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1

Salt-imposed restrictions on the uptake of macroelements by roots of Arabidopsis thaliana

100%
Attia H., Karray N., Rabhi M., Lachaal M.
Acta Physiologiae Plantarum
|
2008
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tom 30
|
nr 5
The aim of this investigation was to identify the growth limiting factors in Arabidopsis thaliana subjected to a mild salt stress. Two natural accessions (Col and N1438) were compared. In spite of their morphological and developmental similarity, they have been previously shown to differ in the response of their superoxide dismutase genes to salt stress (Physiol Plant 132:293–305, 2008). Thirty-day-old seedlings were grown for 15 days using a split-root configuration in which the root system was divided into two equal parts: the first was immersed in a complete nutrient solution with 50 mM NaCl added, while the second part was immersed in either complete or incomplete K-, Ca-, or N-free medium. Using this approach, we demonstrated that K+ and Ca2+ uptake was impaired in the roots subjected to NaCl. There was no indication of the salt-induced inhibition of N uptake. If K+ or Ca2+ were available from salt-free medium, plants were able to grow at normal rate and accumulate large amounts of Na+ in the shoots. These results indicate that the sensitivity of Arabidopsis growth to mild salinity was probably due to an inhibition of K+ or Ca2+ root transport by salt rather than due to salt accumulation in shoots. Furthermore, the salt sensitivity of ion transport in roots seemed to depend on the genotype, since K+ was limiting for Col growth, in contrast to N1438, the growth of which was limited by Ca2+.
2

Sodium transport in basil

88%
Attia H., Karray N., Ellili A., Msilini N., Lachaal M.
Acta Physiologiae Plantarum
|
2009
|
tom 31
|
nr 5
In order to diversify the production of plants with pharmacological interest, it is important to understand the mechanisms involved in their tolerance to environmental constraints, such as salinity. Basil (Ocimum basilicum), known for its therapeutic uses, has been claimed to be salt tolerant, but physiological aspects of this behavior remain unknown. Since salt tolerance is known to be associated with several characteristics concerning Na⁺ transport to leaves, we studied this function in hydroponically grown basil. We analyzed the response of 30-day-old seedlings to 25–50 mM NaCl applied for 15 days. Growth was poorly affected, indicating that these concentrations corresponded to the tolerated salinity range. Leaves accumulated Na⁺ at relatively high concentration, without dehydrating. Potassium concentration in leaf tissues was maintained close to control level, indicating that K⁺ was 15- to 25-fold preferred over Na⁺ for ion transport and deposition. Collection of xylem sap on detopped plants revealed that this preference was only 10-fold for ion introduction into root xylem sap. Short-term (24 h) changes in Na⁺ distribution between organs after stem (steam) girdling suggested that Na⁺ downward recirculation by phloem occurred. Although modest, this transport might have augmented K⁺ selectivity of ion deposition in leaves.
3

Physiological and antioxidant responses of Mentha pulegium (Pennyroyal) to salt stress

76%
Oueslati S., Karray-Bouraoui N., Attia H., Rabhi M., Ksouri R., Lachaal M.
Acta Physiologiae Plantarum
|
2010
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tom 32
|
nr 2
Mentha pulegium L. is a medicinal and aromatic plant belonging to the Labiatae family present in the humid to the arid bioclimatic regions of Tunisia. We studied the effect of different salt concentrations on plant growth, mineral composition and antioxidant responses. Physiological and biochemical parameters were assessed in the plant organs after 2 weeks of salt treatment with 25, 50, 75 and 100 mM NaCl. Results showed that, growth was reduced even by 25 mM, and salt effect was more pronounced in shoots (leaves and stems) than in roots. This growth decrease was accompanied by a restriction in tissue hydration and K⁺ uptake, as well as an increase in Na⁺ levels in all organs. Considering the response of antioxidant enzymes to salt, leaves and roots reacted differently to saline conditions. Leaf and root guaiacol peroxidase activity showed an increase by different concentration of NaCl, but superoxide dismutase activity in the same organs showed a slight modification in NaCl-treated leaves and roots. Moreover, polyphenol contents and antioxidant activity were analysed in M. pulegium leaves and roots under salt constraint. The analysis showed an increase of total polyphenol content (2.41–8.17 mg gallic acid equivalent g⁻¹ dry weight) in leaves. However, methanol extract of leaves at 100 mM NaCl displayed the highest DPPH scavenging ability with the lowest IC₅₀ value (0.27 µg ml⁻¹) in comparison with control which exhibited IC₅₀ equal to 0.79 µg ml⁻¹ .
4

Responses of Arabidopsis thaliana to bicarbonate-induced iron deficiency

76%
Msilini N., Attia H., Bouraoui N., M'rah S., Kosouri R., Lachaal M., Ouerghi Z.
Acta Physiologiae Plantarum
|
2009
|
tom 31
|
nr 4
Morpho-physiological and biochemical responses of Arabidopsis thaliana (accession N1438) to bicarbonate-induced iron deficiency were investigated. Plants were grown in cabinet under controlled conditions, in a nutrient solution containing 5 µM Fe, added or not with 10 mM NaHCO₃. After 30 days, bicarbonate-treated plants displayed significantly lower biomass, leaf number and leaf surface area as compared to control plants, and slight yellowing of their younger leaves was observed. Potassium (K⁺) content was not modified by bicarbonate treatment in roots, whereas it was significantly diminished in shoots. Their content in ferrous iron (Fe²⁺) and in leaf total chlorophylls was noticeably lower than in control plants. Root Fe(III)-chelate reductase and phosphoenolpyruvate carboxylase (PEPC) activities were significantly enhanced, but leaf ribulose 1.5-bisphosphate carboxylase (Rubisco) activity was decreased.
5

Analysis of salinity effects on basil leaf surface area, photosynthetic activity, and growth

76%
Attia H., Ouhibi C., Ellili A., Msilini N., Bouzaien G., Karray N., Lachaal M.
Acta Physiologiae Plantarum
|
2011
|
tom 33
|
nr 3
Basil (Ocimum basilicum L.) seedlings were cultured on liquid medium in controlled conditions. Two varieties differing in leaf size were compared. When plants were 30 days old, the medium was supplemented with 50 mM NaCl. After 15 days of treatment, root, stemand leaf biomass, leaf number, and leaf surface area were measured. Ion accumulation was determined in roots, stems, and leaves. Photosynthetic parameters (CO₂ fixation rate, internal CO₂ concentration, stomatal conductance) as well as transpiration rate were determined on separate leaves. Electrolyte leakage and malondialdehyde content were used to estimate damage to membranes and lipid peroxidation, respectively. Several antioxidant enzymatic activities were used as proxies of oxidative stress. High Na⁺ concentration was reached in leaf tissues. Salt restricted whole plant biomass deposition rate by diminishing leaf number and leaf expansion, as well as photosynthetic activity were estimated from whole plant biomass production per unit leaf surface area. Diminished stomatal conductance restricted CO₂ fixation rate, and decrease in chlorophyll content presumably limited photosynthetic activity. Lipid peroxidation revealed damages to membranes. The magnitude of these responses differed between the two varieties, indicating that an intraspecific variability in salt response exists in basil.
6

Effect of salt stress on growth, fatty acids and essential oils in safflower (Carthamus tinctorius L.)

76%
Harrathi J., Hosni K., Karray-Bouraoui N., Attia H., Marzouk B., Magne C., Lachaal M.
Acta Physiologiae Plantarum
|
2012
|
tom 34
|
nr 1
This study examined the influence of salt treatment on the growth parameters (fresh and dry weights), the mineral content (K⁺ and Na⁺), total lipid contents, fatty acid composition, yields and chemical composition of the essential oil of safflower (Carthamus tinctorius L.) grown in hydroponics for 2 weeks. Results showed that the application of 50 mM NaCl reduced the fresh weight of aerial parts (shoots and leaves) while it enhanced those of the roots. The reduction of dry weight was found to be more pronounced in the aerial parts. Salt treatment increased markedly the concentrations of Na⁺ in both plant parts while it reduced those of K⁺ which resulted in a sharp reduction of K⁺/Na⁺ ratio. In response to salt treatment, total lipids contents decreased in both plant parts and great qualitative changes in the fatty acids profiles were observed. Whatever the plant parts analysed, a redirection of the lipidic metabolism towards synthesis of unsaturated fatty acids as revealed by the increase of double bond index and linoleic desaturation ratio was pointed out. The increased unsaturation index was found to be more important in roots than in aerial parts. Such treatment also reduced the essential oil yields and induced marked quantitative changes in the chemical composition of the essential oils from both plant parts. Of all the identified components, oxygenated components display a prominent salt-induced synthesis and/or accumulation in both roots and aerial parts.
7

Different antioxidant responses to salt stress in two different provenances of Carthamus tinctorius L.

64%
Karray-Bouraoui N., Harbaoui F., Rabhi M., Jallali I., Ksouri R., Attia H., Msilini N., Lachaal M.
Acta Physiologiae Plantarum
|
2011
|
tom 33
|
nr 4
Seedlings of two Tunisian Carthamus tinctorius L. provenances (Kairouan and Tazarka) differing in salt sensitivity were hydroponically grown at 0 and 50 mM NaCl over 21 days. Leaves of Kairouan (saltsensitive) showed a 48% restriction in their growth at 50 mM NaCl although they accumulated less sodium than those of Tazarka (less salt-sensitive) that maintained an unchanged growth. Salt treatment induced oxidative stress in C. tinctorius and the effect was more pronounced in the leaves of the more salt sensitive provenance, Kairouan. Both provenances exhibited a stimulation of antioxidant enzyme activities with higher catalase (CAT) and superoxide dismutase (SOD) activities in Tazarka and higher peroxidase (POD) activity in Kairouan. But, it seems that antioxidant activities were more correlated with polyphenol content. Actually, leaves of Tazarka experienced higher polyphenol and antioxidant activity than Kairouan at 50 mM NaCl. Hence, moderate salinity (3 g NaCl L⁻¹) enhanced bioactive molecule yield in the less salt sensitive provenance, Tazarka. In addition, C. tinctorius was found rich in ascorbic acid, but the moderate salt stress enhanced its production only in the sensitive provenance.
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