The resistance of differentChlorella vulgaris B. strains obtained as a result of chronic influence with chemical and physical factors have been studied. The aim of our work was to establish the relation between the resistance ofChlorella vulgaris populations with ultrastructural cell organization and the level of endogenic thiols. It was established that destructive processes in the cell are reduced to minimum in the more resistant strains and are of a definite recovering character. The higher resistance is accompanied by higher content of endogenic thiols, enlarging of cell pyrenoid and multilayered cell-covering membrane. From the results obtained it may be supposed that one of the probable mechanisms determining the resistance of theChlorella vulgaris strains obtained by the influence of physical and chemical factors and investigated by us, is connected with the changes which took place in the genetic systems controlling the level of the natural protectors in the cell and is accompanied by structural changes affecting mainly the size and number of cell pyrenoid as well as the thickness of the cell-covering membrane.

Using detached leaves of potato plants (Solanum tuberosum cv. Bintje) it was shown that abscisic acid (ABA) induced an oriented transport of ions (⁸⁶Rb,³²P and^3SS) towards the hormone-treated leaflet. In order to understand the hormone effect on cell permeability, pretreatment of discs with hormonal solution was conducted. The pretreatment with ABA stimulated the uptake of K⁺ simultaneously with the decrease of efflux.
The effect of ABA on ion uptake is compared with the action of other hormones, benzylaminopurine (BAP), gibberellic acid (GA₃) known to act over a long distance transport, too.
Three kinds of specificity are underlined: - hormonal specificity (stimulation by ABA and inhibiton by BAP of K⁺ uptake by foliar tissues); - ionic specificity (ABA increase⁸⁶Rb influx, but inhibits³²P and^3SS influx); - tissue specificity shown by a comparative study between foliar tissues (source) and tuber tissues (sink). The autoradiography of foliar discs demonstrated that a treatment of foliar discs can be used, at least for Rb⁺ (K), to study role of ABA in long-distance transport.

Plasma membranes were isolated from young seedlings of cold hardened and non-hardened winter wheat using aqueous polymer two phase system consisting of dextran-polyethyleneglycol. Electron microscopic analysis and activities of various marker enzymes revealed that the upper phase was enriched in plasma membrane and free from contamination by other membranes. The fraction thus obtained possessed Mg ATP hydrolysing activity with an optimum pH 6.5 and the activity was stimulated by K⁺. The activity was highly sensitive to orthovanadate, diethylstilbesterol, dicyclohexylcarbodimide, insensitive to azide and nitrate. It was suggested that the ATP hydrolysis was catalysed by H⁺ ATPase. Mg ATP hydrolysing activity in cold hardened seedlings was 38% higher than that from non-hardened seedlings.

Selected NaCl tolerant and unselected control lines ofHolcus lanatus L.,Lolium perenne L.,Dactylis glomerata L., andFestuca rubra L. were grown in sand culture at 0, 100, 200, 250, and/or 300 ml m^-3NaCl for seven weeks. The tolerant lines of all four species produced significantly greater both shoot and root dry matter at all NaCl treatments compared with the unselected control lines. Na⁺, K⁺, Cl^-, Ca²⁺, and Mg²⁺ contents of leaf, stalk, and roots of each species were determined. The tolerant lines ofH. lanatus contained less Na⁺ and less Ca²⁺ but higher K⁺ in shoots, compared with the unselected line. By contrast theL. perenne tolerant line had higher Na⁺ and Cl^- contents at 250, and 300 mol m^-3 NaCl in shoots than the unselected line suggesting a halophytic nature of the tolerant line.D. glomerata accumulated greater quantities of ions compared with the other species examined. The tolerant line contained significantly less Cl^- but more K⁺ in its shoots than the unselected line. Na⁺, Cl^-, and K⁺ contents in the shoots of the tolerant line ofF.rubra were higher than in the unselected line shoots. Therefore selection for NaCl tolerance may provide useful material for examining the basis of tolerance.

In two maize genotypes, the effect of exogenous phosphate deficiency on acid phosphatase activity of the apical part of primary root was followed in dry and imbided grains. Higher acid phosphatase activity was found in the genotype LG 5. The enzyme activity increased after 18 h grain imbibition in the two genotypes. After 48 h germination no differences were found between the genotypes. After 24 h cultivation of root segments in a solution of 0.25 mM CaSO₄.2H₂O,0.1 mM MgSO₄.7H₂O, and further after 3,6 and 24 h cultivation in solutions with and without phosphate genotypic differences were found in acid phosphatase activity as well as in dry mass production. An increase in enzymatic activity due to exogenous phosphate deficiency was registered in the two genotypes only after 24 h cultivation.

The present work was conducted to evaluate the content of the main polyamines (Spm, Spd, Put) in a series of naturally aged durum-wheat seeds as well as the activities of the enzymes ODC and ADC involved in their biosynthesis. In dry seeds the content of polyamines, especially that of Spd, rose during ageing till 6 years and then declined sharply. However, an increase of PA content upon imbibition was observed only with the youngest seeds, while a decrease was found in the older ones.
The activities of ODC and ADC differed in aged seeds, the ODC activity being constant and lower than the ADC in the course of seed ageing. The ADC increased till the early ageing and decreased then in the very old, ungerminating seeds. Imbibition increased both enzyme activities in the youngest seeds only, in the older ones rather a decrease and changed ADC/ODC ration was found.
The obtained results are discussed in relation to the participation of these enzymes in the biosynthesis of polyamines during seed ageing and in the course of plant senescence or stress.

Anin vitro procedure for micropropagation ofPinus strobus L., consisting of the following four steps has been established: shoot induction, shoot growth, root induction, and root growth. Influence of certain selected factors on each of these steps was determined. Shoot induction was found to be influenced by the age of the explant as well as the concentration of 6-benzyladenine in the medium. Best shoot growth was obtained on the medium of Litvayet al. without any growth regulators. Addition of activated charcoal to shoot growth medium resulted in fewer shoots. Root induction on several media was compared. Best root induction occurred when shoots were put on a half strength Gresshoff and Doy's medium supplemented with 0.5 to 1.0 mg r1^-1 α-naphthylacetic acid (NAA) for two weeks. Shorter exposure of shoots to higher concentrations of NAA or indol-3-ylbutyric acid (IBA) was not as effective. Low temperature seemed to be a requirement for root growth.

Data on (1) permitivity and dielectric losses, (2) free radical concentrations, and (3) potassium, sodium, magnesium, calcium, nitrogen, and amino acid contents in tissues of nodal roots, internodes, and leaves of maize plant are presented in the paper. The participation of these factors in the transport phenomenon and the degree of their cooperation in the transport process are discussed.

Effects of iso-osmotic levels of salts (NaCl, CaCl₂, Na₂So₂) and PEG-6000 on saccharides, free proline and nitrogen contents were studied in cotyledons of pea. Saccharide (total, reducing andnon-reducing) and nitrogen contents decreased with increasing the salt and water stress as compared to control at all the stages of seedling growth. PEG-induced stress had more deleterious effect on total saccharide content and non-reducing saccharide (NRS) content, while salt stress was more harmful to reducing saccharide (RS) and nitrogen content. Free proline content of cotyledons increased with increasing the salt and especially PEG-induced stress at all the stages of seedling growth.

Protein synthesis and accumulation in growing sunflower (Helianthus annuus L.cv.Airelle) seeds are studied. The salt soluble fraction, globulin, is the main soluble protein component. The earlier stages of seed development (10 days after flowering) are characterized by high M_r polypeptides (74, 58 and 44 kDa). Later stages mainly show nature globulin polypeptides. Thus, protein synthesis in seed occurs at a specific period of seed development which follows a period of fast cell divisions (0-14 days after flowering). Protein bodies are isolated and their protein composition analyzed. Globulin subunits are the main polypeptides of protein bodies soluble fraction. Mature globulin is only stored in protein bodies.

Low molecular mass humic acid fractions caused a decrease in the germination rate. Only the highest concentration of humic acid solution decreases the soaking of fruits. Neither sodium content nor water and osmotic potential can account for that decrease.
Seed respiration was increased in the presence of humic acids and their medium molecular mass fraction. This increase did not produce an increment in embryonic growth possibly as a result of interference in the respiration chain or decoupling in the oxidative phosphorylation.

Aminooxyacetic acid (AOA), an inhibitor of ACC biosynthesis, applied together with methyl jasmonate (JA-Me) to mature green and light-green tomatoes cv. Venture greatly inhibited ethylene production stimulated by JA-Me, when analyzed in ripe and overripe stages. AOA applied alone did not affect ethylene production in the same conditions of treatment and analysis. It is suggested that after JA-Me treatment of tomatoes the turnover rate of ACC is higher (JA-Me stimulates EFE activity) in comparison to control tissues, and, consequently, AOA inhibited ethylene production stimulated by methyl jasmonate.

Changes in total phospholipids and activities of two phosphoric diester hydrolases,i.e. phospholipase C and phospholipase D have been studied in inoculated wheat leaves of 25-day old plants, interacting differentially with three races of brown rust,Puccinia recondita, during early stages of pathogenesis. With progressive rust iafection the lipids and phospholipids were found to decrease in all the three interactions except at later stages (48 h and 72 h) in race 104-interaction. However, total phospholipids at various stages were found to be higher in resistant interaction (race 63) as compared to the other two interactions. An initial increase in activities of phospholipase C and D in all the three interactions was followed by a decline at the intermediate stages which continued in case of phospholipase C activity while a reverse trend was observed in phospholipase D activity towards later stages of infection. Further the enzymatic activities at various stages were found to be higher in the susceptible and intermediate interactions (with races 77 and 104 respectively) as compared to the resistant interaction.

Potato plants were transformed by the A.tumefaciens vector which integrates into the plant genome two foreign genes only: pTi C58 T-DNA gene 4 (ipt) responsible for elevated synthesis of cytokinins and kanamycin resistance gene. Three teratoma clones studied showed approximately 3 times, 6 times and 9 times increased levels of zeatin riboside and zeatin in comparison with untransformed controls and slight increase of the IAA level. Shoots formed roots in agar cultures sporadically, if the increase of zeatin riboside and zeatin levels was not higher than 6 times the control level. The chlorophyll content and net photosynthetic rate decreased with increasing levels of zeatin and zeatin riboside.

Spontaneous recovery of regeneration abilities was observed in a long-term (about two-year-old) crownvetch (Coronilla varia L.) tissue culture permanently grown on MS medium containing 1 mg 1^-1 IAA. Somatic embryos and later complete plants differentiated from initially regenerating roots. The formation and development of embryos was accompanied by a 10- to 20-fold increase in the content of cardioactive glycosides hyrcanoside and deglucohyrcanoside in the culture biomass. The effect of auxins (IAA, NAA, 2,4-D) and cytokinins (6-BAP) on calogenesis and somatic embryogenesis was examined; further development of somatic embryos was enhanced by light. Primary explants which were newly isolated from sterile R₁ plantlets showed differential, organ-specific ability of somatic embryogenesis which was highest in root cuttings. Regenerated plants were transferred to field culture; two-year-old cultures of regenerated plants showed in most cases phenotypic deviations from the original material, especially dwarfism.

Transpiration rate, stomatal frequency, growth, contents of pigments, saccharides, total nitrogen, proteins and some nutritive elements (K, Ca, Mg, P) of radish plants were significantly lowere dwith the rise in salinization levels using NaCl. Spraying radish shoots with proline solution (200 g m-³) counteracted the above adverse effects, especially at low and moderate salinity.

The effects of salicylic acid (SA) and other phenolic compounds, acetylsalicylic acid (ASA), benzoic add (BA) and sulfosalicylic acid (SSA), on ethylene production and somatic embryogenesis by carrot (Daucus carota L.) cell cultures were studied. SA and ASA, at concentrations of 10 μM and 100 μM, significantly stimulated somatic embryogenesis and effectively inhibited ethylene production by carrot cell suspension cultures. The observed increase of embryo number was proportional to the inhibition rate of ethylene production. However, BA and SSA affected neither ethylene production nor somatic embryogenesis. The role of SA in somatic embryogenesis is discussed.

Samples of the same kind (rape leaves, wheat crowns, onion bulbs or spruce needles) killed by a slow freeze-thaw cycle or by immersion in liquid nitrogen showed a similar time course of leakage. Leakage was accelerated in treatments when the sample, immersed in water, was killed by heating for 5, 15 or 30 min in a boiling water bath. The longer the boiling, the sooner the maximum conductivity (L_km) was obtained. The L_km did not depend on the way of killing but in samples killed by freezing, it was achieved after a longer leakage time. The leakage rate decreased from onion to rape, wheat and spruce. The relative conductivity [%] allowed a better comparison of various treatments and of samples of different kinds of tissues than the specific conductivity [μS cm^-1].

Callus cultures were initiated from the bud apices of 10-40-year-old Scots pines (Pinus sylvestris L.) at different seasons and maintained on modified MS medium without subculturing. Separate sets of experiments were used for analyses of carbohydrate content, ethylene production, amino acid composition, protein patterns andin vitro translation. In each case the change in the colour of the calli was recorded and the fresh mass of the samples measured. The onset of tissue browning was found to be associated with changes in protein pattern, amino acid content, ethylene production and the occurrence of sucrose and accumulation of starch.In vitro translation experiments using poIy(A)⁺ RNA isolated and purified from the calli indicated that the switch in metabolism accompanying browning is paralleled by activated protein synthesis. Thus, the development of brown colour does not as such seem to be harmful to the tissue. The later, more intense tissue browning and deterioration which is reflected in a reduced capacity for protein synthesis and changes in the free amino acid pool and protein pattern is probably a secondary phenomenon.

The effect of water stress induced by application of polyethylene glycol 6000 during seed germination and seedling growth ofOryza sativa L. cv. IAC 165 was analysed. The seed germination was inhibited by the decrease in the water potential of the medium, the inhibition being greater under white light than under continuous darkness. When the seedling was submitted to water stress (-0.51 MPa) white light inhibited growth of root, coleoptile-and leaf, while under no stress conditions white light caused increase in growth of root and leaf and only inhibition of coleoptile growth.

The content of auxin-, inhibitors-and gibberellin-like substances in freeze-dried humic acids was studied. The results indicate the existence of growth-promoting substances in humic acids, possibly corresponding to IAA or its precursors. Inhibitory activity is more marked during germination than during the growth process. The inhibitory effect caused by high concentration of humic acids could be due to an auxin-like action rather than an input per se of growth inhibitors. A significant amount of both free and conjugated gibberellin-like substances were observed.