Salinity is one of the major environmental factors limiting growth and productivity of rice plants. In this study, the effect of salt stress on phospholipid signaling responses in rice leaves was investigated. Leaf cuts were radiolabeled with 32P-orthophosphate and the lipids extracted and analyzed by thin-layer chromatography, autoradiography and phosphoimaging. Phospholipids were identified by co-migration of known standards. Results showed that 32Pi was rapidly incorporated into the minor lipids, phos-phatidylinositol bisphosphate (PIP2) and phosphatidic acid (PA) and, interestingly, also into the structural lipids phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), which normally label relatively slowly, like phosphatidylcholine (PC) and phosphatidylinositol (PI). Only very small amounts of PIP2 were found. However, in response to salt stress (NaCl), PIP2 levels rapidly (<30 min) increased up to 4-fold, in a time- and dose-dependent manner. PA and its phosphorylated product, diacylglyc-erolpyrophosphate (DGPP), also increased upon NaCl stress, while cardiolipin (CL) levels decreased. All other phospholipid levels remained unchanged. PA signaling can be generated via the combined action of phospholipase C (PLC) and diacylglycerol kinase (DGK) or directly via phospholipase D (PLD). The latter can be measured in vivo, using a transphosphatidylation assay. Interestingly, these measurements revealed that salt stress inhibited PLD activity, indicating that the salt stress-induced PA response was not due to PLD activity. Comparison of the 32P-lipid responses in salt-tolerant and salt-sensitive cultivars revealed no significant differences. Together these results show that salt stress rapidly activates several lipid responses in rice leaves but that these responses do not explain the difference in salt tolerance between sensitive and tolerant cultivars.

Detailed subsurface studies of the northern part of the Suez Rift and adjacent areas indicate the superposition of two different episodes of deformation. During the earlier (Late Cretaceous) phase of deformation, folds with NE‐SW oriented axes were formed in northern Egypt as a result of convergence between Africa and Eurasia and the closure of the Neotethys. During the later (early Miocene) deformation., NW‐oriented normal faults were formed as a result of the opening of the Suez Rift. Borehole data have shown that a belt of NE en échelon folds with NE‐SW axes exists in the subsurface in the northernmost part of the rift, between Ayun Musa and the Sukhna‐1 well, soulth of Geble Ataqa. This fold belt represents the SW continuation of the en échelon folds exposed in the Mitla Pass, to the NE of the rift. Another pre‐rift structure is the offshore extension of the Wadi Araba structure as a SE‐facing monocline. This offshore structure also represents the continuation of the Geble Somar structure, on the eastern shoulder of the Suez Rift. The Geble Somar and Wadi Araba Structures represent the southernmost prerift folds in northern Egypt. Pre‐rift folds in the study area stood high above sea‐level during the Palaeocene and early Eocene. Upper Cretaceous and/or older rocks in the cores of these folds were later unconformably covered by middle Eocene rocks. The presence of Late Cretaceous folds should be taken into consideration when exploring for hydrocarbons in this part of the Suez Rift. Borehole data in NE Egypt also indicate the presence of Late Cretaceous folds underneath the almost flat‐laying Tertiary rocks in the northern part of the Eastern Desert. These folds are condidered to be potential hydrocarbon traps in this relatively poorly‐explored area.

No abstract

Over the last few years, Saint Katherine, South Sinai has seen large scale development in connection with building new cities, land reclamation, and tourism. The Wadi El-Sheikh aquifer constitutes one of the major freshwater recourses in the Saint Katherine area. In that regard, ten Schlumberger vertical electrical soundings (maximum [Formula: see text]) associated with a number of measured and∕or calculated geoelectric and petrophysical parameters of the aquifer were conducted to delineate and assess the aquifer. Furthermore, subsurface stratigraphic data and measured hydrological parameters of shallow boreholes in the study area were integrated with the geoelectrical results. The integration of the sounding results, borehole data, and geoelectric and petrophysical parameters effectively delineated the alluvial fresh water aquifer with true resistivities ranging between 206 and [Formula: see text] and thickness ranging between 32 and [Formula: see text]. The northern part is characterized by a gradual decrease in porosity, electrical anisotropy coefficient, and total dissolved solid (TDS) concentrations. On the other hand, the northern part is characterized by a gradual increase in grain size, tortuosity, permeability, and transmissivity reflecting high aquifer potential. Moreover, the downward gravitational movement of groundwater is greater in the northern direction as well. Based on these findings, deep wide-spaced development water wells ([Formula: see text] depth) are recommended to be drilled in the northern area.

Nuweiba is one of Egypt’s strategic marine harbors and tourist sites located on the western coast of the Gulf of Aqaba. The absence of freshwater resources in Nuweiba necessitates investigations of local groundwater aquifers. Determination of the hydro-geophysical parameters of the Nuweiba alluvial fan constitutes the basic foundation for optimizing groundwater exploitation over time. Fifteen Schlumberger vertical electrical soundings (maximum [Formula: see text]), augmented by borehole stratigraphic data, aquifer tests, hydro-chemical analysis, and numbers of measured and/or calculated hydraulic parameters, were carried out in the study area. The fresh to brackish aquifer of Quaternary and pre-Quaternary alluvium sediments was effectively delineated with true resistivity and thickness ranges of [Formula: see text] and [Formula: see text], respectively. The western part of the aquifer has a large volume of fresh ground water for extraction and is characterized by a gradual increase in thickness [Formula: see text], grain size, transmissivity [Formula: see text], and a possible decrease in total dissolved solids levels [Formula: see text] and electrical anisotropy (1.10–1.11). Porosity (30.3–30.4%), tortuosity (1.348), formation factor (6) and hydraulic conductivity [Formula: see text] are essentially constant across the aquifer. The measured storativity of the aquifer is [Formula: see text], which is in accordance with the typical value of the unconfined aquifer at shallow depths.

No abstract

The Themed Fault marks the southernmost border of the Early Mesozoic passive continental margin of north Sinai. This 200-km long fault transects the northern part of the Tih Plateau that supposedly occupies a tectonically stable area. Post-Middle Eocene–pre-Early Miocene rejuvenation of this fault proceeded by right-lateral wrenching and represents a newly recognized phase of deformation in the history of north and central Sinai. The minimum estimate for the strike-slip movement on this fault is about 300–750 m. To the north of the Themed Fault is a narrow fault belt (Sinai hinge belt) that marks the boundary between a tectonically unstable crustal block to the north (the north Sinai fold belt area) and a tectonically stable crustal block to the south, the main part of the Tih plateau area.Four phases of dextral wrenching rejuvenated the faults of the Early Mesozoic passive continental margin in northern Egypt; one of them affected the Themed Fault. The oldest (Dl) deformation is early Late Senonian and is related to the closure of Neotethys and the Eastern Mediterranean basin. The D1 deformation proceeded by pure wrenching in the north Western Desert of Egypt. In contrast, it proceeded by transpression in north Sinai due to the irregular plate boundary and the relationship of this boundary to the slip vectors. D2 deformation (post-Middle Eocene–pre-Early Miocene) is clear in the Themed Fault area although reported herein for the first time; it is related to continued closure of the Eastern Mediterranean basin and proceeded by pure wrenching. D3 deformation (Late Oligocene–Early Miocene) proceeded by divergent wrenching in the north Eastern Desert and is kinematically related to the transfer of slip from the nearby faults of the Suez rift. D4 deformation (post-Early Miocene to Recent) affected the Sinai hinge belt by pure wrenching and is probably related to the left-lateral slip on the Dead Sea Transform and the related drag of the eastern edges of the fault blocks of this hinge belt. Recent seismic activity in the Sinai hinge belt perhaps indicates that the D4 deformation has continued to the present time, although morphological expression of recent tectonic movement is lacking. In contrast, the Themed Fault is seismically quiet at present.

Geotechnical parameters were used to determine subsurface rock quality for construction purposes. We summarize the mathematical relationships used to calculate the geotechnical parameters from P-and S-wave velocities and density values. These relationships are applied to two field examples; the first is a regional seismic study in Egypt and the second is a 2-D seismic profile recorded in Saudi Arabia. Results from both field examples are used to determine the subsurface rock quality and locate zones that should be avoided during construction. We suggest combining all geotechnical parameters into one map using a normalized-weighted relation, which helps to locate the zones with high versus low rock quality for engineering purposes.