Effect of irrigation water regimes on yield of Tetragonia tetragonioides

The main purpose of this experiment was to study the effect of several irrigation water regimes on Tetragonia tetragonioides (Pall) O. Kuntze in semi-arid regions. During the experiment period, it was measured that several irrigation regimes were affected in terms of growth, biomass production, total yield, mineral composition, and photosynthetic pigments. The experiment was conducted in the greenhouse at the University of Algarve (Portugal). The study lasted from February to April in 2010. Three irrigation treatments were based on replenishing the 0.25-m-deep pots to field capacity when the soil water level was dropped to 70% (T1, wet treatment), 50% (T2, medium treatment), and 30% (T3, dry treatment) of the available water capacity. The obtained results showed that the leaf mineral compositions of chloride and sodium, the main responsible ions for soil salinization and alkalization in arid and semi-arid regions, enhanced with the decrease in soil water content. However, the minimum amounts of chlorophyll, carotenoids, and soluble carbohydrates in the leaf content were obtained in the medium and driest treatments. On the other hand, growth differences among the several irrigation regimes were very low, and the crop yield increased in the dry treatment compared to the medium treatment; thus, the high capacity of salt-removing species suggested an advantage of its cultivation under dry conditions.info:eu-repo/semantics/publishedVersio

Health status of Aleppo pine stands (Pinus halepensis Mill.) in the natural Senalba forest (Djelfa - Algeria)

La présente étude consiste en un diagnostic de l’état sanitaire des peuplements naturels de Pin d’Alep (Pinus halepensis Mill.) dans les massifs forestiers de Senalba Chergui et Gharbi situés dans la zone semi-aride de la région de Djelfa (Algérie). L’échantillonnage adopté est le systématique stratifié, ce qui a conduit à installer 80 placettes au niveau des versants nord et sud de chacun des massifs selon deux transects nord/sud et est/ouest. Différents paramètres dendrométriques (hauteur et circonférence des arbres dépéris à 1,30 m, épaisseur de l’écorce, âge) et stationnels (exposition, altitude, profondeur du sol, pH, taux de calcaire) sont mesurés. Traitées et analysées, ces données nous ont permis de conclure que le phénomène de dépérissement touche majoritairement les peuplements situés sur le versant sud pour la forêt de Senalba Chergui et ceux sur-âgés situés sur le versant nord de la forêt de Senalba Gharbi. Les autres paramètres stationnels ou dendrométriques n’ont pas d’effet significatif sur le phénomène.This study aimed to analyse the health status of the natural Senalba Aleppo pine forest (Pinus halepensis Mill.) located in the semi-arid zone of Djelfa (Algeria). A stratified systematic sampling was adopted and 80 plots were set up along two transects established on south and north-facing slopes. Various dendrometric (tree height; circumference at 1.30 m; bark thickness; age) and site parameters (exposure; altitude; soil depth; calcareous rate; soil pH) were measured. Results showed that the decline process preferentially impacted the trees located on the southern slope of Senalba Chergui forest and old trees located on the northern slope of Senalba Gharbi forest. However, the other parameters have no significant effect on the process of decline

Relation between site parameters and Aleppo Pine (Pinus halepensis Mill.) dendroecology in Senalba forest area (Djelfa, Algeria)

Aleppo Pine (Pinus halepensis Mill.) is a volunteering hardy species, very common in Mediterranean regions. This species has great economical, ecological and social values in Algeria. 120 sample plots were laid out on northern and southern slopes of Senalba forest area (Djelfa) located in a semi-arid region, to investigate the effect of altitude, aspect and soil depth on height, circumference at 1.30 m and annual ring growth. The results shown that aspect and altitude were the determining factors of Aleppo Pine growth. Three classes of fertility were distinguished in relation with dominant tree height and ageÀ partir de transects intégrant les variations d’altitude et d’exposition, 120 placettes de Pin d’Alep (Pinus halepensis Mill.) de 800 m² chacune ont été installées au niveau de quatre stations choisies dans le massif forestier de Senalba (Djelfa, Algérie) situé en région semi-aride. Chaque placette a fait l’objet des mesures dendrométriques suivantes : circonférence à 1.30 m, hauteur totale, hauteur dominante, surface terrière, densité, âge et accroissement moyen du cerne auxquelles ont été associées des caractéristiques stationnelles : altitude, exposition et profondeur du sol. L’analyse des données a mis en évidence que l’exposition et l’altitude sont les facteurs déterminants pour la croissance du pin. Trois classes de fertilité ont pu être distinguées à partir du couple « âge/hauteur dominante

Effect of Some Heavy Metals on Seed Germination of Medicago arborea L. (Fabaceae)

The present work deals with the effect of three heavy metals (zinc, copper and lead) on germination of Medicago  arborea  seeds. Solutions of four concentrations (25, 50, 75  and 100 ppm) of each heavy metal were tested separately, and deionised water was used   as a control treatment. The experiments were conducted during 14 days, under strictly controlled laboratory conditions according to a completely random design with three replicates of 20 seeds/Petri dish, for each treatment. The following germination indices: Final germination percentage (FGP), Mean daily germination (MDG), Mean germination time (MGT), Germination index (GI) and Germination value (GV) were estimated. The results showed that FGP, MDG, GI and GV were significantly affected by heavy metal stress. In contrast, the increase of applied heavy metal dose resulted in prolongation of MGT, and therefore, in significant increase of its value. It should be noted that M. arborea seeds were able to germinate even at 100 ppm, which is a concentration higher than critical limits for agricultural soils and irrigation water. This suggests that M. arborea could be considered as a moderately tolerant species, at least during the germination phase, to metal stress and as a candidate with acceptable potential for phytoremediation. AR-S

Effects of salinity and ascorbic acid on growth, water status and antioxidant system in a perennial halophyte

Salinity causes oxidative stress in plants by enhancing production of reactive oxygen species, so that an efficient antioxidant system, of which ascorbic acid (AsA) is a key component, is an essential requirement of tolerance. However, antioxidant responses of plants to salinity vary considerably among species. Limonium stocksii is a sub-tropical halophyte found in the coastal marshes from Gujarat (India) to Karachi (Pakistan) but little information exists on its salt resistance. In order to investigate the role of AsA in tolerance, 2-month-old plants were treated with 0 (control), 300 (moderate) and 600 (high) mM NaCl for 30 days with or without exogenous application of AsA (20 mM) or distilled water. Shoot growth of unsprayed plants at moderate salinity was similar to that of controls while at high salinity growth was inhibited substantially. Sap osmolality, AsA concentrations and activities of AsA-dependant antioxidant enzymes increased with increasing salinity. Water spray resulted in some improvement in growth, indicating that the growth promotion by exogenous treatments could partly be attributed to water. However, exogenous application of AsA on plants grown under saline conditions improved growth and AsA dependent antioxidant enzymes more than the water control treatment. Our data show that AsA-dependent antioxidant enzymes play an important role in salinity tolerance of L. stocksii.Higher Education Commission of Pakistan for provision of funds under a research grant entitled ‘Salt-induced Oxidative Stress: Consequences and Possible Management’

Seasonal variation in productivity, water relations and ion contents of Atriplex halimus spp. schweinfurthii grown in Chott Zehrez wetland, Algeria

A population of Atriplex halimus spp. schweinfurthii, a perennial halophyte of Algerian saline steppes, was studied for one year under field conditions in chott Zehrez wetland of Djelfa, Algeria. During the one year, the population was exposed to great variations in soil salinity, pH varied from 7.0 to 8.2, soil conductivity was highest (4.47 dSm−1) in summer and lowest (1.99 dSm−1) in autumn. Soil moisture was relatively low and varied from 7.66% in summer to 21.45% in winter. Plants in the winter and spring seasons showed better growth than the other two seasons. The contents of Na+ and K+ in plant were highest during the summer, however Ca2+ ion content in A. halimus tissues remained constant throughout most of the seasons. The high N was recorded in winter and spring seasons. The succulence remained unaffected during winter, spring and summer seasons and then declined during autumn. This indicates that plants minimize their water uptake during stress to achieve osmotic adjustment, which helps them to survive in chott ecosystem

Is salinity tolerance related to osmolytes accumulation in Lygeum spartum L. seedlings?

Lygeum spartum L. (Poaceae) is a plant of commercial relevance used as raw material for manufacturing paper. This species is a newly found salt tolerant species, but its physiological responses to salinity are poorly understood. The effect of salt stress (50 and 100 mM NaCl) on growth, leaf water relations, soluble sugars and free amino acids in L. spartum has been investigated. Fresh and dry weights were reduced significantly above 50 mM NaCl. Transpiration, water potential (Ψω) and osmotic potential (Ψπ) decreased with elevated NaCl. No change was observed in the turgor potential (Ψτ). Subsequently, the composition of free amino acids estimated by high pressure liquid chromatography (HPLC) indicated a significant increase in free amino acid content. It appears that valine was the main amino acid accumulated significantly by the plants for both NaCl treatments. However, tyrosine levels decrease by salt treatment compared to control. Contents of Na+ and Cl− increased with an increase in salinity. The concentration of Na+ of salinized plants (100 mM NaCl) was ∼70-fold greater than that measured in control plants, and this was associated with significant reductions in leaf K+ and Ca2+ concentrations. In addition, a significant accumulation of soluble sugars, probably associated with osmotic adjustment and protection of membrane stability, occurred in roots of salinized plants. Based upon these results, a possible physiological role of soluble sugars and free amino acids was suggested in L. spartum to maintain turgor