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.

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.

In the protonema ofFunaria hygrometrica, predetermined cells run through a period of sensitivity to cytokinins, as part of the morphogenetic system with respect to bud formation. The cytokinin sensitivity is highest immediately after the formation of cells in question. The cells can react if enough hormone is present during the sensitive phase. Kinetin is cleaved very rapidly and at an increasing rate. Most probably the concerned enzyme ("kinetin oxidase") is induced by kinetin. Therefore, cells formed after the beginning of the treatment do not respond by forming buds.

The vegetative apex grows in an indeterminate, iterative mode. When flowers are formed it changes to determinate, sequential growth. The essential change in growth at the transition to flowering seems to be the decrease in primordium size at initiation, relative to the size of the apex. In the formation of the flower itself there may be a further requirement, that primordia undergo a decrease in absolute size at initiation. Where measured, this decrease is parallelled by a decrease in the size of the stem frustum at initiation. While in the case of the stem frustum this decrease in size has a predictable consequence, the reduced size of internodes in the mature flower, it is not clear how the reduction in size of the primordium is related to the subsequent development of flower parts. Reduction in primordium size seems to be fundamental to the changes in primordium arrangement and divergence angle that typically occur on flower formation, but not sufficient to cause the subsequent differentiation of floral parts. This presumably occurs as a consequence of the interactions between the developing primordia and substances present in the flowering apex.
Recent models of flowering show that a realistic simulation of apical growth on the transition to flowering can be made using the equations of catastrophe theory. To account for the growth and development of a flower meristem models must also account for changes in divergence angle and the new developmental pathways followed by the floral organs.
The data on the role of growth substances in the transition to flowering at the apex are at present insufficient. What is needed particularly is information on the identity of the putative inhibitor of primordium initiation that may operate within the apex, and its role in the growth changes that occur during and after the floral transition.

L-tryptophan dehydrogenase (TDH) is a newly found enzyme involved in the metabolism of indole compounds in plants. The substrate specificity of TDH was investigated in extracts prepared fromPisum sativum andProsopis juliflora. The enzyme activity was detected in both plants either in the oxidative or the reductive direction. The occurrence of other dehydrogenases specific to amino acids was also investigated in the experimental plants:e. g. glutamate dehydrogenase was found to be 1.7 to 5.0 times more active than TDH, whereas no activity for phenylalanine dehydrogenase was detected. In pea plants activity of alanine dehydrogenase could be shown as well. In addition to pea and mesquite TDH was also found in wheat, maize, and tomato seedlings, whereas no activity was detected in brassicaceous plants.

The contents of chlorophylls, carotenoids, flavonoids and phytohormones (IAA, ABA and other inhibitors) were determined in green and albino seedlings of cotton (Gossypium hirsutum L.) and pea (Pisum sativum L.) The growth of green and albino seedlings during 1 -2 weeks was similar. The green and albino seedlings do not differ remarkably in phytohormonal content and in the flavonoid concentration. In the etiolated seedlings of green and albino forms the content of flavonoids was rather decreased.

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.

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 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.