Activity of antioxidant enzymes was evaluated during somatic embryogenesis and shoot organogenesis from cultured leaf segments of Gladiolus hybridus Hort. The effect of exogenous antioxidants on somatic embryogenesis and shoot organogenesis has also been monitored. Activity of superoxide dismutase (SOD) gradually increased during somatic embryogenesis. while activities of catalase (CAT) and peroxidase (POX) decreased. In contrast, increase in CAT and POX activity and a concomitant decrease in SOD activity were noted during shoot organogenesis. Exogenous application of antioxidants such as glutathione (GSH), α-tocopherol and ascorbate (AA) inhibited somatic embryogenesis but stimulated shoot organogenesis. The frequency of somatic embryogenesis increased with the addition of H₂O₂. However, H₂O₂ inhibited shoot organogenesis.

Diurnal patterns of CO₂ exchange and fluctuations of tissue malic acid concentrations were investigated in the resurrection angiosperm Haberlea rhodopensis Friv. grown under irradiances of 30 or 300 μmol(photon) m^-2 s^-1 at transition from biosis to anabiosis and vice versa. Different degree of CAM-cycling were exhibited under well-watered conditions and extreme desiccation under both irradiances. The CAM-cycling was proved as efficient mechanism of saving water.

A micro-propagating system based on the young stem node segments of Sophora flavescens Ait. (Fabaceae) was established. Murashige and Skoog (MS) basal medium supplemented with 8.88 μM 6-benzyladenine (BA) plus 2.69 μM α-naphthalene acetic acid (NAA) and that with only 5.37 μM NAA were found the best in promoting proliferation of shoots and induction of root, respectively. Percentages of shoot induction and number of shoot per explant were up to 93.4 % and 4.2 and rooting rate to 82.4 %, respectively. The segments of the regenerated shoots could be continuously induced to reproduce new shoots through subculture on the same medium in 30-d intervals and still kept this activity after being subcultured for 6 generations. After the regenerated plantlets were transplanted to field, they grew well, showing no any visible abnormalities.

In order to control young plant form by modifying culture conditions, plants of Rhododendron catawbiense from in vitro culture were grown in a greenhouse under different photoperiodic treatments (long or short days) combined or not with a several-week nitrogen starvation. After 12 weeks of culture under long days (16 h) with nitrogen supply, plants showed a rhythmic acrotonous development. When long days were combined with a six-week nitrogen starvation, the apical growth pause was extended leading to an increase of the number of acrotonous lateral ramifications. Short-day (8 h) treatment affected distal burst potential and moreover when a concomitant nitrogen starvation was applied. This lack of distal development allowed basal buds swelling, leading to basitonous plants. When plants were returned back to long days after 2, 4 or 6 weeks under short days, distal buds resumption competed with basal shoots development. Durable basitonous plants were obtained by a 12-week short days treatment combined with a 6-week nitrogen starvation.

A study of the genetic variability of a population of Hypericum brasiliense was made using several isozyme systems as well as an investigation of the morphogenic potential of apical buds from plants at different development stages (juvenile and adult) using in vitro culture. The results from nine isozymes systems showed low polymorphism in the alleles. Apical buds from juvenile plants originated plantlets with apical dominance and fast growth while those from adults led to the development of flower buds.

In vitro regeneration of Melia azedarach L. was studied. Shoots were regenerated from calli initiated from leaflets of in vitro growing plants. The best medium for establishment of cultures was Murashige and Skoog (MS) medium with 4.44 μM benzylaminopurine (BAP) + 0.46 μM kinetin (KIN) + 16.29 μM adenine sulphate (ADE). Regenerated shoots were multiplied in MS + 0.44 μM BAP + 0.37 μM KIN + 3.26 μM ADE. Maximal rooting of 89 % was achieved by culture of regenerated shoots in MS + 12.26 μM indole-3-butyric acid for 3 d and subsequently in MS lacking growth regulators for 27 d. Rooted shoots were acclimatized and successfully transferred to soil.

Here we studied whether early development of Silene latifolia is accompanied with changes in acetylation of nucleosomal histones H4. Using acid-urea-triton polyacrylamide gel and immunoblotting with specific antisera the histone acetylation in relationship with transcriptional activity, measured by [¹⁴C]-uridine incorporation, was analysed in dry and germinating seeds, seedlings, and adult leaves. We show that quiescent and germinating seeds, until the root tip is released from testa, are characterised by an absence of transcriptional activity and by a low H4 acetylation level: only mono-acetylated isoforms were present. During the postgermination period and early plantlet development, a high increase of transcriptional activity started and a sharp H4 hyperacetylation, up to the penta-acetylated isoform, was detected. We conclude that epigenetic modification by nucleosomal histone deacetylation plays a role in maintenance of global genome silencing in quiescent seeds.

The effect of exogenous brassinosteroids (BR) on the flowering induction of Pharbitis nil was examined. Generally plants treated with brassinolide and castasterone form less number of flowers than control plants, but degree of flowering inhibition was depended on the concentration and the method of BR application as well as the length of the inductive dark period. In plants regenerated from sub-induced apices treated with brassinolide at concentration of 1 and 10 μM the flower formation was inhibited completely.

Salix alba L. and Populus×euroamericana cv. Robusta cuttings were grown in 10 μM Cd(NO₃)₂ (direct treatment) or in Knop solution and afterwards in Cd(NO₃)₂ (indirect treatment). Cd impact on rooting of directly treated plants and its impact on normally formed roots and shoots of indirectly treated plants were studied. The cumulative length, number and biomass of willow roots, pigment and starch contents, leaf net photosynthetic rate and dry mass/leaf area ratio of willow leaves were positively influenced by indirect treatment. However, indirectly treated poplars were more sensitive to Cd than directly treated ones. Indirect treatment lowered root Cd uptake in willow, Cd accumulation in cuttings of both species and Cd accumulation in poplar shoots. Cd-caused structural changes were similar in both species and in both treatments. Root apices, rhizodermis and cortex were the most seriously damaged root parts. In directly treated willow, the structure of central cylinder (0.5 - 1 cm from apex) remained unchanged in contrast to indirectly treated plants. Formation of cambium close to the apex indicated shortening of root elongation zone of indirectly treated plants. Directly Cd-treated poplar roots exhibited unusual defence activity of root apical meristem and accumulation of darkly stained material around central cylinder.

We employed continuous irradiation (CL) for induction of premature senescence caused by enhanced production of reactive oxygen species. As a model plant we used bean (Phaseolus vulgaris L. cv. Jantar) cotyledons because they have well defined and a quite short life span. Senescence of bean cotyledons induced by CL progressed more rapidly than natural senescence: the life span of CL cotyledons was 13 d compared to 16 d in controls (C). Chl content was significantly lower in 10- and 13-d-old CL plants than in C plants and the change with age was not statistically significant. Activities of all antioxidative enzymes declined either with senescence onset or during whole life span. Activity of antioxidative enzymes, except ascorbate peroxidase, was lower in CL plants compared to C plants. On the contrary, contents of non-enzymatic antioxidants β-carotene and ascorbate were higher in CL plants than in C plants. No significant difference, except in the youngest cotyledons, was observed in glutathione content.

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.

Apical and basal halves of 3 cm long apical segments of in vitro cultured juvenile, adult and rejuvenated Sequoia sempervirens shoots were analyzed for total and tyrosine phosphorylated proteins. The latter was detected by a phosphotyrosine specific antibody. Younger tissues, or the apical halves of shoot terminals, showed larger amounts of 36, 44, 46 kDa proteins and lesser amounts of 29 kDa proteins. These are proposed as age-related changes. Phase-related proteins were also evident. Adult tissues contained more of the 34 and 36 kDa proteins than juvenile and rejuvenated shoots. Western blotting with a phosphotyrosine specific antibody revealed more of 25, 39, and 54 kDa protein in the younger tissues. In addition, tyrosine phosphorylated proteins of 25 and 34 kDa were higher in the adult, than in juvenile or rejuvenated tissues. Our findings showed that protein tyrosine phosphorylation, or the signal transduction pathway, is involved in phase- and age-related processes.

The chloroplast within the plant cell has a dynamic environment where proteases play an important role in processing of precursor proteins, degradation of incomplete proteins lacking cofactors, stress-induced degradation and removal of damaged proteins. A number of proteases in the chloroplast are well characterized and found to be localized within different compartments such as stroma, thylakoids and lumen. In recent years, an increasing number of proteases in chloroplasts have been discovered and identified as bacterial protease homologues. These include the stromal Clp, thylakoidal FtsH and lumenal DegP. The current focus is to understand their role in chloroplast regulation both at the enzyme-substrate and genetic levels.

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.

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.

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.

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.

Mature zygotic embryos of Paspalum scrobiculatum L. cv. PSC 1 on MS or N₆ nutrient medium supplemented with various concentrations of 2,4-D (4.5 - 22.5 µM) formed embryogenic callus, which differentiated into somatic embryos within 5 weeks of culture. The somatic embryos after transfer to hormone-free regeneration medium germinated and formed plantlets. Of the two nutrient formulations, N₆ was relatively better than MS for somatic embryogenesis. A culture for 11 d on 100 µM 2,4-D was essential for the establishment of an embryogenic callus. Shorter duration, 4-d or 7-d culture on 2,4-D medium, supported some proliferation and subsequent differentiation into shoot-buds or multiple-shoots, in high-frequency cultures. This is first instance in monocots of a controlled regeneration response; either somatic embryogenesis or shoot formation.

The effect of soil moisture on gas exchange and growth of an endangered species, Changium smyrnioides, was compared with a non-endangered species, Anthriscus sylvestris. The two species belong to the same family Umbellaceae. With the decrease of soil moisture, the net photosynthetic rate (P_N) and transpiration rate (E) decreased, while water use efficiency (WUE) increased, P_N and WUE of C. smyrnioides were lower than those of A. sylvestris, whereas E was higher than that of A. sylvestris. The biomass, leaf mass ratio (LMR) and leaf area ratio (LAR) of C. smyrnioides were lower than those of A. sylvestris. Under drought, biomass. LMR and LAR of C. smyrnioides decreased more steeply than those of A. sylvestris, whereas specific root length (SRL) of C. smyrnioides was higher, compared to that of A. sylvestris. The present study indicated that C. smyrnioides accumulated less biomass, and directed more biomass to roots than A. sylvestris.

Fatty acid ω-3 desaturase (FAD) is the key enzyme catalyzing the formation of trienoic fatty acids. We utilized an Arabidopsis FAD7 gene and the seven independent transgenic rice plants harbouring 1 to 3 copies of this gene were generated. The expression of FAD7 mRNA was different among independent transgenic lines regardless of the copy number. The total linolenic acid (18:3) contents reduced by about 7 - 32 % in transgenic rice plants but the linoleic acid (18:2) content increased accordingly. With or without wounding treatments, the jasmonate content was higher in transgenic lines than in wild-type rice plant. The transgenic lines overproducing jasmonate also showed increased expression of PR1b mRNA and allene oxide synthase inresponse to wounding.

Buckwheat (Fagopyrum esculentum Moench) is a heterostylous plant displaying heteromorphic sporophytic self-incompatibility (SI). In order to detect proteins involved in SI, pistils from both long and short styles were isolated and then selfed or cross-pollinated. One-dimensional gel electrophoresis revealed that short pistils 2 h after selfing contained an unique 50 kDa protein. In the two-dimensional electrophoresis two distinct groups of proteins possibly involved in SI response were detected in the short, and one in the long pistils.

The objective of the study was to investigate the effect of As on some physiological parameters of maize in the early growth phases. Seedlings grown in a climatic box in a Hoagland-Arnon nutrient solution were treated with 0, 2 and 5 mg(As) dm^-3 (pH 5.5). After 5 d of As treatment the changes in growth, leaf gas-exchange, chlorophyll (Chl) content, Chl fluorescence, peroxidase activity and lipid peroxidation in roots were recorded. The applied As decreased the growth, leaf area, and biomass accumulation, induced lipid peroxidation and increased peroxidase activity, especially at concentration 5 mg(As) dm^-3. It also decreased the Chl, carotenoid (Car) and protein contents. A decrease in the variable to maximum fluorescence ratio (F_v/F_m) indicated lower photosynthetic efficiency.

Strawberry plants (Fragaria×ananassa Duch.) cvs. Nyoho and Toyonoka were exposed to temperatures of 20, 33, and 42 °C for 4 h, and protein patterns in leaves and flowers was analyzed by 2-dimensional polyacrylamide gel electrophoresis and immunoblotting. In leaves and flowers of both cultivars, the content of most proteins decreased, but a few new proteins appeared in response to heat stress. These heat shock proteins (Hsps) were detected in the range of 19 - 29 kDa in leaves, and 16 - 26 kDa in flowers. The intensity of a 43 kDa protein spot increased in response to heat stress in Nyoho flowers, but not in Toyonoka flowers. The peaHsp17.7 antibody recognized one band at approximately 26 kDa in leaves, and two bands at approximately 16 and 17 kDa in flowers of both cultivars. These results show that the effects of heat stress on Hsp synthesis in strawberry plants differ between plant organs and between cultivars.