Priming-induced changes in germination,morpho-physiological and leaf biochemical responses of fenugreek (Trigonella foenum-graecum) under salt stress

Abstract

Seed priming is a simple biotechnological tool which is potentially able to promote seed germination and invigoration as well as seedlings establishment and stress tolerance. In this study, the effects of seed pre-treatment with water (hydro-priming), 100 (HP-NaCl₁₀₀) and 200?mM (HP-NaCl₂₀₀) NaCl (halo-priming) for 6?h on some physiological and biochemical parameters of fenugreek was investigated under saline conditions (100?mM NaCl). For the three priming treatments, no significant changes in the final germination percentage were observed. However, a decrease in seed germination time was observed in hydro- and halo-primed (HP-NaCl₂₀₀) seeds. Salt stress (100?mM NaCl) reduced growth (shoot and root dry weight), pigment content, disturbed the ionic balance and enhanced malondialdehyde content. Salinity-induced changes in lipid metabolism towards synthesis/accumulation of saturated and monounsaturated fatty acids were observed in stressed plants. Seed priming ameliorated the negative effects of NaCl, ensuring significant amelioration on growth, pigment content, increased the activity of catalase and glutathione peroxidase and enhanced the synthesis of very long chain n-alkanes. Taken together, these data provide compelling evidence that priming is an effective alternative that can be used to promote germination and improves establishment and acclimation of fenugreek seedlings under saline conditions.     

Crucial ignored parameters on nanotoxicology: the importance of toxicity assay modifications and "cell vision"

Until now, the results of nanotoxicology research have shown that the interactions between nanoparticles (NPs) and cells are remarkably complex. In order to get a deep understanding of the NP-cell interactions, scientists have focused on the physicochemical effects. However, there are still considerable debates about the regulation of nanomaterials and the reported results are usually in contradictions. Here, we are going to introduce the potential key reasons for these conflicts. In this case, modification of conventional in vitro toxicity assays, is one of the crucial ignored matter in nanotoxicological sciences. More specifically, the conventional methods neglect important factors such as the sedimentation of NPs and absorption of proteins and other essential biomolecules onto the surface of NPs. Another ignored matter in nanotoxicological sciences is the effect of cell "vision" (i.e., cell type). In order to show the effects of these ignored subjects, we probed the effect of superparamagnetic iron oxide NPs (SPIONs), with various surface chemistries, on various cell lines. We found thatthe modification of conventional toxicity assays and the consideration of the "cell vision" concept are crucial matters to obtain reliable, and reproducible nanotoxicology data. These new concepts offer a suitable way to obtain a deep understanding on the cell-NP interactions. In addition, by consideration of these ignored factors, the conflict of future toxicological reports would be significantly decreased.     

Pollen viability of Euro‐Mediterranean orchids under different storage conditions: The possible effects of climate change

• The future impact of climate change and a warmer world is a matter of great concern. We therefore aimed to evaluate the effects of temperature on pollen viability and fruit set of Mediterranean orchids.
• The in vitro and controlled pollination experiments were performed to evaluate the ability of pollinia stored at lower and higher temperatures to germinate and produce fruits and seeds containing viable embryos.
• In all of the examined orchids, pollen stored at ?20 °C remained fully viable for up to 3 years, reducing its percentage germination from year 4 onwards. Pollinia stored at higher temperatures had a drastic reduction in vitality after 2 days at 41–44 °C, while pollinia stored at 47–50 °C did not show any pollen tube growth.
• The different levels of pollen viability duration among the examined orchids can be related to their peculiar reproductive biology and pollination ecology. The germinability of pollinia stored at lower temperatures for long periods suggests that orchid pollinia can be conserved ex situ. In contrast, higher temperatures can have harmful effects on the vitality of pollen and consequently on reproductive success of the plants. To our knowledge, this is the first report demonstrating the effects of global change on orchid pollen, and on pollen ability to tolerate, or not, higher air temperatures. Although vegetative reproduction allows orchids to survive a few consecutive warm years, higher temperatures for several consecutive years can have dramatic effects on reproductive success of orchids.

     

Salt tolerance analysis of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> NOK2 accession under saline conditions and potassium supply

The response to salt treatment and K⁺ provision of two Arabidopsis thaliana accessions grown for 17 days in the presence of 50 mM NaCl was investigated. Leaf and root dry weight deposition was restricted by salt, more in Col accession than in NOK2 accession. In both accessions, the growth inhibition induced by salinity was associated with a decrease in total leaf surface area, which resulted from diminished leaf number, but not from restriction of individual leaf surface area. Comparing the effects of salt on dry matter production and total leaf surface area revealed large difference between Col and NOK2 for net assimilation rate (the amount of whole plant biomass produced per unit leaf surface area), which was augmented by salt and K⁺ in NOK2 but not in Col. This result, which suggested a better capacity of NOK2 to preserve its photosynthetic machinery against salt stress, was in agreement with the effect of NaCl on photosynthetic pigments. Indeed, salt significantly reduced chlorophyll and carotenoid content in Col leaves but had no impact on NOK2 leaf pigment content. Since K⁺ provision had only marginal effects on these responses to salt stress, leaf mineral unbalance was unlikely. Guaiacol peroxidase activity was augmented by salt treatment in leaves and roots of both accessions. Salinity decreased the catalase activity in Col leaves and in roots, and increased this activity in NOK2 organs. In conclusion, when aggressed by salt, NOK2 was able (1) to produce more leaves than Col, and (2) to efficiently protect its photosynthetic apparatus, perhaps by developing more efficient antioxidative defense through increased catalase and peroxidase activities. Consequently, the overall photosynthetic activity was higher and more robust to salt aggression in NOK2 than in Col.     

Variability in the response of six genotypes of N<Subscript>2</Subscript>-fixing <Emphasis Type="Italic">Medicago ciliaris</Emphasis> to NaCl

Genotypic variability was assessed within six Medicago ciliaris genotypes growing symbiotically with Sinorhizobium medicae in order to identify physiological criteria (growth, ion content, and plant health) associated with salt tolerance. Response to salt stress depended on the line and the level of salt. Two lines with lower dry biomass under non-saline conditions (TNC 1.8 from a semi-arid area and TNC 10.8 from a sub-humid area), were more tolerant to NaCl, whereas the most productive lines (TNC 11.5 and TNC 11.9 from a humid bioclime) were more sensitive in terms of growth and nitrogen fixation. Susceptibility of symbiotic nitrogen fixation to saline stress was not associated with a higher accumulation of Na⁺ in nodules, since the most tolerant lines TNC 1.8 and TNC 10.8 accumulated the highest Na⁺ amount in nodules. Leaf area and net photosynthate assimilation rate were conserved in line TNC 1.8 and to a lesser extent in line TNC 10.8 potentially owing to a greater ability to protect aerial organs and nodules from Na⁺ damage and to insure a better supply of leaves with nitrogen. Our results suggest that nodule growth and number and nodule Na⁺ content should not be used as selection tools for tolerance or susceptibility, since two of the tested lines maintained consistent growth in spite of reduced nodule and high Na⁺ content. Instead, the most reliable physiological indicators for tolerance appear to be consistent growth (i.e., no growth changes) and reduced leaf Na⁺ accumulation with increasing concentrations of NaCl.     

Environmental variables and their interaction effects on chlorophyll-a in coastal waters of the southern Caspian Sea: assessment by multiple regression grey models

Main and interaction effects of environmental parameters on variations of chlorophyll-a along the coast of the southern Caspian Sea were determined. Parameters such as temperature, conductivity, turbidity salinity, dissolved oxygen (DO), pH, chlorophyll-a and nutrients were evaluated monthly in four transects and different depths (0, 5, 10, 20, 35 and 50 m), using multiple regression and grey relational analysis. Additionally, the long-term data (1994–2009) on the seasonal phytoplanktonic variation were included in our discussion. There was a good agreement between the observed and predicted values in the models that included the interaction effects during spring, summer, autumn and winter, with the adjusted R ² of 0.64, 0.63, 0.60 and 0.54, respectively. Temperature and its interactions were found to be the most important factor on chlorophyll-a throughout the year. Overall, the most effective factors were seasonally categorized as: organic phosphorus, ammonium and their interactions (spring); organic phosphorus, nitrate, DO, silica and their interactions (summer); organic phosphorus, pH, DO and their interactions (autumn); pH, ammonium, DO and their interactions (winter). Thermocline, riverine transport, nitrification and the presence of Mnemiopsis leidyi and Cyanophyta were found to be the most important phenomena affecting the dynamics of nutrients and phytoplanktonic biomass in the area. In the distribution of chlorophyll-a, the interaction effects of different environmental parameters proved to be more important than their individual effects. The multiple regression and grey analyses were also found to be useful tools to understand the interactions between phytoplankton and environmental factors.