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OALib Journal期刊

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Physiological and Biochemical Changes of Two Halophytes, Nitraria retusa (Forssk.) and Atriplex halimus (L.) Under Increasing Salinity
Faycal Boughalleb,Mounir Denden
Agricultural Journal , 2013, DOI: 10.3923/aj.2011.327.339
Abstract: The effect of NaCl stress on the growth, nutriments contents and antioxidative activities were investigated in two xero-halophytes Nitraria retusa and Atriplex halimus. Plants were grown in 0-800 mM NaCl for 120 days under glasshouse conditions. Both xero-halophytic species showed positive plant growth for low levels of salinity. Increasing concentrations of salinity from 400-800 mM NaCl induced decrease in plant growth and chlorophyll content in the two species, especially in A. halimus. In addition both species were able to accumulate a large quantity of Na+ and to maintain a higher leaf water content which was probably associated with a greater capacity for osmotic adjustment whereas the contents of K+, Ca2+ and Mg2+ decreased significantly at diverse degree, resulting in an increase in the Na+/K+ ratio when NaCl concentrations increased. At higher salinity, it appears that salt excretion was involved in the strategies for salt tolerance in both xero-halophytic species, especially in N. retusa. A significant variability to the response to oxidative stress induced by salinity was found between both species. The relative better salt tolerance of N. retusa compared to A. halimus plants may be related to their higher polyphenols and carotenoids accumulation and antioxidant activity, associated with lower Malondialdehyde (MDA) content and Hydrogen peroxide (H2O2) concentration. In A. halimus, the secondary metabolites contribution in the restriction of oxidative damages caused by salt stress was disputed. As a whole, the data suggest that both N. retusa and A. halimus salt stressed plants might represent potential sources of polyphenols for economical use. But there is distinction in the implication of non-enzymatic antioxidants to limit oxidative damage.
Possible Involvement of Proline and the Antioxidant Defense Systems in the Drought Tolerance of Three Olive Cultivars Grown under Increasing Water Deficit Regimes
Faycal Boughalleb,Mahmoud Mhamdi
Agricultural Journal , 2013, DOI: 10.3923/aj.2011.378.391
Abstract: The possible involvement organic metabolites and the antioxidative defence system in water drought tolerance were investigated in three olive cultivars. About 2 years old olive trees, grown in pots in greenhouse were subjected to increasing Water Deficit (WD) regime (5, 10, 20 and 40 days). After 40 days without irrigation, the biomass production, osmotic potential (Ψs) and turgor Potential (P) were decreased in the three olive cultivars and the lower reduction was observed in Zalmati. Under WD conditions, Chemlali and Zalmati showed a greater accumulation of proline associated with the better maintenance of plant water status and biomass production. Different cultivars developed certain antioxidative defense mechanisms including the accumulation of phenolic compounds and increased antioxidative enzymes activities. However, differences were observed between the three cultivars for these enzymatic and non-enzymatic antioxidants. Zalmati leaves accumulated the larger quantities of phenolic compounds followed by Chemlali which can improve their antioxidant responses. Superoxide Dismutase (SOD) activity was more enhanced in Zalmati than in Chemlali under water stress but was decreased in Chetoui. Catalase (CAT) activity was more enhanced in Chetoui under water stress. The activity of Peroxidase (POD) and Ascorbate Peroxidase (APX) increased under water stress and the higher levels were reached in Zalmati followed by Chemlali. In contrast, Polyphenol Oxidases (PPO) activity decreased under WD conditions in Chemlali and Zalmati, however this reduction was slightly in Chetoui. The lower increase in malondialdehyde content and H2O2 generation suggest that Zalmati was more able to maintain leaf cell integrity than Chemlali, especially Chetoui under severe water stress because of the more efficient osmoprotection and antioxidant defense systems. Thus, the great accumulation of phenolic compounds, the increased activity of SOD and the higher POD, especially APX activity might be linked to the better performance of the antioxidant defense in Zalmati olive cultivar under severe water deficit.
Watermelon Sudden Decay in Tunisia: Identification of Pathogenic Fungi and Determination of Primary Agents
Naima Boughalleb,Mohamed El Mahjoub
Pakistan Journal of Biological Sciences , 2006,
Abstract: Isolation from infected watermelon samples has demonstrated the presence of some fungal complex including Fusarium oxysporum, F. solani, Rhizoctonia bataticola, R. solani, Monosporascus cannonballus, Pythium ultimum and P. echinulatum. These fungal species are different in their distribution among the infected plants and areas surveyed. However, F. oxysporum and F. solani are always predominant. These results showed the almost-presence of the two Fusarium disease of watermelon: Fusarium wilt to F. oxysporum f. sp. niveum and the collars and/or root rot caused by F. solani f. sp. cucurbitae which are the primary fungi of sudden wilt. Analysis in main component of isolation frequency of different fungi showed that their association in homogeneous groups seemed not affected by geographic origin and surveyed year.
In vitro Determination of Fusarium spp. Infection on Watermelon Seeds and their Localization
N. Boughalleb,M. El Mahjoub
Plant Pathology Journal , 2006,
Abstract: In this study, we used direct incubation of watermelon dissected seeds on Komada`s selective medium for Fusarium spp. and incubation of entire seed on the same medium or on 2% agar medium. Identification of fungi was based on morphological criteria and also according to Koch`s postulate. Isolates from dissected seed were identified as F. oxysporum f. sp. niveum and F. solani f. sp. cucurbitae. These fungi were found to be externally and internally seed borne in watermelon. This is the first report of localization of Fusarium spp. transmitted by watermelon seeds in Tunisia.
Effet de la solarisation sur Phytophtora nicotianae Breda de Haan var. parasitica (Dastur) G.M. Waterhouse responsable d'un syndrome associant nécroses racinaires et flétrissement sur piment (Capsicum annuum L.) en Tunisie
Boughalleb, N.,El Mahjoub, M.
Tropicultura , 2005,
Abstract: The Effect of Soil Solarization on Phytophtora nicotianae Breda de Haan var. parasitica (Dastur) G.M. Waterhouse Responsable for Syndrome Associating Root Rots and Damping-off of Pepper (Capsicum annuum L.) in Tunisia. Mycological analysis of soil collected from solarized plot and non solarized plot showed that the inoculum of soil is composed mainly by Fusarium spp. The solarization permitted to reduce the density of this inoculum. Isolations done from peppers wilted plants have revealed the infestation by Phytophtora nicotianae Breda de Haan var. parasitica (Dastur) G.M. Waterhouse. This was on the basis of microscopic observation of different structures. It is assumed that the percentage of wilted plant showed a considerable reduction in solarized plot. In the same time, the impact of the solarization on the agronomic criteria showed an improvement of the vigour and also of the yield.
Photosynthetic and Antioxidant Responses of the Xero-Halophyte Zygophyllum album (L.) to Salt Stress
Faycal Boughalleb,Mounir Denden,Mohamed Neffati
Research Journal of Biological Sciences , 2012, DOI: 10.3923/rjbsci.2012.278.284
Abstract: Zygophyllum album L., plants were exposed to NaCl salinity (0, 100, 200, 400 and 800 mM NaCl) for 60 days. Moderate salinity (100-200 mM NaCl) had a stimulating effect on Relative Growth Rate (RGR), net CO2 assimilation (PN) and stomatal conductance (gs). At higher salinities levels (400-800 mM NaCl), these physiological parameters decreased significantly. Z. album PSII photochemistry was unaffected by salinity, only a slightly decrease in the efficiency of PSII (F v/F m) was occurred at 800 mM. The reduction in photosynthesis is most probably due to stomatal closure rather than damages in the photosynthetic apparatus. Increasing salinity from 400-800 mM NaCl caused a significant accumulation of H2O2 generation and lipid peroxidation and a concomitant decrease in membranes stability index. The antioxidative defence capacity of Zygophyllum album L., plants might be achieved by the increasing activities of Superoxide Dismutase (SOD), Peroxidase (POD) and Ascorbate Peroxidase (APX) and the accumulation of phenols which showed to participate efficiently in restriction of oxidative damages caused by the H2O2 generation while Catalase (CAT) was unaffected under salt stress.
Effect of Salt Stress on Growth, Water Relations, Solute Composition and Photosynthetic Capacity of the Xero-Halophyte Nitraria retusa (L.)
Faycal Boughalleb,Hichem Hajlaoui,Mounir Denden
Environmental Research Journal , 2012, DOI: 10.3923/erj.2012.1.13
Abstract: Nitraria retusa is common fodder shrub. The increasing interest in the utilisation of such shrubs in saline medium of North Africa requires evaluating the salinity effects on growth, water and solutes relationship, photosynthesis parameters in order to investigate salt-resistance mechanisms. Plants were grown in 0-800 mM NaCl under controlled conditions and harvested in three periods (after 60, 120 and 240 days). During the first harvest, the growth of N. retusa was promoted up to 400 mM NaCl, only to 200 mM NaCl in the two last harvests. Salt stress caused a marked decrease in osmotic potential, a significant accumulation of Na+ and Clˉ and a concomitant decrease in K+ and Ca2+ contents while magnesium, nitrogen and phosphorus contents were not greatly affected. Plants are able to maintain a higher leaf water content which was probably associated with a greater capacity for osmotic adjustment. The organic osmotica that can be involved in osmotic adjustment was proline, soluble sugar and at least degree glycinebetaine. Moderate salinity had a stimulating effect on growth rate, net CO2 assimilation (Pn), transpiration (E) and stomatal conductance (gs). At higher salinities levels, these physiological parameters decreased significantly. There was no significant changes on the chlorophyll fluorescence for N. retusa stressed plants. Carotenoid content was highest at 800 mM. For the chlorophyll content, it was unaffected up to 400 mM and then decreased slightly at 800 mM. Mesophyll of N. retusa leaves were thinner in salt-stressed plants while epidermis thickness was unaffected by salinity and the stomatal density decreased significantly with higher salt treatments. The results suggest that N. retusa show high tolerance to high salinity. The tolerance to salinity appears to be achieved through two mechanisms compartimentation of ions at moderate salinity and salt excretion at very higher salinity.
Response of Young Citrus Trees to NPK Fertilization Under Greenhouse and Field Conditions
Faycal Boughalleb,Mahmoud Mhamdi,Hichem Hajlaoui
Agricultural Journal , 2013, DOI: 10.3923/aj.2011.66.73
Abstract: Experiments were conducted with lemon (Citrus limon v. Eureka) and orange trees (Citrus sinensis cv. Maltese) to determine the optimum NPK fertilizer rates for young citrus trees in greenhouse and field conditions. Greenhouse nursery trees received 0-0-0, 0-25-50, 25-25-50, 50-25-50 or 100-25-50 mg L-1 of N-P2O5-K2O via drip irrigation. The results showed that increased N rates improved leaf number, shoot length, total leaf area and stem diameter. The optimum tree growth was occurred with 50 and 100 mg N L-1. Results also showed that the percentages of N in the leaves were increased in proportion to the amount of N added while the percentage of P and K were decreased. However, the concentrations of Ca, Mg, Fe, Mn and Zn were unaffected by N rates but the leaf Cu concentration increased significantly. Leaf Mg concentration was increased by the presence of K in the nutrition solution. Form this study, we recommended the use of 100 N-25 P2O5-50 K2O mg L-1 for the good growth of nursery citrus plants in the absence of any possibility of deficiency or excessive accumulation of mineral elements. In the second experiment, two fertilizers mix 180-90-180 and 360-90-180 of N-P2O5-K2O kg ha-1 were applied to young citrus tree in field condition. Increased the level of N had no effect on leaf number and stem diameter in Eureka lemon however shoot length and total leaf area were slightly increased and these increment in growth was higher in Maltese orange.
Effect of Fungicides on in vitro Infestation Level of Radish, Carrot and Pepper Seeds
Naima Boughalleb,Neji Tarchoun,Wided Dallagi
Plant Pathology Journal , 2006,
Abstract: Through incubation of radish (Raphanus sativus), carrot (Daucus carota) and pepper (Capsicum annuum) seed samples on potato dextrose agar at 25°C, six species of fungi were determined as seedborne in these crops. Alternaria dauci, A. Tenuissima, A. tenuis and Epicoccum sp. were found to be transmitted by radish seed. For carrot seed, A. Tenuissima, A. dauci, A. tenuis, Epicoccum sp. and Fusarium oxysporum were identified. However, Alternaria tenuissima and Botrytis cinerea were isolated from pepper seeds. Seed treated with fungicides such as Maneb, Mancozeb, Benomyl and Thiophanate methyl could reduce the infestation levels of tested crops.
Variability in Pathogenicity among Tunisian Isolates of Phytophthora cactorum as Measured by Their Ability to Cause Crown Rot on Four Apple Cultivars and MM106 Roostock
N. Boughalleb,A. Moulahi,M. El Mahjoub
Journal of Agronomy , 2006,
Abstract: Studies on two isolates of Phytophthora cactorum recovered from apple plants identified the presence of diversity in pathogenicity. These isolates appeared pathogenic to tested apple trees. It revealed that Golden Delicious, Star Crimson and the rootstock MM106 were more susceptible than Richared and Red Delicious cultivars, but with variable levels of aggressiveness according to physiological stages of tested segments of apple plants. Necrosis caused by Phytophthora cactorum isolates was more important on shoot segments than on wood segments.
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