The structure and development of Myrtus communis L. secretory cavities has been studied in young and expanded leaves, using light and scanning electron microscope. Secretory cavities are continuously formed during leaf development, but in mature leaves the rhythm of their appearance shows steep decrease. Each secretory cavity is developed from a single epidermal cell, which undergoes a periclinal division followed by anticlinal and several oblique cell divisions. The lumen of the secretory cavity is initiated by cell wall separation, i.e., schizogenously. The secretory cells line the cavity, where the secreted material is collected. Secretory cavities are covered by modified epidermal cells, which do not seem to form any special aperture. Essential oils seem to be discharged after mechanical treatment of the leaf.

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.

The roles of glucose-6-phosphate dehydrogenase (G6PDH) in paclitaxel production were investigated in cell suspension cultures of Taxus chinensis. In the normal cultures, the trend of G6PDH activity was similar to that of cell growth. Addition of glutamate increased G6PDH activity, while dehydroepiandrosterone (DHEA) decreased G6PDH activity. In elicitor-treated cultures, cell growth was depressed, while G6PDH activity and taxol production were enhanced compared with the control. Glutamate recovered the depression of cell growth, and resulted in further increase in G6PDH activity and taxol production. Contrarily, DHEA exacerbated the depression of cell growth, and decreased G6PDH activity and taxol production induced by fungal elicítor. The results indicated that G6PDH played a critic role of taxol production by affecting cell viability.

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.

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.

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.

Waterlogging of soybean plants (Glycine max L.) led to impaired symbiotic N₂ fixation and a marked decline in glutamine (Gln) concentration in xylem bleeding sap. Xylem Gln concentration increased during the growth cycle of the plant and was correlated with nodule formation. Treatments known to impair N₂ fixation, such as exposing the root system to pure N₂ gas or a mixture of Ar and O₂ (80:20; v/v), led to specific declines in xylem sap Gln. The decrease in Gln observed during waterlogging was also seen on transfer of nodulated plants to aerated hydroponics, where the decline was highly correlated with ureide content in the xylem sap. Upon flooding the nodulated root system, the specific decline in xylem sap Gln could be detected within 10 min and reached a minimum within 60 min, indicating that waterlogging has an immediate effect on N₂ fixation. It is concluded that xylem Gln arises directly from N₂-fixation and is a useful indicator of N₂ fixation activity of symbiotic soybean plants.

Gender based differences in response to low temperature stress in leaf chlorophyll (Chl), and carotenoids (Car) contents and chlorophyllase (Chlase) activity were monitored in male (Kapoori Vellaikodi and Madras Pan Kapoori) and female (Bangla Mahoba, Desi Bangla and Kaker) betel vine landraces. Although female plants contained nearly two fold more Chl than male counterparts, the low temperature induced Chl loss was comparable, however, male plants showed higher Chl a/b ratio than females. Chlase activity increased due to cold stress in all the landraces. Male plants always showed higher activities of Chlase, which may be one of the reasons for the rather low Chl contents in male plants.

The physiological responses to NaCl salinity were investigated in two floating aquatic macrophytes, Pistia stratiotes L. and Salvinia molesta L. With the increasing NaCl concentration a decrease in chlorophyll and carotenoid contents was recorded in Salvinia as compared to Pistia. Also a greater increase in H₂O₂ accumulation and lipid peroxidation was observed in the shoot and root tissues of Salvinia as compared to Pistia. The superoxide dismutase, glutathione reductase, catalase and guaiacol peroxidase activities, and ascorbate and glutathione contents increased in Salvinia and Pistia shoot and root tissues in response to NaCl.

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.

Azolla caroliniana was exposed to 5 °C in darkness for 1, 2, 3, 5 or 7 d and then recovered for 7 d. Plants previously chilled for 2 or 3 d exhibited higher growth rates when transferred to normal temperature than either the control plants or those previously chilled for 5 or 7 d. Increased plant growth may be related to increased contents of chlorophyll, sucrose, and reducing sugars, due to increased photosynthetic capacity. In another experiment Azolla plants were chilled at 5 °C for 7 d and then transferred for 0, 4, 8, 12, or 16 d recovery to the N-free Hoagland solution or Hoagland solution containing 5 mM KNO₃. In previously chilled plants, the growth rate was decreased. In the medium supplemented with nitrogen, the growth rate was greater than in the N-free medium in both chilled and nonchilled plants. In chilled plants the decrease in growth rate may be related to the disturbance of Anabaena azollae cells where the protecting envelope of the heterocysts was deorganized. During the recovery the rate of N₂-fixation increased in both chilled and nonchilled plants up to 12 d after which both rates were similar. However, during the first 4 d the rate of the nonchilled plants was approximately 4-fold that of the previously chilled plants. Nitrate reductase and nitrite reductase activities in control plants were higher than in those previously chilled for 7 d. Both activities increased in nonchilled and previously chilled plants up to 12 d then decreased. The total protein content increased up to 12 d in chilled and nonchilled plants after which it decreased. Under all treatments, the values were higher in nonchilled plants than in those previously chilled ones and were also higher in presence of N than in its absence. Thus the presence of N-source in the medium counteracts the effect of chilling injury particularly during prolonged recovery.

Wild-type and the handshake (has) mutants in Arabidopsis thaliana were analyzed. Compared to the wild-type, has mutants display a number of morphological alterations, which can largely be traced back to altered meristem function. Analyses of apical meristem of mutant plants showed that mutation affected meristem structure and patterns of STM expression.

An efficient protocol of direct somatic embryogenesis (without involving intermediate callus) has been developed from stem segments and shoot tips of Capsicum annuum L. Explants were cultured on Murashige and Skoog (MS) medium supplemented with thidiazuron (TDZ). Among the various concentration of TDZ tested, 0.5 μM was proved to be best for induction of somatic embryos. Induction, maturation and germination were achieved on the same medium. The shoots developed from somatic embryos were transferred for rooting to MS medium supplemented with indole-3-butyric acid (IBA). All the regenerated plants with 85 % survival rate were normal with respect to morphology and growth characteristics.

In vitro salt tolerant rice plants established by step up treatment with 0.5, 1.0, 1.5 and 2.0 % NaCl at 3-week intervals were examined to determine whether they could grow in potted paddy soil containing 0, 0.55 or 0.75 % NaCl till harvesting. All the control plants were necrotic by the 4^th week in the culture. At the 10^th week of culture, 100 % of the salt-tolerant plants subjected to 0 or 0.55 % NaCl survived, and 78 % of the plants at 0.75 % NaCl. The Na⁺ and Cl^- contents in the leaves of salt-tolerant plants grown at 0.55 and 0.75 % NaCl were about 4 times of those without NaCl. The ion contents in non-tolerant plants and seedling plants were 10 to 12 times of those in 0 % NaCl treatment. One of the hypotheses to explain the present data is that the in vitro step up salt selection induces the capability to maintain no lethal concentration of NaCl in the leaves.

A high frequency adventitious shoot regeneration protocol was developed for henbane (Hyoscyamus niger L.) using thidiazuron (TDZ). Hypocotyl, cotyledon and stem explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of N⁶-benzylaminopurine and TDZ. MS medium supplemented with 16 μM TDZ was the most effective for providing 100 % regeneration frequency associated with a 19.53 shoots per hypocotyl explant. Plantlets were rooted on MS medium supplemented with different concentrations of indole-3-butyric acid (IBA) and α-naphthaleneacetic acid. High rooting and survival was achieved using half strength MS medium supplemented with 8 μM IBA.

The effect of elevated CO₂ concentration (CE) on leaf chlorophyll (Chl) and nitrogen (N) contents and photosynthetic rate (P_N) was evaluated during the post-flowering stages of rice grown at CE (570 ± 50 µmol mol^-1) in open top chamber (OTC), at ambient CO₂ concentration (∼ 365 µmol mol^-1) in OTC and at open field. Thirty-five day old seedlings were transplanted in OTCs or in field and allowed to grow till maturity. Chl and N contents were highest at the time of flowering and thereafter it started to decline. The rate of decline in Chl and N contents was faster in plants grown under CE mostly in later part of growth. Irrespective of treatment difference, flag leaf contained the highest amount of Chl and N than penultimate and third leaf. The higher P_N was observed in leaves under CE than in the leaves in other two growing conditions. Considering growth stage, P_N was the highest at flowering which reduced at the later part of growth due to degradation of Chl and N content of the leaf. Under CE it was 40.02 µmol m^-2 s^-1 at flowering and it reduced to only 14.77 µmol m^-2 s^-1 at maturity stage. The beneficial effect of CE in increasing leaf P_N may be maintained by applying extra dose of nitrogen at the later stages of plant growth.

Rice (Oryza sativa L.) was grown in pots with pyridine N-oxide (PNO), 4-morpholino pyridine N-oxide (MNO), and sodium meta silicate as the sources for silicon. Aliquots of these were added in fortnightly intervals to seedlings through anthesis stage. The plants were monitored for plant growth characteristics, chlorophyll content (SPAD values), photosystem 2 activity (variable to maximum fluorescence ratio of dark adapted leaves), and for blast and yellow stem borer resistance. Deposition of silica in the leaves was monitored by scanning electron microscopy and silicon mapping. PNO or MNO application resulted in significant silicon accumulation in leaf bundle sheath cells. Application of PNO and MNO imparted disease and pest resistance by increasing silicon uptake of rice plants.

A protocol of high frequency shoot organogenesis and plant establishment from stem derived callus has been developed for Tylophora indica (Burm. f.) Merrill. - an endangered medicinal plant. Callus was developed on Murashige and Skoog (MS) medium supplemented with 10 μM 2,4,5-trichlorophenoxy acetic acid (2,4,5-T). Multiple shoot induction was achieved from the surface of the callus after transferring onto shoot induction medium. The highest rate (80 %) of shoot multiplication was achieved on MS medium containing 5.0 μM kinetin. The developed shoots rooted best on half-strength MS medium supplemented with 0.5 μM indole-3-butyric acid (IBA). The in vitro raised plantlets with well developed shoot and roots were acclimatized successfully and grown in greenhouse.

Effect of two Ni concentrations (10 and 200 μM) on growth, Ni accumulation, chlorophyll and proline contents, relative water content (RWC) as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione S-transferase (GST) were studied in shoots of wheat plants. Treatments caused a considerable accumulation of Ni in the shoots. However, exposure of plants to 10 μM Ni did not lead to significant alterations in shoot growth except for a slight increase in fresh mass. The other parameters studied were not affected by treatment of plants with 10 μM Ni. In contrast, 200 μM Ni caused inhibition of shoot growth, a decline in RWC and chlorophyll content, accumulation of proline and occurrence of visible symptoms of Ni toxicity. The activities of SOD and CAT decreased in response to 200 μM Ni. Conversely, several-fold enhancements of POD and GST activities were observed following the 3^rd day of 200 μM Ni treatment.

Common polypody (Polypodium vulgare L.) belongs to desiccation-tolerant ferns. The structure of storage parenchyma of their rhizome was examined by transmission electron microscopy after dehydration and subsequent rewetting. Analysis revealed that treatment with supplemental abscisic acid resulted in protection of cells against ultrastructural damage compared to untreated ones. Dehydration rate appears to modify the ability of rhizome parenchyma to stand water stress.

Competition is a major density-dependent factor structuring plant populations and communities in both natural and agricultural systems. Seedlings of the model plant species Arabidopsis thaliana cv. Columbia, and the Columbia-derived stomatal mutants sdd1 and tmm1, were grown under controlled conditions at increasing densities of 1, 10, 20, and 50 plants per pot. We demonstrate significant effects of time (days after planting), density, genotype, density and genotype, and the three-way interaction with time upon several fitness components (plant height, silique number, leaf biomass and flowering stalk biomass) in Columbia and these mutants.

Flow cytometric analysis with 4,6-diamidino-2-phenylindole (DAPI) staining was used to screen for chromosomal changes in Quercus robur during in vitro culture. The initiated cell lines (1992 until 1999) were maintained via secondary embryogenesis on P24 medium with 0.9 μM 6-benzylaminopurine (BAP) in regular subculture intervals of 6 weeks. Regenerated plants established in the greenhouse and in vitro plantlets derived from encapsulated somatic embryos were screened. The embryogenic cell lines were characterized as individual clones by isoenzyme analysis. Flow cytometric relative DNA content analysis of the first screening period revealed that somaclonal variation in form of tetraploidy occurred in two out of 26 tested somatic embryo clones (Alt and Jung). These two clones lost their ability to convert into plantlets. Intraspecific relative DNA content variation including technical variation was below 3 %. In the second screening period, however, 3 out of 37 clones (Alt, E4.31H9 and P3.27H) contained tetraploid cells leading to the assumption that the frequency of tetraploidy seems to be correlated with the duration of in vitro culture. No chromosomal differences were detected in regenerated plants. However, tetraploidy occurred in 8 % of the tested clones over a culture period of 7 years.

We describe the multi-step regeneration system of medicinal plant Schisandra chinensis (Turcz.) Baill. The seeds were pre-treated with 0.005 μM thidiazuron. Subsequently the zygotic embryos of the early heart stage were cultured on medium with 50 μM of 2,4-dichlorophenoxyacetic acid (2,4-D) and after three weeks the embryogenic calli were transferred to a medium with 10 μM of 2,4-D and 4 μM of 6-benzyladenine and were sub-cultured at the 4-week intervals. Abscisic acid (30 μM) and polyethyleneglycol (3 %) significantly influenced the synchronization of development of the somatic embryos (SEs) to the globular stage. The following culture on a medium without growth regulators resulted in full developed cotyledonary stage SEs. Indole-3-butyric acid (0.05 μ) contributed to their rapid conversion to plantlets.

In vitro morphogenesis of sweet potato (Ipomoea batatas) shoot explants after cultures in callus initiation medium (CIM) with two sucrose contents and plant regeneration medium (PRM) with three growth regulator combinations for different durations was studied. After 4 weeks, explants on 5 % sucrose CIM had significantly more shoots but similar or lower root fresh mass and callus fresh mass than those on 3 % sucrose CIM subsequent to transfer for 6 weeks on all three PRM. Cultures transferred to growth regulator-free PRM after 4 and 12 weeks on 5 % sucrose CIM formed plants through organogenesis and embryogenesis, respectively. Embryogenic cultures from 4 weeks on CIM + 10 weeks on callus proliferation medium when transferred to PRM without growth regulator for 4 and 8 weeks produced multiple embryos in the prior and both embryos and shoot buds in the later.

The induction of haploid plants by in vitro gynogenesis is a promising practice in onion breeding. In order to increase the frequency of embryo regeneration and haploid plant production in Valcatorce INTA, Cobriza INTA and Navidena INTA cultivars, putrescine and CCC were used, either as a component of the culture media or by spraying or injecting them to the umbels. Additionally, two concentration of gellam gum were tested. A higher number of gynogenic embryos was achieved by using 7 g dm^-3 gellam gum, and this number was not affected by the addition of putrescine to the media. CCC sprayed at the umbels significantly increased the gynogenic embryo rate, which was more than three times higher than the control. Cobriza INTA showed the highest induced embryo rate (4.76 %).