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.

Explants of Chenopodium rubrum, a short-day plant, were decapitated and exposed to floral inductive treatment, and the extent of flowering of axillary buds was afterwards assessed. Isolated buds never responded to induction, whereas the presence of the petiole of the subtending leaf already assured a high degree of flowering. We may assume either that the petiole is the receptor organ of the photoperiodic signal or that its transporting role is indispensable.

Differential display of mRNA has been recently developed as a tool to detect and characterize changes in gene expression. We applied this technique to fruit trees plantlets induced to root in vitro, in order to isolate and study genes involved in root induction. A reproducible pattern of polymerase chain reaction (PCR) products was obtained, both in almond and apple, in vertical polyacrylamide gels stained with ethidium bromide. Differences in PCR fingerprinting were detected in mRNAs of basal part of either auxin induced or non induced microcuttings. Thus, we suggest that this technique can be used in woody species to detect changes among mRNA populations during root induction.

Tomato (Lycopersicon esculentum Mill. cv. PKM 1) plants growing under field conditions were exposed for 15 d to solar radiation with UV-B component (280 - 320 nm) enhanced to 6.3 kJ m-2 d-1. This simulated a 15% stratospheric ozone depletion over Madurai (9° 50' N latitude). Lipid peroxidation in the leaves of UV-B treated plants was 32% higher compared to the control. Superoxide dismutase (SOD) and catalase activities registered parallel promotion by 126 and 50 %, respectively, in the UV-B treated plants. Further, the contents of total phenols and anthocyanins in the leaves have also been enhanced by 40 and 156%, respectively. On the contrary, polyphenol oxidase activity demonstrated a 58 % inhibition in the leaves of UV-B treated plants. While anthocyanins and phenols are proposed to act as antioxidants, the reduction in polyphenol oxidase activity may maintain the turnover of phenols in the UV-B treated plants.

Normal callus and embryogenic suspensor mass (ESM) were induced from the same immature embryo of Abies alba Mill. These two tissues were found to differ in their isoenzyme patterns of peroxidase, glutamate dehydrogenaseand non-specific esterase and in their requirement for myo-inositol inculture medium.

Potted two-year-old lemon plants (Citrus limon (L.) Burm. fil.) cv. Fino, growing under field conditions were subjected to drought by withholding irrigation for 13 d. After that, plants were re-irrigated and the recovery was studied for 5 d. Control plants were daily irrigated maintaining the soil matric potential at about -30 kPa. Young leaves of control plants presented higher leaf conductance (g1) and lower midday leaf water potential (Ψmd) than mature ones. Young leaves also showed higher leaf water potential at the turgor loss point (Ψtlp) than mature leaves. In both leaf types g1 decreased with increased vapour pressure deficit of the atmosphere. From day 1 of the withholding water, predawn and midday leaf water potentials (Ψpd and Ψmd) decreased, reaching in both cases minimum values of -5.5 MPa, with no significant differences between mature and young leaves. Water stress induced stomatal closure, leaf rolling and partial defoliation. No osmotic adjustment was found in response to water stress in either leaf type, but both were able to enhance the cell wall elasticity (elastic adjustment). After rewatering, leaf water potential recovered quickly (within 2 d) but g1 did not.

Eleven species of nitrogen-fixing cyanobacteria belonging to six genera (Cylindrospermum, Anabaena, Nostoc, Calothrix, Scytonema, and Westiellopsis) tolerate different concentrations of NaCl (from 0.05 to 0.35 M). Wide variation in the chlorophyll (Chl) a content of the species of the same genus and between genera in presence of NaCl was observed. The least tolerant (Cylindrospermum sp., Cy 6), the maximum tolerant (Westiellopsis sp., We 1), and the intermediate tolerant (Westiellopsis sp., We 6) species of cyanobacteria were selected, and their response to various concentrations of NaCl (growth, nitrogen-fixing capacity, and production of extracellular substances) was studied. Nitrogen fixing capacity of both the We 1 and We 6 was greatly impaired in comparison to the decrease in their Chl a content in the NaCl containing media. Cellular and extracellular saccharide and extracellular amino acid contents of the cyanobacteria species in the NaCl supplemented cultures were increased suggesting that presence of saccharides and amino acids enabled the cyanobacterial species to thrive under salt stress. Further, the We 1 did not adapt to the salt whereas Cy 6 showed adaptation to low concentrations of NaCl suggesting that the species which tolerate high concentrations of the salt may not possess the ability to adapt to NaCl.

The experiment was made by using different concentrations of polyethylene glycol (PEG) or salt solutions to decrease the osmotic potential of the growth medium to reveal the response of mung bean (Vigna radiata) to water and salt stresses. No germination (emergence of the seedling) occurred at medium osmotic potential lower than -1.0 MPa in all treatments. It was found that the activity of α-amylase and protease, and contents of proline, saccharides and the soluble proteins decreased in the germinating seeds during 3-d stress. However, after 10-d stress, the contents of organic solutes and the activity of the hydrolytic enzymes increased. Growth, chlorophyll content and mineral uptake were also significantly reduced under stress. The seedlings under water stress induced by PEG were affected much more than under salinity. This may be due to the maintenance of a higher succulence under salt stress than under PEG-induced water stress.