This study was carried out to understand the mechanism of protection of plants under cold stress by exogenous 24-epibrassinolide (EBR). The eggplant (Solanum melongena L.) seedlings were pretreated with five concentrations of EBR (0, 0.05, 0.1, 0.2 and 0.4 °M) and then exposed to day/night temperatures of 10/5 °C for 8 d. The results show that EBR, especially 0.1 °M EBR, dramatically alleviated growth suppression and a decrease in chlorophyll content and photosynthetic rate caused by the cold stress. In addition, EBR also decreased malondialdehyde content and O₂ ^.- production rate induced by the cold stress, and increased the activities of superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase, and proline content. The results of the present study suggest that exogenous EBR could improve cold tolerance of eggplant by regulating photosynthesis and antioxidative systems.

The effect of UV-B irradiation at temperatures of 22 and 4 °C on flash induced oxygen yields, photochemical activity, and energy transfer in pea thylakoid membranes in the absence and presence of scavengers of reactive oxygen species (ROS) was studied. Three different scavengers were used: dimethyl sulfoxide (DMSO), histidine (His), and n-propyl gallate (nPG). As result of the UV-B treatment of isolated membranes, the flash oxygen yields were considerably affected - the amplitudes decreased and the oscillation pattern was lost. The analysis of the flash oxygen yields and initial oxygen burst showed alterations of a number of oxygen evolving centers in the S0 state as well as changes of decay kinetics of the oxygen burst under continuous irradiation. ROS scavengers exhibited more or less expressed protective effects, nPG being the most effective against UV-B induced damages of the flash oxygen yields. At both the temperatures, photosystem II (PS II) mediated electron transport was more sensitive to the UV-B treatment in comparison with photosystem I (PS I). The analysis of 77 K fluorescence spectra showed that the fluorescence ratio F735/F685 increased by the UV-B treatment probably due to a redistribution of excitation energy between both photosystems most likely caused by partial unstacking and due to a decrease of PS II fluorescence resulting from reaction center-type quenching. The nPG was the most powerful scavenger which protected the oxygen evolution capacity of PS II in the absence and presence of an exogenous electron acceptor to the highest extent.

BABY BOOM (BBM), initially identified in Brassica napus, can enhance the shoot regeneration capacity in tissue culture and is involved in the conversion from the vegetative to embryogenic state. This study aimed to isolate BBM orthologue genes from Rosa canina and analyse their functions. Two full-length cDNAs, designated RcBBM1 and RcBBM2, were isolated from R. canina by the rapid amplification of cDNA ends (RACE). The predicted amino acid sequences of the two RcBBMs contained the bbm-1 motif and the motifs typically conserved in the eudicotANT (euANT) lineage. Phylogenetic tree analysis showed that the RcBBMs were most closely related to the BBM orthologue genes identified in Glycine max and Medicago truncatula. The transcripts of the RcBBMs were detected in young roots, calluses, and protocorm-like bodies (PLBs), whereas they were undetectable in stems, leaves, and flowers. RcBBM1-GFP and RcBBM2-GFP fusion proteins were both localized in the nucleus. 35S::RcBBM1 and 35S::RcBBM2 transgenic Arabidopsis thaliana lines exhibited enhanced shoot regeneration capacity in tissue culture, but did not undergo spontaneous somatic embryogenesis. The results suggest that RcBBMs may be candidate genes for improving the shoot regeneration efficiency of R. canina.

Two types of hairpin RNA (hpRNA) constructions were designed using a chimeric gene formed from two genes, the coat protein (CP) gene or the silencing suppressor gene, from the Cucumber mosaic virus (CMV) and the Potato virus Y (PVY_N), respectively; one type generated a single hairpin structure, whereas the other formed a two-hairpin structure. Four constructs, pDCPSH (double CP gene fragments, single hairpin), pDCPDH (double CP gene fragments, double hairpins), pHC2bSH (two silencing suppressor gene fragments, single hairpin), and pHC2bDH (two silencing suppressor gene fragments, double hairpins), were individually introduced into tobacco plants. A transcript analysis demonstrates that the small interference RNA (siRNA) processing efficiency was greater with the double-hairpin construct than with the single-hairpin construct, although the expression of their target genes were similar. A viral resistance assay shows that the transgenic tobacco plants effectively resisted a mixed infection of CMV and Potato virus Y (PVY^N) and that pDCPDH exhibited the highest silencing efficiency. The accumulation of siRNA in the inoculated transgenic plants expressing different hairpin structures was similar. A genetic analysis reveals that viral resistance in the transgenic plants was stably inherited from the T₀ to T₁ generation. A transcript analysis and a viral resistance assay indicate that the double-hairpin structure of the same target sequences tended to produce more siRNA before the virus inoculation and thus strengthened RNA-mediated viral resistance.

Interaction between aluminum (Al) and boron (B) in Al accumulator species has not been characterized so far. In this work, tea [Camellia sinensis (L.) O. Kuntze] plants were cultivated hydroponically and treated with adequate (control) or low B supply (-B) without or with 300 μM Al (-B+Al) for 14 weeks. Growth of B-deficient plants was completely resumed by Al supplementation or even surpassed control plants regarding shoot biomass. Net photosynthetic rate was negatively influenced by the low B supply, and the Al treatment increased it up to the level of the control plants that was reflected in the higher content of saccharides. The activity of ascorbate peroxidase (APX) in the younger leaves decreased at the low B supply accompanied with an increased H₂O₂ content. The Al treatment increased the APX activity up to the level of the control plants simultaneously with the reduction of H₂O₂. Activities of superoxide dismutase (SOD) and peroxidase (POD) increased in the low B plants and the Al treatment augmented this effect. The content of malondialdehyde (MDA) in the leaves increased by low B but declined upon the Al treatment. In the Al-treated plants, the activity of nitrate reductase (NR) and the content of free α-amino acids exceeded those of the control plants, and nitrite concentration diminished. The shoot and root B content of the B-deficient plants supplemented with Al was similar with the B-sufficient ones. The results demonstrate that the up-regulation of C and N metabolism, the activation of antioxidative defense, and the enhancement of B uptake and transport were mechanisms for growth amelioration of the B-deficient plants by Al supplementation in tea.

Two of the abundant transcripts encoding type 2 metallothionein (MT) proteins designated as MET2a and MET2b were selected in our previous study due to their high abundance (16.05 %) in the suppression subtractive hybridization library and their involvement in fruit development and maturation. The present study involves the isolation of the full-length cDNA encoding MET2a and MET2b from the ripening oil palm fruit mesocarp, examining their expression pattern compared to the other two previously reported type-3 MT members (MT3-A and MT3-B) in various oil palm organs including different vegetative and reproductive tissues. The full-length cDNA sequences of MET2a and MET2b were 571 and 553 bp and they were designated as EgMT2a and EgMT2b, respectively. The sequences of the EgMT2a and EgMT2b were then compared for sequence similarities in the database using both BLASTN and BLASTX programs. Their sequences were homologous (67-77 %) with several type-2 MTs in plants. All four MT encoding genes were differentially expressed in the ripening oil palm mesocarp tissues, but undetectable in the vegetative tissues examined. All MT genes examined were significantly up-regulated in the mature developmental stages of oil palm fruit mesocarp, except for EgMT2b which was expressed only at 17 weeks after anthesis. The type 2 MT proteins are related to a greater degree to the late fruit-ripening stage than the type 3 MT proteins consistent with their reported functions in homeostasis or detoxification. The findings in the present study contribute to better understanding the molecular mechanisms involved in fruit ripening in oil palm.

Needles of Larix gmelinii seedlings grown under different irradiances (100, 52, and 26 % of natural sunlight) were collected from June to August 2009. The content of phenolic compounds and condensed tannins in needles were strongly affected by different irradiances. The highest content of phenolic acids occurred under the lowest irradiance. Chlorogenic acid and syringic acid were detected only under the shade. In contrast, the needles under full irradiance showed the highest content of condensed tannins.

Water transport across the cell membranes is regulated largely by a family of proteins known as aquaporins (AQPs). Plasma membrane intrinsic protein (PIP) is an important subfamily of plant AQPs localized on the plasma membrane. To investigate the molecular mechanism of water regulation in seed germination, seven genes encoding PIP were initially cloned and sequenced from the germinating seed cDNA pool of Brassica napus. They belong to the PIP1 and PIP2 subfamilies. The transcription of the seven cloned genes plus three previously identified AQP genes from B. napus were analyzed in different organs and different stages of seed germination by quantitative real-time PCR (qRT-PCR). The results show that the expressions of the ten AQP genes were lower or scarcely detected in dry seeds, but were up-regulated during germination as well as in young seedlings. In addition, the expression of these ten AQP genes in response to an abiotic stress during seed germination was investigated and the results also show differential responses to abiotic stress treatments. Our findings suggest that these ten genes play different roles during plant development and response to abiotic stresses in B. napus.

The effects of salt stress on dry mass, lipid peroxidation, polyphenol and hydrogen peroxide content and activities of antioxidative enzymes were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under a broad range of NaCl concentrations (0, 100, 200, and 300 mM) on Murashige and Skoog medium for 45 d. Dry mass of both species increased at low (100 mM) salinity but decreased at higher NaCl concentrations. Malondialdehyde (MDA) content decreased at low salinity, whereas increased at 200 and 300 mM NaCl. H₂O₂ content in S. europaea was considerably enhanced by salinity, but it was not significantly affected in S. persica. The salt stress progressively enhanced the polyphenol content in S. persica, whereas in S. europaea, it increased with respect to the control only at higher salinities. In both species, the salinity progressively enhanced the superoxide dismutase (SOD) and peroxidase (POD) activities, whereas the CAT activity was only registered at the low salinity and the APX activity decreaseed in both species. The results indicate that S. persica exhibited a better protection mechanism against oxidative damage and it is more salt-tolerant than S. europaea.

Plant vacuoles play several roles in controlling development, pathogen defence, and stress response. γVPE is a vacuolarlocalised cysteine protease with a caspase-1 like activity involved in the activation and maturation of downstream vacuolar hydrolytic enzymes that trigger hypersensitive cell death and tissue senescence. This work provides evidence that γVPE is strongly expressed in Arabidopsis guard cells and is involved in water stress response. The γvpe knock-out mutants showed reduced stomatal opening and an increased resistance to desiccation suggesting a new role of γVPE in control of stomatal movements.

Sulfur dioxide (SO₂) is a well-known and widespread air pollutant but it also acts as signaling molecule in various processes in animals. However, there is limited information on the role of SO₂ in plants except of its toxicity. Here we studied the role of SO₂ on stomatal movements in sweet potato (Ipomoea batatas) leaves. SO₂, generated by Na₂SO₃/NaHSO₃ solutions, was applied on epidermal strips. We found that the SO₂ donor induced stomatal closure in a dose-dependent manner. Rapid increases in endogenous hydrogen sulfide and nitric oxide content levels were observed in leaves after the treatment with the SO₂ donor. The SO₂-induced stomatal closure was reversed by the H₂S scavenger hypotaurine and the NO-specific scavenger cPTIO. Our results indicate that the SO₂-induced stomatal closure was likely mediated by the H₂S and NO signaling pathways.

The present research is aimed towards molecular marker assisted pyramiding Tomato leaf curl virus (ToLCV) disease resistance genes into two ToLCV susceptible tomato (Solanum lycopersicum L.) cvs. Pbc and H-86 (resistance genes recipient parents). Resistance gene donors were EC-538408 (Solanum chilense) and EC-520061 (S. peruvianum) in the case of cv. Pbc, and EC-520061 (S. peruvianum) and H-24 (S. lycopersicum) in the case of cv. H-86. A ToLCV resistance gene associated co-dominant simple sequence repeat (SSR) marker SSR-218 was used to discriminate between homozygotes and heterozygotes at the seedling stage prior to pollination, which enabled the rejection of nontarget back crosses and pyramiding progenies of the crosses PbcxEC-520061 and H-86xEC-520061, whereas SSR-306 was used for the cross PbcxEC-538408. Ty-2 gene cleaved amplified polymorphic sequences (CAPS) marker was used for the cross H-86xH-24. Out of 279 pyramiding progenies of the cross PbcxEC-538408/PbcxEC-520061, total 91 plants showed the presence of both resistance allele 1 and 2 along with both susceptibility alleles, and in 243 pyramiding progenies of the cross H-86xEC-520061/H-86xH-24, total 82 plants showed the presence of both resistance allele 1 and Ty-2 along with both susceptible alleles. The pyramiding lines that carried both pyramided resistance genes were resistant to tomato leaf curl disease throughout its life cycle.

LeAN2 encoding an anthocyanin-associated R2R3-MYB transcription factor was isolated from tomato. The expression of LeAN2 in tomato was induced by low temperature and oxidative stress. Green fluorescent protein was fused to LeAN2 and the complex was expressed transiently in onion epidermal cells. Green fluorescence was observed only in the nucleus. Overexpression of LeAN2 under the control of the CaMV35S promoter in tobacco induced expression of several anthocyanin biosynthetic genes and the content of anthocyanin was markedly higher in transgenic tobacco compared with wild type plants. Transgenic tobaccos conferred tolerance to chilling stress by maintaining a higher chlorophyll content, net photosynthetic rate, and maximal photochemical efficiency of PS II compared to the wild type plants. Furthermore, the transgenic plants showed lower ion leakage, a lower content of reactive oxygen species, and a higher content of non-enzymatic antioxidans under the chilling stress. They also showed an enhanced resistance to the oxidative stress induced by methyl viologen based on a decreased chlorophyll content loss, lower ion leakage, and an enhanced maximal photochemical efficiency of PS II. These results indicate that overexpression of LeAN2 resulted in an increased anthocyanin accumulation and enhanced resistance to the chilling and oxidative stresses in transgenic tobacco.

ATP binding cassette (ABC) proteins constitute one of the largest families of transporters. In Arabidopsis thaliana, over 100 genes encoding ABC transporters have been identified. Here, we described the expression pattern of AtABCC13/MRP11, a member of the multidrug resistance associated protein MRP/ABCC subfamily, previously uncharacterized. The histochemical analysis of transgenic Arabidopsis harboring AtABCC13 promoter-β-glucuronidase gene fusion shows that the AtABCC13 expression was specifically associated with vascular bundles. Moreover, AtABCC13 displayed a complex hormonal regulation. β-glucuronidase (GUS) fluorimetric assays revealed that the gene expression was induced by gibberellic acid and downregulated by naphthalene acetic acid, abscisic acid, and zeatin. Because AtABCC13 is also expressed during seed development and during germination, its expression was assessed upon exposure to various nutrients: nitrate, phosphate, and sucrose stimulated the AtABCC13 expression in seedlings, whereas their lack strongly reduced it.

Interactions between three genotypes of a silver fir (Abies alba Mill.) embryogenic callus and Heterobasidion abietinum, H. parviporum, and H. annosum were examined in dual cultures. The aim of this study was to determine whether dual cultures can be used to evaluate the degree of fungal virulence at an embryogenic level, and whether different genotypes of a callus show different susceptibility. The dual cultures were performed on Schenk and Hildebrandt medium. Mycelial growth of H. parviporum and H. annosum was significantly stimulated in the presence of the callus but was not directional in nature. The embryogenic callus died between six and nine days after being colonized by H. parviporum suggesting that this was the most virulent species. By contrast, the callus remained healthy for up to 50 d after colonization with H. abietinum suggesting that this was the least virulent species. The callus of the A. alba genotype which originated in the mountain region of Poland remained healthy and alive for a significantly longer period than the other two genotypes in the dual cultures with all three Heterobasidion species even though overgrown by mycelium suggesting that the mountain genotype had the strongest defence response to Heterobasidion infection.

To gain a deep understanding of the regulatory mechanism of Cu-responsive microRNAs (miRNAs) in non-heading Chinese cabbage (Brassica campestris ssp. chinensis Makino), the transcription of 10 annotated stress-inducible miRNAs and their target genes were investigated in two cultivars Suzhouqing and Wutacai exposed to excess of copper. Results show that these miRNAs were negatively correlated with their target genes under the Cu stress and showed different transcriptions in different tissues and cultivars. The transcriptions of bra-miR1530a and bra-miR1533v were highest in petioles and lowest in roots. Bra-miR1533ah, bra-miR1533m, bra-miR1533t, bra-miR414a, and bra-miR398b had the highest and lowest transcriptions in leaves and roots, respectively. In contrast, the transcription of bra-miR172f was highest in roots and lowest in leaves. Bra-miR1533aj and bra-miR1533d had similar transcriptions in petioles and leaves. The promoter analysis further revealed that seven miRNAs contained the Cu-response element (CuRE). In addition, miRNAs with more CuREs in the 5'-flanking sequences showed a lower expression following the Cu treatment. It imply that CuREs likely played a role in increasing the response to Cu in non-heading Chinese cabbage.

Anthocyanins from mulberry fruits are used in medicine. However, little anthocyanin can be detected in other tissues and sometimes also mulberry fruits are colorless. The aim of this study was to investigate which gene or genes have the strongest correlation with the anthocyanin biosynthesis. The expression of several anthocyanin synthesis genes were determined in different tissues of two white and two purple fruit cultivars. Genes encoding dihydroflavonol reductase (MaDFR) and anthocyanidin synthase (MaANS) showed a high expression only in fruit tissue of purple-fruit cultivars. During the development of mulberry fruits, the anthocyanin content was well correlated with the transcripts abundance of MaDFR, MaANS, and MaCHS (encoding chalcone synthase). The skin of female mulberry flowers turns red under irradiance because of up-regulated expressions of MaCHS, MaDFR, and MaANS. These three genes may control the anthocyanin biosynthesis in mulberry and up-regulation of them may greatly increase the anthocyanin content.

Aluminum stress usually reduces plant root growth due to the accumulation of Al in specific zones of the root apex. The objectives of this study were to determine the localization of Al in the root apex of Sorghum bicolor (L.) Moech. and its effects on membrane integrity, callose accumulation, and root growth in selected cultivars. Seedlings were grown in a nutrient solution containing 0, 27, or 39 μM Al³⁺ for 24, 48, and 120 h. The Al stress significantly reduced root growth, especially after 48 and 120 h of exposure. A higher Al accumulation, determined by fluorescence microscopy after staining with a Morin dye, occurred in the root extension zone of the sensitive cultivar than in the tolerant cultivar. The membrane damage and callose accumulation were also higher in the sensitive than resistant cultivar. It was concluded that the Al stress significantly reduced root growth through the accumulation of Al in the root extension zone, callose accumulation, and impairment of plasma membrane integrity.

Oxidative stress plays an important role in plant ageing and in response to different stresses. Oxidative DNA damage, unless repaired, may have detrimental consequences and increase genetic instability. Therefore, we determined the role of heat-shock induced oxidative stress on induction and repair of DNA damage in relation to oxidative stress tolerance in senescent tobacco plants. One-month-old (young) and three-month-old (senescent) plants were exposed to 42 °C for 2 and 4 h and left to recover at 26 °C for 24 and 72 h. The progression of senescence was characterized by the lower soluble protein and malondialdehyde content compared to young plants. Immediately after the heat shock, an increase in lipid peroxidation and guaiacol peroxidase activity, as well as DNA damage measured by the Comet assay were induced to higher extent in the young plants than in the senescent ones compared to their respective controls. Moreover, after 24-h recovery, the DNA damage further increased in the young plants whereas tendency of DNA repair was observed in the senescent plants. Upon 72-h recovery, no significant differences were noticed in all parameters studied (regardless of plant age) compared to the controls. The random amplified polymorphic DNA (RAPD) analysis confirmed genetic stability of the tobacco plants during the heat-shock exposures as well as the subsequent recovery periods.

Maize (Zea mays L.) seedlings were pretreated with 0.001 g dm^-3 S-methylmethionine (SMM) in the nutrient solution for 24 h and then subjected to chilling (6 °C for 2, 4, 6, 10, and 24 h). Cold stress significantly decreased the maximum quantum yield of photosystem II (variable to maximum chlorophyll fluorescence ratio, F_v/F_m) during the whole experiment but SMM pretreatment significantly reduced this decline. Content of phenolics and anthocyanins increased in response to low temperature, and SMM pretreatment further intensified the synthesis of these protective agents. These findings were supported by increased expression of genes coding enzymes of the phenylpropanoid pathway leading to synthesis of cinnamate-4-hydroxylase (C4H) and chalcone-synthase (CHS). Our results indicate that SMM pretreatment alleviates the low temperature stress by reducing the damage of the photosynthetic apparatus and stimulating the phenylpropanoid pathway.

The present study was aimed at understanding the effects of long term supplemental UV-B (3.6 kJ m^-2 d^-1) on biomass production, accumulation of reactive oxygen species, lipid peroxidation, and enzymatic antioxidants in leaves and roots of Withania somnifera (an indigenous medicinal plant). Under the UV-B treatment, a reduction in biomass and an increased malondialdehyde content (a characteristic of lipid peroxidation) were observed in both the shoots and roots. Amongst ROS, H₂O₂ content increased under UV-B in the leaves, whereas it decreased in the roots, and superoxide radical production rate decreased in both the plant parts. The activities of all enzymatic antioxidants tested (ascorbate peroxidase, catalase, glutathione reductase, peroxidase, polyphenol oxidase, and superoxide dismutase) increased under the UV-B treatment, the increase being greater in the roots.

MYB transcription factors (TFs) are known to have important functions in regulating the biosynthesis of secondary metabolites in plants. In this study, LeMYB1, a member of the MYB gene family of Lithospermum erythrorhizon, was cloned via the rapid amplification of cDNA ends. The alignment of the predicted translations of LeMYB1 with other MYB proteins revealed that LeMYB1 contained an N-terminal R2R3 repeat and a high degree of amino acid identity to NtMYBJS1 which is involved in jasmonic acid signalling and phenylpropanoid biosynthetic pathway regulation. To determine the expression pattern of LeMYB1, its promoter was cloned and the sequence analysis was performed. The results revealed a number of potential regulatory motifs related to tissue-specific gene expression and abiotic and biotic stress responses. Real-time PCR results suggest that LeMYB1 was induced transiently during the early stage when L. erythrorhizon cells were transferred from a B5 growth medium to a M9 production medium for shikonin formation. Exogenous methyl jasmonate (MeJA), an effective inducer of shikonin biosynthesis, induced the rapid LeMYB1 expression. In contrast, a treatment with ibuprofen (IBU), an inhibitor of jasmonate biosynthesis, significantly inhibited the LeMYB1 expression. Another inhibitor of shikonin formation, 2,4-dichlorophenoxyacetic acid (2,4-D), also markedly repressed the expression of LeMYB1. Tissue-specific expression analysis showed that LeMYB1 mRNA was predominantly accumulated in roots where shikonin was synthesized. Thus, the LeMYB1 gene may be a valuable member of the R2R3-MYB family in L. erythrorhizon and is possibly involved in the regulation of shikonin biosynthesis.

In our previous study on geranium, we showed that increases in growth irradiance from sub-optimal to near-optimal could delay boron deficiency effects on photosynthesis. In this study, we further investigated the effects of growth irradiance on tolerance to B stress by growing geranium (Pelargonium × hortorum cv. Maverick White) under sub- to supra-optimal B concentrations (4.5, 45, and 450 μM) and under three irradiances of 100, 300, or 500 μmol m^-2 s^-1 PAR for 30 d. In general, at low and medium irradiances, sub- and supra-optimal B availability decreased root and shoot dry masses, but at high irradiance, the B stress was prevented. Net photosynthetic rate decreased by the supra-optimal B concentration at the high irradiance only suggesting B-related photoinhibition. Tissue B content and root specific B uptake only modestly decreased by the low B treatment, but increased greatly by the high B availability, and the higher irradiance decreased the tissue B content and the root B uptake only at the low and medium B supplies. Interestingly, the increases in irradiance decreased the content and uptake of all other nutrients, except Fe uptake. Effects of the B stress on the content of other nutrients were variable, but the B stress often exacerbated decreases in nutrient content with the increasing irradiance which would be especially important under nutrient-limiting conditions. Hence, in this study, the B stress effects on growth were mitigated by the increases in growth irradiance, which offset negative effects on physiology, and the protective effects of irradiance were likely caused by its positive effects on plant carbon/energy status rather than on tissue B content or B uptake.

Endogenous salicylic acid (SA) functions in plant response to an aluminum stress were assessed. We used different Arabidopsis thaliana genotypes including snc1 with a constitutively high content of SA, sid2 and nahG (transgenic lines) both with a low content of SA, SA insensitive mutant npr1-1, and snc1/nahG (i.e., the nahG expression in the snc1 background) with a similar SA content as in wild type (WT) plants. Results show that the snc1 plants displayed obvious growth retardation of roots and shoots under the Al³⁺ stress, whereas the sid2, nahG, and npr1-1 plants exhibited alleviated symptoms in comparison with the WT plants. The Al³⁺ content increased in all the tested genotypes with the increasing AlCl₃ concentration applied, but no significant variations were detected among the tested genotypes. The snc1 had much higher superoxide dismutase and peroxidase activities, and a lower catalase activity and the ratio of reduced to oxidized glutathione accompanied by higher accumulations of H₂O₂ and malondialdehyde compared with the WT plants. These changes were largely reversed by the introduction of nahG; the sid2, nahG, and npr1-1 plants were less affected than WT plants in all the above-mentioned parameters. The Al³⁺ stress significantly enhanced malate exudation in all the tested genotypes, but no significant correlation was observed between the SA-involved response to the Al³⁺ stress and the malate exudation. Based on these data, it was concluded that the SA-related functions in Arabidopsis response to the Al³⁺ stress were associated with the control of oxidative stress, but not of malate exudation.

The current work compared the physiological characteristics of plantain (Musa AAB) plantlets micropropagated in temporary immersion bioreactors (TIB) and on a gelled medium (GM). The plantlets were evaluated during in vitro growth (in the shoot elongation phase) and at the end of ex vitro acclimatization. TIB improved rooting and gave rise to longer shoots and higher dry mass. Respiration rate was the highest at the beginning of shoot elongation in both the TIB and GM plantlets. Photosynthetic rate in TIB was significantly higher than in GM from the midpoint of acclimatization, whereas a pyruvate kinase (PK) activity was lower. Starch accumulation was ca. two fold higher in corms than in leaves and always higher in the TIB than GM plantlets. The higher expression of genes coding for carbon metabolism enzymes PK and phosphoenolpyruvate carboxylase (PEPC) in TIB than in PM indicates a more important role of an autotrophic metabolism in the TIB plantlets when compared to the GM ones. The accumulated reserves were used during the first days of acclimatization leading to the higher survival rates and to the better plant quality of the TIB plantlets.

In vitro induction of haustoria from Castilleja tenuiflora Benth. was achieved by applying 25 μM catechin, 25 μM vanillin, or 25 μM H₂O₂. Of the treatments tested, 25 μM vanillin was the strongest inducer of haustoria in C. tenuiflora roots in vitro (up to 3 haustoria per root). Haustorium development occurred laterally and was observable 14 d after inducer application. It was characterized by elongation of the epidermal cells and division of the inner cortical cells which also possessed abundant nuclei. Histochemical analysis using 3,3-diaminobenzidine (DAB) and diphenylboric acid 2-aminoethyl ester (DBPA) indicated that the formation of haustoria was associated with the accumulation of H₂O₂ and flavonoids.

Tomato (Solanum lycopersicum Mill.) is sensitive to chilling stress during all stages of plant development. Genetic variation for chilling tolerance exists between cultivated tomato and its related wild species, but intra-specific variation has not been thoroughly investigated so far. Seedlings of 63 tomato accessions were evaluated under low temperature and two contrasting cultivars were identified for the trait: Albenga and San Marzano, the former being more chillingtolerant. To clarify the molecular mechanisms of chilling tolerance in tomato, changes in candidate gene expressions in the two tomato genotypes were analysed, using quantitative RT-PCR. Candidate genes were chosen among those known to be induced by chilling and/or with putative roles in CBF/DREB and ROS-mediated pathways. Results show that besides a CBF regulon, whose function is conserved, ROS and C2H2-type zinc finger protein-mediated cold signalling pathways were also involved in chilling tolerance. Under the chilling stress, the up-regulation of respective transcripts was consistently higher in the chilling-tolerant genotype than in the chilling-sensitive ones.

Trehalose was supplied to wheat (Triticum aestivum L.) seedlings just before a high temperature (40 °C) treatment and some physiological parameters were measured during the heat stress and recovery. The application of trehalose decreased the net photosynthetic rate (P_N) of wheat seedlings under the heat stress, but to a small extent increased the dry mass (DM) and leaf water content (LWC) after recovery from the heat stress. The trehalose-induced decrease in PN under the heat stress was not associated with a stomatal response. The heat stress slightly decreased the maximal efficiency of photosystem II (PS II) photochemistry (the variable to maximum chlorophyll a fluorescence ratio, F_v/F_m) similarly in the trehalose treated or non-treated plants. Under the heat stress, the actual efficiency of PS II photochemistry (Φ_PSII) and the efficiency of excitation energy capture by open reaction centers (F_v'/F_m') were lower in the trehalose-pretreated seedlings, whereas they were higher after the recovery. The patterns of changes in nonphotochemical quenching (NPQ) were contrary to those of ϕ_{PS II} and F_v'/F_m'. The chlorophyll content was lower, whereas the β-carotene content and the degree of de-epoxidation (DEPS) of xanthophyll cycle pigments were higher in the trehalose-pretreated wheat seedlings under the heat stress. These results suggest that exogenous trehalose partially promotes recovery of wheat by the increase of NPQ, β-carotene content, and DEPS.

Heavy metal toxicity in soils has been considered as major constraints for oilseed rape (Brassica napus L.) production. In the present study, toxic effects of chromium (Cr) were studied in 6-d-old seedlings of four different cultivars of B. napus (ZS 758, Zheda 619, ZY 50, and Zheda 622). The elevated content of Cr inhibited seedling growth, decreased the content of photosynthetic pigments, and activities of antioxidant enzymes, as well as increased the content of malondialdehyde and reactive oxygen species in all the cultivars. The Cr content in different parts of plants was higher in Zheda 622 than in other cultivars. The electron microscopic study showed changes in ultrastructure of leaf mesophyll and root tip cells at 400 μmol Cr, and these changes were more prominent in Zheda 622. An increased size and number of starch grains and number of plastoglobuli, damaged thylakoid membranes, and immature nucleoli and mitochondria were observed in leaves. In roots, enlarged vacuoles, disrupted cell walls and cell membranes, an increased number of mitochondria and a size of nucleolus, as well as plasmolysis (in Zheda 622) were observed. On the basis of these findings, it can be concluded that cv. Zheda 622 was more sensitive to Cr as compared to other three cultivars.

Durum wheat (Triticum turgidum L. var. durum) is mainly produced under rainfed but often sub-optimal moisture conditions in the Mediterranean basin. A set of 114 durum wheat recombinant inbred lines (RILs) developed from the cross of cultivars Omrabi5 × Belikh2 were tested for the ability to tolerate moisture deficiency at the germination and early seedling growth stage. The stress was imposed by exposing the germinating grain to 12 % polyethylene glycol. It induced a measurable reduction in root length, shoot length, and the percentage of normal seedlings. The germination and seedling growth of Belikh2 were more strongly inhibited than those of Omrabi5, and both parents were outperformed by > 50 % of the RILs. A quantitative trait locus (QTL) analysis was carried out by first assembling a linkage map from 265 informative microsatellites. Composite interval mapping revealed nine QTL spread over seven chromosomes. Five of these were associated with coleoptile length, and one of the five explained nearly 29 % of the relevant phenotypic variance. The coleoptile length was significantly correlated with the seedling growth, plant height, and thousand kernel mass derived from field-grown plants of the same RIL population.