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1

Osmoregulation and osmoprotection in the leaf cells of two olive cultivars subjected to severe water deficit

100%

Ennajeh M. , Vadel A. M. , Khemira H.

Acta Physiologiae Plantarum

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2009

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tom 31

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nr 4

EN

In this study, we compared the efficacy of defense mechanisms against severe water deficit in the leaves of two olive (Olea europaea L.) cultivars, ‘Chemlali’ and ‘Meski’, reputed drought resistant and drought sensitive, respectively. Two-year old plants growing in sand filled 10-dm³ pots were not watered for 2 months. Changes in chlorophyll fluorescence parameters and malondialdehyde content as leaf relative water content (RWC) decreased showed that ‘Chemlali’ was able to maintain functional and structural cell integrity longer than ‘Meski’. Mannitol started to accumulate later in the leaves of ‘Chemlali’ but reached higher levels than in the leaves of ‘Meski’. The latter accumulated several soluble sugars at lower dehydration. ‘Chemlali’ leaves also accumulated larger quantities of phenolic compounds which can improve its antioxidant response. Furthermore, the activity of three antioxidant enzymes catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) increased as leaf RWC decreased. However, differences were observed between the two cultivars for CAT and POD but not for APX. The activity of the first two enzymes increased earlier in ‘Meski’, but reached higher levels in ‘Chemlali’. At low leaf hydration levels, ‘Chemlali’ leaves accumulated mannitol and phenolic compounds and had increased CAT and POD activities. These observations suggest that ‘Chemlali’ was more capable of maintaining its leaf cell integrity under severe water stress because of more efficient osmoprotection and antioxidation mechanisms.

2

Occurrence of arbuscular mycorrhizal fungi and nodules in the roots of twelve legume species in South-Western Saudi Arabia

100%

Mahdhi M. , Tounekti T. , Khemira H.

Acta Scientiarum Polonorum. Hortorum Cultus

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2018

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tom 17

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nr 4

EN

The tripartite associations of arbuscular mycorrhizal fungi (AMF), rhizobia and legumes play a vital role in preserving and even restoring fertility of poor and eroded soils. The present study attempted to quantify relationship between legumes and symbiotic microorganisms (rhizobia and mycorrhizal fungi) by describing the mycorrhizal status and the occurrence of nodualtion of legumes growing in different areas of Jazan. The effect of legume species on soil microbial biomass was also investigated. Mycorrhizal and nodulation intensity varied greatly between legume species. The higher number of nodules (14 nodules per plant) and mycorrhization intensity (54%) were registered in root of Argyrolobium arabicum. Rhizosphere soils of all legume species harbored higher AMF fungal spores than bulk soils. Our results suggest also a signiﬁcant effect of legumes species on soil microbial biomass. Thus, legume species investigated in this study are potentially useful for replanting and soil protection of most degraded regions of Saudi Arabia.

3

Influence of NaCl-salinity on growth, photosynthesis, water relations and solute accumulation in Phragmites australis

100%

Gorai M. , Ennajeh M. , Khemira H. , Neffati M.

Acta Physiologiae Plantarum

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2011

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tom 33

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nr 3

EN

The aim of this study was to investigate the effects of NaCl-salinity on the physiological attributes in common reed, Phragmites australis (Cav.) Trin. ex Steudel. Plants grew optimally under salinity treatment with standard nutrient solution without added salt and at NaCl concentrations up to 100 mM. Applied for 21 days, NaCl-salinity (300 and 500 mM) caused a significant reduction in growth allocation of all different tissues of P. australis. Shoot growth of reed plants displayed a highly significant correlation with plant–water relations and photosynthetic parameters. The net photosynthetic rate and stomatal conductance of reed plants treated with NaCl-salinity at varying osmotic potential (ψπ) of nutrient solutions were positively correlated, and the former variable also had a strong positive relationship with transpiration rate. Leaf water potential and ψπ followed similar trends and declined significantly as ψπ of watering solutions was lowered. The increase in total inorganic nutrients resulting from increased Na⁺ and Cl⁻ in all tissues and K⁺, Ca²⁺ and Mg²⁺ concentrations were maintained even at the most extreme salt concentration. Common reed exhibited high K⁺/Na⁺ and Ca²⁺/Na⁺ selectivity ratios over a wide range of salinities under NaCl-salinity. These findings suggest that reed plants were able to adapt well to high salinities by lowering their leaf ψπ and the adjustment of osmotically active solutes in the leaves.

4

Effects of hydrogen cyanamide on antioxidant enzymes' activity, proline and polyamine contents during bud dormacy release in Superior Seedless grapevine buds

100%

Ben Mohamed H. , Vadel A. M. , Geuns J. M. , Khemira H.

Acta Physiologiae Plantarum

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2012

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tom 34

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nr 2

EN

The effect of hydrogen cyanamide (HC) on dormancy release, antioxidant enzyme’s activity and proline and free polyamine contents were investigated in ‘Superior Seedless’ grapevine buds. HC application caused a sharp decrease of catalase (CAT, EC 1.11.1.6) activity and a transient stimulation during the 5 days following treatment of peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) activities. This coincided with an accumulation of total free polyamines, especially putrescine (Put). Proline content increased dramatically. There was a strong correlation between APX and POD activities and total free PAs and Put contents implying a possible stimulating effect of the latter compounds on these enzymes. These observations indicate that HC triggers an oxidative stress leading to bud endodormancy release. Afterward, as budbreak started, we observed a rapid proline and Put degradation; this could be responsible for reactivation of growth. Indeed, the decline in Put to (Spd + Spm) ratio, reported here, may be considered as a reliable biochemical marker of bud growth resumption.

5

Estimating the contribution of arbuscular mycorrhizal fungi to drought tolerance of potted olive trees (Olea europaea)

88%

Ouledali S. , Ennajeh M. , Zrig A. , Gianinazzi S. , Khemira H.

Acta Physiologiae Plantarum

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2018

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tom 40

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nr 05