Recent investigations on plant molybdenum-containing enzymes that include xanthine dehydrogenase (EC 1.1.1.204) and xanthine oxidase (EC 1.1.3.22), nitrate reductase (EC 1.7.1.1-3), aldehyde oxidase (EC 1.2.3.1), and sulfite oxidase (EC 1.8.3.1) are reviewed. The enzymes belong to closely related protein family and share common structural features. Special attention is being paid to the recently solved crystal structures their implications for the substrate binding and catalytic mechanism.

Significant amounts of lepidine was detected in mature and juvenile explants from both in vivo and in vitro grown plants. The yield, however, was variable depending upon the source and type of explant used. Mature in vivo plants at vegetative stage exhibited highest yield. Among all the explants, maximum lepidine was detected after 8 weeks in shoot apex callus on MS medium supplemented with 2 mg dm^-3 naphthaleneacetic acid and 5 mg dm^-3 benzylaminopurine. Addition of 900 μM Zn^2- or 100 μM Cu^2- further enhanced the yield of lepidine.

Tortula ruralis is an important experimental system for the study of plant desiccation tolerance. EST gene discovery efforts utilizing desiccated gametophytes have identified a cDNA TrRpt2 encoding a predicted polypeptide with significant similarity to the 26S proteasome regulatory subunit IV. TrRPT2, the 446 amino acid deduced polypeptide, has a predicted molecular mass of 49.6 kDa, and a predicted pI of 8.15. Phylogenetic analysis demonstrated that previously characterized RPT2 polypeptide sequences could be reproducibly grouped into 3 major clades and that TrRPT2 forms a discrete evolutionary group. RNA blot hybridizations were used to analyze TrRpt2 expression in response to: 1) desiccation and rehydration, 2) abscisic acid-treatment, 3) increased NaCl concentration, and 4) NaCl-shock. TrRpt2 steady-state mRNA transcript levels are unchanged in response to all treatments and the gene is constitutively expressed.

Responses of Artemisia annua to different concentrations of zinc [50, 100, 200, 300 and 400 μg g^-1(soil dry mass)] were studied during plant ontogeny. Total leaf area, dry mass of leaves, length and dry mass of shoots and roots increased with the age of the plant but the magnitude of increase declined significantly under the influence of Zn treatment. Net photosynthetic rate, intercellular carbon dioxide concentration and stomatal conductance were highest at flowering stage in control and treated plants and decreased at post flowering stage. Contents of chlorophyll a, chlorophyll b, carotenoids, proteins and nitrate reductase activity in leaves increased from pre-flowering to maximum level at flowering stage and decreased thereafter in both control and treated plants. Presence of Zn in the soil drastically decreased/inhibited all the parameters, and the magnitude of decline increased with increasing Zn concentration.

A full length cDNA (designated CrETR1) was isolated by polymerase chain reaction amplification of a cDNA library from periwinkle (Catharanthus roseus) cell cultures. CrETR1 cDNA encodes a polypeptide of 740 amino acids with a predicted molecular mass of 82 kDa. The deduced protein contains a hydrophobic ethylene-binding transmembrane region, a GAF domain, a third domain homologous to the histidine protein kinase domain of the prokaryotic two-component systems, and a fourth carboxyl-terminal domain homologous to the receiver domain of the response regulators, as found in the A. thaliana ethylene receptor ETR1. CrETR1 transcripts are strongly accumulated in petals and ovaries of C. roseus young plants whereas no significant changes are detected in cell cultures submitted to various stress or hormonal (including ethylene) treatments. The amount of the monoterpene indole alkaloid ajmalicine in the cells treated by ethylene is reduced after addition of inhibitors of histidine kinases showing a possible involvement of CrETR1 protein in the ethylene-related signalling pathway leading to alkaloid biosynthesis enhancement in C. roseus cell cultures.

Electrophoretic analyses of non-reduced and reduced seed storage proteins from Solanaceae and Cucurbitaceae species and cultivars were performed. High molecular disulfide bonded complexes between intermediary subunits of 11S globulins previously detected in Capsicum annuum cultivars, were found in Solanum melongena cultivars as well. The data obtained might be used for further elucidation of peculiarities of the 11S globulins in dicotyledonous plants.

In vitro protocols for plantlet regeneration and medium-term genotype conservation of eight wild species of Curcuma have been optimized. Both the phenomena were genotype-dependent and influenced significantly by type and concentration of cytokinins used. In general, benzyladenine (BA) was found superior to other cytokinins tested for plantlet regeneration and γ,γ-dimethylallylaminopurine (2iP) for conservation. Number of shoots per culture ranged from 1.3 to 7.2 and conservation period from 264 to 379 d. In 30-d-old cultures, highest frequency of shoot regeneration could be obtained in C. malabarica (7.2 shoots per culture) on MS + 11.4 μM zeatin. Curcuma sp. (unidentified wild species) could be conserved for maximum period (379 d) on MS + 24.6 μM 2iP followed by C. aromatica (363 d) on MS + 22.8 μM zeatin. The tissue culture-raised plantlets were morphologically similar to their parents. The in vitro-conserved plants multiplied rapidly in tissue cultures and produced normal rhizomes upon transfer to soil in net house.

We have assayed different combinations of nutrient media and growth regulators to induce callus and plant regeneration from explants of root, shoot and leaf, complete seed, and isolated mature embryo of barley (Hordeum vulgare L. cv. Hassan). The best results were obtained with mature embryo in J25-8 medium supplemented with 2.0 mg dm^-3 2,4-dichlorophenoxyacetic acid where about 75 % developed friable calli. Some 80 - 85 % of these calli regenerated barley plants in the same J25-8 medium supplemented with 1.0 mg dm^-3 indole-3-butyric acid and 0.1 mg dm^-3 kinetin.

Stable transformation and expression of transgenes was achieved in Centaurium erythraea Gillib. using Agrobacterium rhizogenes-mediated system. Five hairy root clones exhibited the transformed phenotype. Shoot regeneration, with green organized structures, was apparent in 4 clones, after the first subculture on Murashige and Skoog (MS) half strength medium. The integration of Ri-plasmid T-DNA was confirmed by polymerase chain reaction (PCR) analyses.

A protein, identifiable as calmodulin (CaM), has been isolated from the seedling tissue of Pharbitis nil. The method has been developed to isolate a high quality protein from plant tissue containing the high content of polyphenols. This protein was relatively heat-stable and bound to hydrophobic resin in calcium-dependent manner. It was recognized by the antibody against pea and carrot, but did not bind to antibody against Dictyostelium discoideum. This protein had M_r of 15 kDa and 18.5 kDa in the presence and absence of Ca₂₊, respectively, and was able to stimulate calmodulin-deficient cAMP phosphodiesterase. Based on its migration on SDS-PAGE gels, M_r and binding to anti-CaM antibodies it was deduced that calmodulin from P. nil is essentially identical to calmodulin isolated from other plants.

Relative water content (RWC), leaf water potential (Ψ_w) and osmotic potential (Ψ_s), contents of chlorophyll (Chl) a, Chl b, soluble sugars, and seed quality (gum content) were used to evaluate the role of phosphorus in alleviation of the deleterious effect of water deficit in clusterbean (Cyamopsis tetragonoloba L. Taub). Under water stress, Ψ_w, Ψ_s, and Chl and gum contents decreased and soluble sugar contents increased. Phosphorus application increased Chl and sugar contents in control plants and ameliorated negative effects of water stress.

Corchorus olitorius plants treated by 5 μg cm^-3 of Cd, Pb, Al or Cu in hydroponic culture accumulated in leaves 190, 150, 350 and 325 μg g^-1(d.m.) of these metals, respectively, after 6 d of exposure. Exposure of Corchorus plants to tested metals resulted in a sharp rise in content of amino acids in leaf tissues, however the magnitude of accumulation was different from one metal to another. Presence of sulphur in the growth medium significantly increased uptake of Cd and Pb and cysteine (cyst) was more effective than K₂SO₄. Similarly, addition of salicylic acid (SA) in the growth medium significantly enhanced the ability of Corchorus plants to accumulate all these metals. Growth of Corchorus plants was significantly reduced by treatment with any of the four metals except Cu and added cyst, K₂SO₄ or SA alleviated the growth retarding effect of metals.

Net photosynthetic rate (P_N), transpiration rate (E), and stomatal conductance (g_s) during water stress and after rehydration were measured in Phaseolus vulgaris, Beta vulgaris, and Zea mays. Immediately before imposition of water stress by cessation of watering, plants were irrigated with water (control), 100 μM abscisic acid (ABA), and/or 10 μM N⁶-benzyladenine (BA). In all three species, application of ABA decreased g_s, E, and P_N already 1 h after application. However, during water stress g_s, E, and P_N in plants pre-treated with ABA remained higher than in plants pre-treated with water. Positive effects of ABA application were observed also after rehydration. In contrast, the effects of pre-treatment with BA were species-specific. While in bean plants BA application ameliorated negative effect of water stress, only very slight effects were observed in maize, and in sugar beet BA even aggravated the effects of water stress.

A new protocol for micropropagation of endangered Daphne cneorum through multiple shoot formation has been developed. Two different types of explants (dormant apical buds and in vitro seed-derived young seedlings) from plants in two different localities were used for the initiation of multiple shoots on agar woody plant medium (WPM) with 0.2 mg dm^-3 benzylaminopurine (BAP), 0.1 mg dm^-3β-indolebutyric acid (IBA), 200 mg dm^-3 glutamine, and 200 mg dm^-3 casein hydrolysate. From 10 seeds only one germinated and the multi-apex culture bearing 12 shoots sprouted out from in vitro seed-derived young seedling. After 6-month cultivation 35 multi-apex cultures were achieved from in vitro seed-derived young seedling. On 1/3 strength WPM medium supplemented with 2.83 mg dm^-3 IBA 50 % of cultures (clusters of 3 - 5 shoots) rooted but no rooting occurred in the presence of α-naphthaleneacetic acid (NAA). The rooted plantlets were acclimatized for 4 weeks in the greenhouse and then transferred into natural conditions. The plants successfully survived the winter and flowered.

Elevated UV-B radiation (12.2 kJ m^-2 d^-1) as against the ambient level of 10 kJ m^-2 d^-1 affected flowering, productivity and biomass partitioning of green gram [Vigna radiata (L.) Wilczek cv. KM-2]. UV-B stress delayed flowering initiation and achievement of 50 % flowering, reduced flower retention by 25 %, potential yield by 18 % and all yield attributes such as pod number (25 %), pod mass (41 %), seed number (32 %) and seed mass (45 %). Harvest index and shelling percentage were also reduced by 31 and 7 %, respectively. Application of triadimefon (20 mg dm^-3) to unstressed plants accelerated flowering and enhanced flower retention (21 %), potential yield (15 %) and yield attributes (7 to 44 %). The partitioning of biomass between plant parts also showed improvement over the control plants. In UV-B-stressed plants, triadimefon treatment compensated the inhibitions to varying extents.

During ageing of bean (Phaseolus vulgaris L.) cotyledons in plants with modified life span the time-course of four cytokinins, ethylene, and the end products of free radical attack, lipofuscin-like pigments (LFP), were studied. UV irradiation shortened cotyledon life span, while epicotyl decapitation prolonged it. In controls, LFP increased at the senescence onset but at the end of life span it returned to the initial level. Ethylene increased more than 3-fold at the time of abscission. The content of individual cytokinins (zeatin, zeatin riboside, isopentenyl adenine, isopentenyl adenine riboside) varied differently during ageing but they did not decreased in any case under level observed in young cotyledons at the time of abscission. UV irradiation resulted in 14-fold increase in LFP concentration at the end. Ethylene increased 8-fold 2 h after irradiation. Individual cytokinins increased after UV irradiation to a different extent and time-course, nevertheless cotyledon life span was shortened. Decapitation induced LFP decrease. On day 13, LFP abruptly increased and than decreased and stayed lowered until abscission. Ethylene was maximum on day 24, at the time of abscission, it was above 200 % of control. Decapitation produced transient decrease in some cytokinins namely zeatin and isopentenyl adenine riboside.

The effects of 1 mM cadmium, lead and nickel on dry mass, Cd, Pb, and Ni contents, and changes in leaf structure in young wheat plants were studied. In leaves, Cd content was highest, followed by Pb and Ni, in roots Cd content was also highest, but followed by Ni and Pb. Roots accumulated considerably larger amounts of the three heavy metals than leaves. Largest reductions of leaf and root mass were obtained with Cd. Pb and Ni effects were almost equal. Ni excess had a strong negative effect on mesophyll thickness, while Cd mostly reduced the number and size of vascular bundles and vessel diameter. High Pb reduced the diameter of vessels causing their different deformations.

Effects of phosphorus and thiourea application (either alone or in combination) were studied on clusterbean (Cyamopsis tetragonoloba Taub.) plants subjected to water stress by withholding irrigation at pre- and post-flowering stages in pot culture trial. Water stress significantly decreased shoot water potential, relative water content of leaves, net photosynthetic rate, contents of total chlorophyll, starch and soluble proteins as well as nitrate reductase activity at both the growth stages. Application of phosphorus and thiourea or combined application increased most of these parameters. Results revealed synergistic effects of P and thiourea in enhancing net photosynthesis, leaf area, chlorophyll content and nitrogen metabolism leading to significant improvement in plant growth and seed yield under water stress condition.

The work is concerned with the effect of low concentrations (10^-7 mol dm^-3) of sodium naphthenate on total content of Cd and its particular forms in the intercellular space and inside cells, as well as on some physiological and biochemical parameters of young soybean plants grown in the presence of 1 mmol dm^-3 solution of cadmium chloride. Presence of naphthenate reduced in average by 40 % content total and intracellular Cd in root, stem and leaves and alleviated the harmful effect of Cd on activity of nitrate reductase and content of photosynthetic pigments.

The aim of the present work was to evaluate the feasibility of mannose as a selection system for the future genetic transformation of annatto (Bixa orellana L.). Hypocotyl segments, inverted hypocotyls and immature zygotic embryos were inoculated onto a Murashige and Skoog's medium supplemented with B5 vitamins, 87.6 mM sucrose and mannose in different combinations, 2.8 g dm^-3 Phytagel®, and 4.56 μM zeatin (organogenesis) or 2.26 μM 2,4-dichlorophenoxyacetic acid and 4.52 μM kinetin (somatic embryogenesis). Annatto explants did not regenerate on medium with mannose as the only carbon source when inverted hypocotyls and immature zygotic embryos were used. However, organogenesis (5 % frequency) occurred exclusively in hypocotyl-derived explants nearest to the crown (collar) of the seedlings. No further shoot development was achieved. Therefore the substitution of sucrose by mannose inhibited both organogenesis and embryogenesis, and thus the employment of mannose could constitute an alternative selective agent in protocols for genetic transformation of this species.

Multiple shoots were induced from the cotyledonary nodes derived from seedling of Sesbania rostrata on Nitsch (1969; N) medium supplemented with various concentrations of benzyladenine (BA). 1 mg dm^-3 BA proved to be the best, eliciting 5.8 ± 1.0 shoots per explant in 100 % cultures. The elongation of shoots was best at 2.0 mg dm^-3 BA. The shoot proliferation capacity increased to 7.5 shoots per explant following transfer of explants to the fresh shoot multiplication medium (MS + 1.0 mg dm^-3 BA), after an initial incubation of 30 d. To further enhance number of shoots per explant an alternative strategy of cultivation of mother explant on fresh shoot multiplication medium after excision of shoots was adopted. Following the repeated harvesting of shoots an average of 33 shoots per explant could be obtained. The in vitro regenerated shoots produced roots when transferred to half-strength MS medium supplemented with 3 % sucrose and 1 mg dm^-3 IBA. The developed plantlets were planted in the soil and transferred to the field after an acclimatization period of 3 - 4 months. These plants produced flowers and fruits in the field and exhibited the development of prominent and more organized stem nodules as compared to the in vivo raised plants of the same age.

Effect of phosphorus deficiency on photosynthetic and respiratory CO₂ exchanges were analysed in primary leaves of 2-week-old bean (Phaseolus vulgaris L. cv. Golden Saxa) plants under non-photorespiratory (2 % O₂) and photorespiratory (21 % O₂) conditions. Low P decreased maximum net photosynthetic rate (P_Nmax) and increased the time necessary to reach it. In the leaves of P-deficient plants the relative decrease of P_Nmax at 2 % O₂ was larger than at 21 % O₂. The results suggested the influence of photorespiration in the cellular turnover of phosphates.

The growth and the content of endogenous cytokinins (CKs) of current-year-old shoots from juniper plants (Juniperus communis L.) growing over and off ore site were compared. The juniper shoots from ore site (M plants) had higher metal content and exhibited delayed growth. Less bases and nucleosides of Z- and iP- type CK and more iP-conjugates were present in the M shoots. These changes were probably due to inhibited CK export from the roots and/or altered CK metabolism forming less biologically active CKs.

The effect of radiation quality (350 - 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.

Two experiments were conducted independently with plants of cassava (Manihot esculenta Crantz) growing in sand with nutrient solutions with four nitrate concentrations (0.5, 3, 6 or 12 mM). In leaves, nitrate-N was undetectable at the low nitrate applications; total-N, ammonium-N, amino acid-N, reduced-N and insoluble-N all increased linearly, while soluble proteins did it curvilinearly, with increasing nitrate supply. In contrast, soluble-N did not respond to N treatments. Total-N and soluble proteins, but not nitrate-N or ammonium-N, were much higher in leaves than in roots. Plants grown under severe N deficiency accumulated ammonium-N and amino acid-N in their roots. Further, plants were exposed to either 3 or 12 mM nitrate-N, and leaf activities of key N-assimilating enzymes were evaluated. Activities of nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase were considerably lower in low nitrate supply than in high one. Despite the low nitrate reductase activity, cassava leaves showed an ability to maintain a large proportion of N in soluble proteins.

Twenty genotypes of Stylosanthes consisting four species were evaluated under rain fed condition employing biochemical and physiological attributes to select drought tolerant lines. Relative water content measured at 50 % flowering stage of the plants showed significant variations among the lines which ranged from 32.11 in S. scabra RRR94-86 to 83.33 % in S. seabrana 2539. The results indicated that S. scabra genotypes were more tolerant to drought over other lines as evidenced by high leaf thickness, proline accumulation, content of sugars and chlorophyll, and nitrate reductase activity.

The content of glucose, fructose and saccharose as well as changes in the activities of enzymes involved in their biosynthesis and degradation were studied in tobacco plants infected with potato virus Y (necrotic strain) during the acute-infection period. Over the first part of this period, accumulation of saccharose, glucose and fructose was observed concurrently with decreased activities of the enzymes metabolizing saccharose, glucose and fructose (saccharases, saccharose synthase and hexokinases) and enhancement in the activities of enzymes synthesizing these carbohydrates (saccharosephosphate synthase, glucose-6-phosphate and/or fructose-6-phosphate phosphatases). The subsequent period was characterised by a reduction in both phosphatases that (together with just slightly raised saccharosephosphate synthase) could hardly produce enough sugars for the highly stimulated enzymes such as saccharases, saccharose synthase, and both kinases. Presumably for this reason, the previously increased content of sugars was considerably reduced to the level of control plants. The activities of glucokinase, fructokinase, saccharases and saccharose synthase were strongly increased at the culmination of virus multiplication and negatively correlated with the content of free glucose, fructose and saccharose.

Callogenesis, somatic embryogenesis and regeneration capacity in twenty-three agronomically important spring barley (Hordeum vulgare L.) cultivars on induction media with 2,4-dichlorophenoxyacetic acid (2,4-D) or 3,6-dichloro-o-anisic acid (dicamba) and on modified regeneration media were studied. The frequency of zygotic embryos exhibiting callogenesis varied from 88 to 100 % according to genotype. Dicamba was more suitable for somatic embryogenesis induction and exhibited a higher frequency of regenerants than did 2,4-D. Green regenerants were obtained in all cultivars, and there were no albino plants. Except for cv. Victor all cultivars used in the experiment showed lower regeneration capacity as compared to the model cv. Golden Promise.