Effect of two important mycotoxins, aflatoxin B1 and citrinin (concentration 2 g m-3) at various combinations (i.e., 1:1, 1:2, 2:1, 1:3 and 3:1, v/v) on seed germination, seedling growth, chlorophyll, carotenoid, starch, sugar, protein and nucleic acid contents, α-amylase activity, and respiration quotient was studied in maize cv. Suwan composite. The maximum and minimum inhibitions were recorded in most of the above parameters (except starch) at 3:1 and 1:3 combination ratios of these toxins, respectively. However, the inhibition rates varied with the treatments.

We obtained transformed bean shoots by electroporation of intact bean cells with the plasmid pDPG165 containing bar gene conferring herbicide resistance to plants. Transformed shoots were selected from electroporated callus on herbicide containing media. Data of molecular analysis (PCR and Southern blotting) confirmed the insertion of bar gene in the genome of herbicide resistant shoots. Detailed procedures for obtaining regenerative bean callus, optimization of electroporation of intact cells and transgenic shoots are given.

When the proper stimuli are given, somatic plant cells may form adventitious embryos, roots or shoots. The three pathways of regeneration show apparent similarities. They consist of three analogous phases: 1) dedifferentiation (during which the tissue becomes competent to respond to the organogenic/embryogenic stimulus), 2) induction (during which cells become determined to form either a root, a shoot or an embryo), and 3) realization (outgrowth to an organ or an embryo). The first phase may involve a period of callus growth (indirect regeneration), but often cells present in the explant become competent without cell division or without cell division at a large scale (direct regeneration). In an explant, only very few cells show the organogenic/embryogenic response. In direct regeneration, the three regenerative pathways start from cells in different tissues. This is most obvious when the different types of regeneration occur in the same explant. The hormonal trigger for the dedifferentiation phase is a general one, probably auxin. During the induction phase, each pathway requires specific hormonal triggers. During the realization phase, hormones should be absent or at low concentration. The successive steps in the regeneration process coincide with events on the molecular and biochemical levels, but so far no coherent picture has emerged. In particular during the early stages of regeneration, research on these levels is hampered by a technical problem, viz., the very low proportion of cells that participate in the process of regeneration. New methods may overcome this problem.

The localization of peroxidase in cells of horse-radish (Armoracia lapathifolia Gilib.) tumour and teratoma tissues was studied. Both tissue lines were derived from the same primary crown-gall tumour induced on the leaf fragments by a wild type of Agrobacterium tumefaciens B6S3. Enzymatic activity was measured in cell walls, high-density heterogeneous membrane fraction, microsomal and soluble (no particulate) fractions. The subcellular localization of enzymatic activity was distinct for each transformed tissue. Both tumour and teratoma showed similar isoenzyme patterns, but one soluble acidic isoperoxidase could be considered as a marker of cell differentiation.

When seedlings of two rice (Oryza sativa L.) cultivars Ratna and Jaya were raised under 100 and 500 µM cadmium nitrate in the medium, a high proline content was noted in Cd²⁺ stressed seedlings compared to controls. Seedlings grown under 500 µM Cd(NO₃)₂ maintained increased proline level compared to non-stressed seedlings. Kinetic properties of RNase extracted from control grown and Cd²⁺ stressed seedlings showed a marked alteration in Km due to Cd²⁺ treatment. The RNase isoforms were purified from 15-d-old rice seedlings with a total purification of 22.25 fold and 74.75 % yield using conventional biochemical techniques. Three RNase isoforms, namely I, II and III were eluted from DEAE-Sephacel column. The isoform RNase II had Km value of 3.2 mg(RNA) cm^-3. The in vitro osmotic stress created by incorporation of PEG in the enzyme assay medium led to decreased affinity of enzyme towards its substrate with increase in Km. This loss in affinity was partially restored by the addition of 1 M proline in the assay medium, suggesting the possible protective role of proline on RNase under osmotic stress.

In Sedum fabaria, the ovule is anantropus, bitegmic and crassinucellate. The development of the nucellus conforms to the Sedum type. The development of the embryo sac is of the Allium type. The antipodal cells in unfertilized embryo sac occasionally divide and one of them forms four-celled structures resembling embryos and remaining once elongate in the form of haustoria. The entry of the pollen tube is porogamous. After division the primary endosperm nucleus forms two cells: the apical one develops into cellular endosperm according to the Acre type and the basal one acts as the endosperm haustorium of the Sempervivum type. The embryogeny corresponds to the Caryophyllad type.

Secondary somatic embryogenesis and shoot organogenesis from primary somatic embryos of Papaver somniferum L. are described. The embryos became malformed, the root meristem expressed dividing activity without position-dependent cell differentiation, causing abnormal development or arrested growth of primary somatic embryos. The adventitious shoots regenerated from embryo hypocotyl, but secondary somatic embryos had an epidermal origin close to the root meristem. The regeneration occurred without hormonal treatment, indicating endogenous nature of triggering signals. These signals are probably related to the integrity loss of morphogenetic steps during development of primary somatic embryos, which appeared to induce an activation of cells competent to regeneration.

Ten-days-old bean plants (Phaseolus vulgaris L., cv. Cheren Starozagorski) were treated with simulated acid rain (pH 2.4, 2.2, 2.0 and 1.8). Anatomical changes in the primary leaves were studied 3, 48 and 168 h after a single treatment. This treatment induced: 1) change in the shape of palisade cells, contraction of their contact surfaces and expansion of spongy cells (pH 1.8, 3 h after treatment); 2) reduction of symplast connections among palisade cells and of apoplast in the spongy mesophyll (pH 1.8, 48 h after treatment); 3) destruction of adaxial epidermis and portions of palisade mesophyll, plasmolysis of spongy cells (pH 1.8, 168 h after treatment); 4) full destruction of mesophyll (pH 2.4, 2.2, 2.0 and 1.8, 168 h after treatment). The structure of abaxial epidermis was more stable than that of the adaxial one. With respect to anatomical parameters the studied species could be considered as comparatively resistant to acid rain.

Induction and growth of soybean callus cultures were influenced by NaCl, especially at the highest concentration tested (150 mM). Protein content was raised as NaCl was increased in the Murashige and Skoog medium. Total sulfhydryl group (-SH) and glutathione (GSH) concentrations were also increased in NaCl treated cultures. The affinity (Km) of glutathione reductase (GR) for oxidized glutathione (GSSG) was gradually increased as NaCl level was raised in the medium. The GSH/GSSG ratio was raised significantly as the result of GR activity. The increase in GR activity may constitute an adaptive response of soybean callus to NaCl.

The morphogenic response of somatic (leaf and petiole) and de-differentiated tissue (callus) of two blackberry (Rubus fruticosus) and one raspberry (Rubus idaeus) cultivars have been studied in vitro. With the aim to induce regeneration the effect of two sets of plant growth regulator (PGR) combinations (high cytokinin/auxin ratios and high auxin/cytokinin ratios) in Murashige and Skoog basal medium, were analysed. The three cultivars were characterised by a qualitatively different morphogenic response to the PGR combinations. Raspberry adventitious shoot regeneration from somatic tissue was improved by the 6-benzylaminopurine (BAP)/indol-3-butyric acid (IBA) combinations. On the contrary, shoot regeneration of both blackberry cultivars was reduced by high concentrations of BAP and completely inhibited by BAP/IBA combination. Media supplemented with high auxin/cytokinin ratios promoted callus production and root differentiation according to genotype and type of auxin. All the genotypes responded to media supplemented with IBA. 2,4-dichlorophenoxyacetic acid induced good callus formation in blackberry, but was toxic to raspberry. Indirect shoot formation was observed only in callus of blackberry cultivar Hull Thornless cultivated on medium with 10 µM BAP, the same concentration able to trigger efficient direct shoot regeneration from leaf explants of the same cultivar.

Nine F1 crosses of faba bean (Vicia faba L.) and their parental genotypes were evaluated for transpiration decline curves (TDC) and stomatal characteristics. The most common type of TDC had one inflexion. One parent and three crosses were characterized by TDC of two inflexions, while one cross had TDC without inflexion. The genotypes which exhibited TDC with 2inflexions showed later time to stomatal closure (SC). Also stomatal and cuticular transpiration rates differ significantly among studied genotypes. A model for selecting genotypes with effective water retaining features was suggested. This model includes relative water content (RWC) at SC, stomatal density, guard cell length, stomatal pore width at both sides of the leaf, stomatal pore length at lower side and leaflet dry mass

Impact of Cu, Pb and Zn on the growth of Closterium acerosum, Pediastrum simplex, Chlorella vulgaris and Scenedesmus quadricauda was studied in vitro. At concentration 0.1 g m-3 these metals were not toxic, however, at concentration 10.0 g m-3 the growth of phytoplankton was inhibited. Cu was the most toxic followed by Pb and Zn. S. quadricauda expressed highest tolerance to these metals, and least tolerance was exhibited by C. acerosum.

Increasing NaCl concentration (0, 50, 100 and 150 mM) progressively decreased growth and seed yield of clusterbean (Cyamopsis tetragonoloba Taub.) which was associated with decreased concentrations of potassium and calcium and increased concentration of sodium in the shoots. Supplemental calcium (2.5 and 5.0 mM) significantly ameliorated the adverse effects of NaCl due to enhanced Ca and K uptake and reduced Na uptake. Calcium also alleviated the negative effects of NaCl on activities of nitrogen metabolism enzymes as well as on contents of soluble protein and free amino acids.

Somatic hybridization of Brassica oleracea (cauliflower, cabbage, kohlrabi) and Armoracia rusticana (horseradish) protoplasts was performed to test the possibility of the formation of intergeneric hybrids. Out of three B. oleracea crops tested only cauliflower (B. oleracea var. botrytis) yielded viable hybrids when fused with horseradish protoplasts. Regenerated plants were asymmetric hybrids as revealed by morphological, karyological, and DNA analysis. In these plants, extensive elimination of A. rusticana genome occurred during subsequent cultivation. Using a chloroplast DNA probe no A. rusticana-specific hybridization signals were detected thus indicating a rapid elimination of horseradish cytoplasmic (chloroplast) components.

In the present work we try to determine optimum conditions for callus induction in anther culture of Oenothera hookeri and O. picensis. The anther callus yield was increased when the anthers were cultured on modified MS medium supplied with 2 mg dm^-3 2,4-D and 2 mg dm^-3 NAA, in both species. In O. hookeri, best results were obtained when anthers were excised from 7.2 - 9 mm buds at the stage of vacuolated microspores, then pretreated at 4 °C for 2 d and grown under 16-h photoperiod. The response to anther culture of O. picensis was generally very poor compared with that of O. hookeri. The higher yield of calli was obtained when anthers were excised from 6.2 - 8 mm buds at the stage of vacuolated microspores and grown under continuous light. The cold pretreatment of buds decreased anther response in this species.

Cell suspension culture Amsonia tabernaemontana Walt. were permeabilized by Tween 80 and immobilized by glutaraldehyde. The highest α-galactosidase activity was at pH 5.3 and temperature 70 °C. The hydrolysis of substrate was linear for 3 h reaching 70 - 75 % conversion. The cells characterized by high enzyme activity and stability in long-term storage showed convenient physico-mechanical properties (physical protection from shear forces and easy separation of product from biocatalysts).

For screening tolerance of six cultivars of rice (Oryza sativa) to different concentrations of nickel (0, 6, 12, 18, 24 and 30 μg dm3), growth parameters (root and shoot length, root and shoot dry matter production) and root and shoot tolerance indexes were tested after 7, 10 and 13 d of treatment. In presence of nickel in nutrient solution, root growth of cv. Nilgiri was enhanced, while in cvs. Subhadra, Khandagiri, Rudra, Sankar and Annapurna it decreased. The root tolerance index (RTI) and shoot tolerance index (STI) in cv. Nilgiri were high; cvs. Sankar and Khandagiri, however, showed a low RTI. Based on the standard growth parameters, six cultivars of rice were ranked in respect of their tolerance to nickel: Nilgiri > Annapurna > Subhadra > Khandagiri > Rudra > Sankar.

Effects of water stress at different stages of plant growth on leaf relative water content (RWC), osmotic potential (Ψos) and changes in contents of chlorophyll, abscisic acid (ABA), zeatin riboside (t-ZR), ethylene and proline in six cultivars of French bean (Phaseolus vulgaris L.) were studied. Under water stress, Ψos and RWC were highest in cv. Contender and lowest in cvs. IIHR-909 and Sel-2. The increase in contents of ABA and proline was marked in cv. Contender followed by cv. UPF-626. Decrease in t-ZR and chlorophyll contents was prominent in cv. IIHR-909. Ethylene production surged in all the cultivars under 4- and 8-d stress and declined under 12-d stress.

Changes in hexokinase particulate and soluble isozyme composition and activities in leaves of 65- and 115-d-old tobacco plants were determined by ion exchange chromatography on DEAE cellulose. During plant ageing, the activities of glucose and of fructose phosphorylating isozymes of particulate hexokinase decreased to 9.9 and 9.2 % of initial value, respectively. The activity of soluble hexokinase decreased to a lesser extent: that of glucose phosphorylating isozyme to 49.8 % and of fructose phosphorylating isozyme to 37.8 %. The activity of soluble fructokinase isozyme dropped to 34.8 %. Thus also the ratio of particulate and soluble isozymes was dependent on the age of leaf tissue.