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Effects of water stress on growth phenology photosynthesis and leaf water potential in Stipagrostis ciliata(Desf.)De Winter in North Africa

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Journal of Arid Land 2023年第1期15卷 77-90页

作者： Lobna MNIF FAKHFAKH mohamed chaieb Laboratory of Ecosystems and Biodiversity in Arid Land of Tunisia(LEBIOMAT) Faculty of SciencesUniversity of SfaxSfax 3000Tunisia

Stipagrostis ciliata(Desf.)De Winter is a pastoral C4 grass grown in arid regions.This research work focused on assessing the growth of S.ciliata accessions derived from two different climate regions(a wet arid region in the Bou Hedma National Park in the central and southern part of Tunisia(coded as WA),and a dry arid region from the Matmata Mountain in the south of Tunisia(coded as DA))under water stress conditions.Specifically,the study aimed to investigate the phenological and physiological responses of potted S.ciliata seedlings under different water treatments:T_(1)(200 mm/a),T_(2)(150 mm/a),T_(3)(100 mm/a)and T_(4)(50 mm/a).Growth phenology,net photosynthesis(Pn),stomatal conductance(gs),midday leaf water potential(Ψmd),predawn leaf water potential(Ψpd),soil water content(SWC)and soil water potential(Ψs)were observed during the water stress cycle(from December 2016 to November 2017).The obtained results showed that the highest growth potential of the two accessions(WA and DA)was recorded under treatment T_(1).The two accessions responded differently and significantly to water stress.Photosynthetic parameters,such as Pn and gs,decreased sharply under treatments T_(2),T_(3)and T_(4)compared to treatment T_(1).The higher water stress increased the R/S ratio(the ratio of root dry biomass to shoot dry biomass),with values of 1.29 and 2.74 under treatment T_(4)for accessions WA and DA,respectively.Principal component analysis(PCA)was applied,and the separation of S.ciliata accessions on the first two axes of PCA(PC1 and PC2)suggested that accession DA was detected in the negative extremity of PC1 and PC2 under treatments T_(1)and T_(2).This accession was characterized by a high number of spikes.For treatments T_(3)and T_(4),both accessions were detected in the negative extremity of PC1 and PC2.They were characterized by a high root dry biomass.Therefore,S.ciliata accessions responded to water stress by displaying significant changes in their behaviours.Accession WA from the Bou Hedma National Park(wet arid regio

关键词： Stipagrostis ciliata drought stress water deficit gas exchange arid regions Tunisia

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Morphological and physiological responses to drought stress of carob trees in Mediterranean ecosystems

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Journal of Arid Land 2023年第5期15卷 562-577页

作者： Khouloud ZAGOUB Khouloud KRICHEN mohamed chaieb Lobna F MNIF Laboratory of Ecosystems and Biodiversity in Arid Land of Tunisia Faculty of SciencesUniversity of SfaxSfax 3000Tunisia

The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions of carob trees(Ceratonia siliqua L.)with 2-year-old from different climate regions to drought generated by four water treatments:Tc(250 mm),T1(180 mm),T2(100 mm),and T3(50 mm).The first accession(A1)comes from the protected national park of Ichkeul in northern Tunisia.This zone belongs to the bioclimatic sub-humid stage.The second accession(A2)comes from Melloulech,located in the center-east of Tunisia,belonging to the bioclimatic semi-arid stage.The third accession(A3)comes from the mountain of Matmata,located in the south of Tunisia,belonging to the bioclimatic hyper-arid stage.The experiment was undertaken in a greenhouse.Gaz exchange indices(net photosynthesis(A),stomatal conductance(gs),transpiration rate(E),and internal CO_(2) concentration(Ci))were determined.Predawn(Ψpd)and midday(Ψmd)leaf water potentials,relative soil water content(SWC),and morphological parameters(plant height(H),number of leaves(NL),number of leaflets(Nl),and number of branches(NB))were estimated.The results showed that significant differences(P<0.001)were found between physiological and morphological parameters of each accession.The highest growth potential was recorded for Tc treatment in both accessions A1 and A2.Significant decreases in gs,E,Ci,and SWC were recorded with the increases in water stress applied from treatment T1 to T3.Positive and significant correlations were found between SWC andΨpd for all studied accessions.Ψpd andΨmd decreased as water stress increased,ranging from–0.96 to–1.50 MPa at sunrise and from–1.94 to–2.83 MPa at midday,respectively,under control and T3 treatments.C.siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior.Both accessions A1 and A2 showed greater drought tolerance than accession A3.These seedlings exhibit

关键词： Ceratonia siliqua L. water stress soil moisture stomatal conductance predawn leaf water potential minimum water potential

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Effects of temperature and water limitation on the germination of Stipagrostis ciliata seeds collected from Sidi Bouzid Governorate in Central Tunisia

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Journal of Arid Land 2018年第2期10卷 304-315页

作者： Lobna M FAKHFAKH Naser A ANJUM mohamed chaieb Department of Life Sciences Faculty of Sciences University of Sfax Centre for Environmental and Marine Studies and Department of Chemistry University of Aveiro

Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indeed, the majority of steppe ecosystems are characterized by a low density of perennial grass species at present. This study evaluated the effects of temperature and water limitation on the seed germination of Stipagrostis ciliata（Desf.） de Winter, a perennial grass species. The seeds were collected from the Bou Hedma Park, Sidi Bouzid Governorate, Central Tunisia. The thermal time and hydrothermal time models were used to describe the seed germination of S. ciliata under different water potentials and temperatures. The germination response of S. ciliata seeds in darkness was evaluated over a range of temperatures（15°C, 20°C, 25°C, 30°C and 35°C） and across a wide range of osmotic potentials（0.0, –0.2, –0.6, –1.2, –1.6 and –2.0 MPa） of the polyethylene glycol（PEG6000） solutions at each temperature level. Among the tested temperatures, 25°C was found to be the optimal temperature to the germination of S. ciliata seeds. The final germination percentage（75.2%） was obtained with distilled water. The progressive decrease of osmotic potential of the PEG6000 solutions inhibited the seed germination. However, the number of days to first germination was increased with a reduction of osmotic potential. A significant positive relationship was identified between final germination percentage of S. ciliata seeds and osmotic potential of the PEG6000 solutions, with R^2 ranging from 0.5678 to 0.8761. Furthermore, a high degree of congruency between predicted and observed germination time course curves was observed. In general, S. ciliata exhibits a significant adaptation capacity for water limitation and high temperature in arid ecosystems.

关键词： Stipagrostis ciliata germination temperature water potential hydrothermal model arid zone Bou Hedma Park

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Changes in Vegetation Proprieties under Short- and Long-Term Protection in North African Arid Land

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American Journal of Plant Sciences 2014年第7期5卷 899-906页

作者： Fathia Abdallah mohamed chaieb Department of Biology Faculty of Sciences University of Sfax Sfax Tunisia

The objective of this study was to quantify the effects of protection on herbaceous species composition, total plant cover, dry matter, plant density, floristic richness and diversity. Characteristics of vegetation under continued grazing and protected area for 10 and 65 years were examined in a degraded arid environment in South Tunisia. Our results show that protection enhances significantly (two times) different vegetation parameters. However, long-term protection was found to reduce biomass production, plant density and floristic diversity. Some palatable species such as Stipagrostis ciliata, Helianthemum sessiliflorum, Eragrostis papposa, Echiochilon fruticosum and Cenchrus ciliaris were frequently found in the protected sites. In the grazed site, these species were being replaced by less desirable species: Astragalus armarus, Peganum harmala and Artemisia compestris. This emphasized the importance of conservation stocking rates and proper pasture management.

关键词： Arid environment Protection Vegetation Grazing

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Genetic and Metabolic Determinants of Plasminogen Activator Inhibitor 1 (PAI-1) in Tunisian Type 2 Diabetes Patients

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Open Journal of Endocrine and Metabolic Diseases 2017年第6期7卷 141-150页

作者： mohamed Moustapha Molka Chadhli-chaieb Touhami Mahjoub Larbi chaieb Internal Medicine Department Hospital Cheikh Zayed Nouakchott Mauritania Endocrinology Department CHU Farhat Hachad Sousse Sousse Tunisia Research Unit of Biology Genetics of Cancers Haematological and Autoimmune Diseases Faculty of Pharmacy of Monastir University of Monastir Monastir Tunisia

Background: PAI-1 (plasminogen activator inhibitor-1) is a powerful regulator of fibrinolysis and plasma level is high in type 2 diabetes and cardio-vascular disease, which is determined by genetic polymorphisms in PAI-1 gene and environmental factors. The aim of the study was to examine the determinants of plasma PAI-1 Ag level among type 2 diabetes patients. Methods: 491 Tunisian type 2 diabetes patients had clinical evaluation (weight, high, BMI, Waist Circumference), laboratory investigations including FBG Hb1Ac, cholesterol, triglyceride;HDL-cholesterol was done;plasma PAI-1 antigen level was done with ELISA;−675 4G/5G and −844 G/A polymorphisms of PAI-1 gene was done by PCR-ASA and PCR-RFLP respectively. Results: The mean age for our patients was 58.3 ± 10.5 years;sex-ratio = 0.92;mean PAI-1 level was 34.6 ± 21.3 ng/ml. We didn’t find correlation between PAI-1 level and BMI, but we have found significant correlation between PAI-1 and waist circumference (p = 0.032), most enhanced in men (P = 0.002), T2D patients who have FBG > 11 mmol/l had PAI-1 Ag level higher than those who have FBG P = 0.034), but no difference found between T2D with high Hb1Ac > 8% and those with Hb1Ac < 8%, significant correlation was seen between PAI-1 level and LDL-cholesterol (P = 0.05), high correlation between PAI-1 Ag level and −675 4G/5G polymorphism genotype was seen, 4G/4G carriers had the highest PAI-1 level, 4G/5G had intermediary level and 5G/5G had the lowest level (P −844G/A polymorphism genotypes. Using multiple variable linear regression analysis, the independent factor associated with plasma PAI-1 level was −675 4G/5G polymorphism (regression coefficient β = 4.6, P Conclusion: the present study identifies −675 4G/5G not −844 G/A polymorphism of PAI gene as the principal determinant of plasma PAI-1 level in Tunisian T2D patients, the android fat distribution, dyslipidemia and hyperglycemia play a modest role in this variation.

关键词： Plasminogen Activator Inhibitor 1 Polymorphism PCR Type 2 Diabetes Mellitus Metabolic Syndrome X

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−675 4G/5G and −844 G/A of Plasminogne Activator Inhibitor-1 (Pai-1) Gene Polymorphisms and Type 2 DiabetesMellitus in Tunisia: Case-Control Study

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Open Journal of Endocrine and Metabolic Diseases 2019年第7期9卷 75-83页

作者： mohamed Moustapha Molka Chadhli-chaieb Touhami Mahjoub Larbi chaieb Internal Medicine Department Hopital Cheikh Zayed Nouakchott Mauritania Endocrinology Department CHU Farhat Hachad Sousse Tunisia Reserche Unit of Biology Genetic of Cancer Haematological and Autoimmune Disease Monastir Faculty of Pharmacy Monastir Tunisia

Background: The plasminogen activator inhibitor-1 (PAI-1) is a puissant antifibrinolytic factor;plasma PAI-1 level is high in type 2 diabetes. 4G/5G polymorphism of PAI-1 gene is a major genetic determinant of plasma PAI-1 levels, with 4G carriers having high PAI-1 level than 5G, theses pose the question about relation T2 patients and those polymorphisms. The aim of this study was to determine the relationship between the polymorphisms −675 4G/5G and −844 G/A of PAI-1 gene and type 2 diabetes mellitus. Methods: A case control study of 491 diabetic and 400 healthy controls. Genotyping of the polymorphism −675 4G/5G was done by PCR-ASA (polymerase chain reaction, allele specific amplification), and the polymorphism −844 G/A was done with PCR-RFLP (restriction fragment length polymorphism), the allelic frequency is calculated with hardy-Weinberg law, the statistic analysis was done by SPSS version 10. Results: Higher frequencies of The genotypes 4G/4G (p = 0.01) and 4G/5G of polymorphism −675 4G/5G were seen in diabetic (p = 0.05) and higher frequencies of 5G/5G was seen in controls (p −844 G/A was seen in diabetics and G/G was seen in controls (p = 0.01). Conclusion: Our study found association between 4G allele of −675 4G/5G and A allele of −844 G/A of PAI-1 gene and having type 2 diabetes mellitus in Tunisian population.

关键词： Plasminogéne Activator Inhbitor-1 (PAI-1) ?675 4G/5G Polymorphism ?844 G/A Polymorphism Type 2 Diabetes Mellitus

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