The effect of GA₃, IAA and kinetin in concentration range from 5.10^-4 to 5. 10^-8M, single or in combination, was tested on the flowering of short-day plant (SDP)Chenopodium rubrum (selection 374). All substances were applied as a droplet (3 (μl) of water solution before the onset of inductive photoperiod which brought about a threshold level of induction. Flowering was enhanced only in the presence of GA₃ and the other two PGR decreased its effective concentration by one or two orders of magnitude. It is likely that the morphogenesis of the apical meristem was directly affected by such treatment. There is no need to assume that the ratio of employed plant growth regulators is important for the observed morphogenetic effects, but rather the actual concentrations are involved.

Chlorides, nitrates, and sulfates of alkali metals, ammonium, calcium, and magnesium inhibit P_i uptake into maize root cortex segments. The concentration 100 mM brought about 50-100% inhibition, whereas 10 mM concentration (with the exception of salts of NH₄+, Ca²⁺, Mg²⁺) about 15-55%. Also potassium benzenesulfonate (100 mM) dramatically decreases P_i uptake.
Osmotic shock also inhibits P_i uptake. Marked decrease of P_i uptake ability proceeds in concentration range 0.12-0.13 M NaCl. Concomitantly, proteins are released into rehydration medium and their amount is proportional to the degree of P_i uptake inhibition.
The effect of 0.13 M NaCl on P_i uptake and protein release is about the same in roots of intact plants, excised roots, root segments and segments of isolated cortex and stele. Roots of intact plants and excised roots are more responsive to osmotic shock than studied segments.
The degree of salt tolerance of glycophytes is in correlation with NaCl concentration, which brings about 50% inhibition of P_i uptake.

Using different independent procedures for assaying soluble auxin-binding in etiolated pea epicotyls, wo could prove the reliability of the (XH₄)₂SO₄-pelleting assay both for crude cytosols as well as for specific protein fractions obtained after chromatofocusing. Three distinct genotypes (two parent lines, one tall recombinant) investigated so far exhibit characteristic differences with respect to soluble auxin-binding kinetics in their cytosols.

It is generally accepted that plant growth and development are regulated by the known plant hormones. Some objections to the functions of auxins and cytokinins in the induction of shoot and root primordia are reported. Instead of them oligopeptides of special amino acid sequences could be the endogenous signals. There exist structure relationships between auxins and parts of the α-helical oligopeptides of defined amino acid sequences. The same is true for cytokinins.
The most difficult part of this hypothesis is its verification. Using protonemata ofFunaria hygrometrica bud induction by various oligopeptides was investigated. The most active peptide tested is leucine-tryptophan. On the other hand endogenous oligopeptides containing [¹⁴C]-leucine in the moss protonemata during endogenous bud initiation were looked for. Three to four different oligopeptide spots seem to be related to bud induction.

Transversally cut leaf segments ofCentaurium erythraea were cultivated on MS medium. Effects of segment polarity, IAA and sucrose concentrations, light and medium volume on morphogenesis were studied. Shoots generally formed at lower (1.3 × 10^-6 mol 1^-1) IAA concentrations than roots and callus (1.1 × 10^-5-3.4 × 10^-5 mol 1^-1). Leaf polarity strongly modified the effect of IAA concentration, shifting organogenesis at the segment base toward decreased IAA concentrations as compared with segment apex. Light, sucrose concentration above 3 % and high medium volume changed IAA dependence of morphogenesis in various ways and generally suppressed segment polarity.

Wilting of maize seedlings was significantly delayed in the presence of amino acids supplied in the ambient medium along with different levels of osmotic stress. Water saturation deficit (WSD) values at all stress levels were lower in the presence of exogenous amino acids, however, the effect was much clearer in resistant cv. Ageti-76 as compared to susceptible cv. Vijay under similar conditions. The effectiveness of proline in the external medium was in no way better than other amino acidse.g. serine, asparagine, alanine and cystine.

A low frequency androgenesis was inducedin vitro in all experimental variants ofCapsicum anthers cultured in standard and minimalized media. The embryogenic frequency was stimulated by the presence of activated charcoal which also prolonged the vitality of the culture. The percentage of embryoids growing to complete plants increased, if the embryoids were removed from the anthers and cultured separately. The morphogenic initiation of globular embryoids was conditioned by the presence of FeEDTA in the culture medium. The stimulation of androgenesis initiation can be explained by the same change in the decisive factor caused by various effects. In long-term embryoid cultures, which stagnated in growing and seemingly necrotized, a second somatic embryogenesis occurred. About 10% of obtained androgenic plants were fertile and even gave progenies. The process can be recommended for breeding.

The objectives and methodology of metabolic studies of the gibberellins are discussed with particular reference to the rôle of gibberellins in the promotion of stem elongation in gibberellin-responding dwarf mutants of pea.

Exogenoualy applicated indol-3-ylaeetic acid (IAA) is metabolized mainly to IAA aspartate in intact plants and plant segments and to IAA glucose in suspension cultures fromBeta vulgaris andChenopodium album.
Main metabolic product of D-tryptophan is N-malonyltryptophan in both suspension cultures and hypocotyl segments of both species. The turnover rate of L-tryptophan to IAA is comparatively low (0.1 %); inBeta the turnover rate is higher than inChenopodium. In sugar beets phenmedipham leads to a decrease in the IAA. biosynthesis rate in suspension cultures of both plant species. There is, however, an increase in the IAA content in all intact plants. The metabolic activity is substantially higher in suspension cultures than in intact plants and plant segments.

Reorganization of growth in the shoot apex ofChenopodium rubrum during transition to flowering is described. Growth and morphogenic changes - a rise in cell division rate, changes in leaf and bud formation and changes in directions of cellular growth - are viewed from the aspect of a possible role of growth hormones in controlling these changes. Growth and morphogenic effects of exogenous growth regulators in the shoot apex ofChenopodium are summarized and their floral effects explained in terms of changing apical growth correlations. New evidence concerning the timing of increased cell division rate and showing the limited requirement of axillary cell division and a shift to more vertical direction of growth in the apex in the floral developmental pathway was obtained in experiments with kinetin application and by surgical treatments.

Seed protein patterns were compared in 10 species of the genusVigna, and in the generaMacroptilium, Strophostyles, Macrotyloma, Psophocarpus andPhaseolus. ThreeVigna groups could be clearly separated using immunochemical methods:Vigna hosei andVigna luteola;Vigna mungo, Vigna angularis, Vigna umbellata, Vigna trilobata andVigna radiata;Vigna sinensis,Vigna unquiculata andVigna aconitifolia.
Among the other investigated generaPsophocarpus appears to be very distant, the others showing partial similarity in seed protein patterns.

In maturing fruits ofPhaseolus coccineus a soluble glucosyltransferase activity occurs which converts gibberellins into their O-glucosides. The enzyme glucosylates GA₃ and structurally closely related gibberellins (GA₇ and GA₃₀) to their 3-O-glucosides by transfer of glucose preferentially from UDP-glucose.
From cell suspension cultures ofLycopersicon peruvianum cytosolic glucosyltransferases were isolated which in the presence of UDP-glucose converted GA₇ and GA₉ to the corresponding glucosyl esters. In both cases numerous other gibberellins failed to serve as substrates. Thus, the enzymes are UDP-glucose: gibberellin glucosyltransferases of considerable substrate specificity.

Current knowledge about effects of exogenous PGR on cone initiation in coniferous trees is briefly reviewed. Long life-cycles, large tree size and great irregularity in coning have imposed severe restraints, but experimental study of reproduction can now be achieved in small plants of some species. In adult, clonal cuttings ofThuja plicata, standard injections of 50-250 (μg GA₃ induce substantial male and female coning, and have been used to test effects of other PGR on cone initiation and development. In thePinaceae, propagation of naturally heavily-coning genotypes has facilitated research on the effects of PGR.

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.

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.

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.

Pharbitis nil, strain Kidachi and Violet, were grown at 20° C under continuous light in various cases of different sizes, containing the nutrient solution or tap water. Kidachi initiated flowers when seedlings were cultured in small cases containing nutrient solution but did not flower in large cases. The application of NAA, kinetin, ABA or 5-chlorobenzoiec acidvia roots in large cases caused flowering, Floral initiation was always accompanied by the suppression of root elongation. The promotion of root elongation by aeration inhibited flowering. Root cutting inhibited flowering. On the other hand, Kidachi did not flower in tap water irrespective of vessel size. Violet did not flower in the nutrient solution even in small vessels, but initiated floral buds in tap water irrespective of vessel size, though the plants grown in large cases developed very long roots. In both types of flowering, cotyledons are necessary to induce flowering and the removal of cotyledons before the 16th day after the start of culture in Kidachi and before the 12th day in Violet completely inhibited flowering. GA₃ promoted stem elongation without preventing flowering of Kidachi.

Black currant reversion disease causes serious problems in some cultivars of black and red currant. Investigating ultrathin sections prepared from overground parts of diseased red currant plants cv. Heinemann's rote spätlesse, we observed consistently local cell wall disintegration of tracheids in vascular bundles. We have observed these changes in red currant plants showing reversion symptoms during the vegetation period from March to June. The observed phenomenoni.e. cell wall disintegration of tracheids might be utilized as an auxiliary diagnostic criterion m ident ification of red currant reversion disease in the cultivar Heinemann.

The work concerns the senescence of isolated young leaves of oats (Avena sativa) floated on water or solutions. Senescence is rapid in darkness but slow in white light; the effect of light is not due to photosynthesis, but is paralleled by stomatal opening. Closure of the stomata by osmotic or chemical means makes senescence in light proceed as fast as in darkness, while opening the stomata in darkness by cytokinins, fusicoccin,etc., delays senescence to rates typical of light. The osmotic closure in light is mediated by abscisic acid, and since this also accumulates in darkness it appears as a major factor controlling senescence. Efflux of ions into the solution; indicating increased permeability, occurs almost in parallel with senescence. Senescence in light is accelerated by 1-aminocyclopropane-l-carboxylic acid (ACC) and inhibited by cobalt, silver or aminoethoxyvinyl glycine (AVG) which interfere with ethylene production or action; however, ethylene's role is unclear because some reagents, including kinetin, that delay senescence, actually increase ethylene production. At the endogenous level, therefore, ethylene may not be a limiting factor. Finally, a new ethylene-generating system is described in which the dehydrogenation of linoleic acid is coupled through manganese to the oxidation of ACC; it is probably activein vivo.

Evidence is presented to support the generalization that gibberellin A₁ is the main 'gibberellin hormone' that is activeper se in the control of elongation growth in higher plants. The evidence is based on a combination of chemical and genetic studies using single gene mutants of maize, pea and rice.