Suppressive subtraction hybridization (SSH) was used to identify differentially expressed genes caused by a chlorophyll-reduced mutation in B. napus. The cDNA fragments, derived from SSH positive subtractive library (tester: normal wild type, driver: mutant) were cloned into pMD18-T vector. Two hundred SSH cDNA clones were screened by dot blot array, and 151 clones were identified as differentially expressed cDNA fragments in Cr3529 line. Thirty-six positive clones which showed marked expression differences were selected and sequenced. After redundant cDNAs were removed, 33 differentially expressed unique cDNA section clones were obtained. Among the 33 clones, two clones possess different parts of the cDNA sequence of the same gene coding geranylgeranyl reductase, four clones belong to unknown proteins, and the rest share homology to genes of diverse class. Sequence analysis showed that at least 12 genes were discovered to be related to the photosynthesis, seven of them coded the proteins which belong to the subunit of photosystem 2. RNA gel blot analysis showed that compared with 3529, the gene expression of the chlorophyll a/b-binding protein Lhcb2 in photosystem 2 declined markedly in the cotyledons and seedling leaves of Cr3529, indicating that the reduced light-harvesting complex 2 accumulation in thylakoid membrane of Cr3529 was due to the decrease of the related gene mRNA level for translation.

An efficient in vitro plant regeneration system from leaves of Ophiorrhiza japonica Blume was established for the first time. Callus formation rate was more than 90.4 % from leaf segments on Murashige and Skoog (MS) supplemented with either α-naphthaleneacetic acid (NAA) alone or in combination with 6-benzyladenine (BA). The highest shoot regeneration (78.9 %) was achieved on MS medium containing 2.0 mg dm^-3 BA and 0.2 mg dm^-3 NAA, with an average of 9.4 shoots developed per leaf segment. Shoot regeneration was also improved when the leaf explants were cultured in MS basal medium supplemented with 0.5 % (m/v) polyvinylpyrrolidone (PVP). The leaf explants from seedlings with age of about 18-27 d showed the highest shoot regeneration. The regenerated shoots were rooted on half-strength basal MS medium supplemented with 0.5 mg dm^-3 indole-3-butyric acid (IBA), which averagely produced 24.8 roots per shoot. The plantlets were transferred to soil, where 100 % survived after 1 month of acclimatization.

In our present study assessment of genetic diversity and identification of pigeonpea cultivars has been done by employing 76 random amplified polymorphic DNA (RAPD) primers. Out of 796 amplified products, 587 showed polymorphism (73.7 %) and an average of 10.47 bands were amplified per primer. Cluster analysis based on Jaccard's similarity coefficient using UPGMA grouped all the cultivars into three clusters. The cluster I consists of 7 cultivars, cluster II of 11 cultivars in 4 sub-clusters and cluster III 4 cultivars. Two cultivars were not included in any cluster. The clustering was strongly supported by high bootstrap values. Furthermore, high values of the average heterozygosity (H_av) and marker index (MI) also indicated the efficiency of RAPD as a marker system.

Gametophores of mosses Mnium undulatum and Polytrichum commune were submerged in distilled water or in calcium chloride solution (0.9 mM Ca²⁺) to induce hypoxia. The net photosynthetic (P_N) and dark respiration rate (R_D) were measured in the air containing 300-400 µmol(CO₂).mol^-1(air) and 0.21 mol(O₂).mol^-1(air). P_N of M. undulatum gametophores decreased to 58 % of the control after 1-h submersion in water, whereas to 80 % of the control in P. commune gametophores. A smaller decrease in P_N was observed when the gametophores were immersed in CaCl₂ solution. In hypoxia, R_D in the tested mosses species was a little higher than in the control.

Two vacuolar green fluorescent proteins (GFP) were stably inserted in Nicotiana tabacum and Nicotiana benthamiana genome, with unexpected difficulties, and compared with A. thaliana cv. Wassilewskaja transgenic plants expressing the same constructs. GFP fluorescence was strong in all tissues of A. thaliana but it was barely visible in Nicotiana. Confocal microscopy analysis revealed a variable distribution of the marker in those cells where GFP fluorescence was visible. The role of light dependent proteases was the variable pointing out more inter-species diversity. GFPs degradation was much higher in Nicotiana spp. than in A. thaliana. The version of GFP used appeared not to be a good vacuolar marker for Nicotiana differentiated tissues, although it can efficiently label vacuoles in protoplasts or calli. Nevertheless the sensitivity of the reporter protein can be used as an indicator of hidden characteristics of the plant vacuoles, revealing differences otherwise invisible. One of the markers in our system, GFP-Chi, evidenced a clear morphological difference in the vacuolar system of guard cells of the three species.

Total protein patterns were studied in the course of development of pea somatic embryos using simple protocol of direct regeneration from shoot apical meristems on auxin supplemented medium. Protein content and total protein spectra (SDS-PAGE) of somatic embryos in particular developmental stages were analysed in Pisum sativum, P. arvense, P. elatius and P. jomardi. Expression of seed storage proteins in somatic embryos was compared with their accumulation in zygotic embryos of selected developmental stages. Pea vegetative tissues, namely leaf and root, were used as a negative control not expressing typical seed storage proteins. The biosynthesis and accumulation of seed storage proteins was observed during somatic embryo development (since globular stage), despite of the fact that no special maturation treatment was applied. Major storage proteins typical for pea seed (globulins legumin, vicilin, convicilin and their subunits) were detected in somatic embryos. In general, the biosynthesis of storage proteins in somatic embryos was lower as compared to mature dry seed. However, in some cases the cotyledonary somatic embryos exhibited comparatively high expression of vicilin, convicilin and pea seed lectin, which was even higher than those in immature but morphologically fully developed zygotic embryos. Desiccation treatments did not affect the protein content of somatic embryos. The transfer of desiccated somatic embryos on hormone-free germination medium led to progressive storage protein degradation. The expression of true seed storage proteins may serve as an explicit marker of somatic embryogenesis pathway of regeneration as well as a measure of maturation degree of somatic embryos in pea.

The present study investigated whether, depending on the abscisic acid (ABA) concentration, phospholipase C (PLC) would be implicated within a Ca²⁺ mobilizing pathway that would regulate stomatal aperture under standard watering conditions. Among Al sensitive mutants the als1-1 mutant of Arabidopsis thaliana (L.) Heynh. (Columbia-4 ecotype) was selected for a pharmacological approach of stomatal closing in leaf epidermal peels induced by 3, 20 or 30 µM ABA. Comparison with the wild type (WT) revealed that, exclusively in the als1-1 mutant, the stomatal response to 3 or 20 µM ABA was inhibited by about 40 %, whereas the stomatal response to 30 µM ABA and the wilting response to drought were unaffected. In WT, the Ca²⁺ buffer EGTA and the PLC inhibitor, 1-[6-[[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122), specifically inhibited by about 70 and 40 %, respectively, the response to 3 or 20 µM ABA, while the Ca²⁺ buffer 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) inhibited by about 70 % the response to 3, 20 or 30 µM ABA. EGTA, BAPTA and U73122 did not inhibit the part of the response to 3 or 20 µM ABA that was unaffected by the als1-1 mutation. Together, these results showed that ABA closes the stomata through two different Ca²⁺ mobilizing pathways. Since PLC could be indirectly deactivated in the als1-1 mutant, these results might suggest that, under sufficient water supply, PLC-mediated Ca²⁺ mobilization is needed for the regulation of stomatal aperture by endogenous ABA resting at concentrations below a drought-specific threshold value.

Effects of high night temperature on the lipid and protein compositions in the tonoplasts isolated from the leaves of two Crassulacean acid metabolism (CAM) plants, Ananas comosus (pineapple) and Kalanchoë pinnata were studied. The results showed that the phospholipids/protein ratios in the tonoplasts isolated from pineapple and K. pinnata leaves decreased from 1.82 to 1.21 and 2.63 to 1.50, respectively, as the night temperature increased from 20 to 37 °C. Under high night temperature, relative amount of total unsaturated fatty acids in K. pinnata was increased by 6 %, which was mainly caused by increased C18:2 and C18:3, whereas unsaturated fatty acids, C18:2 and C18:3 in pineapple did not show significant change. The distribution patterns of tonoplast proteins in the two CAM species were different between normal and high night temperature and in K. pinnata, especially those with molecular mass ranging from 66.2 to 97.4 KDa. Compared with normal night temperature, more proteins were found in pineapple, but no difference was found in K. pinnata. Thus, above result indicated that the pineapple tonoplasts could keep higher rigidity under high night temperatures compared to the K. pinnata.

The effects of amino acids (arginine, aspargine, cysteine, glutamine, glycine and proline) and polyamines (putrescine and spermidine) on embryogenesis and plant regeneration from cultured anthers of Guizotia abyssinica (L. f.) Cass. cv. Ootacamund was studied. Supplementation of amino acids (0.5-5.0 mM) to the induction medium individually and in combination, improved embryo yield. B5 medium supplemented with 2 mM proline, 10 µM 2,4-dichlorophenoxyacetic acid, 2 µM kinetin and 0.2 M sucrose induced highest number of embryos (63 per 60 anthers cultured). Addition of polyamines (5-200 µM) to the same medium also enhanced the rate of embryogenesis.

An experiment was taken up to find out possibilities of manipulating the in vitro flowering in moth bean. Abscisic acid (ABA) and proline both alone and in combination influenced days to flower induction, number of flowers per plant, number of pods per plant and seeds per pod. Frequency of flowering plants approached 100 % at 1 and 3 µM ABA and 800 µM proline. The range of flowering period (3 to 23.6 d) has also been influenced by various treatments.

A quantitative trait loci (QTL) approach was applied to dissect the genetic control of the common wheat seedling response to osmotic stress. A set of 114 recombinant inbred lines was subjected to osmotic stress from the onset of germination to the 8^th day of seedling development, induced by the presence of 12 % polyethylene glycol. Root, coleoptile and shoot length, and root/shoot length ratio were compared under stress and control conditions. In all, 35 QTL mapping to ten chromosomes, were identified. Sixteen QTL were detected in controls, 17 under stressed conditions, and two tolerance index QTL were determined. The majority of the QTL were not stress-specific. In regions on five chromosome arms (1AS, 1BL, 2DS, 5BL and 6BL) the QTL identified under stress co-mapped with QTL affecting the same trait in controls, and these were classified as seedling vigour QTL, in addition to those expressed in controls. Tolerance-related QTL were detected on four chromosome arms. A broad region on chromosome 1AL, including five QTL, with a major impact of the gene Glu-A1 (LOD 3.93) and marker locus Xksuh9d (LOD 2.91), positively affected root length under stress and tolerance index for root length, respectively. A major QTL (LOD 3.60), associated with marker locus Xcdo456a (distal part of chromosome arm 2BS) determined a tolerance index for shoot length. Three minor QTL (LOD < 3.0) for root length and root/shoot length ratio under osmotic stress were identified in the distal parts of chromosome arms 6DL (marker locus Xksud27a) and 7DL (marker locus Xksue3b). Selecting for the favourable alleles at marker loci associated with the detected QTL for growth traits may represent an efficient approach to enhance the plants' ability to maintain the growth of roots, coleoptile and shoots in drought-prone soils at the critical early developmental stages.

6-Methoxy-2-benzoxazolinone (MBOA) inhibited germination of rice (Oryza sativa L.), wheat (Triticum aethiopicum Jakubz), rye (Secale cereale L.), onion (Allium cepa L.), wild oat (Avena fatua L.), barnyard grass [Echinochloa crus-galli (L.) Beauv.], ryegrass (Lolium rigidum Gaudin), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), tomato (Lycopersicum esculentum Mill.), carrot (Daucus carota L.) and amaranth (Amaranthus retroflexus L) and the inhibition increased with increasing MBOA concentrations. MBOA also inhibited the induction of α-amylase in these plant seeds and the inhibition increased with increasing MBOA concentrations. There were variations in sensitivity of these plant species to MBOA, and species of family Poaceae (barnyard grass, wild oat, rice, rye, ryegrass, and wheat) were less sensitive to MBOA than the other plant species.

A bacterial artificial chromosome (BAC) library of banana (Musa acuminata) was used to select BAC clones that carry low amounts of repetitive DNA sequences and could be suitable as probes for fluorescence in situ hybridization (FISH) on mitotic metaphase chromosomes. Out of eighty randomly selected BAC clones, only one clone gave a single-locus signal on chromosomes of M. acuminata cv. Calcutta 4. The clone localized on a chromosome pair that carries a cluster of 5S rRNA genes. The remaining BAC clones gave dispersed FISH signals throughout the genome and/or failed to produce any signal. In order to avoid the excessive hybridization of repetitive DNA sequences, we subcloned nineteen BAC clones and selected their 'low-copy' subclones. Out of them, one subclone gave specific signal in secondary constriction on one chromosome pair; three subclones were localized into centromeric and peri-centromeric regions of all chromosomes. Other subclones were either localized throughout the banana genome or their use did not result in visible FISH signals. The nucleotide sequence analysis revealed that subclones, which localized on different regions of all chromosomes, contained short fragments of various repetitive DNA sequences. The chromosome-specific BAC clone identified in this work increases the number of useful cytogenetic markers for Musa.

An efficient micropropagation protocol was developed for elite male and female genotypes of Simmondsia chinensis using nodal segments. Bud initiation was found to be best on Murashige and Skoog's (MS) medium supplemented with 4.44 µM 6-benzylaminopurine (BAP) and 88.8 µM adenine. Upon sub-culture, 10-15 shoots per explant were obtained when 4.44 µM BAP and 74.0 µM adenine were incorporated in the medium. Increase in KNO₃ concentration in the medium improved shoot multiplication rate and in vitro flowering in 20 % of male cultures. Elongated shoots were harvested, pulse treated for 48 h on liquid medium supplemented with 49.0 µM indole-3-butyric acid, 5.40 µM α-naphthaleneacetic acid and 5.71 µM indole-3-acetic acid for root induction and rooting (92 %) was achieved on hormonal free half-strength MS medium supplemented with 1.37 µM chlorogenic acid, 1 % activated charcoal and 2 % sucrose. After successful hardening, plantlets were transferred to greenhouse with 99 % establishment.

A highly reproducible system for efficient plant regeneration from protoplast via somatic embryogenesis was developed in cotton (Gossypium hirsutum L.) cultivar ZDM-3. Embryogenic callus, somatic embryos and suspension culture cells were used as explants. Callus-forming frequency (82.86 %) was obtained in protoplast cultures from suspension culture cells in KM₈P medium with 0.45 µM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.93 µM kinetin (KIN), 1.5 % glucose and 1.5 % maltose. Protocolonies formed in two months with plating efficiency of 14 %. However, the callus-forming efficiencies from other two explants were low. The calli from protoplast culture were transferred to somatic embryo induction medium and 12.7 % of normal plantlets were obtained on medium contained 3 % maltose or 1 % of each sucrose + maltose + glucose, 2.46 µM indole-3-butyric acid (IBA) and 0.93 µM KIN. Over 100 plantlets were obtained from protoplasts derived from three explants. The regenerated plants were transferred to the soil and the highest survival rate (95 %) was observed in transplanting via a new method.

A rapid and efficient method for the regeneration of Eucommia ulmoides Oliver has been developed. The ability of hypocotyl segments to produce adventitious buds varied depending upon their position, seedling age and culture medium. The most adventitious buds were induced from the hypocotyl segments near to the root of 2-week-old seedlings on the Murashige and Skoog (MS) basal medium supplemented with 10 µM benzylaminopurine (BAP). However, the MS medium with 6 µM BAP and 6 µM gibberellic acid (GA₃) was most suitable for shoot multiplication and further growth. Shoots longer than 2 cm cultured on the half-strength MS medium supplemented with 0.5 µM naphthaleneacetic acid (NAA) produced a maximum number of roots per shoot. Regenerated plantlets could be successfully acclimatized.

It was observed that the unpollinated flowers of Cymbidium pendulum (Roxb.) Sw. and C. aloifolium (L.) Sw. stayed fresh for 20 and 18 d, respectively, but attained senescence in 8 and 7 d, respectively, after pollination. The higher content of total soluble sugars, reducing sugars and free amino acids was observed in all the floral organs of pollinated flowers than in unpollinated ones. Pollination also up-regulated the activity of hydrolytic (α-amylase, β-amylase, invertase) and proteolytic enzymes (proteases) in floral organs. Amongst floral organs, the lip and perianth possessed highest contents of metabolites. Application of auxin inhibitor (0.25 µM triiodobenzoic acid) and ethylene inhibitor (0.25 µM AgNO₃) to the pollinated flowers partially prevented the process of senescence.

Radicle growth of germinated seed of the root parasite O. ramosa is shown to be rapidly accompanied by secretion of proteins including pectinolytic enzymes, polygalacturonase and rhamnogalacturonase. These secretions peaked between 4 to 8 d after induction of germination and remained constant for some further days in the case of polygalacturonases. After 6 d, germinated seeds secreted proteins which exhibit peroxidase activity. The latter may be correlated with expression of OrPOX1, a putative gene encoding for secreted peroxidase. The involvement of these enzymes in host root attack and haustorium formation by the parasite is discussed.

Exogenous salicylic acid has been shown to confer tolerance against biotic and abiotic stresses. In the present work the ability of its analogue, 4-hydroxybenzoic acid to increase abiotic stress tolerance was demonstrated: it improved the drought tolerance of the winter wheat (Triticum aestivum L.) cv. Cheyenne and the freezing tolerance of the spring wheat cv. Chinese Spring. Salicylic acid, however, reduced the freezing tolerance of Cheyenne and the drought tolerance of Chinese Spring, in spite of an increase in the guaiacol peroxidase and ascorbate peroxidase activity. The induction of cross tolerance between drought and freezing stress was observed: drought acclimation increased the freezing tolerance of Cheyenne plants and cold acclimation enhanced the drought tolerance. The induction of drought tolerance in Cheyenne was correlated with an increase in catalase activity.

Cell lines able to grow on media containing 50, 100, 150 or 200 mM NaCl were established from potato callus cultures by direct recurrent selection or gradual selection. In callus subjected to direct selection only small clusters of cells survived on medium with 150 or 200 mM NaCl, whereas on 100 mM small cell portions appear necrotic. When cell lines were obtained by successive subcultures on media with increased concentrations of NaCl, salt-tolerant calli were more compact and developed a greenish colour free from necrotic areas. The response of calli lines grown on media with NaCl was compared to control line. The NaCl-tolerant calli showed a decrease in relative growth rate and water content, with higher reductions in the 150 mM tolerant callus. Lipid peroxidation was increased in 50 mM and 100 mM NaCl-tolerant calli, while in 150 mM tolerant callus remained similar to 100 mM values. There was a significant increase in ascorbic acid content in 100 mM and 150 mM NaCl-tolerant calli as compared to the 50 mM, that was two-fold the value found in the control. Also, the contents of soluble and insoluble proteins increased in salt-tolerant lines. SDS-PAGE of soluble proteins showed the synthesis of specific polypeptides in the presence of NaCl in culture medium and the synthesis of a new polypeptide.

Carnation plantlets (Dianthus caryophyllus L.) cultured in vitro often develop morphological and physiological anomalies, a phenomenon called hyperhydricity, which impairs their survival ex vitro. When the agar concentration of the growth medium was increased (from 0 to 12 g dm^-3), thereby reducing water availability, the hyperhydricity of those adventitious shoots regenerated from carnation petals decreased. This was accompanied by a progressive fall in the water content of shoots (94.9 to 91.4 %), fresh mass (from 57.2 to 1.8 mg), number of leaf parenchyma cell layers (from 9.3 to 7.7), and the size of these cells (from 968 to 254 µm²). However, the number of regenerated shoots also decreased (17.7 in 2 g dm^-3 agar to 4.3 in 12 g dm^-3). Similarly, in ventilated tubes, which exhibit a lower relative humidity than tightly closed tubes, shoot organogenesis diminished up to 28 %, in tandem with shoot water content. Thus, relative humidity and water availability in culture vessels do not only influence shoot hyperhydricity in carnations, but also greatly affect adventitious shoot organogenesis.

To dissect differences in both lipid accumulation and composition and the role of these modifications during drought stress, four grapevine cultivars exhibiting differential tolerance to drought were subjected to water shortage. Tolerant cultivars, Kahli Kerkennah and Cardinal, exhibited higher leaf water potential (Ψ_w), and lower lipid peroxidation compared to the sensitive cultivars Guelb Sardouk and Superior Seedless during stress. Total lipid amounts increased during stress only in the leaves of the tolerant cultivars. Drought induced increases in the ratios digalactosyldiacylglycerol/monogalactosyldiacylglycerol and phosphatidylcholine/phoshatidylethanolamine of almost all the drought stressed cultivars. Moreover, the overall analysis of the composition of fatty acids revealed that a linolenic acid was prevalent in grapevine and the unsaturation level of lipids increased under water stress in all the cultivars. Specific adjustments in the lipid composition during stress could compromise stress tolerance.

Phylogenetic analysis was conducted based on sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA in 17 species of Kengyilia, together with those of 18 species from Pseudoroegneria, Agropyron, Roegneria and Douglasdeweya by the maximum parsimony, maximum likelihood and neighbor-joining distance methods. The results indicate that species of Kengyilia had close affinities to species of Douglasdeweya and Agropyron. The species in Kengyilia was identified as two subgroups with regard to geographic distribution, indicating that species from the same distribution had a closer phylogenetic relationship. The genus Kengyilia was found as a ligament-group between Roegneria and Agropyron. The ITS sequence is a useful tool for studying the phylogeny of closely related species.

Different lines of cell suspension cultures of Taxus × media Rehd. and Taxus floridana Nutt. were cryopreserved with a two-step freezing method using a simple and inexpensive freezing container instead of a programmable freezer. Four to seven days old suspension cell cultures were precultured in growth medium supplemented with 0.5 M mannitol for 2 d. The medium was then replaced with cryoprotectant solution (1 M sucrose, 0.5 M glycerol and 0.5 M dimethylsulfoxide) and the cells incubated on ice for 1 h. Before being plunged into liquid nitrogen, cells were frozen with a cooling rate of approximately -1 °C per min to -80 °C. The highest post-thaw cell viability was 90 %. The recovery was line dependent. The cryopreservation procedure did not alter the nuclear DNA content of the cell lines. The results indicate that cryopreservation of Taxus cell suspension cultures using inexpensive freezing container is possible.

An efficient micropropagation protocol was established for Capsicum chinense Jacq. cv. Umorok, a pungent chilli cultivar. Shoot-tip explants were cultured on Murashige and Skoog (MS) medium containing cytokinins (22.2-88.8 µM 6-benzylaminopurine, BAP, 23.2-93.0 µM kinetin, Kin, or 22.8-91.2 µM zeatin, Z) alone or in combination with 5.7 µM indole-3-acetic acid (IAA). Maximum number of shoots were induced on medium containing 91.2 µM Z or 31.1 µM BAP with 4.7 µM Kin. The separated shoots rooted and elongated on medium containing 2.5 or 4.9 µM indole-3-butyric acid (IBA). Axillary shoots were induced from in vitro raised plantlets by decapitating them. The axillary shoot-tip explants were used for further multiple shoot buds induction. A maximum of about 150 plantlets were obtained from a single seedling. Hardened and acclimatized plantlets were successfully established in the soil.

Biological control of wilt of egg plant (Solanum melongena L.) caused by Fusarium solani was made with the application of five Trichoderma species, T. harzianum, T. viride, T. lignorum, T. hamatum and T. reesei. The effect of volatile and non-volatile antibiotics of Trichoderma origin on growth inhibition of the wilt pathogen was studied. T. harzianum showed maximum growth inhibition (86.44 %) of the pathogen through mycoparasitism. The non-volatiles produced by the Trichoderma species exhibited 100 % growth inhibition of the pathogen under in vitro condition. Production of siderophores and fungal cell wall degrading enzymes, chitinase and β-1,3-glucanase were found. Treatments with two most efficient Trichoderma species, T. harzianum and T. viride resulted in the decreasing population of Fusarium solani in soil thereby deterring disease incidence in field condition.

The effects of 28-homobrassinolide (HBL) on nickel uptake, protein content and activities of antioxidative enzymes were determined in the seedlings of Brassica juncea L. The seeds were treated with different concentrations (0, 0.01, 1 and 100 nM) of HBL for 8 h and then sown in the Petri plates containing various concentrations (0, 25, 50 and 100 mg dm^-3) of nickel. After 7 d, observations were made on shoot and root length, Ni uptake, protein content and activities of antioxidative enzymes (guaiacol peroxidase, catalase, glutathione reductase, ascorbate peroxidase and superoxide dismutase). The growth of seedlings was inhibited by Ni, however, less after HBL pre-treatment. The protein content and antioxidative enzyme activities were also increased by HBL treatment.

The relation between oxygen evolution rate (OER) and quantum yield of photochemical reactions in photosystem 2 (Φ_PS2) was examined in lichen symbiotic alga Trebouxia erici Ahmadjian (strain UTEX 911) exposed to different irradiances and osmotic stress (2 M sucrose for 60 h). Linear relationship was found between OER and Φ_PS2 in control cell suspension within irradiance range of 0 - 500 μmol m^-2 s^-1. Under osmotic stress, OER and Φ_PS2 were significantly reduced. Relation between OER and Φ_PS2 was curvilinear due to strong osmotically-induced inhibition of OER at high irradiance. The highest used irradiance (500 μmol m^-2 s^-1) was photoinhibitory for osmotically-stressed T. erici because non-photochemical quenching (NPQ) increased substantially. Energy-dependent quenching represented major part of NPQ increase. Osmotic stress led also to the reduction of capacity of photochemical processes in PS 2 (F_V/F_M) and increase in F₀/F_M. These changes indicated negative effects of osmoticum on structure and function of photosynthetic apparatus.