Agrobacterium tumefaciens strain EHA105 carrying a binary vector pCAMBIA2301, which contains a neomycin phosphotransferase gene (nptII) and a β-glucuronidase (GUS) gene (uidA) interrupted with an intron, was used for transformation of Vigna mungo cotyledonary node explants. Various factors such as preculture and wounding of explants, manipulations in inoculation and co-cultivation conditions were found to play a significant role in influencing tissue competence, Agrobacterium virulence and compatibility of both, for achieving the maximum transformation frequencies. The stable transformation with 4.31 % efficiency was achieved using the optimized conditions. The transformed green shoots that were selected and rooted on medium containing kanamycin and tested positive for nptII gene by polymerase chain reaction were established in soil to collect seeds. GUS activity was detected in leaves, roots, pollen grains and T₁ seedlings. Southern analysis of T₀ plants showed the integration of nptII into the plant genome.

Foliar sprays of water or 1, 10 and 100 µM aqueous solutions of gibberellic acid (GA₃) or kinetin (KIN) were applied to 40-d-old plants of Nigella sativa (L.) to study their effects on net photosynthetic rate, nitrogen metabolism, and the seed yield. 10 µM solutions of both the hormones, especially GA₃, appreciably increased the activities of nitrate reductase and carbonic anhydrase, chlorophyll and total protein contents and net photosynthetic rate in the leaves, along with capsule number and seed yield plant^-1, at harvest.

Immunocytochemical analysis using antibody raised against human H2AX histones phosphorylated at serine 139 (γ-H2AX) demonstrates that root meristem cells of Vicia faba exposed to UV-radiation or incubated with hydroxyurea (HU) reveal discrete foci at the border of the nucleolus and perinucleolar chromatin or scattered over the whole area of cell nucleus. Western blots detected only one protein band at the position expected for the phosphorylated form of H2AX. The dose-effect relationship was demonstrated following treatment with 2.5 and 10 mM HU. Proteins extracted from root meristems incubated for 2 h either with HU and caffeine or with HU and sodium metavanadate showed unchanged amounts of bound γ-H2AX antibodies, as compared to root meristems treated with 2.5 mM HU. Higher quantities of phosphorylated H2AX histones were detected in proteins extracted from roots treated with HU and 2-aminopurine. All treatments were effective in producing evident aberrations of premature mitosis: broken and lagging chromatids, acentric fragments, chromosomal bridges and micronuclei. Our results show that phosphorylation of H2AX at the carboxy-terminal Ser-Gln-Glu sequence is among the earliest responses to double-strand breaks and, presumably, one of the key ATM/ATR-dependent signals indispensable for the repair of spontaneous and induced DNA damage in plant cells.

Plants of Miscanthus sinensis (cv. Giganteus) were grown in hydroponics for three months in nutrient solution with 0, 2.2, 4.4 and 6.6 μM CdNO₃. Growth parameters, catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities were analysed in leaves and roots collected after 1-and 3-month exposure. Dry biomass of all miscanthus organs was affected by Cd concentration both after 1-and 3-month exposure. No visible symptoms of Cd toxicity were observed in shoots and rhizomes of plants grown in presence of Cd. In contrast, roots became shorter and thicker and the whole root system more dense and compact already after one month of treatment with 6.6 μM Cd. The lower Cd concentration increased the enzymes activities after 3 months in leaves and only after 1-month in roots, while a decrease in activity was observed at higher Cd concentrations.

The plants of pigeonpea (Cajanus cajan L.) cv. H77-216 were subjected to moderate [soil moisture content (SMC) = 7.3 ± 0.5 %] and severe (SMC = 4.3 ± 0.5 %) drought by withholding the irrigation at vegetative stage (45 d after sowing). The control plants were maintained at SMC of 11.0 ± 0.5 %. Half of the stressed plants were re-irrigated and their recovery was studied after 2 d. Leaf water potential, osmotic potential, and relative water content of leaf and root decreased significantly while a sharp rise in proline and total soluble sugars contents were noticed. Drought induced a significant increase in 1-aminocyclopropane 1-carboxylic acid (ACC) content and ACC oxidase activity which caused a considerable increase in ethylene evolution. Malondialdehyde content and relative stress injury were increased under drought whereas reverse was true for ascorbic acid content. The membrane integrity of roots decreased during stress and recovered on rehydration. The specific activity of total superoxide dismutase, ascorbate peroxidase, glutathione reductase, and glutathione transferase decreased to 37 - 78 %, 17 - 62 %, 29 - 36 % and 57 - 79 % at moderate and severe drought, respectively. The increase in activity of catalase and peroxidase could not overcome the accumulation of H₂O₂ content in the roots.

The human papillomavirus type 16 (HPV 16) oncogene E7 fused with the gene for β-glucuronidase (gus) was used in plant transformation experiments. The E7 gene modified for lower cancerogenicity and fused with the 5' end of the gus in cassettes with cauliflower mosaic virus 35S promoter and transcription terminator produced high contents of fusion proteins in potato protoplasts. Expression vectors harbouring E7 fusion cassettes were used for Agrobacterium tumefaciens LBA4404 mediated transformation of either potato (Solanum tuberosum L. cv. Bintje) or tomato (Lycopersicon esculentum Mill. cv. Moneymaker). A fusion gene was found in all rooted regenerants using polymerase chain reaction with primers providing amplified fragments from E7 and gus genes. GUS activity was revealed in all regenerants obtained. Nevertheless, the level of GUS expression in different constructs varied much more than in transient expression experiments with potato protoplasts. Especially, expression level in plants carrying vectors with the whole E7 gene fused with gus was lowered by 2-3 orders of magnitude comparing with fusion of the first 41 codons of E7 and gus. Southern hybridisation of 18 tomato and 23 potato regenerants revealed mostly multiple tandem integration of T-DNA into the plant genome and Western blot proved the presence of the fusion protein in 9 tomato and 11 potato plants out of 41 tested individuals.

The adventitious bud development was induced in epicotyl segments of Valencia sweet orange (Citrus sinensis L. Osbeck). Seeds were cultured in vitro for three weeks in the dark, followed by one week at a 16-h photoperiod. Epicotyl segments were cultured horizontally for the induction of organogenesis in Murashige and Tucker (1969, MT) culture medium supplemented with 1.0 mg dm^-3 benzylaminopurine. Samples were observed by light and scanning electron microscopy from day zero to day 25, when buds were well grown. It was shown that the adventitious buds originated directly from the cambial region on the cut ends of the explants.

The present study evaluated the use of γ-radiation to physically remove selective marker genes previously introduced into the soybean genome. Homozygous seeds from a transgenic soybean line carrying the gus and ahas transgenes were irradiated with γ-rays. Six plants presenting a deleted gus gene were analyzed by Southern blot to confirm removal of both ahas and gus genes. Line 1A presented an absence of the gus gene cassette and presence of the ahas gene cassette.

The effect of excessive Cd on the growth and metal uptake by leafy vegetables Brassica chinensis L. (cv. Wuyueman) and Brassica pekinensis (Lour.) Rupr. (cv. Qingyan 87-114) were studied in hydroponic solution culture. The Cd concentration higher than 10 µM significantly decreased the root elongation and leaf chlorophyll contents of both plant species. The shoots of B. pekinensis had significantly higher concentrations of total and water-soluble Cd than B. chinensis. The roots of both species accumulated more Cd than the shoots in all the Cd treatments. Most of the Cd in the roots was found in the cell walls. The shoot/root ratio of Cd concentrations in B. pekinensis was always greater than that in B. chinensis. But, the concentration and proportion of Cd in the cell walls in B. chinensis were higher than that in B. pekinensis. Cadmium treatments also increased the concentrations of total non-protein thiols (NPT) in the shoots of the both species. A significant correlation was found between the concentrations of soluble Cd and NPT in plant shoots.

Agrobacterium rhizogenes A4M70GUS-mediated transformation of Savoy cabbage (Brassica oleracea L. var. sabauda) and two local lines of cabbage (B. oleracea L. var. capitata) was obtained using hypocotyl and cotyledon explants. The percentage of explants which formed roots was very high in all genotypes: 92.3 % in Savoy Gg-1, 64.4 % in cabbage P₂₂I₅, and 87.2 % in P₃₄I₅. Spontaneous shoot regeneration of excised root cultures grown on the hormone-free medium occurred in all three genotypes. In cabbage lines P₂₂I₅ and P₃₄I₅ shoot regeneration was higher (9.3 and 2.6 % respectively) than in Savoy cabbage Gg-1 (1.3 %). Transgenic nature of hairy root-derived plants was evaluated by GUS histological test and PCR analysis. All the tested cabbage shoots were GUS positive whilst in a Savoy cabbage GUS expression was registered only in 55 % of tested clones. PCR analysis demonstrated the presence of the GUS gene in regenerated shoot clones and in T₁ progeny.

To study the defense mechanism of the resistance to the disease of Chinese wild Vitis species and offer powerful bases for the molecular breeding of highly disease-resistant grape cultivars, using mRNA differential display reverse transcript-PCR (DDRT-PCR) and RACE, a full-length cDNA was isolated from Chinese wild Vitis pseudoreticulata clone Baihe-35-1 inoculated with Uncinula necator by pressing infected leaves under natural field conditions. The cDNA designated as GLOXrg is 1708 bp in length with an open reading frame of 1572 bp encoding 523 amino acids, containing the conserved domain, glyoxaloxid N domain (pfam07250). No homologous nucleotide sequence was found, but the deduced amino acid sequence of GLOXrg shows 74 % identity with a putative protein from Arabidopsis thaliana (accession No. CAB88357). GLOXrg was cloned into pGEX-4T-1 vector. The recombinant vector expressed an about 83-kDa GST-GLOXrg fusion protein as insoluble inclusion bodies in Escherichia coli BL21. Fusion protein GST-GLOXrg was isolated and used to raise the polyclonal anti-(GST-GLOXrg) in rabbits. Western blot analysis showed a high titer (10 000) and the high specificity of the polyclonal anti-(GST-GLOXrg). This is the first report on the cloning of the full-length GLOXrg cDNA from the plant except Arabidopsis thaliana. Through the differential expression, GLOXrg probably plays a crucial role in the resistance to Uncinula necator of Chinese wild Vitis species. An optimized system on prokaryotic expression, protein purification and preparation of the polyclonal antibodies of GLOXrg was also established.

The photosynthetic and growth characteristics of Mosla hangchowensis, an endangered species and M. dianthera, a weed, were compared under three irradiances (PPFD) similar to shaded forest understory, forest edge and open land. Both species grown at lower PPFD had lower PPFD-saturated photosynthetic rate (P_max), saturation PPFD, compensation PPFD, apparent quantum yield, total mass and root/shoot ratio and higher specific leaf area, leaf area ratio and height ratio. At the same PPFD treatment, however, specific leaf area and leaf area ratio of M. hangchowensis were higher than those of M. dianthera, other above parameters were lower than those of M. dianthera. Water use efficiency did not differ between M. hangchowensis and M. dianthera, but it reached its maximum at 70 % of full PPFD. These results suggested the optimum habitat of M. hangchowensis is the forest edge.

Hydroponically grown African rice (Oryza glaberrima) was exposed for 72 h to a high Fe²⁺ concentration (500 mg dm^-3) to identify the first steps of iron toxicity response in various organs. Iron accumulated in all plant parts analysed and had only a limited impact on absorption and translocation of other nutrients. The content of the iron-storage protein ferritin increased as a consequence of transcription stimulation or increase in mRNA stability and culminated after 48 h of treatment in laminae and to a lesser extent in sheaths but was not detected in roots. Although endogenous iron concentrations were similar in sheaths and laminae, superoxide dismutase activity was stimulated only in sheaths while ascorbate peroxidase activity increased mainly in laminae. It is concluded that both ferritin synthesis and antioxidative response may play a key role in the resistance of Oryza glaberrima to iron toxicity but that their relative importance are not the same in all organs.

Leaf morphology, longevity, and demography were examined in Quercus ilex and Phillyrea latifolia growing in a holm oak forest in Prades mountains (northeast Spain). Four plots (10 × 15 m) of this forest were submitted to an experimental drought during three years (soil moisture was reduced about 15 %). Leaf area, thickness and leaf mass per area ratio (LMA) were measured in sun and shade leaves of both species. Leaf longevity, the mean number of current-year shoots produced per previous-year shoot (Sn/Sn-1), the mean number of current-year leaves per previous-year shoot (Ln/Sn-1), and the percentage of previous-year shoots that developed new ones were measured once a year, just after leaf flushing. LMA and leaf thickness increased since leaf unfolding except in summer periods, when stomatal closure imposed low photosynthetic rates and leaves consumed their reserves. LMA, leaf area, and leaf thickness were higher in Q. ilex than in P. latifolia, but leaf density was higher in the latter species. Drought reduced the leaf thickness and the LMA of both species ca. 2.5 %. Drought also increased leaf shedding up to ca. 20 % in Phillyrea latifolia and decreased it up to ca. 20 % in Q. ilex. In the later species, Sn/Sn-1 decreased by 32 %, Ln/Sn-1 by 41 %, percentage of shoots developed new ones by 26 %, and leaf area by 17 %. Thus the decrease of leaf number and area was stronger in the less drought-resistant Q. ilex, which, under increasingly drier conditions, might lose its current competitive advantage in these Mediterranean holm oak forests.

Forty-five-days old plants of Indian senna (Cassia angustifolia Vahl.) were subjected to 0-500 µM lead acetate (Pb-Ac) in pot culture. Changes in contents of thiobarbituric acid reactive substances (TBARS), ascorbate, glutathione, proline, sennosides (a+b), and activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), and catalase (CAT) were studied at pre-flowering (60 d after sawing, DAS), flowering (90 DAS) and post-flowering (120 DAS) stages of plant development. Compared with the controls, the Pb-Ac treated plants showed an increase in contents of TBARS, dehydroascorbate, oxidized and total glutathione at all stages of growth. However, sennoside yield and contents of ascorbate and reduced form of glutathione declined. Proline content increased at 60 DAS but declined thereafter. Activities of SOD, APX, GR and CAT were markedly increased. Sennoside content was higher at 60 and 90 DAS but lower at 120 DAS, compared to the control.

The effect of silicon on the growth, boron concentrations, malondialdehyde (MDA) content, lipoxygenase (LOX) activity, proline (PRO) and H₂O₂ accumulation, and the activities of major antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] and non-enzymatic antioxidants (AA) of wheat grown in soil originally with toxic B concentrations were investigated. Applied of 5.0 and 10.0 mM Si to the B toxic soil significantly increased Si concentration of the wheat and counteracted the deleterious effects of B on shoot growth. The contents of PRO, H₂O₂, MDA, and LOX activity of wheat grown in B toxic soil were significantly reduced by Si treatments. Compared with control plants, the activities of SOD, CAT, APX and content of AA were decreased by applied Si. Based on the present work, it can be concluded that Si alleviates B toxicity of wheat by preventing oxidative membrane damage and also translocation of B from root to shoot and/or soil to plant.

The in vitro rooting of myrtle (Myrtus communis L.) plantlets was performed in containers with gas permeable (V) and non-permeable (C) closures characterized by a different number of gas exchanges (1.4 and 0.3 h^{- 1}, respectively). The rooting was induced on Perlite, soaked with half strength Murashige and Skoog (MS) medium with 0.5 mg dm^-3 IBA, either with and without 15 g dm^-3 of sucrose. During the rooting phase, it was demonstrated that C cultures without sucrose (C-) negatively affect the growth of myrtle plantlets. The net photosynthetic rate and the starch content showed the lowest values in C cultures with and without sucrose (C+ and C-) while chlorophyll a content did not vary among treatments, therefore it could not be considered an indicative parameter to evaluate the autotrophic metabolism in myrtle plantlets. Electron microscopy and image analysis were employed to evaluate the leaf ultrastructure at three sample dates. Plantlet rooted in vented vessels with and without sucrose (V+ and V-) showed chloroplasts with numerous starch inclusions, while several osmiophilic plastoglobules (frequently related with leaf senescence) were found in chloroplast of leaf cells of C- myrtle plantlets.

The aim of this work was to estimate genetic variability for in vitro culture response of recombinant inbred lines (RILs) of the genus Lycopersicon. The callus percentage (C), the regeneration percentage (R) and the productivity rate (PR) were evaluated 45 d after culture initiation in a set of 16 elite tomato RILs and their parents. The narrow sense heritability (h²) values were 0.38 ± 0.04 for C, 0.46 ± 0.04 for R, and 0.28 ± 0.03 for R, while the genetic correlation (r _g ) values were -0.96 ± 0.07 between C and R, 0.81 ± 0.14 between PR and R, and -0.79 ± 0.16 between PR and C. Three AFLP markers associated to the in vitro traits were identified.

Differential mRNA display was used to identify pathogen-responsive, stress-related genes in potato cell suspensions treated with salicylic acid and a cell wall-derived elicitor from Phytophthora infestans. Among the positive clones identified, one was found to be expressed at a significantly higher level in elicited cells than in control cells. DNA sequencing of this amplicon revealed high homology and identified it as a potato cyclophilin cDNA. The maximum amount of the cyclophilin mRNA was found 9 to 12 h after elicitation. Cyclophilin (CyP) mRNA synthesis was also up-regulated from 12 to 24 h in potato leaves locally infected with zoospores from Phytophthora infestans. However, untreated leaves responding systemically to the pathogen showed only a weak, delayed response at 24 h post infection. The observed accumulation of potato CyP mRNA in response to salicylic acid, P. infestans elicitor and P. infestans infection, suggest that CyPs play an important role in plant stress responses.

Glass microelectrodes were inserted into Dionaea muscipula (Venus flytrap) lobes and the action potentials (APs) were recorded in response to a sudden temperature drop or a direct current (DC) application. The effect of potassium channel inhibitor, tetraethylammonium ion, was the lengthening of the depolarization phase of AP. APs were also affected by the anion channel inhibitor, anthracene-9-carboxylic acid, that made them slower and smaller. Neomycin, which disturbs inositol triphosphate-dependent Ca²⁺ release, caused the visible inhibition of AP, too. Ruthenium red, which blocks cyclic ADP-ribose-dependent Ca²⁺ release, totally inhibited DC-triggered APs and induced the decrease in the amplitudes of cold-evoked APs. Lanthanum ions significantly inhibited both cold- and DC-induced membrane potential changes. It was concluded that during excitation Dionaea muscipula relied upon the calcium influxes from both the extra- and intracellular compartments.

Four rice indica genotypes of local importance were transformed with RC7, rice chitinase cDNA clone through Agrobacterium-mediated gene transfer method using mature seed derived calli as explants. The putative hygromycin resistant calli showed varied level of regeneration efficiency ranging from 2.0 to 7.6 %. The stable integration and expression of RC7 was confirmed through polymerase chain reaction (PCR) and Western analysis. Transformation efficiency ranged from 0.9 to 5.2 %. The expression of RC7 (35 kDa chitinase) in different tissues of transgenic plant (root, sheath and leaf) was proved through Western analysis and in terms of increased chitinase activity. The inheritance of transgene was studied through PCR and Western analysis in transgenic plants of Pusa Basmati 1. Bioassays with transgenic plants of local cultivars exhibited enhanced resistance up to 33.3 % to rice sheath blight pathogen Rhizoctonia solani under glasshouse conditions. Enhanced expression or 3-to 4-fold increased activity of chitinase in transgenic plants was correlated with sheath blight resistance.

The phytoremediation is an environment friendly, green technology that is cost effective and energetically inexpensive. Metal hyperaccumulator plants are used to remove metal from terrestrial as well as aquatic ecosystems. The technique makes use of the intrinsic capacity of plants to accumulate metal and transport them to shoots, ability to form phytochelatins in roots and sequester the metal ions. Harbouring the genes that are considered as signatures for the tolerance and hyperaccumulation from identified hyperaccumulator plant species into the transgenic plants provide a platform to develop the technology with the help of genetic engineering. This would result in transgenics that may have large biomass and fast growth a quality essential for removal of metal from soil quickly and in large quantities. Despite so much of a potential, the progress in the field of developing transgenic phytoremediator plant species is rather slow. This can be attributed to the lack of our understanding of complex interactions in the soil and indigenous mechanisms in the plants that allow metal translocation, accumulation and removal from a site. The review focuses on the work carried out in the field of metal phytoremediation from contaminated soil. The paper concludes with an assessment of the current status of technology development and its future prospects with emphasis on a combinatorial approach.

Growth parameters and cadmium accumulation were investigated in alfalfa seedlings treated with 10 μM salicylic acid (SA) at the beginning of seed imbibition. Shoot and root growths were accelerated by SA treatment and suppressed by Cd both in presence and absence of SA. Cd accumulation was stimulated by SA in alfalfa seedlings in dependence of the treatment duration. K, Mg, Ca and Fe contents in roots are decreased in the presence of Cd alone, while SA induces a decrease of Mg, Ca and Fe. Shoot K, Mg and Ca concentrations are increased by Cd only in the absence of SA, while SA induces also an increase of these concentrations, but only in the absence of Cd. High negative correlation of Cd concentration with K and Ca concentrations in root indicates a competition for the same carrier not regulated by SA. Positive correlation between Cd and Mg concentrations in shoots, which is decreased by SA pre-treatment, together with the increase of positive correlation between Cd and Fe concentrations in shoots under the influence of SA, indicates a possible mechanism of SA action through maintenance of ionic homeostasis.

Randomly amplified polymorphic DNA (RAPD) markers were used to assess genetic stability of 80 micropropagated Hagenia abyssinica plants, 40 of axillary origin and 40 of adventitious origin. The shoots were isolated from the same mother tree and micropropagated for over two years. Among the 83 RAPD primers screened, 16 gave reproducible band patterns. These 16 primers produced 115 bands for each plant. One plant from axillary origin showed two unique bands with primer OPC-11. All other plants showed identical band patterns. Generally, there was no significant difference in the shoot multiplication rate between shoots of axillary and adventitious origin. Indole-3-acetic acid (IAA) resulted in better ex vitro rooting compared to indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA). Non-micropropagated plants that were grown in the greenhouse for about one year were better in ex vitro rooting compared to those of juvenile material and mature tree derived micropropagated plants of the same treatment. Adventitious rooting related oxygenase gene (ARRO-1) isolated from apple (Malus domestica) was not expressed in H. abyssinica using a complementary DNA representational difference analysis fragment (cDNA RDA14) as a probe.

Young plants of a rhizomatous grass Calamagrostis epigejos (L.) Roth were grown from seed in nutrient solutions containing nitrogen in concentrations 0.1, 1.0, and 10 mM. After six weeks of cultivation the plants were defoliated and changes in growth parameters and in content of storage compounds were measured in the course of regrowth under highly reduced nitrogen availability. Plants grown at higher nitrogen supply before defoliation had higher amount of all types of nitrogen storage compounds (nitrates, free amino acids, soluble proteins), which was beneficial for their regrowth rate, in spite of lower content of storage saccharides. Amino acids and soluble proteins from roots and stubble bases were the most important sources of storage compounds for regrowth of the shoot. Faster growth of plants with higher N content was mediated by greater leaf area expansion and greater number of leaves. In plants with lower contents of N compounds number of green leaves decreased after defoliation significantly and senescing leaves presumably served as N source for other growing organs. Results suggest that internal N reserves can support regrowth of plants after defoliation even under fluctuating external N availability. Faster regrowth of C. epigejos with more reserves was mediated mainly by changes in plant morphogenesis.

Plant enzymes participating in degradation of nitroaromatic compounds have not been biochemically characterized in details so far. From suspension culture of soapwort (Saponaria officinalis L.) we isolated a novel plant oxidoreductase involved in degradation of trinitrotoluene (TNT). The enzyme catalyses first steps of reduction of TNT nitro groups in the presence of NAD(P)H under anaerobic conditions. The enzyme is monomeric with molecular mass 29 kDa, its two isoforms have pI 4.8 and 5.1. According to the spectral and activation analysis the enzyme contains flavinmono-nucleotide as a prosthetic group. The structure properties suggest an evolutional relationship to oxophytodienoate reductase. The N-terminal amino acid sequence shows homology to family of Old Yellow Enzyme (E.C. 1.6.99.1).

Apical parts of stems of Brassica napus L. var. oleifera cv. Gorczanski (winter rape) and cv. Mlochowski (spring rape), grown in vitro, were subjected to direct electric current (DC) of different polarity, duration and voltage. The positive orientation of DC, i.e. anode attached to the apical part and cathode to the medium, markedly enhanced the differentiation of the apical meristem in winter rape. The reverse polarity was without effect. DC treatment of positive polarity resulted in spring rape in transition of all explants to generative state while 70 % of non-treated plants remained at vegetative stage. Even negative orientation of DC brought about a rise in percentage of flowering plants with regard to control. The developmental effects of DC were dependent only to a low degree or not at all on duration and voltage of the treatment.

This study concerns the efficacy of partial agar substitution by galactomannans as support in plant regeneration media for Nicotiana tabacum. The production of multiple shoots from leaf-derived callus and their rooting were evaluated. The galactomannans applied were obtained from Cassia fastuosa (cassia) and Cyamopsis tetragonolobus (guar gum - a commercial galactomannan) seeds. The results obtained on media solidified with mixtures of agar/galactomannan (3 g dm^-3 each) gels were compared with those on media gelled with a standard concentration of agar (6 g dm^-3). The in vitro performance allowed to conclude that the use of galactomannans raised the number of shoots and improved their quality. Furthermore, the length of roots and the size of leaves were significantly higher in the media solidified with agar/guar galactomannan mixtures.

The responses of water relations, stomatal conductance (g_s) and growth parameters of tomato (Lycopersicon esculentum Mill. cv. Royesta) plants to nitrogen fertilisation and drought were studied. The plants were subjected to a long-term, moderate and progressive water stress by adding 80 % of the water evapotranspirated by the plant the preceding day. Well-watered plants received 100 % of the water evapotranspirated. Two weeks before starting the drought period, the plants were fertilised with Hoagland's solution with 14, 60 and 110 mM NO₃ ^- (N14, N60 and N110, respectively). Plants of the N110 treatment had the highest leaf area. However, g_s was higher for N60 plants and lower for N110 plants. At the end of the drought period, N60 plants showed the lowest values of water potential (Ψ_w) and osmotic potential (Ψ_s), and the highest values of pressure potential (Ψ_p). N60 plants showed the highest Ψ_s at maximum Ψ_p and the highest bulk modulus of elasticity.

The growth of kiwifruit explants was affected by boron (B) and methionine (Meth) in the culture medium. The longest shoots, the greatest number of shoots and the highest amount of fresh mass per explant were produced in Murashige and Skoog medium with 2 mM B and 2 μM Meth. Furthermore, by increasing B concentration in the culture medium from 0 to 2 mM, an increased rate of shoot proliferation was observed for the various Meth concentrations employed.