The treatment ofLemna minor L. plants with Pb(NO₃)₂ for 90 min, 8 and 24 h resulted in intensified deposition of (l,3)-P-glucan (callose) in plants roots. It was localized in the protodermis of the root tip, and in the center of the stele in the region at the proximal part of the root cap and slightly above

An investigation was carried out on chickpea (Cicer arietinum L.) cv. C-235 inoculated withRhizobium sp.Cicer strain cv 4 Az^r. Nodule functioning was monitored at 15 d intervals starting from 45 days after sowing (DAS) and inoculation in order to study nodule development and senescence under natural and stress conditions (dark treatments of 18 and 66 h). Maximum rate of N₂-fixation was observed between 50 - 60 DAS. After this acetylene reducing activity (ARA) fell and it was negligible 75 DAS. This decline in ARA with ageing of plants and nodules was accompanied by a decline in leghemoglobin content and greening of the nodules. When 60 % of the nodule tissue had turned green 75 DAS, a sharp increase in nodule peroxidase activity (3.7 fold) was observed whereas the catalase activity was reduced by 50 % in comparison with the control. The glutathione-reductase and ascorbate-peroxidase activity followed a trend parallel to that in N₂-fixation, but the variation was much smaller. The changes in the total soluble carbohydrates, cytosolic proteins and nitrogen content per se were not expressive. Dark treatments induced premature senescence of the nodules as was evident from the marked decrease in ARA. However, the decline in leghemoglobin content was relatively small as compared to ARA. The changes in cytosolic proteins, total soluble carbohydrates, peroxidase activity, catalase activity, glutathione reductase activity and ascorbate peroxidase activity of nodules under dark-induced nodule senescence were almost parallel to those observed under natural senescence.

The effect of irradiance on the ratio of variable to maximum fluorescence (F_v/F_m) and on the anthocyanin content of chilled (0.5 °C) young maize plants was investigated after returning the plants to a non-chilling temperature (25 °C). Compared to control plants grown throughout at 25 °C in the light, the F_v/F_m hardly changed during chilling or when returned to a non-chilling temperature in the dark, but there was a decrease in this parameter if the plants were shifted to the light after the cold treatment. Similarly, compared to the control plants there was no change in the anthocyanin content either at low temperature or after transfer to 25 °C in the dark. However, there was a sudden increase in the anthocyanin level after returning the plants from dark cold conditions to a non-chilling temperature in the light.

Dry mater, water content, water, osmotic and pressure potentials, content of saccharides and potassium were measured duringin vitro cultivation ofVitis rootstocks. Three cases were compared: a) the micro-cuttings with normal growth; b) micro-cuttings which stop their growth after 15 d of culture, and c) micro-cuttings reactivated by 6 d of continuous darkness.
Major differences were observed in water content and osmotic potential. The stopping of growth was not a specific property of buds, but was probably due to restriction of translocation of saccharides and water in the shoot.

Exposure of intact cells of theSynechococcus 6301 to UV-B radiation induced a loss in photosystem 2 (PS 2) electron transport activity prior to the alteration in pigment complexes. Thus the degradation of PS 2 was not directly related to pigment alteration.

Seven plant species including three chenopods:Suaeda fruticosa, Kochia indica, Atriplex crassifolia and four grasses:Sporobolus arabicus, Cynodon dactylon, Polypogon monspeliensis, Desmostachya bipinnata, varied greatly in their seed germination and growth responses to soil moisture or salinity. The germination percentage of each species was significantly lower at soil moisture level of 25 % of water holding capacity than at the levels ranging from 50 to 125 %. Increase in salinity resulted in gradual decrease in seed germination of each species. Growth responses of species to salinity varied widely from significant decrease with slight salinity to stimulation up to salinity levels of 20 dS m^-2. Higher K⁺Na⁺ratios in plant shoots of all species compared to that in the root medium indicated selective K⁺uptake. Higher tolerance in chenopod species seems to be attendant on their ability for internal ion regulation.

Sampling of natural cocksfoot (Dactylis glomerata L.) populations was carried out on the O Morrazo peninsula in NW Spain, characterized by a strong moisture gradient. The plants were kept in greenhouse under standard conditions. Nevertheless, they differ in height of plants, length and width of flag leaves, panicle size, stomatal density and size as well as in flowering period. The effects of two levels of soil water deficit and two levels of salinity on photosynthetic rate were tested. One population was exceptionally well adapted to its original environment with great tolerance to water deficit and salinity

The striking diversity in the expression pattern of the stress-related anionic peroxidase was observed during development of female cucumber flower. While the isoenzyme Prx3 was accumulated constitutively in the course of flower development, the expression patterns of other two isoenzymes (Prx1 and Prx2) were restricted to the period after flower opening. The virus infection was simulated by careful opening of the intact female flower buds 3 d before anthesis followed by exposition to the glasshouse environment for 3 d. The results obtained in this experiment revealed a marked accumulation of the isoenzyme Prx1 and Prx2 at anthesis. Under normal flower development, the pistils did not accumulate these isoenzymes at this stage. In contrast, the pattern of expression of Prx3 as well as of the pistil-specific peroxidase isoenzyme remained unchanged, confirming a constitutive type of expression. Beside the pistil, a 3-d exposition of the stripped flowers resulted in a marked accumulation of Prx1 and Prx2 isoenzymes also in both adjacent flower organs - the ovary and the pedicel. At the same time of the normal development of female flower these organs did not accumulate these isoenzymes.

Five cultivars ofOenothera biennis have been tested for callogenesis and organogenesis on different media. The cultivar CV3 has been transformed byAgrobacterium tumefaciens strain which introduces into the plant genome kanamycin resistance gene and the T-DNAipt gene which causes increased levels of cytokinins. Transformed tissues showed elevated levels of cytokinins and grew as teratomas forming clumps of short, branched shoots with small modified leaves. Roots appeared rarely in later subcultivations of some teratomous clones.

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.

The 24 h effect of low (20°C) and high (43°C) temperature on the antioxidant enzyme activities and lipid peroxidation was investigated in intact cells of the cyanobacteriumSynechocystis PCC 6803 grown at 36°C. At low temperature treated cells, the superoxide dismutase, catalase and glutathione peroxidase activities were significantly higher and the protein content lower than in high temperature treated cells. The increase of hydroxyl free radical level and malonyldialdehyde formation, when algal cells were exposed to low temperature, were due to the stimulated production of superoxide radicals O₂ ^- and hydrogen peroxide (H₂O₂).

Wheat seedlings were grown hydroponically in absence and presence of 100 mM NaCl for 7 d. Cell membrane permeability to nonelectrolytes and water was determined by the plasmometric method for individual intact cells. NaCl increased membrane permeability to urea, methylurea and ethylurea and decreased permeability to water. Membrane lipid partiality was decreased by NaCl. The effects of NaCl on cell permeability parallel changes in the lipid composition of the plasma membranes induced by NaCl stress suggesting that nonelectrolyte permeability is a useful tool to probe alterations in the lipid matrix of the membrane.

The ontogenetic changes in growth, and the diurnal changes in net photosynthetic rate (P_N) and stomatal conductance were studied in two peanut cultivars of different habit groups. Significant cultivar differences were noticed: the prostrate cv. M 13 was found superior to the erect cv. J 11 in all the parameters studied. Specific leaf mass and the rates of gross photosynthesis and respiration were higher in cv. M 13 than in cv. J 11. In vegetative phase, the maximum P_N was in cv. J 11, but in pod filling phase, it was in cv. M 13. The differences in growth and P_N of the cultivars were significant after the onset of reproductive sink. Therefore, the screening for higher P_N has to be made at the pod-filling phase, and between 09.00 and 10.00 of the day (at optimum temperature).

An influence of some Random Amplified Polymorphic DNA (RAPD) reaction factors on resulting banding pattern and the ability of RAPD technique to detect DNA polymorphism among six economically important pea cultivars was tested. Relatively high level of DNA polymorphism among peas was observed, using polyacrylamide/urea gels and silver staining. Altogether 13 arbitrarily designed primers produced 313 amplification products. In addition 59 polymorphisms were found. These polymorphisms can serve as potential genetic markers. RAPD data were processed using cluster analysis and plotted as dendrogram. Each tested cultivar was clearly distinguished from the others. Moreover,Pisum sativum andP. sativum subsp.arvense cultivars were separated into 2 different clusters, according to their systematic relationships.

Esterase isoenzyme spectra of different organs of seedlings and field-grown plants of fiber flax (Linum usitatissimum L., cv. Belinka) were studied by electrophoresis in polyacrylamide gel for estimating ontogenetic variability of gene expression. Formation of individual isoesterases depended on the type of tissue and the stage of its development. Isoesterases characteristic of exclusively one or some tissues of the same developmental stage were revealed simultaneously with basic esterase isoforms active in all analysed parts of seeds, seedlings and field-grown plants. The revealed changes of esterase isoenzyme spectrum during germination show tissue and time specificity of the endogenous regulation of genes controlling their formation.

The changes in the content of indole-3-acetic acid (IAA) were investigated in the youngest needles ofPinus mugo in the course of year. In newly formed needles, the content of IAA increased, starting from July and reaching its maximum in August to October. The IAA content decreased with a decline in the intensity of apical dominance during dormancy but no changes were observed in budbreak (May and June).

Spectroscopic characterization of phycobiliprotein (PBP) isolated fromSpirulina platensis indicated that it had a molecular formula of C₃₃H₄₀N₄O₆ with molecular ion peak at m/e 586. The PBP was rich in aliphatic and acidic amino acid residues. The specific ultra-violet absorbance, infrared transmittance, specific absorbance coefficient, nuclear magnetic resonance and mass spectral analysis revealed thatS. platensis PBP was composed mainly of C-phycocyanin and allophycocyanin.

Mechanical stress exerted on youngBryonia dioica internodes which resulted in reduced elongation and increased radial expansion induced a rapid and transient increase in specific mRNAs. Hybridizations were performed using ubiquitin, cyclophilin and heat-shock protein cDNAs as probes on RNA extracted at successive time intervals in control and rubbed internodes. Changes in ubiquitin and cyclophilin were rapidly enhanced after mechanical perturbation. Levels of mRNAs reached a maximum 0.5 h and 1.5 h after rubbing and then decreased. The heat shock protein gene was constitutively expressed; it was however slightly stimulated following the rubbing treatment. All the three genes encoded for molecular chaperones and they were regulated in response to environmental stimuli. The role of chaperones was discussed with regard to the plant response to several natural stresses.

The effects of NaCl and polyethylene glycol (PEG) on superoxide dismutase (SOD) and peroxidase (P) activities, lipid peroxidation (LP) and proline content in seeds and leaves of drought tolerant (FC-506 and MS-100) and drought sensitive (MS-612 and MS-13) sugar beet cultivars were examined. After PEG and NaCl treatment in tolerant cultivars both in seeds and leaves SOD activity mainly increased, though P activity increased only in leaves of tolerant cultivars. In drought sensitive cultivars the decrease of SOD and P activity was mostly observed. LP increased in seeds and leaves of all examined cultivars. The proline content increased in the leaves of examined cultivars and was significantly higher in drought tolerant plants. On the other hand, in the seeds only slight increase in proline content was found. The results obtained indicated that drought tolerance could be correlated with high proline content and enzymatic defense against lipid peroxidation.

We describe a rapid and efficient procedure for isolating leaf mesophyll protoplasts fromSaintpaulia ionantha (African violet). Because of the unusual surface properties of the leaf, efficient digestion required bisection of the lamina into abaxial and adaxial halves to expose the mesophyll. Enzymatic digestion occurred during a 3 h incubation with 2% (m/v) driselase in 0.50 M mannitol, yielding 2-3 × 10⁵ protoplasts g^-1 (f.m.), with 70% viability. Protoplasts ranged in size from 50 to 100μm, and were derived from mostly non-photosynthetic mesophyll parenchyma.