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The present study was performed to characterize the interaction between nitrogen (N) form and availability with respect to growth, water relations, and mineral nutrition of wild swiss chard (Beta macrocarpa Guss). Plants were cultured hydroponically with two levels of N concentrations, high-N (2.5 mM) or low-N (0.5 mM), added as nitrate (NO-3) or ammonium (NH+4). At high N, growth was affected significantly by N form. If the NO-3 medium was considered as control, the use of NH+4 decreased dry matter production and leaf area by ca. 35%. Use of NH+4 led to water economy and did not affect the nutrient content of the plant tissues. Compared to growth with high N, plants growth fell in either low- NO-3 or low- NH+4 medium. In this case, the difference between the two N sources was not significant. Our results showed that the replacement of NO-3 by NH+4 as the N source decreased the NO-3 concentration in consumable leaves and increased the water use efficiency. [ABSTRACT FROM AUTHOR]

The present work was aimed at determining the limits of tolerance to sodium chloride (NaCl) of a halophyte, Beta macrocarpa Guss (wild Swiss chard). Five week-old plants were cultivated with a nutritive solution to which was added 0, 100, 200, and 300 mM NaC1. Plants were harvested after four weeks of treatment. The growth (fresh and dry weight, leaf surface area, and leaf number), water contents, and the mineral composition (meq. g-1 DW) of roots and leaves (reduced nitrogen (N), K-+, Ca2+, Na+, Cl-) were determined on individual plants. Results show that Beta inacrocarpa can tolerate up to 200 mM NaCI. A significant decrease in biomass production (to 50% of control) was observed only for 300 mM NaCI. In the latter treatment, leaf mean surface area was 25% of control. The shoot-to-root ratio was not changed. Leaf hydration was not modified by salt treatment. This ability of the plant to maintain the hydric equilibrium of its leaves seemed associated with an efficient intracellular compartmentalization of Na+ and Cl- ions. Salt treatment had little effect on N content (80% of control), but decreased significantly K+ and Ca2+ contents. These three essential elements could be limiting for growth of leaves and roots of plants challenged by NaCI. [ABSTRACT FROM AUTHOR]

For this study, the diversity of some effects of salinity on rosette growth, seed production, and seed viability in Arabidopsis thaliana was explored. Plants from 5 accessions (“ecotypes”) were grown on a sand-peat mixture irrigated with nutritive medium. At the emergence of inflorescence axis, 35 mM NaCl was added to the solution. Several morphological parameters of the rosette were measured at the beginning of silique opening, irrigation was interrupted and the substrate was allowed to dry. The siliques and the mature seeds were harvested, and assayed for K+, Na+ and Cl−. Seeds were sown on pure water and germination kinetics were determined. There was a large inter-ecotype variability of the effect of salt on the rosette growth and on all factors contribution to reproduction (number of inflorescence axes, number of flower per axis, flower fertility, and seed viability). Among the five ecotypes, those with highest levels of Na+ and Cl− in the silique valves produced the less viable seeds. This comparison, (i) suggests that salt accumulation in the former organs has detrimental effect on seed maturation, and (ii) indicates that there is a natural variability for control of ion transport to fruits in A. thaliana. [ABSTRACT FROM AUTHOR]

In saline media, the building of high concentration of Na+ and Cl- in plant leaves may be delayed by rapid growth. This dilution effect may improve the salt tolerance of plant by increasing the time necessary for ion accumulation to reach toxic levels. This could permit new leaves to be produced faster than elimination of older leaves by excess salt accumulation. The present study is aimed at studying this hypothesis on lentil (Lens culinaris L.). Various mild environmental constraints have been used to restrict growth rate, and the effect on salt sensitivity was evaluated. Three week-old plants were cultivated for 4 or 8 weeks on medium supplemented with 10 or 36 mM NaCl and submitted to one of three environmental conditions aimed to limit growth: low illumination, high temperature, and competition (high planting density). Whole plant dry weights were used to estimate mean relative growth rates (RGR). Increasing NaCl concentration from 10 mM to 36 mM reduced RGR more severely under limited light, or at high temperature, or at high planting density. In the presence of 36 mM NaCl, this increased sensitivity of growth was concomitant with Na+ accumulation in leaves, leaf withering and leaf necrosis. In the case of the high temperature treatment, the increase in Na+ concentration in the leaves was clearly attributable to reduction of growth rate, since Na+ amounts imported into the leaves were independent of temperature. These results support the hypothesis that glycophyte plants growing slowly are more sensitive to salt than those growing rapidly. This behavior contrast with that of halophytes, for which slow growth rate can be of advantage to overcome salt stress. [ABSTRACT FROM AUTHOR]

The variability of the sensitivity to sodium chloride (NaCl) in relation with leaf ionic content has been explored in Arabidopsis thaliana. Seedlings of eight ecotypes (WS, COL, LER, NOK0, NOK1, NOK2, NW40, and N273) were grown on a peat substrate mixed or not with 50 mM NaCl. The effect of NaCl treatment on rosette leaf dry weight after 18 days (vegetative stage) was used to establish a scale of sensitivity to salt, where COL was the most sensitive ecotype and NOK2 the more tolerant one. The tolerance to NaCl was associated to a better growth of plants, responsible for a dilution of Na+ in leaf tissues, and to a better supply of K+ to leaves. These two characteristics were responsible for maintenance of a high K/Na ratio in leaves of to the most tolerant ecotypes (NOK1, NOK2), as compared to the other ones. Responses of leaf peroxidase activity to a five-day treatment with NaCl in light and darkness conditions suggest that oxidative status is changed only in the sensitive ecotypes. [ABSTRACT FROM AUTHOR]

The agriculture industry is frequently affected by various abiotic stresses limiting plant productivity. To decrease the negative effect of salinity and improve growth performance, some strategies have been used, such as exogenous application of plant growth regulators (i.e. gibberellic acid, GA 3 ), or arbuscular mycorrhizal fungi (AMF) inoculation. To gain insights about the cross-talk effect of exogenous GA 3 application and AMF inoculation on growth under salinity conditions, tomato plants ( Solanum lycopersicum, cv. TT-115) were inoculated or not with the AMF Rhizophagus irregularis and exposed to different treatments during two weeks: 0 M GA 3 + 0 mM NaCl, 10 −6 M GA 3 + 0 mM NaCl, 0 M GA 3 + 100 mM NaCl and 10 −6 M GA 3 + 100 mM NaCl. Results have revealed that AMF inoculation or GA 3 application alone, but especially their interaction, resulted in growth improvement under salinity conditions. The growth improvement observed in AMF-inoculated tomato plants under salinity conditions was mainly associated to ionic factors (higher K concentration and K/Na ratio) while the alleviating effect of GA 3 application and its interaction with AMF appear to be due to changes in the hormonal balance. Foliar GA 3 application was found to increase the active gibberellins (GAs), resulting in a positive correlation between GA 3 and the growth-related parameters. Furthermore, cytokinins, indoleacetic acid and abscisic acid concentrations increased in AMF inoculated or GA 3 treated plants but, notably, in AMF plants treated with GA 3 , which showed improved growth under salinity conditions. This suggests that there is an interactive positive effect between GAs and AMF which alleviates growth impairment under salinity conditions by modifying the hormonal balance of the plant. [ABSTRACT FROM AUTHOR]

Simple Summary: Potassium deficiency is a constraint that causes numerous dysfunctions at the plant level, notably a reduction in leaf growth, photosynthesis and production. Among the multiple physiological disturbances induced by potassium deficiency, some are manifested very early and others only when the deficiency is severe. Therefore, we studied the effect of insufficient potassium supply on physiological, biochemical and anatomical parameters in basil, Ocimum basilicum. Results revealed a decrease in root and leaf biomass production in K+-deficient plants in association with an inhibition of root elongation and a reduction in leaf expansion. Similarly, a decrease in photosynthetic pigments and variability in the response of phenolic compounds content was recorded, depending on the organ and the K+ concentration in the medium. Analysis of the anatomical structure of stems showed that exposure to potassium deficiency in basil decreased the diameter of these organs and the amount of lignin produced. The aim of this study was to investigate the effect of a variable supply of potassium to culture medium on physiological and anatomical parameters (histological sections at the third internode) in basil, Ocimum basilicum. Thirty-four-day-old plants grown on basic nutrient medium were divided into four batches and grown on media with varying doses of potassium: 0.375 mM, 0.250 mM, 0.125 mM and 0 mM K+. After 64 days of culture, a final harvest was performed. The results showed that root and shoot growth in basil was decreased with decreased K+ concentration. This restriction was associated with a reduction in root elongation and leaf expansion, which was coupled with a decrease in chlorophyll and carotenoid contents. The estimation of electrolyte leakage reveals that this parameter was increased by potassium deficiency. With respect to total polyphenol and flavonoid contents, only the third leaf-stage extracts exhibited a decrease under low-K+ conditions. However, variability in response of phenolic compounds was recorded depending on the organ and the K+ concentration in the medium. Stem cross sections of potassium-deficient basil plants revealed a decrease in the diameter of these organs, which can be attributed to a restriction of the extent of different tissue territories (cortex and medulla), as well as by a reduction in cell size. These effects were associated with a decrease in the number of conducting vessels and an increase in the number of woody fibers. [ABSTRACT FROM AUTHOR]

Abstract: Arabidopsis thaliana plants (Col, Columbia, and N1438) were grown for 15 d under two light regimes providing different growth rates. The medium contained 0–85mM NaCl. Shoot biomass and ion accumulation were measured. Superoxide dismutase (SOD) activity was assayed on gels, and the expression of six SOD genes was studied using real-time PCR. Mean growth rate was increased in high light (HL) regime as compared to low light (LL) regime. Parallely, most of SOD genes were overexpressed in Col and underexpressed in N1438 in response to HL. At 50mM NaCl, plant growth was inhibited and a complex pattern of SOD gene expression was recorded. These responses varied according to the light regime, and differed between the accessions. This pattern, including the differences between the accessions, could be interpreted as a consequence of interaction between light and salt, hypothesizing that oxidative stress occurred when light energy input exceeded energy utilization when salt inhibited growth, and that oxidative stress induced overexpression of some SOD genes. Salt-induced excess Na+ accumulation in leaves and limitation of K+ provision to these organs might also participate in eliciting SOD genes’ response. Variability was observed between the two accessions for all these traits. [Copyright &y& Elsevier]

Highlights • CaCl 2 induced osmotic, nutritional, and toxic effects in C. tinctorius plants. • Root Mg uptake efficiency was maintained constant in all treatments. • The uptake selectivity of Mg over Ca substantially increased under CaCl 2 stress. • Mg use efficiency for chlorophyll synthesis was noticeably enhanced under CaCl 2 stress. • CaCl 2 salinity was the dominant stress that oriented plant physiological responses. Abstract CaCl 2 effects on growth, photosynthesis, and Mg nutrition were investigated in safflower ( Carthamus tinctorius L.) plants at low and optimal Mg availability. After seed germination on sand, obtained seedlings were grown under greenhouse conditions and subjected to 3 treatments for 4 weeks: control ( C: 1.5 mM Mg), CaCl 2 salinity ( S: 40 mM CaCl 2 ), and combined effects of CaCl 2 salinity and Mg deficiency ( DS: 0.1 mM Mg and 40 mM CaCl 2 ). The application of 40 mM CaCl 2 severely affected root, stem, young leaf, and old leaf growth. This was due to a combination of the three types of effects (osmotic, toxic, and nutritional). Indeed, in response to CaCl 2 presence under both Mg-sufficient and deficient conditions, photosynthetic activity was reduced by stomatal closure to prevent cell dehydration. As a consequence, plant water status was not severely affected in S treatment and this osmotic effect disappeared under Mg-deficient conditions (DS treatment). Membrane integrity was slightly impaired in both S and DS treatments. Mg and Ca imbalances were also detected although plants exhibited adaptive responses to cope with Mg deficiency coupled or not with excessive Ca accumulation. Treated plants substantially increased Mg/Ca uptake selectivity, which allowed them to maintain Mg uptake efficiency unaffected. They also markedly increased their Mg use efficiency for chlorophyll synthesis. Nevertheless, amongst the three salt effects, nutritional imbalances seem to be the most harmful component. As a whole, the responses of the plant to the combined effects of CaCl 2 application and Mg deficiency were dominated by salinity stress responses. [ABSTRACT FROM AUTHOR]

In polluted protected areas, using phytoremediation raises the question of the choice of the plant species to select. As an example, Atriplex halimus has been identified as a proliferative plant species that needs to be eradicated in the Calanques National Park (PNCal). Since it has been proven that the spontaneous populations of this plant species could phytostabilize shore waste deposits generated by past industrial activities within the PNCal territory, its status seems controversial, presenting a dilemma between biodiversity management of a protected area and ecological solutions for pollution management. To address this issue, we assessed the ability of A. halimus to grow on different soils from this territory, in order to estimate the potential invasiveness of this plant in this territory. Petri dish germinations and pot-growth experiments showed 50% germination of seeds collected on local individuals from the most polluted PNCal soil and 20% growth reduction of seedlings. Soil analysis showed that limitation of growth was caused by high pH value and sparsely available micronutrients as well as metal and metalloid contamination. Our results suggested that local populations of A. halimus may stabilize the highly metal and metalloid polluted salt-affected soils of the PNCal, with low seed germination potential lowering the eventuality of a propagation over the PNCal territory. As a consequence of this study, the administration of the PNCal decided not to remove A. halimus populations along the polluted coastline until another solution to prevent pollution dispersal had been found. This laboratory approach may be extended to other similar situations where plant species may be evaluated not only in term of phytoremediation potential but also in term of biodiversity preservation. [ABSTRACT FROM AUTHOR]

Aims: We tested here the effect of low nitrogen (N) availability and of UV-C radiations (a physical agent) on the susceptibility of Lactuca sativa L. towards Botrytis cinerea ( BC 87) and Sclerotinia minor ( SM). Methods: We assessed first that a dose of UV-C radiation of 0.85 kJ. m is effective in triggering a positive effect without entailing any negative effect on plants. We then tested the effect of this dose on 62-day-old lettuce plants grown at three N concentrations: 2 (low), 10 (normal) and 20 mM (high). Plants were inoculated 24 h after exposure to UV-C radiation and monitored for 4 days. Results: Analysis of lesion areas showed that leaf susceptibility towards Botrytis cinerea ( BC 87) and Sclerotinia minor ( SM) substantially increased with the increasing N concentrations. Results also showed that the UV-C treatment can reduce MDA and HO concentrations and lesion areas. Reduction of lesion areas reached 67 % on day 4 in the Sclerotinia minor ( SM)-10 mM N trial and 52 % in the Botrytis cinerea ( BC 87)-20 mM N trial. The UV-C treatment also resulted in an increase in the concentration of total phenolics in leaves which could be observed on days 1, 2 and 4 in Sclerotinia minor SM trial and days 1 and 2 in Botrytis cinerea BC 87 trial. Conclusions: Taken together, our observations suggest that UV-C irradiation stimulate the capacity of lettuce plants to resist against Sclerotinia minor (SM) and Botrytis cinerea (BC 87) and that phenolic compounds may be involved in this resistance. [ABSTRACT FROM AUTHOR]

The aim of this research was to examine the effect of UV-C on resistance of lettuce to Botrytis cinerea and Sclerotinia minor. Analysis of the lesion surfaces showed that plants exposed to UV-C were less susceptible to the two pathogens, especially on the fourth day after inoculation. Chlorophyll, carotenoid contents and malondialdehyde and hydrogen peroxide were assayed after 1 day and 4 days. Lettuces treated with UV-C and inoculated showed an increase in chlorophyll and carotenoid content, especially 24 h after inoculation, and low values of the two indicators of oxidative stress as compared with lettuces which were inoculated but did not receive UV-C treatment. [ABSTRACT FROM AUTHOR]

Several studies have used A. thaliana as a model to identify the physiological and molecular mechanisms underlying iron deficiency tolerance in plants. Here, Arabidopsis thaliana and Thellungiella salsuginea were used to investigate the differential responses to iron deficiency of these two species. Plants were cultivated in hydroponic medium containing 5 or 0 µM Fe, for 10 days. Results showed that rosette biomass was more reduced in T. salsuginea than in A. thaliana when grown on Fe-deficient medium. As a marker for iron deficiency tolerance, the induction of ferric chelate reductase (FCR) and phosphoenolpyruvate carboxylase (PEPC) activities was observed only in A. thaliana roots. In addition, we found that the accumulation of phenolic acids in roots of N1438 ecotype of A. thaliana was stimulated by Fe deficiency. Furthermore, an increase of flavonoids content in the root and exudates was observed under Fe-deficiency in this ecotype. Unlike other abiotic stresses, it appears that iron deficiency effects were more pronounced in Thellungiella than in Arabidopsis. The higher tolerance of the Arabidopsis plant to iron deficiency may be due to the metabolic changes occurring in the roots. [ABSTRACT FROM AUTHOR]

Abstract: The changes observed photosystem I activity of lettuce plants exposed to iron deficiency were investigated. Photooxidation/reduction kinetics of P700 monitored as ΔA 820 in the presence and absence of electron transport inhibitors and acceptors demonstrated that deprivation in iron decreased the population of active photo-oxidizable P700. In the complete absence of iron, the addition of plant inhibitors (DCMU and MV) could not recover the full PSI activity owing to the abolition of a part of P700 centers. In leaves with total iron deprivation (0μM Fe), only 15% of photo-oxidizable P700 remained. In addition, iron deficiency appeared to affect the pool size of NADP+ as shown by the decline in the magnitude of the first phase of the photooxidation kinetics of P700 by FR-light. Concomitantly, chlorophyll content gradually declined with the iron concentration added to culture medium. In addition, pronounced changes were found in chlorophyll fluorescence spectra. Also, the global fluorescence intensity was affected. The above changes led to an increased rate of cyclic electron transport around PSI mainly supported by stromal reductants. [Copyright &y& Elsevier]

The volatile compounds emitted by living leaves of basil ( Ocimum basilicum L. cv. Genovese) plants under saline conditions were investigated by means of headspace-solid phase microextraction (HS-SPME) and gas chromatography coupled with mass spectrometry (GC-MS). Furthermore, the composition of the essential oil obtained by hydrodistillation of the leaves was studied. Plants were grown for 15 d without salt or with an equimolar concentration of Na+ in the form of Na2SO4 (25 mM) and NaCl (50 mM), after which the growth, the essential oil, and the volatile constituents of the leaves were determined. Fifty-four components were identified belonging to different chemical classes. Under control conditions, the essential oil was rich in linalool (45.9%), 1,8-cineole (16.7%), eugenol (10.3%), trans-α-bergamotene, and epi-α-cadinol (4.9%). The main volatiles detected in the headspace of leaves of untreated basil plants were linalool (29.8%), followed by 1,8-cineole (19.2%), trans-α-bergamotene (10.0%), and eugenol (7.0%). Under saline conditions, leaf growth was more depressed by 25 mM Na2SO4 than 50 mM NaCl, and essential oil concentration increased by 22% in the NaCl, but decreased by 18% in the Na2SO4 treatment, respectively. Both salts caused some changes in the essential oil and composition of volatile compounds. Most prominent was a strong negative correlation between eugenol and methyleugenol proportions, which may indicate an enhancement of the O-methyltransferase activity. In comparison to the essential oil, the composition of volatiles showed some variations in their emission profile under both salts, the most important was an increase of eugenol. It is therefore concluded that the decrease of eugenol occurring in basil essential oil caused by both salts could be due to the enhancement of the eugenol O-methyltransferase activity, an enzyme that accepts eugenol as substrate, generating methyl eugenol, and also to the increase of the eugenol emission as shown by the SPME profile. [ABSTRACT FROM AUTHOR]

BACKGROUND Fe deficiency affects food growth and quality in calcareous soils. In this study, the effect of Fe deficiency on growth parameters, phenolic content and antioxidant capacities of two lettuce shoots varieties (Romaine and Vista) were investigated. RESULTS Fresh matter production, pigment (chlorophyll and carotenoid) and Fe2+ content were significantly reduced by Fe deficiency in both varieties. However, restriction of these parameters was particularly pronounced in Romaine variety as compared to Vista. Moreover, Fe deficiency caused decreases in the activity of antioxidant enzymes such as catalase and guaiacol peroxidase, whereas ascorbate peroxidase and malondialdehyde concentrations were not significantly affected. On the other hand, Fe deficiency in Vista variety induced an increase in polyphenol and flavonoid content as compared to Romaine variety. In addition, total antioxidant capacity and antiradical test against DPPH radical decreased in leaves of Romaine variety after 15 days of treatment. CONCLUSION These results suggest that the higher polyphenol content in Vista variety supports the involvement of these components in the stability of antioxidant capacities and then in its protection against oxidative damage generated by Fe deficiency in lettuce plants. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Diplotaxis species are edible and medicinal plants. This study investigates phenolic contents and biological activities in stems, leaves, and flowers of Diplotaxis harra and Diplotaxis simplex. Flowers exhibited the highest polyphenol content and D. harra was significantly more phenol-rich than D. simplex. Similarly, the highest antioxidant activities were found in D. harra flowers. Fractionation of D. harra extract revealed that 60% MeOH fraction showed the best antioxidant activities. Indeed, flower fractions were assayed for their activity against human pathogenic bacteria and the inhibitory percentages reached 100%. As regards fraction polarity, 60% and 80% MeOH fractions were the most active ones. Moreover, HPLC analysis showed that the main phenolic compound was cafeic acid for the two species, whereas p-Coumaric and 3,4-dimethoxybenzoic acids were identified only in D. simplex and sinapic acid was exclusive to D. harra. Overall, our findings indicate that Diplotaxis flowers could be used as a potent source of natural antioxidants and antibiotics. [Copyright &y& Elsevier]

Abstract: BACKGROUND: Two varieties of Origanum majorana (Canadian and Tunisian) were evaluated for their phenolic, flavonoid and tannin contents, individual phenolic compounds and antioxidant activities under NaCl constraint. RESULTS: The results showed a significant variability in phenolic composition and antioxidant behavior between the two varieties under salt stress. The phenolic composition of methanolic extracts was determined by reversed‐phase high‐performance liquid chromatography. Amentoflavone was the predominant flavonoid compound; in addition, trans‐2‐hydrocinnamic acid became the major phenolic acid with salt treatment of the Tunisian variety. In the control, Canadian variety extract was characterized by high levels of gallic acid and amentoflavone. However, under 75 mmol L−1 NaCl, gallic acid content doubled, whereas amentoflavone content was maintained in the Canadian variety. Stimulation of phenolic acid biosynthesis was observed in these two varieties under salt treatment despite the fact that shoots of the Tunisian variety showed higher antioxidant activities compared to those from the Canadian variety. Tunisian O. majorana might have developed tolerance to salinity and avoided tissue damage by activating enzymes involved in the galactosylation of quercetin into quercetin‐3‐galactoside and quercetin‐3‐rhamnoside. CONCLUSION: Our results confirmed the tolerance of Tunisian O. majorana plants. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Seeds of lettuce, variety Romaine were subjected to different priming treatments such as water, potassium nitrate (KNO3) and gibberellic acid (GA3). Seedlings obtained from primed (Pr) and nonprimed (NP) seeds were grown in a hydroponic culture system supplemented with 0, 100 or 200 mM sodium chloride (NaCl). The different physiological and biochemical responses were studied 15 days after treatment. Under NaCl, the dry weight was higher in plants derived from hydro-primed (HP) seeds when compared to NP, osmoprimed (KNO3P), and hormonal primed (GA3P) ones. Under control and 100 mM NaCl treatment, malondialdehyde (MDA) content and EL did not show any correlation with activities of gaiacol peroxidase (GPX) and catalase (CAT), but did with the increase in reduced ascorbate (AsA) and total ascorbate contents. The results indicated that plants derived from HP seeds exhibited higher adaptive potential under salinity stress. Our findings suggest that a hydropriming technique can be used as a simple commercial approach to alleviate the effects of NaCl induced stress in lettuce plants. [ABSTRACT FROM PUBLISHER]

In this study, we report on the relationship between individual antioxidant carotenoids, phenolic fractions, and flavonoids and attenuating NaCl toxicity in two contrasting varieties of lettuce ( Lactuca sativa L., var. Verte and Romaine), as a means of developing more precise targets for lettuce breeding. In seedling leaves, carotenoid levels increased under NaCl stress in Verte, but remained unchanged in Romaine. Chlorogenic acid (CGA), a soluble polyphenol abundantly present in leaves, was the only phenolic acid that accumulated significantly in both varieties and was predominant under salinity. Remarkably, CGA was more prominent in Verte than Romaine at moderate salinity levels (100 mM). Foliar flavonoid levels were also differentially increased in both seedling types grown under 100 mM NaCl, but dropped significantly in both varieties under 200 mM NaCl. Germination, which was overall more salt-resistant in Romaine, was significantly increased under salt stress by application of low dosage (10-6 to10-5 M) of CGA to Verte, but not to Romaine. These results suggest that CGA is involved in modulating NaCl-induced oxidative-stress responses during seed germination in Verte. [ABSTRACT FROM AUTHOR]

Abstract: Fenugreek (Trigonella foenum graecum) seedlings were exposed to increasing NaCl concentrations in the growth medium to examine the effect of salt stress on the electron transport reactions of photosynthesis. Activities of both photosystem II (PSII), measured by chlorophyll fluorescence, and photosystem I (PSI), measured by P700 photooxidation, were decreased by salt stress. The inhibition proceeded in a two step manner. At the lower salt concentrations used and shorter exposition periods, electron transfer between the quinone acceptors of PSII, Q A and Q B, was strongly retarded as shown by an increased amplitude of the OJ phase of the OJIP chlorophyll fluorescence induction traces and slowed chlorophyll fluorescence relaxation kinetics following a single turn-over flash. The above indicated a disturbance of the Q B binding site likely associated with the first step of photoinhibition. In the second step, strong photoinhibition was observed as manifested by increased F 0 values, declined Fv /F 0 and loss of photoactive P700. [Copyright &y& Elsevier]

idopsis thaliana seedlings were grown in hydroponic culture under controlled conditions in mediums with different NO/NH ratios. The mediums were not buffered, against pH change, but their pH was reset at pH 5.5 each 2 days. When ammoniacal N source was predominant, the whole plant biomass deposition was diminished, parallely to several parameters which revealed degraded leaf physiological status, such as leaf chlorosis associated with diminished chlorophyll content, lowered K, Ca, and water content, along with restricted leaf expansion, and apparition of cellular stress symptoms. However, leaf functioning for biomass production did not seem affected, since biomass production rate per unit leaf surface area remained unchanged. Indeed, the main factor of decrease biomass production was leaf elimination and/or repression of leaf initiation. The results are discussed in the context of literature data on the effects of NH on ion fluxes at the root level and properties of K transport systems in Arabidopsis. Disturbance of mineral (cationic) nutrition by NH seemed to be a major cause of the detrimental effect of ammoniacal nutrition. [ABSTRACT FROM AUTHOR]

We investigated the relative contributions of the environment and development stage on total polyphenols, flavonoids and condensed tannins contents, as well as 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide scavenging activities in four Tunisian Mentha pulegium. Shoot total phenolics and antioxidant capacities were significantly dependent on environment, development stage and their interaction. Environment effects were considerably larger than development stage effects for total phenolics, flavonoids, DPPH and superoxide scavenging capacities, whereas development stage was much stronger than environment for tannin content and, although small, interaction effects of the two factors (environment and development stage) were significant for all antioxidant properties analyzed. The highestantioxidant activities were related to high phenolic contents. Three behaviors were revealed; the best antioxidant capacities in Soliman at floral bud stage, followed by Takelsa and the lowest potentialities (Bouarada and Jdeida). These findings indicate that antioxidant properties of M. pulegium were respectively influenced by environment, development stage and their interaction. PRACTICAL APPLICATION Mentha pulegium L. belonging to the Lamiaceae family, which is a highly advanced and homogeneous family, is largely used in food preparation, perfumery, pharmaceutical products and as an insect repellent. In traditional medicine, M. pulegium essential oil is used for digestive, liver and gallbladder disorders, for gout colds and increased micturition and externally for skin diseases ( Gruenwald et al. 1998 ). M. pulegium is a folkloric medicinal plant with interesting shoot antioxidant properties. According to our results, high antioxidant properties of the leaves of M. pulegium might be beneficial to the antioxidant activity. [ABSTRACT FROM AUTHOR]

Abstract: Two pea (Pisum sativum L.) cultivars were compared: cv Lincoln and cv Douce de Provence. Seedlings grown for 14d on standard medium were challenged for 21d with salt using a split-root system. This protocol allowed salt-treated plants to absorb nutrients through a part of their root system maintained in control medium (C), the other part of the root system being placed in medium added with 75mM NaCl (S). Full salt treatment (S/S) resulted in severe but non-lethal growth inhibition, high concentration of Na+ and Cl− in leaves, and decrease in leaf K+ and chlorophyll contents. The two latter effects were more pronounced in Lincoln than in D. Provence. Growth inhibition was partially (Lincoln) or totally (D. Provence) alleviated in S/C configuration, and K+ content was less diminished than in full salt treatment. S/C treatment mitigated Na+ and Cl− accumulation in Lincoln, but not in D. Provence. Thus, in the latter cultivar, growth inhibition by salt in S/S condition likely did not result from excessive Na+ and Cl− accumulation in leaves. Increased electrolyte leakage from leaf tissues evidenced damages to leaf cell plasma membrane of both cultivars in S/S condition. However, damages to chloroplasts, as inferred from chlorophyll loss, were much pronounced in Lincoln than in D. Provence. Antioxidant enzymic activities in leaves were measured as proxies for oxidative stress. Catalase activity was stimulated by S/S treatment in both cultivars, but superoxide dismutase (Fe and Cu/Zn isoforms) and gaiacol peroxidase activities were augmented only in Lincoln. The absence of superoxide dismutase activity stimulation by salt in D. Provence could signify either that constitutive activity was sufficient to ensure protection against oxidative stress, or that intrinsic salt tolerance of this cultivar mitigated cellular oxidative stress. Thus, intraspecific variability for salt response exists between pea cultivars presenting similar growth sensitivity to salt. [Copyright &y& Elsevier]

Abstract: The aim of the present work was to study salt effect on the yield and composition of shoot essential oil (EO) and the structures responsible for its biosynthesis in Mentha pulegium L. Shoot EO was extracted by hydrodistillation and composition was determined by GC–MS method. Apical and basal leaves were taken for microscopy analyses; small fresh samples were observed directly without fixation or metallisation with environmental scanning electron microscope (ESEM) and stereomicroscope (SM). Fresh separate epidermis was used for light microscopy (LM). Salt stress enhanced EO yield by about 2.75 times and affected the percentage of menthone, which is the major compound (∼51%), increasing that of pulegone. Menthone, pulegone, and neomenthol constituting the monoterpene class were found to be the principal components. The anatomical study showed three types of trichomes: (i) non-glandular, multicellular, simple hairs; (ii) small, capitate glandular trichomes; (iii) and peltate glandular trichomes. In control plants, the density and size of trichomes varied with leaf side (abaxial or adaxial) and developmental stage. Salt stress results in significant modifications affecting trichome distribution and size on both sides. [Copyright &y& Elsevier]

Abstract: Potassium-sodium interaction was compared in two natural accessions of Arabidopsis thaliana, Columbia-0 and NOK2. Seedlings were grown in the presence of 0 or 50 mM NaCl and 0.1; 0.625 or 2.5 mM K+. At the lowest K+ concentration, salt treatment inhibited both K+ uptake and growth. Increasing the K+ availability did not modified salt response in Columbia-0, but restored nearly normal net K+ uptake in NaCl condition and alleviated NaCl growth reduction in NOK2. The effect of K+ and NaCl on transcript level of several K+ and Na+ transporters in both shoots and roots was assessed using semi-quantitative RT-PCR. The mRNA abundance of the NHX1 and SOS1 Na+/H+ antiporters was significantly increased by 50 mM NaCl in the two accessions. NHX1, which is responsible for Na+ sequestration into vacuoles, was more up-regulated in NOK2 leaves than in Columbia-0''s in NaCl stress condition. AKT1, which is the major channel involved in K+ absorption, was down-regulated in salt stress condition, but was not responding to K+ treatments. Only in NOK2, SKOR and AKT2, which respectively control xylem and phloem K+ transport, were markedly up-regulated by 2.5 mM K+ in both roots and shoots, independently of NaCl. Phenotypic and gene expression analyses suggest that the relative salt tolerance of NOK2 is mainly due to a high ability to sequester Na+ in the vacuole and to take up and transport K+. Up-regulation of SKOR and AKT2 by K+, and of NHX1 by NaCl could participate in determining this phenotype. To cite this article: R. Kaddour et al., C. R. Biologies 332 (2009). [Copyright &y& Elsevier]

Arabidopsis thaliana plants (wild-type accessions Col and N1438) were submitted to a prolonged, mild salt stress using two types of protocols. These protocols allowed salt-treated plants to absorb nutrients either through a part of their root system maintained in control medium (split-rooted plants) or during episodes on control medium alternating with salt application (salt alternation experiment). Full-salt treatments (salt applied continuously to whole root system) resulted in severe (but non-lethal) growth inhibition. This effect was partly alleviated in split-rooted plants on mixed salt–control medium and in plants submitted to salt–control medium alternation. The activity of the various isoforms of superoxide dismutases (SODs) did not appreciably change with the treatments. The abundance of the mRNAs of the seven SOD genes present in Arabidopsis genome was determined using real-time polymerase chain reaction. The two protocols gave qualitatively identical results. The expression level was increased by full-salt treatments for some genes and diminished for other genes. However, the nature of these genes differed according to the accessions: the responses to salt of FSD1 and MSD were opposite in Col and N1438. In Col, salt treatments inhibited the expression of FSD1 and strongly stimulated that of CSD1 and MSD. In N1438, the stimulation by salt concerned FSD1 and CSD1 and MSD expression being inhibited. In both accessions, the expression of CSD2 and CSD3 was lowered by salt. For all genes, the treatments that mitigated stress partially restored SOD expression to control level. Thus, the changes in SOD transcript abundance accurately reflected the severity of the salt stress. [ABSTRACT FROM AUTHOR]

Summary: Nodule conductance to O2 diffusion has been involved as a major factor of the inhibition of N2 fixation by soil salinity that severely reduces the production of grain legumes. In order to determine the effect of this constraint on the nodule conductance, oxygen uptake by the nodulated roots of Cicer arietinum was measured by recording the concentration of O2 as a function of pO2 in a gas-tight incubator. After germination and inoculation with the strain Mesorhizobium ciceri UPMCa7, the varieties Amdoun 1 and INRAT 93-1 were hydroponically grown in a glasshouse on 1L glass bottles filled with nutrient solution containing 25mM NaCl. Salinity induced a marked decrease in shoot (30% versus 14%), root (43% versus 20%), and nodule biomass (100% versus 43%) for Amdoun 1 relative to INRAT 93-1. Although salinity completely prevented nodule formation in the sensitive variety Amdoun 1, nodule number and biomass were higher in the first than in the second variety in the absence of salt. This effect was associated with a significantly higher O2 uptake by nodulated root (510 versus 255μmolO2 plant−1 h−1) and nodule conductance (20 versus 5μms−1) in Amdoun 1 than in INRAT 93-1. Salinity did not significantly change the nodule conductance and nodule permeability for INRAT 93-1. Thus, the salt tolerance of this variety appears to be associated with stability in nodule conductance and the capacity to form nodules under salt constraint. [Copyright &y& Elsevier]

Abstract: Morpho-physiological responses to bicarbonate-induced Fe deficiency were investigated in five Vitis vinifera L. Tunisian varieties (Khamri, Blanc3, Arich Dressé, Beldi, and Balta4). One-month-old woody cuttings were cultivated for 85days on a free calcareous soil irrigated with tap water containing increasing bicarbonate levels (0, 4, 8, 12, and 16mM NaHCO3). After this screening, a second experiment compared root biochemical responses of two contrasting genotypes (tolerant-sensitive) dealing with bicarbonate-induced iron deprivation (20μM Fe±10mM HCO3 −) for 75days. Using morpho-physiological criteria, grapevine tolerance to HCO3 −-induced Fe shortage appeared to be genotype-dependent: Balta4 and Beldi varieties showed the highest leaf-chlorosis score (especially at the extreme HCO3 − levels), in contrast to Khamri variety. Growth parameters (shoot height, total leaf area, leaf number, and biomass production) as well as juvenile leaf chlorophyll content were also differently affected depending on both genotype and bicarbonate dose. At 16mM HCO3 −, Khamri was the less sensitive variety, contrasting with Balta4. On the other hand, chlorophyll content correlated positively with HCl-extractible Fe content of the juvenile leaves, suggesting that the grapevine response to iron deficiency may partly depend on to the plant ability to adequately supply young leaves with this element. Root biochemical responses revealed a relatively higher root acidification capacity in Khamri (tolerant) under Fe-deficiency while no significant changes occurred in Balta4 (sensitive). In addition, Fe(III)-reductase and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activities were strongly stimulated by Fe-deficiency in Khamri, while remaining constant in Balta4. These findings suggest that biochemical parameters may constitute reliable criteria for the selection of tolerant grapevine genotypes to iron chlorosis. [Copyright &y& Elsevier]

Summary: Thellungiella halophila and Arabidopsis thaliana were irrigated with medium containing NaCl at various concentrations. The salt treatment resulted in a restriction of rosette biomass deposition in both species. In A. thaliana leaves, this inhibition was stronger than for T. halophila and was associated with strong inhibition of both leaf initiation and leaf expansion. At highest medium salinity, A. thaliana accumulated Na+ and Cl − at higher levels than T. halophila, but similar leaf dehydration was observed in the two species. Proline accumulation, which increased with NaCl concentration, did not differentiate the two species. The magnitude of the electrolyte leakage and the level of lipid peroxidation (assessed through hydroxy fatty acid content) were modest in T. halophila and quite marked in A. thaliana. The detrimental effects of the salt on photosynthetic activity and stomatal conductance of A. thaliana leaves were much more important than in T. halophila leaves. The abundance of the CDSP32 thioredoxin, a critical component of the defence system against oxidative damage and lipid peroxidation, was found to be higher in T. halophila than in A. thaliana under control conditions and salt treatment. These results suggest that the rosette leaves of T. halophila exhibit more efficient protective mechanisms against Na+ metabolic toxicity than those of A. thaliana. [Copyright &y& Elsevier]

Several phenotypic markers were used in this study to determine the biodiversity of rhizobial strains nodulating Cicer arietinum L. in various areas of Tunisia. They include symbiotic traits, the use of 21 biochemical substrates, and tolerance to salinity and pH. In addition, restriction fragment length polymorphisms (RFLPs) of PCR-amplified 16S rDNA were compared with those of reference strains. Numeric analysis of the phenotypic characteristics showed that the 48 strains studied fell into three distinct groups. This heterogeneity was highly supported by the RFLP analysis of 16S rRNA genes, and two ribotypes were identified. Chickpea rhizobia isolated from Tunisian soils are both phenotypically and genetically diverse. Results showed that 40 and 8 isolates were assigned, respectively, to Mesorhizobium ciceri and Mesorhizobium mediterraneum. [ABSTRACT FROM AUTHOR]

Summary: Thellungiella halophila seedlings grown on a solid substrate for 25 days on standard medium were challenged with NaCl. Growth, tissue hydration, ion accumulation, photosynthesis, lipid peroxidation and antioxidant enzymatic activities were studied on rosette leaves. Three accessions of Arabidopsis thaliana were cultivated under the same conditions. During the first two weeks of salt treatment, the growth of T. halophila leaves was restricted by NaCl. No significant difference appeared between T. halophila and A. thaliana concerning biomass deposition, or hydric and ionic parameters. However, all A. thaliana plants displayed foliar damage, and died during the third week of salt (50mM NaCl) treatment. Almost all (94%) T. halophila plants remained alive, but did not display any sign of altered physiological condition. Tissue hydration, chlorophyll content, stomatal conductance, photosynthetic quantum yield, and photosynthetic rate were very similar to those of control plants. Lipid peroxidation, estimated from thermoluminescence, was very low and insensitive to salt treatment. Only slight changes occurred in antioxidant enzymatic activities (SOD, several peroxidases, and catalase). From the absence of physiological disorder symptoms, we infer that salt was efficiently compartmentalized in leaf vacuoles. In salt-treated A. thaliana, the photosynthetic quantum yield was diminished, and lipid peroxidation was augmented. These observations reinforce the conclusion that T. halophila could accumulate salt in its leaves without damage, in contrast to A. thaliana. [Copyright &y& Elsevier]

Biochemical responses to direct or bicarbonate-induced iron (Fe) deficiency were compared in two Tunisian native grapevine varieties, Khamri (tolerant) and Balta4 (sensitive), and a tolerant rootstock, 140Ru. Woody cuttings of each genotype were irrigated with a nutrient solution containing one of the following: 20 µM Fe (control), 1 µM Fe (direct Fe-deficiency), or 20 µM Fe + 10 mM HCO 3 - (indirect bicarbonate-induced Fe-deficiency). Under direct Fe-deficient conditions, lower leaf chlorosis score and higher chlorophyll and leaf Fe contents were found in Khamri and 140Ru compared with Balta4. Moreover, indirect Fe deficiency caused similar effects on these parameters, which were more pronounced in Balta4. Both tolerant genotypes, Khamri and 140Ru, showed higher roots-acidification capacity and phenol release under the direct Fe deficiency compared with the bicarbonate-induced condition. In the sensitive variety, Balta4, no significant changes were found between the control and Fe-deficient plants. Root Fe(III)-reductase activity was strongly stimulated by both types of Fe deficiency in Khamri and 140Ru, and displayed no significant changes in Balta4. In the three genotypes, root and leaf activities of two Fe-containing enzymes, catalase and guaiacol peroxidase, were significantly affected under Fe deficiency (either direct or induced), though to a greater extent in the sensitive variety, Balta4. The latter also displayed higher leaf malonyldialdehyde (MDA) content, traducing an important membrane lipid peroxidation. [ABSTRACT FROM AUTHOR]

Summary: Two legumes, lentil and chickpea, were cultivated in nutrient solutions: Fe lacking or containing 30μM Fe. After 12 days of Fe starvation, lentil showed a severe yellowing of young leaves, a large decrease in chlorophyll concentration, and a significant decline of plant biomass. Chickpea showed a better response than did lentil, primarily due to a stronger acidification capacity. In addition, no chlorosis symptoms were observed in chickpea until the end of treatment. There was no significant difference in potassium uptake between the two species, but an enrichment of the young leaves at the expense of the old ones was noted in chickpea, and at a lesser extent, in lentil, when they were exposed to Fe deficiency. Moreover, this constraint led to a significant decrease of iron content in the two legumes. However, chickpea displayed higher accumulation levels of HCl-extractible iron in young and old leaves than did lentil. This protection of young leaves against K+ and Fe2+ impoverishment confers to these organs the capacity to preserve their chlorophyll status and their photosynthetic integrity. Furthermore, the better performance of chickpea under conditions of low Fe availability could be partially related to its seed iron reserves, higher than those of lentil. [Copyright &y& Elsevier]