In this work, the response of the halophytic shrub Prosopis strombulifera to lowering an osmotic potential (Ψ_o) to -1.0, -1.9, and -2.6 MPa generated by NaCl, Na₂SO₄, and the iso-osmotic combination of them was studied at 6, 12, and 24 h after reaching such values in the growing media. By analyzing the content of abscisic acid (ABA) and related metabolites and transpiration rates, we observed that ABA content varied depending on type of salt, salt concentration, organ analyzed, and age of a plant. ABA content in leaves was much higher than in roots, presumably because of rapid biosynthesis and transport from roots. Leaves of Na₂SO₄-treated plants had the highest ABA content at Ψ_o -2.6 MPa (24 h) associated with sulfate toxicity symptoms. Significant content of ABA-glucose ester (ABA-GE) was found in both the roots and leaves, whereas only low content of phaseic acid (PA) and dihydrophaseic acid (DPA). The roots showed high ABA-GE accumulation in all treatments. The highest content of free ABA was correlated with ABA-GE glucosidase activity. The results show that ABA-GE and free ABA work together to create a specific stress signal.

The present study examined the effect of salicylic acid (SA) pre-treatment on soybean seedlings exposed to cadmium and/or UV-B stress. Dry mass, pigment content, net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E) were decreased by the Cd and/or UV-B stress. SA alleviated the adverse effects of Cd and/or UV-B on growth, pigment content, PN, and gs, but did not mitigate the inhibitory effect of Cd/UV-B on E, or that of Cd on chlorophyll fluorescence parameters. Cd and/or UV-B induced oxidative stress and increased lipid peroxidation that was significantly decreased by SA pre-treatment. The Cd and/or UV-B increased superoxide dismutase (SOD) activity, decreased peroxidase (POD) activity, and catalase (CAT) activity was mostly unaltered. SA might act as one of the potential antioxidants as well as a stabilizer of membrane integrity to improve plant resistance to the Cd and/or UV-B stress.

Nitric oxide (NO), gibberellic acid (GA), and phosphorus (P) have been reported to regulate primary root (PR) growth, but interactions between them in the growth of Arabidopsis PR remain unknown. This work confirmed that low P availability significantly inhibited PR growth and that NO arrested PR growth in either high P or low P conditions. Moreover, NO counteracted the stimulatory effects of GA on PR growth under low P conditions. Finally, the dependence of low P and NO inhibition of PR growth on the DELLA-SLY pathway revealed that NO stabilized a major DELLA protein. We therefore conclude that antagonistic interactions between NO and GA regulate PR growth under both the high and low P conditions, and a DELLA-SLY module is the node where NO, GA, and P pathways converge and interact.

Globe artichoke (Cynara cardunculus L. var. scolymus) is rich in flavonoids which contribute to its health-promoting properties. With the aim of understanding the genetic control of flavonoid accumulation in artichoke, we isolated an artichoke full-length cDNA sequence encoding flavonoid 3'-hydroxylase (F3'H), a major enzyme of the flavonoid hydroxylation pattern. In silico studies confirmed that the deduced amino acid sequence of CcF3'H is highly similar to F3'Hs isolated from other Asteraceae. The Northern blot analysis demonstrated that CcF3'H was highly expressed in leaves and in specific parts of the heads. Its expression differed slightly among artichoke cultivars. The overexpression of CcF3'H in tobacco plants led to the accumulation of flavonoids and to an increase of flower colour intensity, thus identifying CcF3'H as promising candidate for genetic engineering. CcF3'H represents the first structural gene of the flavonoid biosynthesis isolated from C. cardunculus, and its characterization sheds light on the accumulation of flavonoids.

We have earlier reported that the endophyte infection can enhance photosynthetic capacity and antioxidant enzyme activities in rice exposed to salinity stress. Now, the changes in primary photochemistry of photosystem (PS) II induced by Na₂CO₃ stress in endophyte-infected (E+) and endophyte-uninfected (E-) rice seedlings were studied using chlorophyll a fluorescence (OJIP-test). Performance indices (PI_ABS and PI_Total) of E- and E+ rice seedlings revealed the inhibitory effects of Na₂CO₃ on PS II connectivity (occurrence of an L-band), oxygen evolving complex (occurrence of a K-band), and on the J step of the induction curves, associated with an inhibition of electron transport from plastoquinone A (Q_A) to plastoquinone B (Q_B). In E+ seedlings, Na₂CO₃ effects on L and K bands were much smaller, or even negligible, and also there was no pronounced effect on the J step. Furthermore, the OJIP parameters indicated that 20 mM Na₂CO₃ had a greater influence on the photosystem (PS) II electron transport chain than did the 10 mM Na₂CO₃, and that changes were greater in E- than in E+. Endophyte infection was therefore deemed to enhance the photosynthetic mechanism of Oryza sativa exposed to salinity stress.

Amino acids (AAs) play significant roles in metal binding, antioxidant defense, and signaling in plants during heavy metal stress. In the present study, the essential amino acids (EAAs), non-essential amino acids (NEAAs), as well as the enzymes of proline and cysteine biosynthetic pathways were studied in contrasting arsenic accumulating rice genotypes grown in hydroponic solutions with addition of arsenate (As^V) or arsenite (As^III). Under a mild As stress, the total AAs content significantly increased in both the rice genotypes with a greater increase in a low As accumulating rice genotype (LAARG; IET-19226) than in a high As accumulating rice genotype (HAARG; BRG-12). At the equimolar concentration (10 μM), As^III had a greater effect on EAAs than As^V. Conversely, As^V was more effective in inducing a proline accumulation than As^III. Among NEAAs, As significantly induced the accumulation of histidine, aspartic acid, and serine. In contrast, a higher As concentration (50 μM) reduced the content of most AAs, the effect being more prominent during As^III exposure. The inhibition of glutamate kinase activity was noticed in HAARG, conversely, serine acetyltransferase and cysteine synthase activities were increased which was positively correlated with the cysteine synthesis.

A gene (named BcFLC1) homologous to the AtFLC gene, which encodes a floral repressor, was isolated from the nonheading Chinese cabbage (Brassica campestris L. ssp. chinensis) cv. NJ074. The gene showed high similarity to AtFLC. For studying the gene function, we designed to introduce the BcFLC1 gene into Arabidopsis thaliana. The results showed that BcFLC1 had effects on flowering time similar to AtFLC. We also found that Arabidopsis cold-tolerance was enhanced by BcFLC1 overexpression. Under low temperature stress, the BcFLC1 transgenic plants exhibited stronger growth than wild-type plants. The elevated cold tolerance of the BcFLC1 over-expressing plants was also confirmed by the changes of electrolyte leakage and malonyldialdehyde and proline content.

In vitro flowering protocols were developed for a limited number of early flowering pea (Pisum sativum L.) cultivars. This work was undertaken to understand the mechanisms regulating in vitro flowering and seed-set across a range of pea genotypes. Its final goal is to accelerate the generation cycle for faster breeding novel genotypes. We studied the effects of in vivo and in vitro applications of the antigibberellin Flurprimidol together with radiation of different spectral compositions on intact plants, plants with the meristem removed, or excised shoot tip explants. Based on our results, we present a simple and reliable system to reduce generation time in vitro across a range of pea genotypes, including mid and late flowering types. With this protocol, more than five generations per year can be obtained with mid to late flowering genotypes and over six generations per year for early to mid flowering genotypes.

This study investigated the effects of exogenous hydrogen sulfide (H₂S) on the redox states of ascorbate (AsA) and glutathione (GSH) in maize leaves under NaCl (100 mM) stress. Salt stress increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), Γ-glutamylcysteine synthetase (Γ-ECS), and L-galactono-1,4-lactone dehydrogenase (GalLDH), malondialdehyde content and electrolyte leakage, and reduced the ratios of reduced and oxidised forms of AsA (AsA/DHA) and GSH (GSH/GSSG) compared with control. Pretreatment with NaHS (H₂S donor) further enhanced the activities of the above enzymes except MDHAR and ameliorated the decrease in the ratios of AsA/DHA and GSH/GSSG compared with the salt stress alone. Pretreatment with NaHS significantly reduced the malondialdehyde content and electrolyte leakage induced by the salt stress. Pretreatment with NaHS alone did not affect any of the above mentioned parameters compared with the control. Our results suggest that exogenous H2S could maintain the redox states of ascorbate and glutathione by up-regulating the ascorbate and glutathione metabolism and thus play an important role for acquisition of salt stress tolerance in maize.

To identify genes involved in the susceptibility to powdery mildew in wheat, genechip hybridization experiments were performed applying interactions between resistant and susceptible wheat cultivars and powdery mildew. Ten genes were found to express exclusively in the susceptible host after inoculation. The single cell transient expression experiments revealed that the RNA interference (RNAi) of two expressed sequence tag (EST) sequences (accession No. BQ168479 and CA648596) could enhance host resistance by 22 and 15 %, respectively. Full-length cDNA cloning revealed that they represented long non-coding RNAs (lncRNAs) and markedly accumulated during the powdery mildew primary infection.

The ATP binding cassette B/multidrug-resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily is a member of the ABC protein family. Significant progress has been made in the functional characterization of ABCB genes, particularly in Arabidopsis thaliana. This review evaluates recent advances concerning the plant ABCB subfamilies including their evolution and structure, the involvement and regulation of ABCB-mediated auxin transport, and the roles of ABCBs in plant growth and development. Insights into specific functions of members of the ABCB subfamily and their mediation of various regulatory pathways are also presented.

The main task of annually grown fibrous roots is to supply aboveground organs with water and nutrients. The key for this function, the development and mortality of primary tissues during a root lifespan is still poorly understood, especially in plants grown under field conditions. The goal of this study was to investigate the differentiation and maturation of fibrous roots from the initial appearance until the senescence and death. We monitored the histogenesis and anatomy of first order fibrous roots of black cottonwood (Populus trichocarpa Torr. & Gray) sampled at a known age. The daily examination of the first order fibrous roots revealed that only primary tissues were differentiated during the first seven days after their initiation and were maintained during the root lifespan. We observed all stages of exodermis and endodermis formation regulation a fibrous root water and nutrients uptake capacity. A cytological analysis, examined if any cellular symptoms of autophagy could be detected in senescent roots, indicated that vacuolar cell death was involved in root mortality. Our results are the first report strongly suggesting that programmed cell death (PCD) could be engaged in the senescence of ephemeral fibrous roots. The anatomical results advance our understanding of how roots absorptive ability is related to precise timing of tissue development during primary growth and of fibrous root senescence after fulfilment of its tasks.

Rice (Oryza sativa L.) is seriously impacted by global soil salinization. To determine the quantitative trait loci (QTLs) related to salt tolerance in rice roots, F_2:3 and BC₁F_2:3 populations derived from a cross between the cv. Dongnong 425 of high quality and yield and the salt-tolerant cv. Changbai 10, were studied at different development stages. Two genetic linkage maps of F_2:3 and BC1F_2:3 populations were constructed. A 66 mM NaCl solution was used to irrigate the field and to analyze the dynamic QTL of some rice root traits. Using unconditional and conditional QTL mapping methods, 30 unconditional QTLs and 16 conditional QTLs related to the 6 root traits were detected on the 9 rice chromosomes during different developmental stages. Fourteen pairs of unconditional and conditional QTLs were detected at the identical developmental stage in the identical population. A number of QTLs were detected at different developmental stages, however, many did not appear at the last stage. Remarkably, qRKC1 appeared continuously at multiple stages in both the populations suggesting its key role in regulating the salt tolerance of rice roots.

Seasonal dimorphism (summer/winter) has been so far studied only in a few plants and has been focused on summer drought stress. However, Thymus sibthorpii in the study area appears to be affected by winter chilling stress and not by summer drought stress. Thus, the winter leaves were thicker and more compact compared to the summer leaves and they had more stomata and peltate hairs, more sclerenchymatous fibers, vacuoles with phenolics, and chloroplasts than the summer leaves. In addition, their chloroplasts possessed large grana and starch grains. In the summer leaves, cell vacuoles in mesophyll did not contain phenolics, and chloroplasts were devoid of starch grains and had large plastoglobuli. Physiological measurements revealed higher net photosynthetic rate and chlorophyll content in the winter leaves than in the summer leaves. Proline and soluble sugar content along with antioxidative enzyme (superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione reductase) activities were increased in the winter leaves.

C-repeat binding factor (CBF), also called the dehydration-responsive element binding factor 1 (DREB1), can be induced by low-temperature (LT), and plays an important role in abiotic stress tolerance in higher plants. In present study, two new homologous genes of CBF from Prunus mume (PmCBFb and PmCBFc) have been identified and characterized. The complete coding sequences of PmCBFb and PmCBFc were 714 and 723 bp, respectively. They encoded putative proteins of 237 and 240 amino acids. Neither of them had introns. Genome PCR sequencing showed that PmCBFb was arranged in tandem with PmCBFa (another CBF/DREB1 homolog in P. mume) within a region of nearly 4 kb. Promoter prediction analyses indicated that multiple types of cis-elements related to abiotic stress and irradiance existed in the putative promoter region of PmCBFb. LT treatment of seedlings showed that the expression of PmCBF genes were induced by 2 °C within 30 min, and their expression reached a peak after 8-12 h. In addition, PmCBFa and PmCBFb appeared more sensitive to LT than PmCBFc. However, the exact roles of PmCBF genes in plant cold tolerance need to be further investigated.

Plant glutathione peroxidases (GPX) catalyze the reduction of H₂O₂ or organic hydroperoxides to water, mitigating the toxicity of these compounds to cells. In rice plants, the GPX gene family is composed of five members that are distributed in a range of sub-cellular compartments including cytosol, mitochondria, chloroplasts, or endoplasmic reticulum. Of these, OsGPX1 and OsGPX4 are located in mitochondria and chloroplasts, respectively. To understand the role of these GPX in rice, the effect of knockdown of OsGPX1 and OsGPX4 in rice plants was evaluated. Our data show that OsGPX4 was essential for in vitro rice regeneration because no plants were obtained from calli carrying a hairpin construct against OsGPX4. Although the knockdown of OsGPX1 did not impair plant regeneration, the plants with silenced OsGPX1 (GPX1s plants) showed reduced shoot length and a reduced number of seeds compared to the non-transformed rice plants. These results indicate that OsGPX1 and OsGPX4 are essential for redox homeostasis which leads to normal growth and development of rice.

We studied the influence of inorganic nitrogen sources (NO₃ ^- or NH₄ ⁺) and potassium deficiency on expression and activity of plasma membrane (PM) H⁺-ATPase in sorghum roots. After 15 d of cultivation at 0.2 mM K⁺, the plants were transferred to solutions lacking K⁺ for 2 d. Then, K⁺ depletion assays were performed in the presence or absence of vanadate. Further, PMs from K⁺-starved roots were extracted and used for the kinetic characterization of ATP hydrolytic activity and the immunodetection of PM H⁺-ATPase. Two major genes coding PM H⁺-ATPase (SBA1 and SBA2) were analyzed by real-time PCR. PM H⁺-ATPase exhibited a higher V_max and K_m in NH₄ ⁺-fed roots compared with NO₃ ^- -fed roots. The optimum pH of the enzyme was slightly lower in NO₃ ^- -fed roots than in NH₄ ⁺-fed roots. The vanadate sensitivity was similar. The expressions of SBA1 and SBA2 increased in roots grown under NH₄ ⁺. Concomitantly, an increased content of the enzyme in PM was observed. The initial rate of K⁺ uptake did not differ between plants grown with NO₃ ^- or NH₄ ⁺, but it was significantly reduced by vanadate in NH₄ ⁺-grown plants.

In this study, we cloned flowering-related genes FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) from domesticated octaploid strawberries (Fragaria × ananassa) and analyzed their expression patterns in cultivars Tochiotome and Akihime. The floral meristem generation was induced under the short day and low temperature (SDLT), but not under the long day and high temperature (LDHT). We found that FaFT1, which is an orthologue of the Arabidopsis floral activator FT, was highly expressed in leaves under LDHT but not expressed in leaves under SDLT. On the other hand, the expression of FaTFL2, which belongs to the TFL1 family of flowering repressing genes, decreased in crowns (stem tissue including meristem) under SDLT. These results suggest that FaTFL2, as opposed to FvTFL1 in wild diploid strawberry Fragaria vesca, is related to flowering of the cultivated strawberry. Moreover, the FaTFL2 expression might be regulated by temperature rather than by photoperiod. We demonstrated that a reduction of the FaTFL2 expression is a key signal for flowering in domesticated strawberries.

Fluorophore tagged proteins are used in Arabidopsis thaliana to understand their functional role in plant development. This requires the analysis of their spatial localization in planta. However, the localization analysis is often perturbed by a significant overlap of the fluorophores used to label proteins of interest and the optical filtering methods available on the confocal microscope. This problem can be addressed by the use of spectral imaging with linear unmixing the image data. We applied this method to help us identify double transgenic A. thaliana lines which expressed two fluorescently tagged auxin transporter proteins: the auxin efflux protein PIN-FORMED-3 (PIN3), tagged with green fluorescent protein (GFP), and the auxin influx protein LIKE-AUX1-3 (LAX3), tagged with yellow fluorescent protein (YFP). This method allows the reliable separation of overlapping GFP and YFP fluorescence signals and subsequent localization analysis highlighting the potential benefit of this methodology in studies of lateral root development.

The performance of control and water-stressed 10-d-old wheat seedlings was compared. During short-term water stress (irrigation was withheld for 9 d), rates of photosynthesis and transpiration, stomatal conductance, and relative water content decreased whereas the proline content increased. Chloroplast proteins were extracted from the leaves, separated by iso-electric focusing through two-dimensional electrophoresis, and stained with CBB R-250. Differentially expressed proteins were detected and analyzed with MALDI-TOF/TOF mass spectrometry. Under water stress, 9 proteins were up-regulated whereas 11 proteins were not affected. The ribulose-1,5-bisphospate carboxylase/oxygenase (Rubisco) small and large subunits, chloride carrier/channel family, and H⁺-ATPase were up-regulated by water stress whereas membrane-bound ATP synthase subunit b and cytochrome b6-f complex were down-regulated.

Abscisic acid (ABA) regulates plant responses to various environmental stresses. Oxidative cleavage of cis-epoxycarotenoids catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED) is the critical step in the biosynthesis of ABA in higher plants. Using a homologous cloning approach, a NCED-like gene (designated as TaNCED1) was isolated from wheat (Triticum aestivum). It contained an open reading frame of 1 848 bp and encodes a peptide of 615 amino acids. Multiple sequence alignments showed that TaNCED1 shared high identity with NCEDs from other plants. Phylogenetic analysis revealed that TaNCED1 was most closely related to a barley HvNCED1 gene. The predicted 3D structure of TaNCED1 showed high similarity with other homologues. Southern blot analysis indicated that TaNCED1 was a single copy in the genome of wheat. TaNCED1 was differentially expressed in various organs and the expression was up-regulated by low temperature, drought, NaCl, and ABA. Heterologous expression of TaNCED1 in tobacco (Nicotiana tabacum) significantly improved its drought tolerance. Under drought treatment, TaNCED1-overexpressing transgenic tobacco plants exhibited higher germination rate, higher relative water content, content of soluble sugars and of ABA when compared with the wild type plants.

Content of malondialdehyde (MDA), proline, phenolics, and saccharides was analyzed during different developmental stages of in vitro root and shoot organogenesis in saffron. The highest content of MDA, proline, and phenolics was detected in nodular calli. Significant changes were also found in the content of polysaccharides, soluble saccharides, oligosaccharides, and reducing saccharides during developmental stages. Histological investigation of nodular calli showed meristematic zones with small and densely stained cells situated at peripheral zones of calli. The meristematic zones surrounded some vascular areas from which de novo organs originated. The parenchymatic cells of inner zones of calli converted to procambium cells that produced vascular tissues.

The present study was carried out to examine the effects of seed soaking in 1 mM ascorbic acid (AA) or 1 mM proline on the growth, content of photosynthetic pigments and proline, relative water content, electrolyte leakage, antioxidant enzymes and leaf anatomy of Hordeum vulgare L. Giza 124 seedlings grown in greenhouse under 100 or 200 mM NaCl. The plants exposed to the NaCl stress exhibited a significant reduction in growth, relative water content, leaf photosynthetic pigments, soluble sugars, as well as alterations in leaf anatomy. However, the treatment with AA or proline ameliorated the stress generated by NaCl and improved the above mentioned parameters. NaCl increased electrolyte leakage, proline content, and activities of antioxidant enzymes (SOD, CAT, and POX). The antioxidant enzymes and leaf anatomy exhibited considerable changes in response to AA or proline application in the absence or presence of NaCl.

In chloroplasts and mitochondria, antioxidant mechanisms include the ascorbate-glutathione cycle, and monodehydroascorbate reductase (MDHAR) is important for regeneration of ascorbate (AsA) from monodehydroascorbate (MDHA). To improve detoxification of reactive oxygen species (ROS), we established a construct of the MDHAR gene from Brassica rapa fused to the targeting signal peptides of Pisum sativum glutathione reductase (GR), which was controlled by a stress-inducible SWPA2 promoter, and introduced this expression system into Arabidopsis thaliana. Transgenic (TG) plants overexpressing BrMDHAR targeted to chloroplasts and mitochondria through signal peptides showed an elevated MDHAR activity and an increased ratio of AsA to dehydroascorbate (DHA) when compared to wild-type (WT) plants under a freezing stress. These led to increased photosynthetic parameters, redox homeostasis, and biomass in TG plants when compared to the WT plants. Our results suggest that the overexpression of the BrMDHAR gene targeted to chloroplasts and mitochondria conferred an enhanced tolerance against the freezing stress, and a stress adaptation of dual-targeted BrMDHAR was better than that of single BrMDHAR.

In order to elucidate the role of lanthanum (La) in response of Vigna radiata to a salt stress, we investigated the effects of La on the ascorbate and glutathione metabolism. The results show that in comparison with a control, the salt stress increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), γ-glutamylcysteine synthetase (γ-ECS), and L-galactono-1,4-lactone dehydrogenase (GalLDH), and the content of ascorbic acid (AsA) and glutathione (GSH). It also increased the malondialdehyde content (MDA) and electrolyte leakage. The salt stress significantly decreased the ratios of AsA/dehydroascorbate (DHA) and GSH/glutathione disulphide (GSSG) compared with the control. The pretreatment with La not only significantly increased the activities of the above enzymes, the content of AsA, GSH, and the ratios of AsA/DHA and GSH/GSSG, but also significantly reduced the MDA content and electrolyte leakage compared with the salt stress alone. Our results suggest that La could up-regulate the ascorbate and glutathione metabolisms and could have an important role for acquisition of salt stress tolerance in Vigna radiata.

Low temperature is the main limiting factor for cultivation expansion, fast growth, and high yield of Eucalyptus species. To investigate the mechanism of their cold tolerance, a cDNA subtraction library representing the cold-induced genes of Eucalyptus dunnii was constructed using suppression subtractive hybridization (SSH) technique. A gene encoding a calmodulin-binding protein (CaMBP) was identified from the SSH library, and the expression pattern of CaMBP under cold stress was further evaluated through reverse transcription - quantitative polymerase chain reaction (RT-qPCR). The expressions of EguCBF1a and EdCaMBP increased already after 4 h of the cold stress, supporting the idea that the CaMBP gene may have a function in the survival of Eucalyptus during winter. A full-length mRNA sequence of 1 808 bp was obtained via a rapid amplification of cDNA ends method, and the sequence was subsequently deposited to GenBank (accession No. JX401571). The CaMBP cDNA of E. dunnii contained a single open reading frame of 1 362 bp, a 5t' untranslated region of 175 bp, and a 3t' untranslated region of 268 bp. Multiple sequence alignment and phylogenetic analysis indicated that CaMBP of E. dunnii shared 56 to 84 % identities with the CaMBPs of other plants and was similar to that of Ricinus communis, Medicago truncatula, and Gossypium hirsutum.

In the present study, we measured the markers of oxidative stress as well as activity of antioxidative enzymes and content of α-tocopherol in the acclimated and non-acclimated cucumber (Cucumis sativus L.) cell suspension cultures subjected to 150 and 200 mM NaCl. The content of carbonyl groups and lipid peroxidation were lower in the acclimated cultures than in the non-acclimated ones as well as their increases after NaCl treatments. Both NaCl concentrations enhanced activity of glutathione peroxidase in the examined cultures whereas activity of glutathione-S-transferase rose only in the acclimated ones. The increase in content of α-tocopherol induced by NaCl was more pronounced in the acclimated cultures. NaCl caused high decline in cell vigour in the non-acclimated cultures up to 80-90 % at the end of the experiment. The presented data suggest that the acclimated cultures coped with the salt stress better than the non-acclimated ones.

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg^-1) for 100 d. Results indicate that Cd in concentrations of 5-50 mg kg^-1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100-200 mg kg^-1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7-6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25-200 mg kg^-1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.

Interactions between indole-3-acetic acid (IAA), abscisic acid (ABA), and ethylene (ET) in the photoperiodic flower induction of a short-day (SD) plant Pharbitis nil were investigated. It was shown that both IAA and ABA applied just before and during the first half of the 16-h-long inductive night inhibited flower induction in P. nil. Ethylene is also thought to be a strong flowering inhibitor of SD plants but only when it is applied in the second half of the inductive night. The application of IAA just before the inductive night decreased the content of endogenous ABA in cotyledons only during the first half of the inductive night. Additionally, the application of 2-aminoethoxyvinylglycine (AVG) - an ethylene biosynthesis inhibitor - partially reversed the inhibitory effect of IAA and ABA on flowering. The results suggest that the mechanisms of P. nil flower inhibition by IAA and ABA might be independent. However, both the hormones influenced ethylene production which directly inhibited flowering. We also show that ABA applied on the cotyledons of P. nil seedlings just before the inductive night caused a clear increase in the expression of PnACS1 and PnACS2 genes (encoding enzymes involved in ethylene biosynthesis) from the first hours after its application. The transcripts of PnACO1 and PnACO3 genes were also increased but their maximal values were shifted in relation to the PnACS1 and PnACS2. The data presented here strongly support the idea that both IAA and ABA inhibit P. nil flowering through the modulation of ethylene biosynthesis.

Plant regeneration through indirect somatic embryogenesis was attempted from the immature cotyledon-derived explant of Cassia angustifolia Vahl. - a valuable leguminous shrub. The highest frequency (90.5 %) of somatic embryos was obtained on a Murashige and Skoog (MS) medium augmented with 10.0 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 μM benzyladenine (BA) with the production of a maximum of 22.8 embryos per explant, of which 35.3 % germinated on the same medium after 6 weeks of culture. A half strength MS medium without plant growth regulators facilitated better conversion of embryos into complete plantlets compared to a full strength MS medium. Regenerated plantlets were successfully acclimatized in sterile Soilrite and transferred to field conditions with a 70 % survival rate. Histological studies performed at different stages of embryogenesis revealed the mode of differentiation of embryos from the callus. The content of chlorophylls (a + b) and carotenoids, and the net photosynthetic rate (P_N) in the regenerated plantlets were tested during different periods of acclimatization.