Chemical polymorphism of some North Tunisian autochthonous halophytes

The study aims to explore and analyse osmoticums synthesized by four perennial halophytic Chenopodiaceae : Salicornia arabica, Atriplex portulacoides, Atriplex halimus and Suaeda fruticosa from Menzel Jemil, Soliman and Gammarth regions which belong to sub-humid and semi-arid bioclimatic zones. A sampling of aerial vegetative organs of these four halophytes has been made. Analyses focused on reducing sugars, starch, total proteins, soluble proteins and total lipids. Atriplex portulacoides harvested from Menzel Jemil station accumulates large amounts of starch, indicating a high photosynthetic activity. This could suggest that this species avoids drought and high salinity by an acceleration of its growth cycle and reproductive systems. Suaeda fruticosa is characterized by the highest levels in soluble sugars. This would mean that it is capable of synthesizing carbohydrate osmoticums for its osmotic adjustment. Atriplex sp. and Suaeda fruticosa have the highest levels of soluble protein indicating the possible intervention of amino acids in the regulation of intracellular osmotic pressure. This behavior was essentially observed at Soliman sampling site characterized by an upper semi-arid bioclimate and saline soilsL'étude a pour objet l'exploration puis l'analyse des osmoticums synthétisés par quatre Chenopodiaceae pérennes halophytes: Salicornia arabica, Atriplex portulacoides, Atriplex halimus et Suaeda fruticosa dans les régions de Menzel Jemil, Soliman et Gammarth appartenant aux étages bioclimatiques subhumides et semi-arides. Un échantillonnage des organes végétatifs aériens de ces quatre halophytes a été effectué. Les analyses ont porté sur les sucres réducteurs, l'amidon, les protéines totales, les protéines solubles et les lipides totaux. Atriplex portulacoides, récolté à la station de Menzel Jemil, accumule d'importantes quantités d'amidon, traduisant une forte activité photosynthétique. Ceci laisse suggérer que cette espèce évite la période de sécheresse et de forte salinité par une accélération de son cycle végétatif et reproducteur. Suaeda fruticosa se caractérise par les teneurs les plus élevées en sucres solubles. Ceci signifierait qu'elle est capable de synthétiser des osmoticums glucidiques pour son ajustement osmotique en condition de stress. Atriplex sp. et Suaeda fruticosa présentent les teneurs les plus élevées en protéines solubles, traduisant probablement une intervention des acides aminés dans la régulation de la pression osmotique intracellulaire. Ces comportements ont été observés, essentiellement, au niveau du site d'échantillonnage de la région de Soliman, caractérisé par un bioclimat semi-aride supérieur et des sols salés

Effects of temperature and water stresses on germination of some varieties of chickpea (Cicer arietinum)

Chickpea production did not progress, in spite, of intensification of agricultural practices. Drought and thermal stresses were the major factors that decreased yield when the crop is generally sown in spring. Nevertheless, winter sowing has opened new opportunities for increasing chickpea production in arid areas. This culture is based on two essential factors: (i) preclude rainfall during the flowering and fruiting period (April/May) after a beneficial one in January and February for a good crop development and (ii) reducing the risk of infection by Ascochyta rabiei (considered as the main pathogen of chickpea) whose development is limited in arid area. The influence of temperature on seeds germination of the four varieties (Ghab4, Neyra, Kasseb and Chetoui) has been evaluated with seven temperatures (5, 10, 15, 20, 25, 30 and 35°C) and the effect of drought stress has been determined with seven water stresses induced by different solution of PEG 4000 (0, 1, 2, 3, 4, 5 and 10 g/L). During germination, the tested varieties presented differential sensitivity to thermal stress. The Chetoui and Ghab4 varieties were more tolerant, to cold temperature, than the other varieties. Osmotic potential induced by PEG 4000 had significant effects on seeds germination. Chetoui and Ghab4 were the best tolerant to drought stress. Therefore, we opted for the Chetoui variety that better meets the conditions of stresses induced by low temperatures and water deficit. This best performing variety must have, throughout their development cycle, been tolerant to environmental stresses; which allows us to obtain early tools for discriminative selection between chickpea genotypes.Keywords: Chickpea, thermal stress, drought stress, germinationAfrican Journal of Biotechnology Vol. 12(17), pp. 2201-220

NaCl protects against Cd and Cu-induced toxicity in the halophyte Atriplex halimus

The objective of the present work was to evaluate the extent of Cd- and Cu-induced oxidative stress and the antioxidant response triggered in the halophyte species Atriplex halimus after metallic trace elements exposure. Plants were treated for one month with Cd2+ or Cu2+ (400 μM) in the absence or presence of 200 mM NaCl in the irrigation solution. The interaction between salinity and heavy metal stress was analyzed in relation to plant growth, tissue ion contents (Na+, K+ and Mg2+), oxidative damage and antioxidative metabolism. Data indicate that shoot and root weight significantly decreased as a consequence of Cd2+- or Cu2+-induced stress. Metallic stress leads to unbalanced nutrient uptake by reducing the translocation of K+ and Mg2+ from the root to the shoot. The levels of malondialdehyde increased in root tissue when Cd, and especially Cu, were added to the irrigation solution, indicating that oxidative damage occurred. Results showed that NaCl gave a partial protection against Cd and Cu induced toxicity, although these contaminants had distinct influence on plant physiology. It can be concluded that salinity drastically modified heavy metal absorption and improved plant growth. Salinity also decreased oxidative damage, but differently in plants exposed to Cd or Cu stress.Ministerio de Economía y Competitividad, Spain (GL2013-42038-R; AGL2016-76574-R); Universitat Jaume I (P1- 1B2012-06)

Accumulation of trace elements and tolerance to metal stress of the halophytes that colonize the edges of the lagoon of Bizerte (Tunisia)

The lagoon of Bizerte underwent a mixed anthropic pollution, essentially enhanced by the unlimited industrial waste derived from Iron Factory “El Fouledh”, Industrial Refining Tunisian Company, Cement Company and from 400 industrial units established around it. This waste includes major pollutants conducive to a degradation of the ecological conditions of this lagoon. Previous research dealt with most of the different ecosystem components: soil, sediments, water, and aquatic organisms. In the present study, we have been interested in the halophytes inhabiting the edges of Bizerte lagoon. This study would allow us to identify the accumulating species to be used in the programs of phytoremediation. Shoots of Atriplex portulacoides, Arthrocnemum indicum, Salicornia arabica and Suaeda fruticosa were harvested, rinsed, dried and then crushed. Analyses were focused on few trace metals: Pb, Cu, Zn and Cd. Our results have allowed us to classify the halophytes “A. portulacoides, A. indicum, S. arabica and S. fruticosa” among the accumulating species of Pb (respectively 84.6, 92.2, 102.9 and 86.3 μg.g-1 DW), of Cu (respectively 14.5, 15.1, 24.2 and 14.9 μg.g-1 DW) and of Zn (respectively 1370.1, 625.1, 1601.4 and 772.5 μg.g-1 DW). Also, A. portulacoides and S. arabica are distinguished by their ability to store significant amounts of Zn which gives them a potential utility in the remediation programs. As regards Cd, we have shown that all studied species are hyper-accumulators of this metal (A. portulacoides: 274.0 μg.g-1 DW; A. indicum: 280.4 μg.g-1 DW; S. arabica: 211.6 μg.g-1 DW and S. fruticosa: 209.0 μg.g-1 DW). It should be noted that the harvested halophytes do not show any sign of toxicity, and they are able to accumulate more important amounts of heavy metals and to tolerate the metallic stress. These results show that the studied halophytes can be recommended for all programs of phytoremediation in polluted and salty areasLa lagune de Bizerte subit une pollution anthropique mixte engendrée essentiellement par les rejets industriels non limités provenant de l'usine sidérurgique « El Fouledh », de la société tunisienne des industries de raffinage, de la cimenterie et des 400 unités industrielles recensées autour d'elle. Ces rejets constituent des polluants majeurs conduisant à une dégradation des conditions écologiques de ce plan d'eau. Les travaux de recherche antérieurs ont touché à la plupart des composantes de cet écosystème: sol, sédiments, eau, organismes aquatiques. Dans le présent travail, nous nous sommes intéressés à l'étude des halophytes peuplant les bordures de la lagune de Bizerte. Cette étude permettrait d'identifier les espèces accumulatrices en vue de les utiliser dans les programmes de phytoremédiation. Les parties aériennes d'Atriplex portulacoides, Arthrocnemum indicum, Salicornia arabica et Suaeda fruticosa ont été récoltées, rincées, séchées puis broyées. Les analyses ont porté sur quelques éléments traces: Pb, Cu, Zn et Cd. Nos résultats ont permis de classer les halophytes "A. portulacoides, A. indicum, S. arabica et S. fruticosa" parmi les espèces accumulatrices de Pb (respectivement 84.6, 92.2, 102.9 et 86.3 μg.g-1 MS), de Cu (respectivement 14.5, 15.1, 24.2 et 14.9 μg.g-1 MS) et de Zn (respectivement 1370.1, 625.1, 1601.4 et 772.5 μg.g-1 MS). A. portulacoides et S. arabica se distinguent par leurs capacités à piéger d'importantes quantités de Zn d'où la possibilité de les utiliser dans les programmes de dépollution. En ce qui concerne le Cd, nous avons montré que toutes les espèces étudiées sont des hyper-accumulatrices de ce métal (A. portulacoides: 274.0 μg.g-1 MS ; A. indicum: 280.4 μg.g-1 MS ; S. arabica: 211.6 μg.g-1 MS et S. fruticosa: 209.0 μg.g-1 MS). Il faut noter que les halophytes récoltées ne présentent aucun symptôme de toxicité, elles sont capables d'accumuler des quantités plus importantes d'éléments traces et de tolérer le stress métallique. Ce résultat montre que les halophytes étudiées peuvent être recommandées pour tous programmes de phytoremédiation des sols pollués des zones non cultivées

Involvement of Abscisic Acid and Jasmonic Acid Biosynthesis‑related Genes in Cucurbita pepo L. Tolerance to Trace Metal Stress

Trace metal induced stress is an abiotic factor that limits crop yield, having the additional hazard of their accumulation along trophic chain. This fact supposes an emerging problem concerning the health of the population in the case of edible plants such as Cucurbita pepo (zucchini). Most of the plant physiological responses to this adverse situation are regulated by phytohormones, being abscisic acid (ABA) and jasmonic acid (JA) the most important ones, which biosynthesis comprises a key step in this hormone-mediated signaling. In this work, genes involved in ABA and JA biosynthesis have been searched in the zucchini genome, and their expression has been analyzed in leaves of adult plants subjected to Cd- or Ni-induced stress. The results showed the higher sensitivity of zucchini plants to Ni in comparison to Cd, with a higher phenotypic affection and a major decrease of total dry weight. The study of the expression of 12 target genes (5 related to JA biosynthesis and 7 related to ABA biosynthesis), allowed determining a similar genetic response in C. pepo to these metals. The results extend our knowledge of the role of phytohormones on trace metal stress tolerance. Among all the studied genes, the main ones involved in plant responses to trace metal stress were the ABA-related CpAAO3, CpZEP, and CpNCED4, as well as the JA-related CpLOX2, CpOPR3, CpAOS2, and CpJAR1. These results provide relevant information to be used in future breeding programs.Funding for open access charge: CRUE-Universitat Jaume

Identification and expression of the Cucurbita WRKY transcription factors in response to water deficit and salt stress

WRKY transcription factors (TFs) have been reported to play important roles in plant responses to various stress conditions. Although several studies on the genomic organization of the WRKY gene family in various species have been reported, the information related to the genus Cucurbita is scarce, and null in the case of Cucurbita pepo. The present study aimed to examine the response of Cucurbita pepo to water deficit and salt stress. Additionally, WRKY gene family has been identified and characterized in this species. Shoot growth was negatively affected by both adverse situations. Similarly, both salt and water stress conditions reduced transpiration and stomatal conductance in C. pepo plants. However, the quantum efficiency of PSII decreased only in those plants exposed to salt stress. The increase in proline concentration recorded in C. pepo plants subjected to salt or drought stress point out the important role of this amino acid for plant tolerance to both stress conditions. Based on the genome sequence, 95 CmWRKY genes were found and classified into three main groups according to their orthologues in Arabidopsis. Among these, 24 and 14 CmWRKY genes were responsive to water and salt stresses, respectively. Three water stress-responsive genes were upregulated under the adverse condition. The expression of six CmWRKY genes was induced by NaCl treatment. Therefore, a total of nine up-regulated genes related to both stresses were identified, suggesting their putative involvement in the plant response to water deficit and salt stress

Physiological and Biochemical behaviours and antioxidant response of Helianthus annuus under Lanthanum and Cerium Stress

The continuous progress of global manufacturing and anthropogenic activities has resulted in excessive environmental metallic pollution, particularly with rare earth elements (REEs) which have become a prevalent issue of global concern due to their high toxicity and widespread existence. REEs-contaminated soils could ruin agriculture by inducing plant physiology disturbances in various crops that are considered the principal link of the human food chain. The main purpose of the present work is to assess the phytotoxicity of two light REEs, lanthanum (La) and cerium (Ce), in Helianthus annuus after 14 days of exposure to different concentrations of La and Ce (0, 1, 2.5, 5, and 10 µM). Plants showed different variations in shoot and root lengths at the end of the trial period. The accumulation of photosynthetic pigments, such as chlorophylls and carotenoids, as well as the photosynthetic efficiency, the non-photochemical quenching, the photosynthetically active radiation, and the electron transport rate, increased in the two REE treatments. Hydrogen peroxide significantly increased in all applied concentrations of La and Ce. A significant increase in malondialdehyde content was noticed only when plants were exposed to 2.5 µM La and 10 µM Ce. Results also demonstrated that La and Ce induced an increase in the activity of superoxide dismutase, peroxidase, and catalase (only the highest concentration of La decreased catalase activity). The exposure to different REE concentrations induced the accumulation of La and Ce in the plants, mainly in roots. Helianthus annuus showed an effective resistance behaviour facing La- and Ce-induced stresses

Biophysical and Biochemical Markers of Metal/Metalloid-Impacts in Salt Marsh Halophytes and Their Implications

As a major sink, estuarine/salt marsh ecosystem can receive discharges laden with myriads of contaminants including metals/metalloids from man-made activities. Two among the major consequences of metal/metalloid-exposure in estuarine/salt marsh ecosystem flora such as halophytic plants are: (a) the excessive accumulation of light energy that in turn leads to severe impairments in the photosystem II (PS II), and (b) metal/metalloids-accrued elevation in the cellular reactive oxygen species (ROS) that causes imbalance in the cellular redox homeostasis. On one hand, plants adopt several strategies to dissipate excessive energy hence eventually to avoid damage in the PS II and maintain optimum photosynthesis. On the other hand, components of the cellular redox system quickly respond to metal/metalloid-exposure, where plants try to maintain a fine-tuning among these components, and tightly control the level of ROS and its potential consequences. Herein, major insights into, and the significance and implications of important biophysical and biochemical markers in metal/metalloid-exposed halophytes are overviewed and also highlighted main aspects so far least explored in the present context. Discussion advocates to regularly monitor and integrate studies on the highlighted herein biophysical and biochemical markers taking into account the missing aspects such as essential and non-essential metal/metalloid-speciation, -availability, and -methylation, role of the obvious microbial activities, and a comparative account of the outcomes of the studies on mixture of metal/metalloid performed in laboratory and field conditions. Thus, consideration of these missing aspects in future studies on the subject can help us to: (a) unveil the status of the metal/metalloid-contamination and -impact; (b) understand adaptive responses of salt marsh halophyte to metals/metalloids, and also (c) to devise sustainable strategies for the environmental or ecosystem management and safety.info:eu-repo/semantics/publishedVersio

Assessment of lanthanum (La) and cerium (Ce) phytotoxicity in a halophyte species: Limbarda crithmoides L.

Rare earth elements (REEs) can harmfully affect the growth and development of several plant species. However, there is a lack of studies providing the effect of REEs on Limbarda crithmoides seedlings. In the present study, the growth parameters, chlorophyll content, macroelement uptake, phenolic compounds and flavonoid contents of the halophyte L. crithmoides were analysed, after 14 days of exposure to increasing concentrations (up to 10 µM) of two light REEs; lanthanum (La) and cerium (Ce), to assess the phytotoxicity level of these REEs in the chosen species. La and Ce contents in the plant tissues were determined as well. Results revealed an inhibitory effect of La and Ce on plant growth; the length and the dry biomass production of the shoots and roots significantly decreased in all REEs concentrations, when compared to the control. Similar trend was recorded in chlorophyll a and b contents in plant leaves. Moreover, La and Ce treatments significantly decreased the uptake of potassium, calcium and magnesium in the shoots and roots of L. crithmoides while the amounts of both La and Ce were found elevated in the same organs. All La and Ce treatments promoted the stimulation of phenolic compound biosynthesis in shoots and roots. According to our experiments, the halophyte L. crithmoides was very sensitive to both La and Ce toxicity

Treatment of contaminated well water with coagulants of different Opuntia ficus-indica L. populations

Opuntia ficus-indica (OFI) is a high added value species which different organs are used in several fields, including water purification. The present study intended to treat contaminated well water using naturally prepared coagulant from the cladodes of four local OFI populations in Tunisia. Physicochemical characterization of the water was carried out before and after treatment. The treatment applied allowed to decontaminate the well water studied. Most of the parameters tested were significantly influenced by the "population used" factor. The treatment by the "Amless" population of OFI resulted in the best reduction rates of the contents of Mg, Na, Cu, and Pb. "Loki" population allowed obtaining the best pH and EC reductions. The “Violet” population resulted in the highest COD, BOD5, and TSS reductions. The effectiveness and simplicity of this treatment method would encourage farmers to use it to improve the quality of the well water that is used for irrigation