Mesophyll derived protoplasts ofCatharanthus roseus cv. Little pinkie were fused with protoplasts derived from an habituated cell line ofC. roseus. Polyethylene glycol was used as agglutinating agent while fusions were induced by square pulses. Best results were obtained by fusing protoplasts from primary leaves with those from three-day-old cell cultures. Adding calcium ions considerably enhanced heterofusion rate. Good cell viabilities indicated that this fusion process was not cytotoxic. The heterofusion frequency was up to 10% or more. Most of the heterokaryons were able to regenerate their cell walls and underwent division.

The responses of seedlings of three fast growing tree species,Eucalyptus hybrid(E. camaldulensis × E. teriticornis), Casuarina equisetifolia andMelia azedarach, to different levels of soil moisture in controlled glasshouse conditions were compared. The survival percentage, height of plants, number of leaves per plant, number of branches, fresh mass and dry mass of roots, stems, branches and leaves decreased in the three species with increasing water stress. Stomatal frequency and length of stomata inEucalyptus andMelia also decreased with increasing water stress. However, no significant difference was obtained in the width of stomata and the ratio of number of open stomata to total number of stomata per unit area. The leaf thickness decreased, but the thickness of palisade parenchyma increased with increasing water stress inEucalyptus hybrid andCasuarina. Leaf thickness ofMelia did not show any significant variation due to water stress.

The effect of different NaCl regimes was examined on the growth and ion accumulation in whole plants and callus cultures ofVigna radiata. Whole plants grown in sand culture were watered with Hoagland's solution supplemented with 0-350 mol m^-3 of NaCl. Callus cultures were initiated from leaves of 7-d old seedlings of the same seed stock and grown in modified PC-L2 medium containing the same levels of NaCl as in Hoagland's solution. Callus showed the same tolerance to salt as did the whole plant suggesting thatV. radiata appears to have a mechanism(s) for salt tolerance which operates at the cellular level. Ion analysis of whole plant showed that root sodium concentrations of the tolerant cultivar G-65 was much higher while shoot sodium was much less than those of salt sensitive cultivar ML-1. Callus cultures of cv. G-65 also accumulated higher Na⁺ levels. Thus, the greater salt tolerance of cv. G-65 was associated with the control of sodium accumulation at the shoot or cellular level.

Chlorella fusca was subjected to evaporative dehydration under air humidity of 72%. Ca²⁺ pretreated cultures lost water as rapidly as untreated cultures. Nevertheless, an ameliorative effect of Ca²⁺ pretreatment in droughted cells was found as membrane stability index was improved and K⁺ leakage was reduced. In addition, higher chlorophyll content and stability was observed. These parameters enabled droughted cells to recommence growth upon rewatering. Thus Ca²⁺ might increase survival ofC. fusca cells subjected to drought through membrane stabilization.

Leaves ofQuercus serrata seedlings were sprayed with solutions of different concentrations of Mg, Zn and Mo-salts and activity of nitrate reductase (NRA) and soluble protein contents were determined in fresh leaves of different ages. The optimum dose for magnesium sulphate and zinc sulphate was 2.5 mM while for ammonium molybdate it was 0.01 mM. Under optimum doses of these nutrients high levels of NRA and protein contents were maintained upto 28 d of spray. Observations on NRA were further confirmed by leaf direct treatment and excised shoot-dipping experiments which showed maximum NRA at comparatively much lower concentrations of ions than those used for spray.

When stem explants of kale (Brassica oleracea L. var.medullosa), containing pith parenchyma and a strip of vascular tissue, were cultured on simple sucrose medium, a hormone-like factor was transported from the vascular tissue to the adjacent pith, where it stimulated accumulation of starch. Similarly, up to a sevenfold increase of starch content in explants could be induced by cytokinins added to the culture medium. The relative stimulatory effect of several cytokinins (5×10^-6 M) and hormone-like product of vascular tissue (HPVT) in a typical experiment were: control (1.0), trans-zeatin (6.7), HPVT (6.2), N⁶-[2-isopentenyl]adenine (5.4), transzeatin riboside (5.2), N⁶-[2-isopentenyl]adenosine (5.4), kinetin (3.6), 6-benzylaminopurine (3.5), and adenine (2.1). Concentration of endogenous cytokinins was determined using ELISA (trans-zeatin, N⁶-[2-isopentenyl]adenine and their ribosides) andAmaranthus bioassay (total cytokinins). No effect of vascular tissue on the level of endogenous cytokinins in explants was found. The results support the conclusions of previous experiments that the HPVT stimulating starch accumulation is not a cytokinin.

Addition of 0.5 and 2.5 gm^-3 of metribuzin into Hoagland nutrient media, either alone or in combination with NaCl, induced significant decreases in nitrate-, amino-, ammonia-, and total soluble-N contents, whereas significant increases in these nitrogen fractions were apparent in maize and castor bean seedlings and plants treated with high concentrations (5 and 10 g m^-3) of the herbicide, again either alone or in combination with NaCl. Protein- and total-N contents increased and decreased at low and high concentrations of the herbicide, respectively. The contents of chlorophyllsa andb, as well as carotenoids of both castor bean and maize seedlings and plants treated with low concentration of herbicide, either alone or supplemented with NaCl, were unaffected, whereas at high concentrations of the herbicide a significant decrease in chloroplast pigments was found. Nitrate reductase activity (NRA) was increased significantly at low concentrations of the herbicide alone and decreased significantly at high levels. Inclusion of NaCl into the herbicide media induced significant decreases in NRA of both castor bean and maize seedlings and plants. Unlike NRA changes, protease activity was increased significantly with high concentrations (5 and 10 g m^-3) of metribuzin and decreased significantly with its low (0.5 and 2.5 g m^-3) concentrations.

Two staining methods for aspartate aminotransferase were compared after electrophoretic resolution of its isozymes in polyacrylamide gels. The first one uses L-aspartic acid and Fast Blue BB salt (classical method), the second uses L-cysteine sulfinic acid and a redox system with phenazine methosulfate and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide. The seeds of pea, horse bean and soybean were used as a model plant source of the enzyme. The staining method with L-cysteine sulfinic acid is very reliable and more sensitive than the Fast Blue BB method and allows detection at very low isozyme activities in the gel.

Growth parameters (leaf area, length of shoot and root, water content and dry matter accumulation), contents of reducing sugars and saccharose as well as activities of α- and β-amylases of castor bean and maize seedlings and adult plants supplemented with 0.5 μg g^-1 and 2.5 μg g^-1 of metribuzin either alone or in combination with 50 μg g^-1 NaCl, were increased significantly whereas at high concentrations (5 and 10 μg g^-1) of herbicide, an opposite response was apparent. On the other hand, polysaccharide content and invertase activity of castor bean and maize seedlings and adult plants were significantly decreased in response to low concentrations (0.5 and 2.5 μg g^-1) of metribuzin and increased significantly at high concentrations (5 and 10 μg g^-1) of the herbicide either alone or in combination with 50 μg g^-1 NaCl. Total carbohydrate contents of castor bean and maize seedlings and whole plants treated with herbicide either alone or in combination with NaCl did not change significantly. Growth parameters, carbohydrate fractions contents and activities of enzymes in both castor bean and maize seedlings and whole plants treated with herbicide alone were consistently higher than those values detected in plants treated with herbicide in combination with NaCl.

The influence of the type of nutrient medium (meat-peptone nutrient agar, KING B medium, YDC medium) and the age of bacterial cultures ofErwinia amylovora andE. herbicola on reactivity of their antigens with homologous antisera were examined. In the case ofE. amylovora, the best agglutination reactions were observed with isolates cultivated on the YDC nutrient medium. After 192 h of cultivation, seven outof ten isolates reacted positively. The reactivity ofE. herbicola antigen decreased in dependence on culture age more rapidly than withE. amylovora. The highest rates of positive agglutination reactions were observed withE. herbicola cultivated on the YDC and KING B nutrient media. After 144 h of cultivation on both these nutrient media eight out of ten isolates reacted positively.

The cytological investigation of 12 taxa ofPanicum L. revealed that the vast majority of them have the basic number x=9 at different ploidy levels. The basic number x=8 was recorded only in the tetraploid speciesP. maximum with 2n=32. The diploid number 2n=18 was encountered inP. capillare, P. laevifolium, P. antidotale andP. coloratum (2) with 3B-chromosomes recorded in the latter species. The tetraploid chromosome number 2n=36 was found to exist inP. miliaceum, P. miliare, P. coloratum (1) andP. virgatum. The hexaploid number 2n=54 was recorded inP. bulbosum, P. dichotomiflorum andP. esculentum. The karyotypes of all accessions were mostly symmetrical and mainly comprised of meta- and submetacentric chromosomes with little variation in length among them within each karyotype. Investigation of chromosome association during metaphase I of meiosis revealed that the frequency of bivalents/cell was the highest among all investigated diploid, tetraploid and hexaploid accessions. Univalents were also frequently encountered in various accessions. These results may indicate that segmental alloploidy has been the major process by which polyploid species have originated.

The net assimilation rate (NAR), relative growth rate (RGR) and yield were negatively correlated with different exchangeable sodium percentage (ESP) levels; maximum reduction in NAR, RGR and yield was observed at 30 ESP. However, the cultivar NDP-2 showed maximum percent reduction in all the characters at 30 ESP as compared to cultivars NDP-7 and Rachna.

Two tomato species (Lycopersicon esculentum andL. pennellii) were grown under unheated plastic greenhouse and irrigated with 0 or 140 mM NaCl. Salinity induces a more important reduction in predawn leaf water potential (ψ_pd) inL. esculentum than inL. pennellii. In both species the osmotic adjustment was achieved by active solute accumulation. The leaf water potential at turgor loss point (ψ_tlp) seemed to be controlled by leaf osmotic potential (ψ_os). The results revealed the existence of limits to the accumulation of osmotic solutes in leaf tissues and the existence of an ontogenetic effect on the solute accumulation. In both species, but essentially inL. pennellii the inorganic solutes contribution especially Na⁺ and Cl^- accumulation to ψ_os was higher than the organic solutes. Therefore, wild species save energy more markedly.

We have investigated the influence of 2,4-dichlorophenoxyacetic acid (2,4-D) on the appearance of nuclear fragments, caused by direct nuclear division, as well as on mitotic activity in cultivated internodial stem segments ofPisum sativum L., cv. Bördi, during 180 d of cultivation. Direct nuclear fragmentation (dNF) was indicated by the shape and structure of the nucleus as well as by the occurrence of 1C- and 3C-values of DNA, investigated cytophotometrically. The dNF occurred during the whole cultivation period in segments treated by 2,4-D in concentrations from 4 to 32 mg 1^-1. In the presence of 2 mg 1^-1 of 2,4-D the dNF existed in the explants only up to 90 d. Mitotic activity was not observed in the 2,4-D-free control but occurred during the whole cultivation period when 2,4-D was added in concentrations from 2 to 16 mg l^-1. In the presence of 32 mg l^-1 of 2,4-D the level of mitotic activity was very low at the beginning and ceased after 60 d in culture.

Parameters of water relations were measured throughout the season in phenologically identical leaves of rose plants grown in a heated greenhouse. The increase in osmotic potential observed from spring to early autumn seems to result from the decrease in the non-osmotic water fraction, and, conversely, its decrease from early autumn to winter seems to be due to an increase in the non-osmotic water fraction. These observations support the hypothesis that the non-osmotic water fraction may be correlated to starch concentration in rose leaves.

The effect of radiation of different spectral composition on axillary proliferation of lavandin (Lavandula officinalis Chaix ×Lavandula latifolia Villars cv. Grosso) was studied in combination with application of exogenous benzyladenine (BA) and putrescine (Put) and endogenous ethylene production. The effect of BA was predominant over the radiation. Continuous far-red showed a fluence rate-dependent promotion of shoot proliferation in the presence of BA. On BA-free medium, shoot number was enhanced under blue, white, and red radiation, at low photon fluence rates. BA, however, could reduce the inhibiting effect of blue and ultraviolet radiation, at high photon fluence rates. Exogenous Put stimulated axillary bud proliferation under some radiation treatments in the presence of BA. Moreover, Put, analogously to BA, could overcome the detrimental effect of ultraviolet radiation. A positive correlation between biotic ethylene production and shoot formation was evidenced under far-red at high photon fluence rate in the presence of BA, and under white, red and blue radiation at low photon fluence rate in the BA-free medium. However, when abiotic ethylene (released from the agarized medium) was stimulated by UV, no improvement of shoot formation was observed.

A low activity of peroxidase (POD, EC 1.11.1.7) was found in crude extracts fromin vitro plants ofSyngonium podophyllum cv. Butterfly sealed in the multiplication vessels. Removal of the lids from the vessels increased the POD activity. A greater increase in the POD activity was measured whenin vitro plants were transplanted into a weaning growth medium. The POD activity was further promoted by removal of the phenolic substances from the extracts by polyvinyl-polypyrrolidone (PVPP).

Sugar beet protoplasts (Beta vulgaris L.) were isolated from hypocotyl-derived suspension cells and cultured on modified Murashige and Skoog medium supplemented with 5 μM naphthaleneacetic acid (NAA) and 2 μM 6-benzyl-aminopurine (BAP). Protoplasts were plated at a density 1.0-1.5×10⁵ cm^-3 and incubated in either liquid medium or in medium solidified by 1.2% agarose, at 25°C in the dark. Comparison of two methods of culture unequivocally showed the second to be superior. Immobilizing the protoplast in agarose proved to be essential for obtaining sustained protoplast division and reproducible colony formation. The plating efficiency after two weeks of culture, expressed as the percentage of protoplasts which developed to form colonies, reached 40%. Subsequent subcultures of protoplast-derived callus to regeneration media with different concentrations of BAP (5 μM, 10 μM, 20 μM, 30 μM) resulted in very good callus proliferation at the three lowest concentrations, although organogenesis was not achieved.

Phytotoxic micromycetes appear to be responsible for the apple replant disease (ARD). This was suppressed by the inoculation of apple-tree seedlings with some species of vesicular-arbuscular mycorrhizal (VAM) fungi-Glomus fasciculatum andG. macrocarpum. After the inoculation, growth of apple-tree seedlings improved in dependence on the type of soil, on VAM fungus species and on the ARD appearance. After 12-month cultivation, plant biomass (height, shoot and root dry masses) was markedly increased by inoculation withG. fasciculatum. Similarly, the numbers of colony forming units per unit soil (CFU) of phytotoxic micromycetes and of diazotroph bacteria (associative dinitrogen-fixing bacteria) in the rhizosphere was affected; CFU of phytotoxic micromycetes decreased, whereas CFU of the genusAzospirillum was higher. These bacteria could also serve as antagonists against phytotoxic micromycetes. It is also suggested that the ratio of CFU of diazotroph bacteria to CFU of phytotoxic micromycetes can be used as an indicator of the degree of ARD. It may be assumed that the use of some VAM fungi can replace the chemcial treatment of the soil with ARD.

Pretreatment ofVicia faba root tip cells with low doses of⁶⁰Co γ-radiation can reduce the yield of micronuclei induced by a subsequent high dose of γ-radiation (1.5 Gy). This adaptation to γ-radiation possesses the following characteristics: (1) this phenomenon can be induced by an optimal range of low doses of γ-radiation applied acutely or fractionally; (2) the expression of this response seems to be transitory and depends on the time interval between adapting and challenging doses of γ-radiation.

The relative rate of precarthamin extractability and floret protein inactivation by organic solvents were compared. Upon trituration of the floral tissues ofCarthamus tinctorius L., usually less extractable precarthamin is released at a markedly high level, while the releasability rate is changed conspicuously by macerating the florets in the test solvents of increased concentrations; the amount of releasable precarthamin also varies according to the solvents used. 30% (v/v) acetone promotes the pigment solubility about twice, whereas, its capacity decreases abruptly in reverse proportion to the increment of acetone content. Methanol accelerates the precarthamin release, but the rate is very low. Ethanol acts in far lesser extent. The data indicate that these varied aspects are more or less attributed to the inactivation of possible factors dissociating precarthamin from cellular components in freezed safflower florets.