The effect of salinity on leaf superoxide dismutase (SOD) activity of lemon trees of different rootstock-scion combinations was studied. In leaves from Citrus limonum cv.Verna scions on Citrus macrophylla and C. reticulata rootstocks, salinity treatment clearly caused a significant depression in both Fe-SOD and Mn-SOD activities and an increase in Cu,Zn-SOD activity. However, in leaves from Citrus limonum on Citrus aurantium rootstook, the reduction observed in the activity values of Fe-SODs and Mn-SODs was not statistically significant. Salt stress also produced a decrease in the content of soluble proteins and chlorophylls. However, this drop was greater in C. limonum leaves on C. macrophylla than for other combinations.

All seeds of Aeluropus lagopoides and Urochondra setulosa germinated under non-saline conditions except for Sporobolus ioclados which showed only 40 % germination. Increase in salinity substantially inhibited germination and few seeds germinated at 400 mM NaCl. Germination at 200 mM NaCl was alleviated in U. setulosa by the application of gibberellic acid and fusicoccin, in A. lagopoides by thiourea, betaine, kinetin, fusicoccin and ethephon, and in S. ioclados by gibberellin and ethephon. High salinity (400 mM NaCl) induced germination inhibition was alleviated by proline, kinetin, fusicoccin and ethephon only in A. lagopoides.

Pyruvate kinase is an important enzyme of glycolytic pathway that also functions in providing carbon skeleton for fatty acid biosynthesis. It has been purified to near homogeneity from Ricinus communis, Selenastrum minutum, Cynodon dactylon, Brassica campestris and B. napus, and characterised. Partially purified preparations are reported from several other sources. A phosphoenolpyruvate (PEP) phosphatase accompanies pyruvate kinase. In plants, two isozymes of pyruvate kinase are reported, namely cytosolic and plastidic. Isoforms of cytosolic pyruvate kinase have also been reported from spinach. In most cases pyruvate kinase is a tetrameric protein and the molecular mass lies between 200 to 250 kDa. The pH optimum is in the range of 6.2 to 7.5. It requires both Mg²⁺ and K⁺ for maximum activity. ATP, citrate, and oxalate inhibit pyruvate kinase in most cases. A sequential compulsory ordered mechanism of binding of substrates to the enzyme has been proposed.

Heat shock (HS) reduced total lipid and phospholipid contents and their synthesis in germinating seeds of pigeonpea [Cajanus cajan (L.) Millspaugh]. Lipid peroxidation was also enhanced with increasing temperature and HS duration. HS influenced lipid metabolism to a higher extent at 45°C than at 40°C. This altered lipid metabolism and lipid peroxidation was associated with the loss of various solutes from the germinating seeds, and modification of growth and development. Pretreatment of germinating seeds at 40°C for 1 h or at 45°C for 10 min followed by incubation at 28°C for 3 h prior to 45°C for 2 h ameliorated solute leakage due to reduced lipid peroxidation and improvement in lipid content and membrane function.

Influence of increased K supply on growth and nutrient content in pearl millet (Pennisetum glaucum) under severe water stress was assessed in a pot experiment under glasshouse conditions. Nineteen-day-old plants of two lines, ICMV94133 and WCA-78 were subjected for 30 d to 235, 352.5, and 470 mg(K) kg^-1(soil) and two water regimes (100 and 30% field capacity). Increasing soil K supply did not alleviate the adverse effect of water deficit on the growth of two lines of pearl millet. Accumulation of N and K in the shoots of both lines was higher under water deficit than that under well-watered conditions, but such effect was not observed for P or Ca.

The effect of storage conditions on the serological activity of two isolates of potato virus Y^NTN strain (PVY^NTN) was studied by ELISA. Purified virus, intact and homogenized infected leaves stored freeze-dried and frozen at various temperatures were tested. Purified virus was the most stable at +4 °C and non-purified virus was best preserved as a freeze-dried leaf homogenate at -20 °C. Their serological activity did not change after three months of storage.

Callus induction was obtained on Murashige and Skogg agar medium with 45 μM 2,4-dichlorophenoxyacetic acid under dark at 25°C. Among the four explant types investigated, the best callus induction was obtained from two-week old fronds to which a surgical incision was applied in the basal (meristematic) region. This treatment resulted in 89.11% of fronds producing callus which continued to proliferate for another 24 months. To obtain plant regeneration pieces of calluses were transferred onto Murashige and Skoog agar medium containing 22 μM indole-3-acetic acid and 4.6 μM kinetin and maintained under 16-h photoperiod (irradiance of 30 μmol m^-2 s^-1) at 23°C. Green fronds formed on all callus pieces. The regenerated fronds were later transferred onto Wang medium where they formed roots. The regenerated Lemna minor L. plants obtained through indirect organogenesis did not differ morphologically from individuals forming the stock collection.

Effects of NaCl (150 mM), proline (10 mM) and their combination on growth and contents of chlorophyll, proline and protein of bean (Phaseolus vulgaris cv. Kizilhaç) seedlings in vitro were investigated. NaCl decreased seedling growth. Proline added to control seedlings did not change seedling growth but decreased chlorophyll and increased protein contents. When proline added to NaCl-treated seedlings growth was increased in comparison with NaCl-treated only. Thus, proline alleviated salinity stress in bean seedlings.

Artichoke (Cynara scolymus L.) leaf size and shape, glandular and covering trichomes, stomatal density, stomata shape, pore area and epicuticular waxes during micropropagation stages were studied by scanning electron microscopy (SEM) and morphometric analysis with the aim to improve the survival rate after transfer to greenhouse conditions. Leaves from in vitro shoots at the proliferation stage showed a spatular shape, ring-shaped stomata, a large number of glandular trichomes and juvenile covering hairs, but failed to show any epicuticular waxes. Leaves from in vitro plants at the root elongation stage showed a lanceolated elliptic shape with a serrated border, elliptical stomata, decreased pore area percentage, stomatal density, and mature covering trichomes. One week after transfer to ex vitro conditions, epicuticular waxes appeared on the leaf surface and stomata and pore area were smaller as compared to in vitro plants. Artichoke acclimatization may be improved by hormonal stimulation of root development, since useful morphological changes on leaves occurred during root elongation.

Pot culture experiments were conducted using different NaCl concentrations to assess their impact on the growth and metabolic changes in senna (Cassia angustifolia Vahl.). Five treatments (0, 40, 80, 120, and 160 mM NaCl) were given to the plants at three phenological stages, i.e. at pre-flowering, (45 days after sowing, DAS); flowering (75 DAS) and post-flowering (90 DAS) stages. A significant reduction in the biomass and length of the roots and shoots, photosynthetic rate, stomatal conductance, the total chlorophyll content, protein content, nitrate reductase activity, and reduced nitrogen content of the leaves was observed at each phenological stage with each salt concentration applied. Contrary to this, proline and nitrate contents of the leaves increased markedly. The post-flowering stage was most sensitive to NaCl treatment.

The contents of several photosynthetic metabolites - 3-phosphoglyceric acid (3-PGA), pyruvate, nicotinamide adenine dinucleotide phosphate (NADP) and adenosine triphosphate (ATP) - were determined in leaves of cotton plants (Gossypium hirsutum L. cv. H-777) subjected to waterlogging at vegetative stage, and/or drought at the reproductive stage. In controls, soil moisture contents was kept at field capacity. One day prior to stress, the plant shoots were sprayed with 5 μM aqueous solution of indole-3-acetic acid (IAA), gibberellic acid (GA₃), benzylaminopurine (BAP), abscisic acid, and ethrel. In control plants, various growth regulators reduced contents of 3-PGA and ATP while increased contents of NADP and pyruvate. During waterlogging IAA promoted 3-PGA content, and BAP enhanced pyruvate content. During drought, GA₃ enhanced ATP and 3-PGA contents, while IAA enhanced pyruvate content.

Electrophoretic patterns of malate dehydrogenase (Mdh), alcohol dehydrogenase (Adh), and 6-phosphogluconate dehydrogenase (Pgd) of Zea mays L. × Tripsacum dactyloides L. hybrids and their parents were compared. The components of enzymes specific to T. dactyloides may be used as markers to identify the following T. dactyloides chromosomes in the hybrids: Tr 16 (Mdh 2 and Pdg 1), Tr 7, and/or Tr 13 (Adh 2). The isozymes of Mdh 2 are supposed as a possible biochemical marker to evaluate the introgression of genes, determining an apomictic mode of reproduction from T. dactyloides (localized on Tripsacum 16 chromosome) into Z. mays. The isozymes may be used as markers for the identification of maize chromosomes 1 and 6 in the hybrids as well. Chromosome count taken on the examined hybrids showed the addition of 9 to 13 chromosomes of T. dactyloides to maize chromosome complement.

The ratio of activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (G6P DH/6PG DH), and the contents of glucose-6-phosphate (G6P), 6-phosphogluconate (6PG) and fructose-6-phosphate (F6P) were studied at various stages of potato virus Y (PVY) multiplication in Nicotiana tabacum cv. Samsun. G6P DH/6PG DH increased through the experiment from 0.42 to 0.53 in leaves of healthy tobacco, and up to 0.59 in PVY systemically infected leaves. However, these ratios in the ruptured protoplast preparations, and the chloroplast and cytosol fractions of healthy protoplasts were similar to that from infected ones. The ratio lower than 1, found in the healthy and/or PVY- infected leaf tissues and in the infected protoplasts as well, confirms the assumption that G6P DH is the control enzyme of oxidative pentosephosphate pathway not only in the healthy but also in the infected plants. The contents of G6P, 6PG and F6P in the period of the highest PVY multiplication were strongly decreased (to 30 - 50 % when compared with control healthy leaves) and were negatively correlated with the G6P DH and 6PG DH activities.

The experiments were carried out with germinating maize seeds (Zea mays L.), grown 6 d in the dark at 26°C. Before germination the seeds were soaked for 4 h in solutions containing 1 mM abscisic acid (ABA), 0.1 mM N₁-(2-chloro-4-pyridyl)-N₂ phenylurea (4PU-30) and their combination. The influence of plant growth regulators on the length, fresh (FM) and dry (DM) masses, proteolytic activities and soluble protein fractions in shoots, roots and endosperm were studied. As compared to control the seedlings treated with ABA showed lower length, FM and DM of shoots and roots, and lower proteolytic activities. As a consequence of suppression of both growth and protein breakdown, these seedlings possessed higher protein content in endosperm. 4PU-30 partially decreased the ABA suppressing effects.

Exogenously applied methyl jasmonate (MeJA) might induce the formation of necrotic lesions that closely resemble hypersensitive response lesions. Cellular damage, restricted to the infiltrated zone, was accompanied with the production of H₂O₂ from the oxidative burst. H₂O₂ generated in response to MeJA can be histochemically detected in cells surrounding the necrotic lesions as well as in the vascular tissues. The response is systemic and maximizes with time. Among 12 plant species from different families that were assayed for both hypersensitive reaction (HR)-like response and H₂O₂ generation, only woody species exhibited both MeJA-inducible HR cell death and the generation of H₂O₂. To assess the role of H₂O₂ in MeJA-induced HR-like cell death, a gain and loss of function strategy was employed. The cumulative results indicate that H₂O₂ is neither necessary nor sufficient for MeJA-inducible cell death and that O₂^- rather than H₂O₂ might be responsible.

Zinc adsorption by two green algae, Scenedesmus obliquus and Scenedesmus quadricauda, was investigated. The maximum adsorption capability of zinc ion obtained from the Langmuir adsorption isotherms was higher for S. obliquus (6.67) than for S. quadricauda (5.03), and S. obliquus was more tolerant to zinc phytotoxicity than S. quadricauda. Lower concentrations of zinc increased dry mass, chlorophylls a and b, carotenoids, and total amino acid contents in both algae. On the other hand, higher concentrations of zinc were inhibitory for growth and the other metabolic activities in a concentration dependent manner.

A protocol was developed for direct differentiation of multiple shoot buds from leaf explants of Cajanus cajan. In a modified Murashige and Skoog's medium supplemented with 2.22 µM benzyladenine (BA), 0.57 µM indole-3-acetic acid (IAA) and 41 µM adenine sulphate (AdS), the segments of basal halves of the first two leaves of a young seedling incubated on filter paper bridges in liquid medium took 20 - 25 d to differentiate shoot buds. The explants after transfer to solidified medium, with lower concentration of BA (0.22 μM) resulted in fast growing healthy shoots. The developed shoots (measuring ca. 3 cm) were rooted in a medium supplemented with 1.42 µM IAA. They were subsequently grown in pots with soil with more than 80 % transplantation success.

The effects of increasing relative humidity on the growth and salt tolerance of two melon (Cucumis melo L.) cultivars, Revigal C-8 (salt sensitive) and Galia (salt tolerant) was investigated. One month after germination, the plants were exposed for 15 d to 0 (control) and 80 mM NaCl, under relative humidity (RH), 30 and 70 %. The growth of the whole plant, leaf, stem and root of cv. Revigal C-8 was increased with increasing RH. On the other hand, cv. Galia showed an increase in root growth with increasing RH only under the NaCl treatment. Under salinity, most of the Na⁺ was withheld in the stems. An increase in RH in the NaCl treatment significantly decreased Na⁺ and Cl^- concentrations in leaves of cv. Revigal C-8, while it had no effect on their concentrations in cv. Galia. In both cultivars, increasing RH under NaCl condition significantly decreased water contents in leaves and stems, and increased osmotic potential in roots. The amount of the root exudate of cv. Galia was significantly decreased with increasing RH, while it was not affected in cv. Revigal C-8. Under the NaCl treatment, cv. Galia had significantly higher leaf osmotic potential than cv. Revigal C-8 at both relative humidities and higher amount of root exudate at 30 % RH.

Direct somatic embryogenesis in celandine (Chelidonium majus L.) was achieved in epicotyl explants of seedlings after prolonged cultivation on Murashige and Skoog medium with or without plant growth regulators. Somatic embryos developed into plantlets which entered additional cycles of somatic embryogenesis. Cultures consisting of plantlets with prolonged embryogenic potential were maintained for five years on plant growth regulator free medium. Embryos which developed into rooted plantlets could be acclimated in a glasshouse enabling thus a continuous propagation scheme to be established.

Diamine oxidase (DAO, EC 1.4.3.6.), which participates in oxidative catabolism of polyamines (PAs), was not detected in the dry viable chickpea (Cicer arietinum L.) seeds. From the time when the embryonic axis acquired an aerobic metabolism, DAO increased concomitantly with the growth of the embryonic axis and at the same time with the deterioration of the cotyledons, although in these organs the values were clearly lower than in the axis. The highest DAO activity in the embryonic axis of seedlings grown for 72 and 96 h was found in the elongation, differentiation and hypocotyl zones, while the lowest was in the apex and plumule. The absence of cotyledons promoted the early appearance of DAO in the embryonic axis. When germination occurred at supraoptimal temperatures (30 - 35 °C), DAO activity was sharply inhibited both in the cotyledons and in the embryonic axis. This inhibition was accentuated further in the presence of cyclohexylamine, an inhibitor of spermidine synthase activity, to such a degree that DAO was undetectable in the cotyledons. DAO inhibition by EGTA and the pronounced reversal induced by Ca²⁺ implies that calcium may be related to DAO activity. The presence of putrescine, spermidine and spermine in the germination medium stimulated DAO activity, although this activity was inhibited when the exogenous PA was cadaverine.

Greenhouse experiments were conducted in two years (1993-1994) with eggplants supplied with 1, 2 or 4 mM NH₄NO₃ as the N source in order to determine its influence on molybdenum (Mo) and nitrate (NO₃^-) content in leaf blades, petioles, and fruits as well as leaf nitrate reductase (NR) activity. The results reveal that 2 and 4 mM NH₄NO₃ altered shoot Mo distribution and thus affecting the NR activity.

The aim of this research was to set up a regeneration protocol from mature explants of Prunus avium L. cv. Hedelfinger and to develop an early screening method for selection of putative somaclones based on morphological and physiological traits regulated by the spectral quality of radiation. DNA analyses of a new somaclone named HS, conducted using Inter Simple Sequence Repeat (ISSR), revealed a polymorphism between the somaclone HS and wild type propagated by microcuttings. When grown under different spectral quality of radiation, somaclone HS showed a different pattern of growth and development compared to the wild type with the main modifications related to apical dominance and chlorophyll production. Somaclone HS showed reduced apical dominance compared to the wild type. Wild type shoots grown in darkness showed chlorophyll a and b contents at levels in both cases comparable to those recorded under red radiation while HS did not retain the same capability.

The study was focused on changes of anatomical and histochemical parameters of buds of 4-year-old Norway spruce (Picea abies L. Karst) trees subjected to simulated acid rain (SAR). Solutions of pH 2.9 and 3.9 were applied by spraying on shoot and/or by watering for two years. No macroscopic changes of buds or needles were observed in connection with SAR application and the only induced change was 2-week earlier onset of bud break in all treated variants compared to the control. Two-year treatment caused decrease in number of leaf primordia and increase in number of living bud scales in treated dormant buds while these parameters remained unchanged in the control buds. Treatments with solution of pH 2.9 caused decrease of flatness of bud apical meristem during the vegetative season. Increased activity of non-specific esterase in treated buds occurred during dormancy and bud break and the enhanced accumulation of phenolic compounds was detected at the beginning of shoot growth. Changes in histochemical parameters of bud tissues were induced mainly by spraying of shoots and can thus be qualified as primary damage.