Telomere-binding proteins have recently been recognised not only as necessary building blocks of telomere structure, but namely as components which are of central importance to telomere metabolism being involved in regulation of telomere length as well as in protective (capping) function of telomeres. Although the knowledge on plant telomeric DNA-binding proteins lags behind that in human and yeast, recent data show both analogies and plant-specific features in the composition and interactions of telomeric proteins. This review focuses primarily on proteins with known amino acid sequence. These can be classified into following groups: 1) the family of proteins with Myb domain at C-terminus, 2) proteins with Myb domain at N-terminus, both binding double-stranded DNA of telomeric repeats TTTAGGG, 3) the single-stranded DNA-binding proteins, and 4) other proteins that act also in non-telomeric chromatin regions. Proteins with C-terminal Myb domain reported as IBP family were previously found in human, whereas Smh family representing proteins with Myb domain at N-terminus was identified only in plants. Also RRM family of the single-stranded DNA-binding proteins is likely to be plant specific.

The aim of the present work was to evaluate oxidative stress and plant antioxidant system of three contrasting bean (Phaseolus vulgaris L.) genotypes in the response to drought. Drought was imposed 14 d after emergence, by withholding water, until leaf relative water content reached 65 %. Water stress increased lipid peroxidation (LPO), membrane injury index, H₂O₂ and OH^⋅ production in leaves of stressed plants. Activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APOX) increased significantly under water stress in all the studied cultivars, while catalase (CAT) increased in cvs. Plovdiv 10 and Prelom, but decreased in cv. Dobrudjanski ran. Furthermore cv. Plovdiv 10 which had the highest APOX and CAT activities also showed the lowest increase in H₂O₂ and OH^⋅ production and LPO while cv. Dobrudjanski ran showed the lowest increases (and often the lowest values) in the antioxidant enzyme activities and the highest increases of H₂O₂ and OH^⋅ production, and LPO. On the basis of the data obtained we could specify cv. Plovdiv 10 and cv. Prelom as drought tolerant and cv. Dobrudjanski ran as a drought sensitive.

Multiple shoots were induced by culturing nodal explants excised from 1-month-old aseptic seedlings of red pepper (Capsicum annuum L. cv. Pusa Jwala) on Murashige and Skoog (MS) medium supplemented with (0.1-10 μM) thidiazuron (TDZ). The rate of multiple shoot induction per explant was maximum (14.4 ± 0.06) on MS medium supplemented with 1.0 μM TDZ. Regenerated shoots were elongated well on growth regulator free MS medium. Adventitious roots were induced two weeks after transfer of elongated shoots to MS medium supplemented with auxins (IAA, IBA or NAA) in different concentrations. Optimum root formation frequency was obtained in medium containing 1.0 μM IBA. Ex-vitro rooting was also achieved by pulse treatment with 300 μM IBA for 10 min. Rooted shoots were transplanted in plastic pots containing garden soil (with 90 % survival rate), where they grew well and attained maturity. Regenerated plants were phenotypically and cytologically normal.

Plant regeneration through somatic embryogenesis of Areca catechu L. was established using leaf, root and stem segments as explants. Embryogenic callus was induced and maintained on medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) or 3,6-dichloro-2-methoxybenzoic acid (dicamba) at concentrations 2, 4, 6 and 8 mg dm^-3 in darkness. Somatic embryos were found on primary callus in the presence of 2 and 4 mg dm^-3 dicamba and during subculture on 2 - 8 mg dm^-3 2,4-D or 2 - 4 mg dm^-3 dicamba-containing media. Plantlet conversion from embryos was successfully achieved on growth regulator-free medium. The plants grew well when transplanted to containers in shaded greenhouse.

Hydroponically grown cucumber plants were exposed to 14-d period of salinity (0, 50, 100 mM NaCl). NaCl caused reduction in the relative water content in the leaves. The Na⁺ content increased and the K⁺ content decreased. The net photosynthetic rate, stomatal conductance and transpiration rate were markedly decreased by all of the salt treatments. Salinity decreased also the maximum quantum efficiency of photosystem 2 (PS 2) determined as the variable to maximum fluorescence ratio, the photochemical quantum yield of PS 2 and the photochemical fluorescence quenching, while the non-photochemical quenching increased. Above results indicate that NaCl affects photosynthesis through both stomata closure and non-stomatal factors.

The possibility of improving the recovery of plant photosynthesis after water stress by cytokinin-induced stimulation of stomatal opening or delay of leaf senescence was tested. The 6-benzylaminopurine (BAP) in concentrations 1 and 10 μM was applied to the substrate (sand + nutrient solution) or sprayed on primary leaves of 14-d-old Phaseolus vulgaris L. plants sufficiently supplied with water or water-stressed for 4 d. The later ones having relative water content decreased to 69 % were fully rehydrated during the following three days. Parameters of photosynthesis and water relations were measured in primary leaves of 7-, 10-, 14-, and 17-d-old plants. Application of 1 μM BAP slightly delayed leaf senescence: in 17-d-old control plants, net photosynthetic rate (P_N) and chlorophyll (Chl) content, and when sprayed on leaves also some of Chl a fluorescence kinetic parameters of BAP-treated leaves were slightly higher than those of untreated leaves. Both types of application of 1 μM BAP slightly improved recovery of plants during rehydration after water stress in terms of increased g_ad, g_ab and P_N, i.e., parameters which were markedly decreased by mild water stress. However, contents of Chl a, Chl b and carotenoids and parameters of Chl a fluorescence kinetic were not markedly affected by mild water stress and after rehydration were not stimulated by 1 μM BAP. 10 μM BAP had mostly negative effects on the parameters measured.

Methods for induction of callus and cell suspension cultures have been developed for the medicinally important herb Centella asiatica (L.) Urban. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) analysis showed the presence of asiaticoside in the in vitro grown leaves, callus and cell suspension cultured cells.

Ferredoxin-dependent glutamate synthase (Fd-Gogat; EC 1.4.7.1) in leaf and root plastids is the last enzyme involved in the pathway of nitrate assimilation in higher plants. Arabidopsis thaliana expresses two different genes: the first, light regulated, specific of green tissues and the second expressed in other tissues. In this work, we investigated whether in our clone, OsGog2 AC Y12595, this gene is up-regulated by light or it is expressed under darkness. Fd-Gogat specific activity, protein and mRNA increased after light treatment in rice shoots. In roots, the activity and the protein content remained constant, whereas the mRNA is repressed by light treatment. The results obtained using a specific probe, situated in the 3' untranslated region of the OsGog2 cDNA, indicated that OsGog2 gene is up-regulated by light and that its expression is tissue specific and suggested that a dark expressed Fd-Gogat gene could be present in rice similarly as in Arabidopsis.

The effects of boron and NaCl induced salinity on growth and mineral composition of the pear (Pyrus communis L.) rootstock OH × F 333 shoots cultured in vitro were investigated. Shoots were grown in vitro for seven weeks on a Murashige and Skoog medium containing two B concentrations (0.1 and 2 mM) combined with five NaCl concentrations (0, 10, 20, 40, and 80 mM). The longest shoots were produced at 0.1 mM B and 80 mM NaCl, but highest number of shoots were produced at 0.1 mM B and 0-20 mM NaCl. Inclusion of 20 and 40 mM NaCl in the culture medium significantly increased fresh mass of cultures compared to 0 mM NaCl for all B concentrations tested. The concentrations of P, K, Ca, Mg, Na, Fe, Mn and Zn of plants were affected by B and NaCl concentration of the medium.

The effect of five antibiotics: carbenicillin, chloramphenicol, cefotaxime, kanamycin and hygromycin on the organogenesis from callus cultures of Coryphantha elphantidens (Lem.) Lem. have been studied. Carbenicillin and cefotaxime stimulated shoot regeneration from callus. All antibiotics under study suppressed rooting of in vitro formed shoots. After five sequential subcultures on kanamycin supplemented medium, antibiotic resistant callus was obtained. To study the impact of kanamycin on resistant callus, total protein content was also studied. Selected callus showed a remarkable increase in callus mass. Antibiotic resistant plants have been selected by screening callus pieces on kanamycin supplemented media. Total protein content increased with subsequent subcultures in kanamycin resistant callus. The kanamycin selected shoots withstood the stability test after 2 months on antibiotic free medium. Plants were raised from the callus, which formed roots in 20 mg dm^-3 kanamycin, which was under study.

Fe deficiency was imposed in Citrus sinensis L. cultivars Valencia and New Hall grafted on C. aurantium and Swingle citrumelo rootstocks by the absence of Fe (-Fe) or by the presence of bicarbonate in the Hoagland nutrient solution. In Fe-deprived leaves total and active Fe concentration, and peroxidase and catalase activities were decreased while the ratios carotenoids/chlorophylls, P/Fe, and K/Ca were increased. Fe(III) chelate reductase activity was induced in (-Fe)-treated roots whereas it was depressed in bicarbonate-treated roots.

A rapid and efficient procedure is outlined for in vitro clonal propagation of an elite cultivar of jewel orchid (Anoectochilus formosanus). Multiple shoot proliferation was induced in shoot tip explants on Hyponex (H3) media supplemented with 1 mg dm^-3 benzyladenine or 1 - 2 mg dm^-3 thidiazuron (TDZ). Addition of activated charcoal (1 g dm^-3) to the TDZ containing medium promoted multiple shoot formation (11.1 shoots per explant). However, the regenerated shoots had slow growth rate and failed to elongate. This problem was overcome by transferring the shoot clumps to a hormone free H3 medium supplemented with 2 % sucrose and 0.5 g dm^-3 activated charcoal. Rooting was induced in 100 % of the regenerated shoots in the same media. The plantlets were acclimatized and established in greenhouse.

Oxygen evolution and chlorophyll a fluorescence transients of two barley (Hordeum vulgare L) cultivars subjected to polyethylene glycol induced osmotic stress was examined. The relative water content of the plants was used as a measure of their water status. The results suggested that although dehydration was considerable, photosystem 2 was weakly affected by the osmotic treatment.

Plant regeneration through indirect somatic embryogenesis was attempted from leaf, internode, node and shoot-tip derived callus of Leptadenia reticulata. Somatic embryos at the highest frequency was induced on Murashige and Skoog (MS) medium supplemented with 8.87 μM benzyladenine (BA) and 2.46 μM indole-3-butyric acid (IBA). From different explants, only shoot-tip and node explant derived calli induced somatic embryos. Transfer of the embryogenic callus to suspension cultures of the same concentration of growth regulators facilitated the development of embryos. Suspension cultures with reduced concentration of BA (2.22 μM) either alone or in combination with 0.49 μM IBA fostered maturation of embryos. Half-strength MS solid medium with 1.44 μM GA₃ and BA (0.22 or 0.44 μM) facilitated conversion of embryos into plantlets at higher rate compared to that on with BA alone. About 77 plantlets were recovered from 10 mg callus. Plantlets transferred to small cups and subsequently to field survived in 80 %. All the plantlets established in the field exhibited morphological characters similar to that of the mother plant.

The effects of different cadmium concentrations [17 mg(Cd) kg^-1(soil) and 72 mg(Cd) kg^{- 1}(soil)] on Cannabis sativa L. growth and photosynthesis were examined. Hemp roots showed a high tolerance to Cd, i.e. more than 800 mg(Cd) kg^-1(d.m.) in roots had no major effect on hemp growth, whereas in leaves and stems concentrations of 50 - 100 mg(Cd) kg^-1(d.m.) had a strong effect on plant viability and vitality. For control of heavy metal uptake and xylem loading in hemp roots, the soil pH plays a central role. Photosynthetic performance and regulation of light energy consumption were analysed using chlorophyll fluorescence analysis. Seasonal changes in photosynthetic performance were visible in control plants and plants growing on soil with 17 mg(Cd) kg^-1(soil). Energy distribution in photosystem 2 is regulated in low and high energy phases that allow optimal use of light and protect photosystem 2 from overexcitation, respectively. Photosynthesis and energy dissipation were negatively influenced by 72 mg(Cd) kg^-1(soil). Cd had detrimental effects on chlorophyll synthesis, water splitting apparatus, reaction centre, antenna and energy distribution of PS 2. Under moderate cadmium concentrations, i.e. 17 mg(Cd) kg^-1(soil), hemp could preserve growth as well as the photosynthesis apparatus, and long-term acclimation to chronically Cd stress occurred.

Pollen embryogenesis was successfully induced in Solanum nigrum L. (2n=6×=72). Stimulation of androgenesis expressed as the frequency of androgenic responsive anthers was observed after 10 and 20 mM ethyl methanesulphonate (EMS), 10 and 20 mM sodium azide (NaN₃) and 0.2 mM N-nitroso-N-methylurea (MNU) treatment applied on seeds for 24 h. The frequency of androgenesis on the medium with sucrose was higher than on the medium with maltose. Androgenic regenerants originated also in the anthers collected from donor plants where survival after mutagenic treatment was lower than 50 %. Green haploid (3x), aneuploid (to 8x) and dihaploid (6x) plants were obtained. The high frequency of aneuploids among androgenic plants is explained by cell division irregularities in microsporial calli.

Direct somatic embryogenesis from ray floret explants of five chrysanthemum cultivars has been obtained within 12 - 15 d on Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzyladenine (BA). Scanning electron microscopic observation also confirmed the direct origin of somatic embryos from explants. Somatic embryos developed asynchronously on the adaxial surface of explants. Among the five cultivars tested, Birbal Sahani was best responding (40 % explants responded on 4 mg dm^-3 2,4-D and 2 mg dm^-3 BA supplemented medium). Precocious germination of somatic embryos was noticed on the same medium. The best sucrose concentration in the medium was found to be 60 g dm^-3 where 70 % explants responded while 55 % embryogenic response was obtained on medium supplemented with 400 mg dm^-3 inositol. Plants developed from somatic embryos were transferred to soil and produced true-to-type flowers.

Chrysanthemum morifolium cv. Regol Time plants were found to be infected with Chrysanthemum B carlavirus (CVB). They were made CVB-free by using meristem tip culture, chemotherapy and thermotherapy. The plants were indexed by biological assay, double antibody sandwitch enzyme linked immunosorbent assay (DAS-ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR). The maximum number of virus-free plants (26.7 %, as indexed by RT-PCR) was obtained with 2-thiouracil at 0.04 g dm^-3 concentration. Only 12 % plants were found to be virus-free, after being kept at 38 °C for 30 d. For indexing CVB in chrysanthemums, RT-PCR was found to be the most reliable method.

The special conditions during in vitro culture result in the formation of plantlets of abnormal morphology, anatomy and physiology. After ex vitro transfer, these plantlets might easily be impaired by sudden changes in environmental conditions, and so need a period of acclimatization to correct the abnormalities. This review is focused upon contemporary information on the changes in leaf structure, water relations and photosynthesis during acclimatization of plantlets to ex vitro conditions. It also describes some ways of improving plant survival and for the speeding up of acclimatization.

Transformation of fenugreek (Trigonella foenumgraecum) was carried out with A281 oncogenic strain of Agrobacterium tumefaciens using root, cotyledon and hypocotyl explants excised from 1-week-old seedlings, which showed that the plant was highly susceptible to transformation. Tumors (calli) were selected on 50 mg dm^-3 kanamycin. They were analyzed for β-glucuronidase (GUS) expression. Presence of uidA (gus) gene, was confirmed by polymerase chain reaction (PCR) amplification.

Thirty-six F₂ hybrid poplar (Populus trichocarpa × P. deltoides) clones were fumigated with ozone to record its effects on growth, correlate them with stomatal response and screen for ozone sensitivity. Fumigation was applied for 6 to 9 h each day for approximately 3 months at ozone concentrations of 85 to 128 μg g^-1 using open-top chambers. Height, diameter, number of leaves, stomatal conductance, transpiration rate, total biomass, biomass components and root/shoot ratios were reduced by ozone stress. Percent of leaf fall in ozone-treated plants was nearly three times higher than in control plants exposed to charcoal-filtered air. Leaf senescence, because of ozone exposure, did not appear to be associated with reduced biomass production. Some clones had a high percentage of leaf-fall with ozone exposure, but were able to maintain total biomass production near that of the control. Their response may be an example of an ability to adjust or compensate for ozone damage. There was no significant or consistent relationship between stomatal conductance and total biomass or the change in stomatal conductance as a result of ozone exposure and the change in total biomass. Taken together, these results suggest that effects of ozone on poplar growth cannot be solely correlated to changes in stomatal conductance, more physiological and biochemical parameters should be examined.

The effects of treatment with NaCl (3, 100 and 300 mM) for 1, 2, 3 and 7 d on plant growth and ion accumulation were analyzed in 2-week and 8-week-old Annona muricata and A. squamosa plants. Fresh mass and root growth inhibition were directly related to the increase in salinity, particularly for A. squamosa. Two-weeks old seedlings were sensitive to 100 and 300 mM NaCl particularly after 7 d, whereas 8-week-old plants were shown to be more resistant to NaCl even at 300 mM NaCl. Na⁺ and Cl^- mostly accumulated in young leaves. Our results suggest that A. squamosa is more sensitive than A. muricata to salt stress and that older seedlings of both species are more tolerant than younger seedlings.

The purpose of this research is micropropagation of Ginkgo biloba L. Apical and nodal meristems removed from plantlets or apical buds from a tree were used as explants. Meristems produced an extensive callus and single or rare multiple shoots on Murashige and Skoog medium with different growth regulators and endosperm extract (En) obtained from mature seeds of the same species. For successful root production it was necessary to transfer the shoots to a rooting medium with En.

A simple histo-cytochemical method, combining Evans blue staining to assess cell death and in vivo 3,3'-diaminobenzidine uptake for H₂O₂ localisation, has been used to evaluate O₃ damages in leaf tissues of three Phaseolus vulgaris L. cultivars (Cannellino, BLF, Saxa) with different sensitivity to the pollutant. Bean plants were exposed to a single pulse of O₃ (150 ± 10 mm³ m^-3 × 3 h) and leaves were examined at different time-span after fumigation. Cannellino proved to be the most sensitive, showing chlorotic spots 2 h after fumigation and chlorotic lesions 24 h later. In BLF, necrotic spots appeared 4 h after fumigation and reddish necrotic lesions (bronzing) developed in further 24 h. Saxa remained symptomless up to 10 d of observation, thus appearing tolerant. The early appearance of symptoms in Cannellino correlated with H₂O₂ accumulation in leaf tissues and consequent extensive cell death, involving both palisade and spongy mesophyll. H₂O₂ accumulation was observed also in BLF, though to a lesser extent and dead cells were rare at 2 h after fumigation. However, they increased in number 24 h later, forming small groups in the palisade mesophyll. These groups further enlarged in the next 24 h, again involving only palisade mesophyll. In Saxa leaves, H₂O₂ accumulation was found only in the epidermal cells, though the number of dead cells was very similar to BLF, at least up to 24 h after fumigation. However, in Saxa, dead cells have been always found singly scattered through the palisade mesophyll, or forming very small groups around substomatal cavity, thus remaining invisible at a macroscopic level.

The effect of a short heat treatment in combination with different culture medium composition on the efficiency of in vitro induced androgenesis in Silene latifolia ssp. alba was studied. The heat shocks (33 and 37°C) were applied for 1, 3, and 5 d. The best androgenic response was observed at 25°C and after a one-day treatment at 33°C. All other treatments reduced androgenic response. Among different media compositions tested, the most satisfactory results were obtained on BMS medium supplemented with 6-benzylaminopurine (0.5 mg dm^-3) and sucrose. The green, albino and chimeric, only female, plants were regenerated. Flow cytometry of 110 regenerants identified haploids, mixoploids (n+2n and 2n+4n) and dihaploids.

Stable transformation of Coffea canephora P. was obtained by particle bombardment of embryogenic tissue. Leaf explants were cultured on medium supplemented with 5 µM isopentenyl-adenosine to induce direct embryogenesis. Explants with somatic embryos were transferred to half strength MS medium with 9 µM 2,4 dichlorophenoxyacetic acid. After 2 weeks, the explants with somatic embryos and embryogenic tissue were bombarded with tungsten particles (M-25) carrying the plasmid pCambia3301 (containing the bar and uidA genes) using a high pressure helium microprojectile device. The bombarded explants were submitted to selection on medium containing 5 µM ammonium glufosinate herbicide as selective agent. After 6 months, putative transgenic embryos were transferred to a growth regulator-free medium for germination. The regenerated plantlets were β-glucuronidase (GUS) positive whereas no GUS activity was observed in non-transgenic controls. Incorporation of the bar gene into the genome was confirmed by PCR and Southern blot analysis of the regenerated transformed plants. Greenhouse grown transgenic coffee plants were found to withstand the recommended level of the herbicide Finale™ for weed control.

Tobacco plants infected with the potato virus Y (PVY) were studied during the acute-infection period. The control enzymes of metabolic pathway of host's RNA degradation tending to biosynthesis of PVY-RNA, its coarse/fine regulation and content of host's RNA were monitored. Activities of ribonucleases, phosphomonoesterases and phosphodiesterases in both the crude homogenates and the partially purified enzyme preparations from the diseased leaves were markedly increased when compared to the tissues from healthy plants. The curves of enzyme activities positively correlated with the multiplication curve of the PVY and negatively correlated with the decreased contents of host's RNA. The enzyme activity in homogenate samples did not significantly differ from the corresponding purified enzyme preparations.

Young maize plants, grown hydroponically, were supplied with 1/10 the optimal amount of iron (0.75 mg dm^-3). Foliar treatments with solutions, containing N⁶-benzyladenine (BA), indole-3-acetic acid (IAA) or (2-chloroethyl)-trimethylammoniumchloride (CCC) were conducted after chlorosis had been well manifested. Changes in growth, chlorophyll content, rate of photosynthesis, catalase and peroxidase activities in leaves, and the contents of Fe, Cu, Zn, Mn, and P in leaves were recorded. Growth regulators improved (CCC, IAA) or aggravated (BA) the physiological state of chlorotic plants. Their effect might be explained by changes in Fe transport towards the leaves, by increased efficiency of Fe utilization, and by effects on plant metabolism not involving Fe.

Hypocotyl, cotyledon and cotyledonary node explants of Calendula officinalis L were cultured on Murashige and Skoog (MS) media supplemented with various concentrations of thidiazuron (TDZ), kinetin (KIN), α-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) to induce adventitious shoot regeneration and micropropagation. The highest frequency of adventitious shoot regeneration was achieved from hypocotyl and cotyledon explants on MS media supplemented with 0.75 mg dm^-3 TDZ and either 0.25 or 0.50 mg dm^-3 IBA. Efficient in vitro clonal propagation was also induced from cotyledonary nodes on a range of media supplemented with 0.75 mg dm^-3 TDZ and 0.05 mg dm^-3 NAA or 2 mg dm^-3 KIN and 1 mg dm^-3 NAA. Regenerated shoots were excised and rooted in MS medium supplemented with 1 mg dm^-3 NAA. The rooted plantlets were finally transferred to pots.