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.

In vitro method has been developed for propagation ofWrightia tinctoria R.Br. using cotyledonary node segments. Murashige and Skoog's (MS) medium supplemented with 5.0 mg dm^-3 of 6-benzylaminopurine (BAP) and 0.01 mg dm^-3 of naphthaleneacetic acid (NAA) induced up to eight shoots per explant with an average shoot length of 1.4 cm in 21 d. Three fold multiplication rate was achieved during every subculture of regenerated shoots on the same medium producing an average of 230 shoots per node within 84 d. Reduction in BAP concentration from 5.0 to 1.0 mg dm^-3 during subculture promoted shoot length without affecting the rate of multiplication. The differentiated shoots could be rooted by a dip treatment into preautoclaved indole-3-butyric acid (IBA-500 mg dm^-3 for 5 min) followed by their implantation onto MS medium containing 1/4 salts. Rooting was observed within 8-10 d in approximately 80% of shoots inoculated after IBA treatment. 15 d after rooting, the plantlets were transferred to culture bottles containing soil-Soilrite^TM (1∶1) and liquid nutrient solution comprising 1/4 MS salts. After their partial hardening in these bottles for 10 d they were transferred to pots containing soil-Soilrite (1∶1) mixture with 60% transplantation success. Methods are being standardized to improve the rate of survival and large scale field transfer.

Glyphosate tolerant cell lines were selected from highly embryogenic cell suspension culture ofMedicago sativa L. Resistant cell lines showed significant reduction of embryogenic ability and during long-term culture in the presence of glyphosate gradual loss of this ability was observed. After glyphosate treatment the increased activity of 5-enolpyruvylshikimate-3-phosphate synthase in tolerant cell lines overcame the block in aromatic amino acid synthesis which was observed in control cell lines. Glyphosate caused marked increase in the content of shikimic acid in both control and tolerant cell lines but the accumulation of shikimic acid was considerably lower in tolerant calli. Significant qualitative and quantitative differences were found in the content of individual phenolic acids. The considerable decrease in the amount of cinnamic acid derivates and broader spectrum of hydroxybenzoic acids suggest in tolerant cell lines the activation of alternative pathway not regulated by phenylalanine ammonia lyase. The possible role of altered pool of phenolic acids on the embryogenic ability is discussed.

Contents of phenolic acids, peroxidase activities and growth curves showed significant differences in embryogenic (EC) and nonembryogenic (NEC) suspension cultures ofMedicago sativa L. NEC gave a typical growth curve while in EC the distinct phases were absent. The total content of phenolic acids was higher in NEC (related to EC), changed during the growth cycle and most of the acids occurred in ester-bound methanol soluble form. The level of phenolic acids in EC was significantly lower and did not change during 12-d cultivation. The major fraction was formed by phenolic acids ester-bound to the cell wall. The cytoplasmic peroxidase activity in NEC increased continuously during the growth and reached the maximum value at the end of exponential phase. In EC the extremely low cytoplasmic peroxidase activity did not change during cultivation. Ionically bound peroxidases in NEC represented 14 to 30% of the total extracted activity in dependence on the growth phase while in EC formed about 50% of the total activity and did not change during studied period. A possible participation of ionic peroxidase in the incorporation of phenolics into the cell wall is discussed.

Osmotic priming of aged onion seeds with 25% polyethylene glycol-8000 for 5 d resulted in a marked increase in the rate of germination and early seedling growth. Priming reduced electrolyte leakage as well as lipid peroxidation in seeds implying the activation of membrane repair processes. Priming was also associated with increased levels of antioxidants,i.e. ascorbic acid and tocopherols particularly the latter and the activities of catalase and peroxidase involved in the mitigation of oxidative damage. In comparison with the priming of unaged seeds, the aged seeds experienced a diminution of response in terms of changes in the levels of antioxidants and scavenging enzymes.

Changes in the content and subcellular localization of ribonuclease isoenzymes were determined in mesophyll protoplasts prepared fromNicotiana tabacum L. cv. Samsun from healthy and potato virus Y (PVY) infected plants. Intact chloroplasts, mitochondria and soluble cytosolic proteins were obtained after protoplast disintegration by means of differential centrifugation. The 1 000g pellet from healthy protoplasts contained 7.3 %, the 15 000g pellet 13.5 % and 15 000g supernatant 82.1 % of the total activity of ribonucleases. The 1 000g pellet from infected protoplasts contained 10.4%, the 15 000g pellet 10.0% and 15 000g supernatant 89.6 % of the total activity of ribonucleases. The activity of these enzymes in infected protoplasts was enhanced in crude homogenate to 137.0 % (P<0.001), in 1 000g pellet to 194.8 % (P<0.001), in 15 000g pellet to 101.3 % (NS), and in 15 000g supernatant to 149.4 % (P<0.001) of that in healthy noninoculated protoplasts.

This paper compares the repair of DNA single strand breaks (ssb) induced by γ-radiation in two strains ofChlamydomonas reinhardtii (137C/+/ and UVS-I) and three lines ofPisum sativum (NN 131, 198, 140) differing in the degree of radioresistance. DNA ssb in cells exposed to γ-rays (50, 100, 200, 500 Gy) were measured by electrophoresis and alkaline unwinding method with subsequent chromatography on hydroxyapatite immediately after irradiation and after 30 min of post-irradiation incubation at 25°C. An increase of double-strand DNA (in%) was found in cells after 30 min post-irradiation incubation.C. reinhardtii strains displayed an equal level of DNA degradation and repair efficiency in the DNA single strand breaks. The radioresistant line N 198 ofP. sativum is characterized by a lower level of induced DNA ssb and higher efficiency of repair of these breaks as compared with less radioresistant lines NN 131 and 140.

Increasing soil acidity (from pH 6.5 to pH 2.0) decreased chlorophyll (Chl)a andb contents, dry matter accumulation by plants and the transpiration coefficient. Chl stability to heat significantly increased with increased soil acidity. The Chla/b ratio was increased significantly at pH 5 and 4 and decreased at pH 3 and 2. SprayingSorghum shoots with kinetin solutions counteracted the above adverse effects on Chl content and dry matter accumulation. Kinetin-treated plants showed a lower transpiration coefficient than the untreated plants.

Responses of a salt tolerant and a normal population of an oilseed crop,Eruca sativa Mill. were assessed after four weeks growth in sand culture salinized with 0 (control), 100, 200, or 300 mol m^-3 NaCl. The salt tolerant plants produced significantly greater dry biomass than the normal population. The populations did not differ significantly in leaf osmotic potential, relative water content and leaf soluble proteins. However, the tolerant population accumulated significantly greater amounts of soluble sugars, proline and free amino acids in the leaves compared with the non-tolerant population. It is established that leaf soluble sugars, proline, and free amino acids are important components of salt tolerance inEruca sativa.

Plant regeneration through somatic embryogenesis was obtained in chickpea (Cicer arietinum L.) using immature cotyledons and immature embryonal axes as explants. 2,4-dichlorophenoxyacetic acid (2,4-D), 4-amino-3.5-6-trichloropicolinic acid (picloram) and 3.6-dichloro-0-anisc, acid (dicamba) in concentrations 1, 2, 5, 10 mg dm^-3 were found better than naphthaleneacetic acid (NAA) (10-20 mg dm^-3) for the induction of globular and heart-shaped somatic embryos. The embryos developed upto the dicotyledonary stage on medium supplemented with saccharose, mannitol and silver nitrate (AgNO₃) and developed further into plantlets on medium containing gibberellic acid (GA₃) and abscisic acid (ABA). The frequency of somatic embryogenesis was dependent on the genotype and auxins used.

10-d-old wheat seedlings were grown hydroponically in presence and absence of 100 mM NaCl for 7 d. Salt stress decreased growth of shoots and roots of both cultivars; fresh mass of sensitive cultivar being more affected. NaCl increased membrane permeability to urea, methylurea and ethylurea and decreased membrane partiality in root cortex cells of sensitive cultivar. Neither parameter changed by NaCl in resistant cultivar. NaCl treatment decreased water permeability and osmotic potential in both cultivars; sensitive cultivar was more affected. The results extends our previous data that cell membrane properties are different in salt sensitive and resistant genotypes and so cell permeability could be a potential trait indicating salt tolerance.

The lengths of roots and shoots, fresh and dry matter yield, and the contents of insoluble saccharides and free amino acids were reduced with the rise in NaCl concentration. However, under combination of NaCl with Ca²⁺ ions, these parameters generally raised. Contents of soluble saccharides, proline and quaternary ammonium compounds increased with increasing NaCl concentration, but under addition of CaCl₂ or CaSO₄, contents of these compounds were decreased. Low concentrations of NaCl stimulated soluble proteins, production, but higher concentrations decreased the content of soluble proteins. Addition of Ca²⁺ in the media did not improve the soluble protein production. Insoluble proteins content was increased with the rise of salinity level, but these effects were more pronounced with NaCl and CaCl₂ or CaSO₄ than with NaCl only.

The slot-immunobinding assay (SIBA) was adapted for detection of plum pox virus (PPV) and compared with DAS-ELISA. SIBA was easy to perform and as sensitive as DAS-ELISA in detection of various PPV isolates in herbaceous and woody plants, but not in aphids (Myzus persicae).

Between 1986 and 1989 we studied the influence of γ-irradiation (2.5-80 Gy) on growth processes and the content of arbutin glycoside. Bearberry [Arctostaphylos uva-ursi (L.) Sprengel] shows polycyclic characteristics of growth; the vegetation period is divided by summer dormancy (June) into periods of spring and summer growth. As plants age the summer dormancy gets longer and the period of summer growth is shorter. Irradiation with a dose of 80 Gy was lethal and a dose of 60 Gy damaged plants so much that they were not able to grow in the first spring after irradiation. Significant growth stimulation (both in the height of plants and in branching) was shown only in the second year after irradiation (2.5-60 Gy). In the fourth year the growth in all irradiated variants was weaker than in the control. Doses of 2.5 and 5 Gy did not influence the content of arbutin significantly; higher doses of irradiation changed the dynamics of production and decomposition which is connected with growth changes.

Eleven genotypes of sunflower were used to screen their regeneration potential in a meristem regeneration test. The inbred line HNK-81 showed the best regeneration of shoots directly from apical meristems and meristem derived calli, and rarely also the formation of adventious shoots from leaves of regenerated shoots.

Floret pieces prepared from the methanol-treated and air-dried flowers of safflower (Carthamus tinctorius L.) were subjected to an enzymatic hydrolysis in a buffered solution and the rate of precarthamine solubilization was assessed spectrophotometrically. The amount of precarthamine was risen by treating the floral pieces with a β-glucosidase (EC 3.2.1.21), supporting a previous assumption that precarthamine is in the floral tissues associated with cellular components. The enzyme activity was reduced by various inhibitors. On the basis of the experimental data, it is proposed that the precarthamine may be bound through 0-β-glucosyl linkage(s).

For clonal propagation ofAsparagus cooperi, shoot tips and node explants of 7, 20 and 35 d old spear from the region within 10 cm and below 25 cm from the apex were cultured in modified Murashige and Skoog's (1962) medium containing 6-benzylaminopurine (BAP). The required concentration of BAP varied in explants of different ages and types. In shoot tip culture, the rate of shoot multiplication was higher after 40 d than 60 d of culture. The maximum mumber (62-65) of shoots were obtained from shoot tip explants of 20 d old spear in the medium containing 2.0 mg dm^-3 of BAP, 80 mg dm^-3 of adenine and 0.02 mg dm^-3 of α-naphthalene acetic acid after 60 d of culture. From node cultures, high number of shoots were obtained after 30 d. Pretreatment with BAP in liquid medium for 48 h was effective for semirejuvenescence. The individual shoots produced roots in presence of indole-3-butyric acid and also in potassium salt of indole-3-butyric acid, the later being more effective. All regeneratns were cytologically stable.

The intracellular enzyme activities ofChlorophyllum molybditis (Mayerex. Fr.) Massee andCortinarius melliolens Fries were determined at different stages of sporophore maturity. In both mushroom species, total amylase, α-amylase, proteinase, lipase, peroxidase, catalase and polyphenol oxidase activities were increased with sporophore maturity. In contrast, glucose-6-phosphatase activity was higher in the young sporophore than in very young and mature ones. All the enzymes assayed except cellulase and β-amylase showed greater activity in the pilei than in the stipes.C. molybditis showed greater total amylase, α-amylase, cellulase, proteinase, catalase and glucose-6-phosphatase activities thanC. melliolens.