Springer Science and Business Media LLC

The effects of increasing arsenic (0, 10, 50, 100 mg L−1) and zinc (0, 50, 80, 120, 200 mg L−1) doses on germination and oxidative stress markers (H2O2, MDA, SOD, CAT, APX, and GR) were examined in two Brazilian savanna tree species (Anadenanthera peregrina and Myracrodruon urundeuva) commonly used to remediate contaminated soils. The deleterious effects of As and Zn on seed germination were due to As- and Zn-induced H2O2 accumulation and inhibition of APX and GR activities, which lead to oxidative damage by lipid peroxidation. SOD and CAT did not show any As- and Zn-induced inhibition of their activities as was seen with APX and GR. We investigated the close relationships between seed germination success under As and Zn stress in terms of GR and, especially, APX activities. Increased germination of A. peregrina seeds exposed to 50 mg L−1 of Zn was related to increased APX activity, and germination in the presence of As (10 mg L−1) was observed only in M. urundeuva seeds that demonstrated increased APX activity. All the treatments for both species in which germination decreased or was inhibited showed decreases in APX activity. A. peregrina seeds showed higher Zn-tolerance than M. urundeuva, while the reverse was observed with arsenic up to exposures of 10 mg L−1.

One of the most important stresses imperiling plant production in arid and semi-arid areas is salinity. By slow pyrolysis, a solid organic material, which is called biochar (BC), has been produced from waste organic substances. In this research, a pot factorial arrangement on the basis of randomized complete design was accomplished to evaluate the influence of BC on some physiological traits and growth at two different growth stages of summer savory (Satureja hortensis L.) under salinity stress. The treatments were included of three levels of BC (0, 1 and 2% w/w in the soil) and four salinity levels (0, 40, 80 and 120 mM of NaCl) with four replications. According to the findings, application of BC, especially at 2% w/w in the soil under salinity stress, reduced electrolyte leakage (EL) and antioxidant enzyme activities, i.e., ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX) activities and MDA content at vegetative and flowering stages. On the other side, the highest amounts of biomass and water content were observed when using BC 2% w/w of soil without salinity stress. The results confirmed that BC usage can contribute to the protection of the summer savory against salinity stress by alleviating the oxidative stress.

Recent studies showed, that ozone-induced gene expression occurs via at least two different signalling mechanisms that are ethylene-dependent (β-1,3-glucanases) and ethylene-independent independent (stilbene synthase). To identify trans-acting factors involved in ozone-induced gene expression we analyzed a 150 bp PCR fragment of an ozone-responsive promoter segment of the grape vine resveratrol synthase gene (Vst1) in combination of a cDNA library prepared from ozone-treated tobacco plants, using the yeast one-hybrid screening system. Two cDNA clones that encode WRKY binding proteins were isolated by this screening technique. The open reading frame of NtWRKY10 and NtWRKY11 showed an identity of 93.5% and the deduced amino acid sequence an identity of 89.3%. According to the WRKY domain classification in Arabidopsis, both proteins belong to subgroup II. Comparison with known tobacco WRKY proteins indicate that WRKY10 and WRKY11 belong to a new class of tobacco WRKY transcription factors. Electrophoretic mobility shift assays (EMSA) of yeast extracts, containing the WRKY fusion protein showed a weak binding to the radioactively labelled 150 bp ozone-responsive Vst1 fragment. These results are consistent with an involvement of WRKY proteins in ozone-induced phytoalexin gene expression.

Flax suspension cultures have been established from the callus induced from the cotyledons, hypocotyls, and immature zygotic embryos (iZE). The growth of flax suspension culture (expressed as a sedimented cell volume) was compared in both conditioned (by liquid from embryogenic Pinus nigra suspension culture) and non-conditioned media. Conditioning of media significantly increased the growth of the cell lines of hypocotyl and iZE origin; however, it had no promotive effect on embryogenic response of these flax liquid cultures. Formation of embryo-like structures (ELS), confirmed also histologically, has only been found in the cell line derived from iZE and cultivated in non-conditioned MS medium supplemented with 1 mg l−1 2,4-D. The process of ELS formation in this cell line was accompanied by the expression of the protein(s) with chitinolytic activity and molecular weight approximately of 25 kDa. The relationship between the formation of ELS and secretion of chitinase(s) is discussed.

Populus spp., had the characteristics of rapid growth and high biological yield, is one of the major tree species in the world’s afforestation and shelterbelt. But the growing soil salinization has become an important limited factor in the application of poplar planting. High-throughput sequencing technology was used to analyze the transcriptome of Populus × euramericana cv. ‘74/76’ under treatments with different NaCl concentrations to determine the formation pathway of the poplar response to salt stress and further reveal the mechanism of resistance to salt stress, so providing theoretical guidance for the salt tolerant breeding of poplar. Sequencing obtained 31.5G sequencing data and generated a total of 263 million reads, which were mapped to 32,840 non-repeatable genes with a sequencing quality value of Q30 > 96.70%. After filtering, 292 and 3284 differentially expressed genes (DEGs) were obtained from 3 and 6‰ NaCl treatments, respectively. There were a large number of stress-induced genes differentially expressed under the 6‰ NaCl treatment. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis results showed that the salt resistance mechanism of poplar 107 was different under different NaCl treatments. Poplar 107, under a high NaCl concentration treatment had a more salt resistant metabolic pathway, which included the citric acid cycle [tricarboxylic acid (TCA) cycle], terpenoid backbone biosynthesis, flavone and flavonol biosynthesis, carotenoid biosynthesis, zeatin biosynthesis, calcium signaling pathway, and other important salt-related pathways. We excavated the genes that affected the electron transport involved in the process of photosynthesis under salt stress and the key enzyme genes in response to salt stress involved in glutathione and terpenoid backbone metabolism. A total of 52 transcription factors (TFs), including 24 new TFs closely related to the salt stress response mechanism, were identified in the co-expression genes. This result provided important theoretical guidance for the establishment of the poplar salt resistance database, excavation of salt tolerant genes, and breeding of new species of poplar by means of molecular biology.

In vivo effect of aluminium on nitrate uptake and reduction by cucumber seedlings was investigated. The high-performance liquid chromatography was used to analyse the rate of nitrate uptake. Low (0.5 mM) concentration of AlCl3 in the nutrient solution stimulated nitrate uptake during the first 3 h. On the other hand, 6 h exposure of the cucumber seedlings to 1 or 5 mM of AlCl3 resulted in inhibition of nitrate uptake and at 5 mM concentration of AlCl3 the efflux of nitrate was observed. Furthermore, the amount of nitrate accumulated in cucumber roots after aluminium treatment was decreased. The noteworthy fact was observed, that at all concentrations of aluminium tested on increase of the nitrate reductase activity. This stimulation was concentration depended, but independent of the source of the enzyme. The activity of both the cytosolic and the plasma membrane bound nitrate reductase activity was enhanced in vivo. On the other hand, AlCl3 applied in vitro only slighty decreased nitrate reductase activity.