Simultaneous uptake of NH⁺ ₄, Na⁺, Mg²⁺, Ca²⁺, NO^- ₃, SO^2- ₄, (NO^- ₂), H²PO^- ₄ and C1^- ions by N-limited winter wheat seedlings(Triticum aestivum L., cv. Regina) in a single depletion experiment was investigated. Individual ion species in uptake solution samples were determined using capillary isotachophoresis. The operating systems used are described in detail. Processing of obtained concentration data allow to construct time curves of individual ions concentration in uptake solution, time curves of accumulative uptake, and curves for uptake rate versus time and uptake rate versus external concentration. From these curves there is possible to reveal a more complex picture of behaviour of individual ions during uptake process as well as to assess interactions among them. Attention was paid to the points of intersection of time curves of NO^- ₃ and NH⁺ ₄ uptake rates. These points characterized by equal uptake rates may be considered as limits for preference of given ion species under given experimental conditions.

In this study the pattern of storage protein deposition in the developing seeds of xHaynaldoticum sardoum was examined. The accumulation of the various protein classes did not differ greatly between the two lines tested (Culmo Pieno and Culmo Vuoto). Nevertheless, some differences in the deposition pattern were revealed by polyacrylamide gel electrophoresis. In particular, the mature seeds of the two lines presented different electrophoretograms for the prolamin and glutelin proteins. These patterns reflect the differences between the two lines, which could play a role in their ability to adapt to environmental changes.

The hypocotyls, cotyledons, leaf blades, whole leaves and petioles of seedlings ofAilanthus altissima are capable of producing callus and budsin vitro. Buds and callus were also obtained from whole leaves and internodes of 2-years old plantlets grownin vitro. From the calli buds differentiated and later, both from buds developing directly without a callus phase and alsovia a callus phase, well developed shoots were formed. The cultures were mainained on MS medium in 2 combinations: A) IAA - 0.2 mg 1^-1, BAP - 1 mg 1^-1, GA₃ - 0.5 mg 1^-1, thiamine - 4 mg 1^-1 and sucrose 3 %; B) BAP - 0.5 mg 1^-1, IAA - 1 mg 1^-1, casein hydrolysate 400 mg 1^-1, thiamine 4 mg 1^-1 and sucrose 3 %. Excised shoots, which had developedde novo in culture, produced roots when incubated on the basic mineral medium of MS with the addition of IAA. The regenerative potential ofA. altissima is very high and this woody species seems to be an ideal object for various morphogenetic studies.

Growth of soybean was not altered, whatever the inorganic N-source (NO₃, NH₄ or a NO₃/NH₄ mixture); conversely, growth of Erica x darleyensis plants in vitro decreased more in. NH₄ medium than in a NO₃ medium, compared to a NO₃/NH₄ medium. The GS/GOGAT pathway (in NH₄ medium), the nitrate and nitrite reductase activities (in NO₃ medium), as the contents in free nitrogenous forms and total nitrogen (in NO₃ and NH₄ media) were not more altered in Erica than in soybean, compared to a NO₃/NH₄ medium. PEPCase activity was the highest in soybean irrespective of the N-treatments; the involvement of PEPCase in N-metabolism could be explained by its function in ionic and osmotic balances rather than its function in supplying carboxylates as acceptors for NH₄-assimilation.

The possible implication of ethylene on the growth regulation of etiolated lupin hypocotyls was investigated. Excised hypocotyl sections from actively growing seedlings produced ethylene at a rate of 3 nmol h^-1 g^-1 min^-1. The rate of ethylene production was increased about 7 times when sections were treated with 10 mM 1-aminocyclopropane-1-carboxylic acid (ACC). Measurement of endogenous ACC showed that 95 % of total ACC (64.2 nmol g^-1 min^-1) corresponded to conjugated ACC.
Treatments to intact seedlings with the ethylene precursor ACC, and the ethylene generating compound, 2-chloroethyl phosphonic acid (ethephon) during the cell elongation phase of the hypocotyl (from 7 to 21 dage), modified the cell growth of the organ. ACC (1 or 5 mM) or low concentrations of ethephon (0.66 mM) produced a transient decrease in the growth rate without modifying the final length of the hypocotyls. Higher concentrations of ethephon reduced the final length; the younger the seedlings were, the greater the reduction. Simultaneously to inhibition of cell elongation, ethephon produced stimulation of the radial expansion of cells in pith and cortex.
The growth inhibition period, which lasted for 2 days after the treatments, was followed by another period in which the growth rate of treated plants surpassed that of the control. In both cases differences were observed along the hypocotyls due to the different growth status of the cells. It is suggested that the sensitivity to ethylene and the metabolism of ethylene depend on the growth status of the cells.

A pre-treatment of 40 °Cprovided thermoprotection to wheat seedlings against 43 °C, which was otherwise a lethal temperature. Due to temperature pretreatment, the rate of protein synthesis at 45 °C increased in both plumules and radicles. The HPLC profile of plumule and radicle proteins of thermoprotection-acquired seedlings was different from the plumules and radicles of non-treated seedlings.

Primary roots ofVicia faba were grown for 24 h in the presence of tritiated thymidine (1.85-18.5 kBq ml^-1) and then irradiated with a dose of 1.5 Gy of⁶⁰Co-gamma- rays. The aim of these experiments was to determine whether low-level endogenous beta-irradiation from incorporated radioactive thymidine could influence the frequencies of sister chromatid exchanges (SCEs) and the numbers of micronuclei induced by subsequent external irradiation with high doses of gamma-rays. The results demonstrated that the pretreatment with³H-dTh had no significant effect on the frequencies of SCEs in gamma-irradiated root tip cells ofVicia faba. In contrast to SCEs, the yields of micronuclei in the³H-dTh pretreated cells were altogether less than the yield induced by gamma-rays alone (protective effects).

Spring barley seedling were grown in the dark for 21 d and respiration rates of the whole plant (including the seed), of the shoots, and of the roots were determined. A function describing the growth and maintenance components of respiration was interpolated through the experimental points and its parameters in plants under different mineral nutrition were compared. The plants grown in a complete nutrient solution showed the highest growth rate in the initial phase of development and thus reached the maximum respiration rate earlier than plants in the other variants. The highest proportion of substrate was respired in the shoot. Plants grown under deficiency of phosphorus and magnesium had a slower respiration rate than plants grown in the complete nutrient solution (NP), whereas the amount of respired substrate in plant parts was similar to that recorded in the NP plants. Plants grown in distilled water showed the lowest growth efficiency and respirated the highest proportion of substrate in the root.

A 2,4-D dependent cell line, accumulating only traces of indole alkaloids under standard conditions of subculture, was grown in two different production media. Removal 2,4-D from maintenance culture medium enhanced the production of ajmalicine and serpentine and increased the activities of the NADPH-producing enzymes: glucose 6-phosphate dehydrogenase, 6-phospho-gluconate dehydrogenase, malic enzyme and cytosolic isocitrate dehydrogenase.
Adding zeatin to a 2,4-D depleted medium further increased the alkaloid content but the activities of the NADPH-producing enzymes remained unchanged.

Two forms of α-glucan phosphorylase were isolated fromDioscorea cayenensis by ammonium sulphate gradient solubilization and further purified using starch adsorption and ion exchange chromatography on DEAE-Sephadex A-25 colunm. Fraction DC₁was purified 80 fold with specific activity of 400 umol min^-1 mg^-1 protein, while fraction DC₂showed 60 fold purification with specific activity of 300 umol min^-1 mg^-1 protein. Both enzyme forms were activated by AMP, magnesium, calcium and inhibited by ATP, ADP, ADP-glucose and sodium sulphate. They showed absolute primer requirement and obeyed Michaelis-Menten kinetics. The two forms have different Km values and different pH optima. The presence of amino acids and intermediates of glycolysis had no effect on the activities of the enzymes. There are no unusual properties of the enzymes which suggest that they function primarily in starch biosynthesis inD. cayenensis tuber.

Three isolates of strawberry mottle agent (SMA) from strawberry plants were regularly maintained and multiplied by mechanical inoculation onChenopodium quinoa plants showing mosaic and mottle symptoms. The use of 5 mM borate buffer pH 8.6 or tap water pH 6.6-7.9 with 4 % (m/v) charcoal for homogenization resulted usually in 100 % infection. The total of 2090 plants were infected from 2264 inoculated ones under the same conditions. The infectivity of SMA isolates in crude sap ofC. quinoa was retained from 48 h to 72 h at 20 °C. The dilution end points of SMA isolates were 10^-3 while the inactivation temperatures were between 50 and 55 °C. The infectivity of SMA isolates in frozen leaves ofC. quinoa was detected still after six months.
Purification procedure of SMA is based on using low molar 25 mM borate buffer pH 8.3 with cysteine hydrochloride, DIECA and Tween 20 for homogenization of infectedC. quinoa leaves, polyethyleneglycol precipitation, clarification with octanol, low and high speed centrifugation and sucrose density-gradient centrifugation. Partially purified preparations are highly infectious, causing mosaic, mottling and tip necrosis ofC. quinoa plants. The agent could not be completely separated from host proteins and it could not be concentrated to a high extent. Isometric virus-like particles 14-16 nm were observed in partially purified preparations.

The time-evolution of germination of oat seeds, suspended in the standard 5mm N. M. R. tube and supplied by water, was investigated continuouslyin vivo by the pulsed N. M. R. of water protons at the level of the seed. The results show that the spin- lattice relaxation time T1 yield the physiological information: in the germinated (living) seeds, the T¹'s are higher than in the killed seeds.

The enhancement of fruit abscission zone formation with ethephon treatment caused an increase in soluble proteins, endo-cellulase, exo-polygalacturonase and peroxidase activities. Exo-cellulase and endo-polygalacturonase did not show any relationship with apple abscission. The separation of cells initiated in the cortex region and progressed towards vascular tissue. Cell separation in the cortex appeared to be due to dissolution of middle lamella but vascular tissues ruptured mechanically.

During the growth of multiple-shoot cultures of Ruta graveolens, oxygen and carbon dioxide exchanges were continuously and simultaneously measured. The shoots subcultured on a medium containing 166 mM glucose showed a marked respiration rate. Even under light, CO₂ concentrations reached 4000 to 6000 cm³ m^-3. Photosynthesis never compensated for respiration. These cultures were photomixotrophic. A change of respiration and photosynthesis occurred between the 30th and the 32nd day of culture, with a high respiration rate. When the shoots were subcultured on a medium containing 41 mM glucose, it was possible to obtain photoautotrophy after two weeks under high irradiance (150 umol m^-2 s^-2), and after three weeks under low irradiance (60 μmol m^-2 s^-1), the CO₂ concentrations being 1100 and 600 cm³ m^-3 respectively.

An improved method for the isolation of leaf mesophyll protoplasts ofSolanum tuberosum L. cvs. Xenia and Bintje, their culture and regeneration to plants is described. The improvements involve the culture of nodal stem explants on Schenk and Hildebrandt (SH) medium supplemented with AgNO₃ (7.5 mg 1¹) and Alar 85 (5 mg 1^-1), and the pre-treatment of donor plants for 2-3 weeks at a short photoperiod (6 h), a low irradiance (17 (μmol m^-2s^-1) and a low temperature (20 °C). Regeneration of cell wals was observed within 2-3 d and cell divisions within 7-12 d after resuspending freshly isolated protoplasts in Sidorov et al. (SW) medium. The resulting microcalli were cultured on solid media containing zeatin (1-2,5 mg 1^-1) and/or NAA (0.1 and/or 0.01 mg 1^-1) and subsequently on medium with BAR (0.25 mg1^-1) and GA^-3 (0.1 mg 1¹) for shoot regeneration.

Changes in the activity and localization of nonspecific esterase, acid phosphatase, α-galactosidase and β-glucosidase inL. regale pistils after pollination with μ-irradiated pollen were studied. In the embryo sac and in the ovule reduction of AS-esterase and α-galactosidase and, at the same time, enhancement of α-esterase, acid phosphatase and β-glucosidase activities were observed. The changes in hydrolytic enzyme activities are discussed as manifestations of lethal factors resulting from structural disturbances of DNA in the generative nucleus and in sperms caused by irradiation.

The effect of crude volatile oils from the leaves ofEucalyptus globulus andE. citriodora and the pure terpenes - cineole and limonene from these oils, (in vapour form) was studied onPhaseolus aureus, Lens esculentum, Hordeum vulgare and Avena sativa. The parameters like germination of seeds, seedling growth, values of cell survival, and content of water and chlorophyll of the crops formed the system of bioefficacy study. The allelopathic impact of the oil vapours from the eucalypt tree becomes evident from the negative response of the parameters studied. The impact of the E. citriodora oil vapours compared to that ofE. globulus oil or the pure terpenes was seen to be relatively greater in almost all parameters under investigation. A strong reciprocal correlation that exist between the concentration and the seedling growth or the water content of the crops under study supports the dose linked allelopathic phenomenon. It is suggested that oil vapours ofEucalyptus exert their effect through impairing the respiratory as well as photosynthetic ability of the target plants.

Correlations within a shoot ofChenopodium rubrum L. ecotype 374 grown under continuous light or photoperiodic flower induction were studied using surgical treatments. Removal of a single pair of shoot organs had a variety of effects depending on position: significant changes in the number of leaf pair on the main axis or in axillary buds and in the height of shoot apices; or no effect on the parameters scored. Flowering was not affected by any of the treatments carried out. Decapitation brought about a significant increase in the number of leaf pairs in axillary buds and flowering was inhibited in 8- and 9-d old plants. Flowering was not affected in 21-d old plants. The role of shoot organ correlations, especially that of apical dominance, in regulation of flowering inC.rubrum is discussed.

Nuclei fromZea mays L. root tip meristematic cells were treated according to the conventional method for nuclear matrix isolation and according to a recently adapted procedure for isolation of nuclear shells from plant cells. In the first case, after high salt extraction of proteins and DNase I and RNase digestions, residual structures are obtained consisting of a periferal layer and an internal network. The obtained structures are very similar to the nuclear matrix preparations from animal cells. In case nuclei are swollen in EDTA first, digested with DNase II and RNase prior high salt treatment, structures devoid of internal network are obtained. The analogous residual structures were shown forPhaseolus vulgaris L. meristematic root cells nuclei (Galcheva-Gargovaet al. 1988). The morphology and the protein composition of the two types of residual structures suggest that the organization of scaffold structures from plant nuclei is very similar to the one from animal cell nuclei.

Plasticity of the tobacco genome was studied by testing the DNAs of protoplast-derived regenerants with three different repetitive DNA sequences by the method of quantitative DNA/DNA hybridizations. A large population of 91 regenerants belonging to 35 different protoclones was analysed and a high degree of heterogeneity in the contents of the different DNA repeats was detected. The contents of middle repetitive sequences of two types were more stable or changed in the same direction, while the highly repetitive sequence varied independently and displayed a significant reduction in comparison with the two other sequences. Comparing the variation within the subpopulations of plants of the same clonal origin and the variation among the protoclones led to a conclusion that the pre-existing DNA variability in the starting plant material and/or thein vitro stress during the very early stages of protoclone regeneration played a decisive role in the formation of modified genomes in regenerants.

It is shown that, contrary to what is generally found, treatment with abscisic acid (ABA) of potato leaf tissues resulted in an increase of K⁺ uptake. Comparison with other hormones was made: BAP induced an inhibition and GA₃ a stimulation of K⁺ uptake. The uptake was sensitive to several metabolic inhibitors, external pH and ATPase inhibitors while p-chloromercuribenzenesulfonic acid (PCMBS) had no effect. Uptake kinetics revealed the presence of both saturable and linear components which were both stimulated by ABA treatment. Our data are consistent with an effect of ABA on the active and passive components of K⁺ uptake. These results are discussed in relation to the action of ABA on foliar senescence and the action on ion partitioning in the whole plant.

Rose achene imbibition is difficult. Comparison of sulphuric acid treated, Cross and Beavanś reagent (C. B. reagent) treated seeds with untreated seeds showed that, during imbibition, water is essentially found in the most external pericarp layer. Inner layers appear less permeable. It is possible to distinguish three layers in the pericarp by taking into account results from imbibition assays, X-ray radiographies and scanning electron microscopic observations. They can be interpreted as representing the epi-, meso- and endocarp.

Maize seeds and five-day-old maize seedlings were incubated in media containing Pb²⁺ at concentrations of 50, 100, and 200 mg 1^-1 and Cd²⁺ at concentrations of 1, 5, 10 and 50 mg 1^-1. After five days of incubation, both heavy metals were determined by means of AAS following wet mineralisation of roots and shoots. The results obtained indicate that Pb²⁺ were transported to shoots from roots at a lower rate than Cd²⁺.
Phosphoenolpyruvate carboxylase (PEPC) isolated from germinating maize seeds was inhibited to a comparable degree by solutions containing 0.001 mmol 1^-1 Pb²⁺, 0.01 mmol 1^-1 Cd²⁺, and 0.005 mmol 1^-1 Cu²⁺. The enzyme was protected against this inhibition by the addition of mercaptoethanol, the substrate (PEP), or the cofactor (Mg²⁺). The inhibition increased during a 20 min incubation of the enzyme with salts of the metals. Mn²⁺, Ni²⁺, and Co²⁺ ions could partially substitute for the metal cofactor Mg²⁺. K_m values for these metal ions were as follows: for Mg²⁺ 0.07 mmol 1^-1 in the range from 0 to 0.30 mmol 1^-1 Mg²⁺; 0.71 mmol 1^-1 for 0.30 to 2.50 mmol 1^-1 Mg²⁺; for Mn²⁺ 0.36 mmol 1^-1; for Ni²⁺ 0.34 mmol 1{-1}; and for Co²⁺ 0.20 mmol 1^-1. The activity of the enzyme reached with Mn²⁺ 85 %, with Ni²⁺ 65 %, and with Co²⁺ 55 % of the activity recorded with Mg²⁺.