case of the concentrated extract of the leaves of non-vernalized plants. This growth promoting zone was found at R_f 0.5-0.8 in the leaves of flowering plants after cold treatment and at flowering time. This zone of growth promoting action was suggested to have a major role in the flowering of sugar-beet.

There are several differences between monocotyledonous and dicotyledonous plants. The sensitivity towards added galactose which inhibits auxin-induced coleoptile elongation but not stem elongation is one of the conspicuous differences between the two types of plants. InAvena coleoptile segments, galactose, probably as galactose-1-phosphate, inhibits the formation of UDP-glucose from glucose-l-phosphate. The inhibition of UDP-glucose formation due to galactose is not found inPisum epicotyl segments. InAvena UTP: α-D-glucose-1-phosphate uridyltransferase (EC 2.7.7.9) which catalyzes the reaction from glucose-1-phosphate to UDP-glucose seems to be inhibited by galactose-1-phosphate.

Lemna gibba G3 is an ideal system for studying the chemical control of flowering in a photoperiodic plant due to its small size and aquatic growth habit which allow substances to be taken up continuously and rapidly distributed throughout the plant. Each of the known plant growth regulators has been tested onL. gibba G3 and only the gibberellins appear to be important for flowering, although they are not the limiting factor for flowering on short days. Salicylic acid (SA) and ferricyanide will both induce flowering inL. gibba G3 with ferricyanide being most effective on short days where flowering is daylength limited and SA most effective where flowering is limited by factors other than daylength. The ferricyanide action is probably due to HCN and it may act during photoperception or photoinduction. SA is most effective when reversing the inhibition caused by various parameters including copper and agar, and its effect is always strongly daylength dependent. It is postulated that SA may interact with the flowering stimulus to promote flowering and thus that SA acts at some point following photoinduction and the formation of the flowering stimulus.

Foliage and tuber fresh matter and chlorophyll content in cvs. Atom alue, Multa, Kufri, Desiree and Patrones were decreased with the increase in soil acidity. However, tuberization was enhanced at pH 5.5 and decreased significantly at pH 4.5 in all cultivars tested. At pH 4.5 the specific mass of all the cultivars was slightly increased. The highest content of reducing sugars and proteins was found at pH 5.5. No definite pattern was observed in total glycoalkaloids content under different acidic range.

The plant growth regulator 2-ohloroethylphosphonic acid inhibited the elongation of growth inPhaseolus aureus seedlings. In comparison to the control, the polyphenol oxidase and peroxidase activity of treated seedlings was low up to 24 and 48 h of germination, respectively and that of phenylalanine ammonia-lyase and tyrosine ammonia-lyase was slightly less at 120 h and that of α- and β-glucosidases were less at 48 and 72 h, respectively. At other stages of germination, it greatly stimulated the activities of these enzymes.

The effect of gibberellic acid, benzyladenine and a mixture of these compounds on the activity of some hydrolytic enzymes was studied in hyacinth bulbs non-exposed to low temperatures. Plant growth regulators were applied on the heel of dormant bulbs in the middle of July. An intensive elongation of the inflorescence was observed only in the plants treated previously with GA₃ and grown in a warm greenhouse for 63 and 84 days. The activities of amylase, invertase and acid phosphatase were higher in the flower buds of unrooted bulbs treated with growth regulators than in the control plants, although growth regulators did not affect the level of extractable proteins. The elongation of the inflorescence in the plants treated with gibberellic acid was correlated with a sharp increase of invertase activity in this organ. The effect of GA₃ and BA on the activity of other enzymes in buds and scales varied with the period of plant growth.

Polyacrylamide gel electrophoresis was used to study the differences in patterns of the isoperoxidase spectrum in leaf tissues of the genome series (2n, 3n, 4n) of twoNicotiana tabacum L. cultivars,i.e. in the growth stage of the 5th-6th and 10th-11th leaf, and in the stage of elongation growth. Mutual comparisons of the cultivars showed that the variability and difference in patterns between the cultivars in later growth stages was more important. In both cultivars only one rapidly migrating main band of isoenzymes was registered within the range of Rm 0.45-0.77; only in the stage of elongation growth on the 2n and 4n levels two bands were recorded. No association between the number of genomes and the number or distribution of isoperoxidases was found.

The characteristic micromorphology of the tobaoco cell strains, or its cyclic changes in the course of the subcultivation interval can be affected by auxin composition of the medium,i.e. by the application of either 2,4-D alone, or NAA, or their combination. On omitting one of the auxins, the over-all growth of the cultures is not substantially affeoted; however, the participation of various oell types, as well as the occurrenoe of starch grains are altered. The presenoe of 2,4-D alone results in an inhibition of starch occurrence, NAA alone causes a stimulation. There is no causal dependence of the occurrence or absence of starch grains on the stimulation of elongation (volume) growth, or, on the contrary, on cell division.

Exogenously applied IAA, GA₃ and Niagara (ethyl-hydrogen-1-propyl-phosphonate) activated dormant lenticel meristems of stem cuttings ofCedrela toona Roxb. Maximum activation was achieved by IAA at 0.5 mg ml^-1 concentration.

Alterations in protein pattern were observed in the callus tissues ofVigna unguiculata (L) Walp. up to tenth passage from its initiation. A gradual increase in quantity of protein was found up to sixth passage of culture. Decrease in the quantity of protein after eight months of culture might be correlated with the cytodifferentiation of the tissues. It has been recorded that with the initiation of morphogenesis there is an increase in the number and intensity of protein bands at the anionic end of the polyacrylamide gel.

Root primordia initiate in poplar stems in the secondary growing parts, that is in the parts where the elongation growth is terminated and the leaves are mature. Their initiation is connected with the occurrence of unusual biseriate, rarely multiseriate rays. A small cell group in the secondary phloem is initiated by cell division of the ray. It gradually enlarges by continuing cell division, by the addition of cells adjacent to the cell group and by cambial activity. Thus, a hemispherical root primordium is formed, for which a permanent occurrence of reserve lipids is characteristic. In stems several years old the intraprimordial mitotic activity is rhythmically renewed together with the cambium function renewal. Latent root primordia slightly enlarge with the passing years, whereas mainly the cells localized in their centre divide. Further organization and root histogenesis was not observed either in older root primordia. Adjacent to root primordia, cambial initials produce the secondary xylem elements increasingly. Xylem protuberances are thus formed under root primordia. Primordia initiation is most frequent within the first year of stem development, though they can also initiate in later years.

Deficiency in Ca and P in mineral medium reduced the growth and nitrogen content ofAzolla pinnata but increased the content of soluble sugars in the plant; the deficiency in K and Mg was less effective in retarding the growth. The pH of the medium from 5 to 8 encouraged the growth and nitrogen fixation, whereas acidic pH of 4 as well as alkaline pH of 9 inhibited the growth and nitrogen fixation.

A low reproducibility of some characteristics in the life cycle of the volvocal algaChlamydomonas geitleri was observed in repeated experiments. The sets of the cultures were very similar in the number of the studied characteristics, but some of them differed significantly in one or several characteristics whereas the others agreed in a whole set. This is documented by the growth in a nitrogenless medium, the formation of zygotes, and their maturation and germination. The results of a small representative set of experiments were treated by an analysis of variance. Some possible explanations are discussed.

It is wellknown that following the amputation, or darkening of one cotyledon in decapitated flax seedlings, the opposite remaining, or illuminated, cotyledon exerts a stimulatory effect on the growth of its axillary bud. For the induction of this stimulating effect a 21-72 h continuous darkening of the cotyledon is sufficient. Endogenous gibberellins take part in the stimulation effect of the illuminated cotyledon, since their level in the illuminated cotyledon increases as early as 12-48 h following the darkening of the opposite cotyledon. The apical part of the cotyledon has a higher growth stimulatory effect on the growth of the cotyledonary axillary bud than the basal half. This again is associated with endogenous gibberellins the level of which is higher in the apical half of the cotyledon than in the basal one.
Upon removal of the root and hypocotyl base in decapitated flax seedlings deprived of one cotyledon, the remaining cotyledon loses its stimulatory influence, so that the bud of the amputated cotyledon grows more vigorously (Dostál 1955). In this growth correlative phenomenon the root may be substituted by cytokinin BA applied in the form of a 0.1-1.0 per cent paste onto the remaining cotyledon, for again in this case the bud of the preserved cotyledon grows more vigorously. Following the decapitation of the axillary of the amputated cotyledon in decapitated pea seedlings with an intact root and deprived of one cotyledon, the axillary of the remaining cotyledon grows more intensively than the serial of the removed one. If the plants operated on in the same way are deprived of the root, the serial of the removed cotyledon gains a correlative growth predominance. If the plants deprived of root are cultivated at the same time in a solution of BA (10-20 mg 1^-1), the correlative predominance is acquired by the axillary of the remaining cotyledon. In growth correlations between cotyledons and their axillary buds in pea seedlings the root may thus be substituted by exogenous cytokinin, as well.

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.

Gmelina arborea L. seedling growth and diurnal stomatal opening (as measured by stomatal resistance) were studied at soil matric potential 0, -0.1 and -0.72 × 10^-5 Pa. Leaf area, leaf number, plant height and dry weights of the vegetative parts were significantly reduced as soil matric potential decreased from 0 to -0.72 × 10^-5 Pa. The growth responses followed the same trend as net assimilation rate and relative growth rate. The highest moisture stress induced leaf senescence and leaf fall. Leaf water potential decreased from - 2 × 10^-5 Pa to - 20 × 10^-5 Pa with increasing soil moisture stress. Results indicate that the diurnal stomatal opening is controlled by photon flux density when this species is grown at soil matrio potential 0 Pa. However, with decreasing soil matrio potential (- 0.10 and -0.72 × 10^-5 Pa) the internal plant water deficit appears to oontrol the stomatal opening.

The P uptake inAzolla pinnata in mineral medium increased linearly with increasing phosphate doses and optimum growth and chlorophyll content of fern were recorded at 1.2 mM of K₂HPO₄. The higher doses of phosphate reduced growth and chlorophyll, but an increase in soluble sugar and amino nitrogen was noticed. Addition of combined nitrogen sources decreased the fern growth, soluble sugar, chlorophyll and heterocyst frequency but amino nitrogen was comparatively higher. The growth and chlorophyll content were always high when the fern was grown in the absence of added nitrogen sources; this supports the thesis about the specific importance of symbiosis for the nutrition of fern with nitrogen which cannot be replaced by mineral compounds.

This paper deals with some morphological and histological changes observed during regular intervals inMatricaria inodora L. tissue cultures derived from leaf expiants. The expiants were cultivated on Murashige-Skoog's culture medium supplemented with 1.0 mg 1^-1 2,4-dichlorophenoxyacetic acid. The callus formation started about a week after isolation. During the second week the meristematic centers were differentiated from which root and shoot apices were later formed. During long term cultivation under the same culture conditions the inhibition of development of shoot apices took place. Only roots of unorganized growth have been regenerated. The influence of culture conditions on morphogenetic potential is discussed.

The effect of different growth substances on the development of normal and abnormal stomata are presented. Anomocytic, paracytic, anisocytic and stoma with a single subsidiary cell are observed. Abnormal developments like persistent stomatal cells, degeneration of guard cells, unusual thickening, unequal guard cells, single guard cells and size and shape of the pore are noticed in various growth substances. The growth substances also affect the stomatal frequency, stomatal index, epidermal frequency and size of guard and epidermal cells in both the plants. The highest meristematic activity is found in MOR 100 ppm in brinjal and in GA 25 ppm in tomato. The largest size of stomata is found in COL 25 ppm in brinjal and in MH 50 ppm in tomato. The same growth substance responds differently in the two plants.

3-day-old seedlings ofVicia faba L. were put onto a diluted Knop's solution containing the tested substances within the intentional concentration range and left there for 7 days. In comparison with controls in plain nutrient solution, the DHPA treated plants revealed a suppression of shoot and root development. The main root growth was less sensitive than root branching. 8 h exposure was sufficient to gain a distinct effect. Microscopically the block of mitosis and/or cytokinesis, the formation of binucleate cells and local tissue damage were revealed. Under the given conditions, the cytokinins (BAP, (9R)BAP, iP, (9R)iP) proved to be much more powerful inhibitors than DHPA, whereas adenine and adenosine were less impairing.

An improved system of plant cultivation at stable and specific levels of polyethyleneglycol (PEG, mol. mass 1400-1600) - induced water stress has been described. To set up this system a perforated tubular glass vessel containing soil to support seedling growth was wrapped externally first with a layer of macroporous silica gel-G and then with three layers of a dialysis membrane of a lower exclusion limit (2000 mol. mass). Effects of 8 days of PEG - induced stress have been studied on uptake and translocation of N and P and growth of barley (Hordeum vulgare L. cv. KN 16) seedlings. Some of the noteworthy improvements of the system were exelusion of PEG from the plant consequent upon use of silica gel-membrane combination, shorter time (2 days) for the soil-plant-air continuum to attain steady state, and stability of the plant water potential over a period of a few days.

Supply of 0.01 to 5.0 mM salicylic, caffeic and gallic acids, either during imbibition of seeds for 24 to 48 h or during seedling growth increased anthocyanin production in maize (Zea mays L. cv. Ganga safed-2) roots. While tyrosine had no effect, phenylalanine either in the presence or absence of the phenolic acids increased anthocyanin content. Glucose in a concentration range of 1 to 20 mM and shikimic acid in 0.01 to 5.0 mM range also increased pigment level, which was higher in the presence of salicylic acid than in it.s absence. The experiments demonstrate the possibility of some indirect effects of salicylic acid and other phenolic acids on anthocyanin synthesis.

The effects of some growth regulators on the dark-germinating seeds ofCucumis anguria have been investigated. GA₃, 6-BA and ethrel strongly promoted the germination of seeds kept in white light. GA₃ had no effect in counteracting the far red effect, but did counteract partially the blue light. Ethrel partially counteracted both the far red and blue light effect. No interaction could be found between red light and GA₃ or 6-BA.

During high altitude acclimatization the highest number of amino acids were found in temperateArtemisia species (A. vestita) and the lowest one in tropical species (A. scoparia). The amount of free amino acids in temperateArtemisia species was higher when this was grown at 3600 m altitude. InA. scoparia, A. vulnaris andA. parviflora, the higher amount of individual amino acids was ascertained in plants grown at lower altitudes.
InA. vestita, the nitrogen contents per unit dry matter was lower in plants grown at high altitude. In the other three species, the contents were significantly higher in the leaves of plants grown at a higher altitude. The nitrogen contents per unit leaf dry matter determined during active growth of plants were minimum inA. parviflora and maximum inA. vestita. With progressing plant senescence the concentration of nitrogen decreased in all species studied.

The mode of transport and regulative properties of phenylacetic acid (PAA) were studied in 11-cm long segments of pea epicotyls capable of growth. The transport of PAA m both the basipetal and aeropetal direction was limited to tissues situated immediately below and/or above the site of its application. PAA was able to promote the flow of¹⁴C-ABA in the acropetal direction. PAA-initiated thickening growth was probably the cause of this promotion.

Salinity caused a consistent reduction in the growth of cowpea plants and water content in their leaves. The total as well as the pigment fractions, except carotenoids, exhibited lower values than those of control plants at almost all salinity levels. With the rise of salinization, the total nitrogen and potassium contents in the leaves were decreased but the sodium content was increased and phosphorus content was not significantly affected as compared with the controls.
The application of IAA to salt-treated plants increased the water content in the leaves but it had no effect on the number of leaves and the stem length. The pigment contents in the leaves were either promoted or inhibited with the application of IAA, depending upon the level of salinization. The application of IAA to plants irrigated with water of the highest salinity level was effective in increasing the potassium content in the leaves as compared with the control, but it had no effect on the other mineral elements.