The study revealed a marked qualitative and quantitative differences in the pattern of expression of three stress-related cucumber (Cucumis sativus L., cv. Laura) isoperoxidases. Activity staining, as well as the protein gel blot (Western blotting) confirmed that the proteins studied are differentially expressed in both male and female sepals, in male but not in female pedicels and in, pistil. By using antibodies specific to three stress-related peroxidases, one serologically related pistil-specific anionic peroxidase was detected. This specific band had never been observed in other flower organs. Differential appearance of the stress-related peroxidase isoenzymes in both male and female flowers demonstrates that these proteins are developmentally regulated, showing an organ-specific expression.

Treatment of vegetative parts of potato plants two weeks before the harvest with 0.2% 2-chloroethylphosphonic acid (CEPA) delayed the sprouting of tubers and increased the resistance of tubers to infections caused byPhytophthora infestans, Erwinia carotovora andFusarium spp. during the storage period. Levels of free, soluble ester- and glycoside-bound phenolic acids and cell wall-bound phenolics were determined in cortical parenchyma of tubers (periderm). The enhancement of phenolic acids in tubers from treated plants was caused primarily by the increase in the contents of free vanillic, caffeic andp-hydroxybenzoic acids and cell wall-bound ferulic, vanillic andp-coumaric acids.

Nodules of faba bean (Vicia faba L. cv. Giza 3) plants grown in pots containing clay-loam soil for 90 d have an active nitrate reductase (NR), while the leaves did not show detectable activity. Spraying the plant with increasing concentrations of Al³⁺ or Cd²⁺ (0-1000 μM) significantly inhibited the nodules NR activity, the decline being more pronounced in Cd²⁺ treatment. The specific activity of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) were more prominent in the 60- than in 90-d-old plants; GOT was always higher than GPT. Furthermore, GOT was more sensitive to Al³⁺ and Cd²⁺ treatments and its activity was significantly decreased when the metal concentration increased. Also, Cd²⁺ proved to be more effective than Al³⁺ in suppressing the GOT activity in the nodules, with less significant effect observed in the leaves. In contrast, GPT was hardly affected by the various metal treatments, particulary in the leaves.

For maximum avoidance of somaclonal variation risks, the commonly used medium for somatic embryogenesis inPhoenix dactylifera has been lowered in growth regulators and activated charcoal. When initially cultured on MS basal medium containing only 150 mg dm^-3 charcoal, 5 mg dm^-3 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg dm^-3 benzylaminopurine (BAP), 10 to 20% of shoot-tip explants developed into embryogenic calli. The embryogenic potential has been maintained for over 24 months with no decline. In addition, this medium has been found to be more efficient than conventionaly one containing 3 g dm^-3 charcoal, 100 mg dm^-3 2,4-D and 3 mg dm^-3 2-isopentyladenosine (2IP). Plantlet regeneration was achieved when somatic embryos were subcultured to medium with 0.1 mg dm^-3 2,4-D and 0.5 mg dm^-3 BAP or without growth regulators.

Reserves of twig nitrogen of drought-deciduous species changed seasonally and provided some of the nitrogen required for canopy reconstruction after drought relief. By contrast, in evergreen species, nitrogen mobilization from old leaves and use in expanding leaves occurred simultaneously at the time of leaf exchange and twig nitrogen remained constant

Changes in various components of photosynthetic apparatus during the 4 d dark incubation at 25°C of detached control and ultraviolet-B (UV-B) treatedVigna unguiculata L. leaves were examined. The photosynthetic apparatus was more degraded in younger control seedlings and for a longer time UV-B treated seedlings than in the older or for a shorter time UV-B treated seedlings. This was shown by determining the losses in chlorophyll (Chl) and protein contents, variable fluorescence yield, photosystem (PS) 2, PS1 and ribulose-1,5-bisphosphate carboxylase (RuBPC) activities, and photosynthetic¹⁴CO₂ fixation. In contrast, the Car/Chl ratio increased during the dark incubation due to less expressed degradation of Car.

Changes in glucose-6-phosphate dehydrogenase, ribonucleases activities and chlorophyll content were studied in leaves of plants systemically infected by potato virus Y, necrotic strain (PVY^N). Potato cultivars Jara and Adretta differing in resistance to potato virus Y were used. No statistically significant differences were observed between healthy and infected plants of both cultivars in chlorophyll content. Activity of glucose-6-phosphate dehydrogenase slowly increased in connection with virus multiplication and reached 203.4% of the values of non-infected control in susceptible cv. Jara and 160.4% in the resistant cv. Adretta. Differences between cultivars were significant from 60 d after inoculation (P≤0.05). The activity of ribonucleases quickly increased in the initial period of the experiment and then slowly decreased. Their activities reached 195.6% in susceptible cultivar and 183.5% in the resistant one. Significant differences (P≤0.01) between susceptible and resistant cultivars was found from 18 to 35 d after inoculation. The activities of enzymes corresponded to PVY^N multiplication which was since 40 d considerably higher (P<0.01) in susceptible cultivar in comparison with the resistant one. Thus the activities of studied enzymes could be considered as markers of resistance of potato cultivars to PVY^N multiplication.

The fungal elicitor prepared fromBotrytis cinerea affected sanguinarine alkaloid formation and accumulation in callus cells ofPapaver somniferum L. Ultrastructural changes have been observed in association with the accumulation and secretion of sanguinarine in elicitor-treated cells. Alkaloid content in elicited cells was showed as a electrondense material (osmiophilic aggregations), which occurred on the tonoplast and in freely floating bodies in the vacuole. A 30-times increasing of sanguinarine content was observed in elicitor-treated cultures.

Phaseolus aureus Roxb. was exposed to HgCl₂ and Cd(NO₃)₂ either at the germination stage in concentration 0.5, 5 and 25 μM for 48 and 96 h, or at the seedling stage (5^th day of germination) in concentration 0.5, 5 and 20 μM for 6, 24 and 48 h. The germination and the growth of roots (germination stage treatment) were less in Hg than in Cd treatment. The seedlings (seedling stage treatment) were, however, more susceptible to Cd than Hg. Both root and leaf tissues of the plant treated at the germination stage showed enhanced lipid peroxidation and activities of the antioxidative enzymes (catalase, guaiacol peroxidase and ascorbate peroxidase), except the catalase in leaf in 25 μM Cd treatment. At seedling stage the content of malondialdehyde increased significantly only in the leaf tissue, during 6 h exposure. The activities of all the enzymes exhibited an increasing trend in both the tissue of the seedlings, particularly the leaf, at least after 24 and 48 h, except the catalase whose activity declined in response to Cd. Active involvement of the guaiacol and ascorbate peroxidases, rather than catalase, in scavenging cellular H₂O₂ was indicated. It was concluded that the two metals had little primary damaging effect on membranes.

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.

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.