Vol. 2 Issue 2

A. Mahmoud, A.M. El-Sheikh and S. Abdul Baset
Euryops arabicus is a perennial shrub whose distribution in Saudi Arabia is limited to the high mountainous region (2280- 3000 m above sea level) of the southern region and south Hijaz. The freshly harvested seeds were germinated over a range of alternating (12 hourly) temperature regimes; 18/8, 21/10, 28/14, 32/16, 36/21 and 40/26 C. The geobotanical distribution of E.arabicus is reflected in its germination temperature responses. The germination of the seed of E. arabicus is not regulated by genetically fixed innate dormancy. However, the germination temperature responses of the seeds of the species serve as a mechanism specific to environmental cues, which indicate the probability of favourable conditions for subsequent growth and seedlings establishment. The ecological significance of the temperature responses of the seeds is discussed.

A.M. El-Sheikh
Zygophyllum decumbens is a low perennial shrublet. Freshly collected seeds of Z. decumbens were germinated over a range of fluctuating temperature regimes. They were also germinated in varying salinity levels at two fluctuating (12 hourly) temperatures regimes: 21/10-36/21 C. Seeds germinated to comparable high percentages over the whole range of the temperature regimes tested but the rate of germination increased with rising temperature reaching an optimum within the range 21/10 - 36/21 C The inhibition of germination of the seeds of this species by excessive salinities (40, 80 and 100% seawater) is due to high osmotic potential of the medium.

Bashir M. Jarrar and R.M. Natour
Ten different foodstuffs consumed in several countries of the Middle East were tested for their suitability as substrates for aflatoxin production. Out of these, pine nut and Licorice Root (Sweet Root = Glycyrrhiza gabra) were found to favor the production of aflatoxin, which make them, under certain conditions, a source of risk

R.A. King and K.J. Kay
A checklist and field key (with illustrations) to the genera and species of Caryophyllaceae (including Illecebraceae) recorded from the Arabian peninsula and Socotra is presented. The checklist includes a selective synonymy and distribution by country and the keys include brief subfamily and generic descriptions

Iftikhar Ahmad and C. Muhammad Ashraf
A kinetic study of the oxidation of allyl alcohol by copper (II) acetate in the presence of palladium (II) chloride is reported. The progress of the reaction was observed by measuring the disappearance of copper (II) acetate concentration spectrophotometrically. The reaction is first order with respect to allyl alcohol and palladium (II) chloride, inverse first order with respect to [Cl-] and zero order with respect to copper (II) acetate. The rate is found to increase linearly with acetic acid concentration

S.B. Salama, D. Diab and S. Wasif
The refractive indices, dielectric constants, densities, vapour pressures and viscosities of acetonitrile (MeCN)- dimethyl sulphoxide (DMSO) mixtures were determined. The data point to deviations from ideality confirming the existence of solvent- solvent interactions. These interactions appear to reach a maximum in the 1 : 1 mole ration and are confirmed from infrared and Raman spectra of solvent mixtures

Iftikhar Ahmad and EI Fatih Abdel Wahab
The kinetics and mechanism of the oxidation of maleic and fumaric acids by hydrogen peroxide in the presence of ferrous sulphate has been studied. The oxidation rate of fumaric acid is faster than that of maleic acid. The reaction is first order with respect to maleic acid or fumaric acid and first order with respect to ferrous sulphate but zero order with respect to hydrogen peroxide. The energies of activation have been calculated to be 24.36 and 38.29 kj mol-1 for maleic and fumaric acids, respectively. A reaction mechanism has also been proposed.

N.R. El-Rayyes
The Michael acceptors (chalcones II) react with the ethyl phenylacetate carbanion I in the presence of sodium hydride at room temperature and yield the corresponding Michael products: gamma- aroyl butyrates III(from one mole each of I and II), the corresponding acids IV, or 2, 4-diaroyl- cyclohexanones V(from mole I and two moles of II). The nature of these products depends on the reaction conditions. The mechanism of the formation of the cyclohexanone derivatives (Va-g) as well as the regression of the Michael reaction are discussed.. The structure of all products were inferred by chemical and spectroscopic methods.

A.M. El-Naggar, F.S.M. Ahmed, A.M. Abd El-Salam and M.A. El-Gazzar
The synthesis of a number of beta- (2-quinolyl)- acryloyl amino acid methyl esters (II-IX), beta- (2-quinolyl)- alpha, beta-dibromo acryloyl amino acid methyl esters (XXVI- XXX) and beta- [2-(4- hydroxy-6-nitro)- quinolyl]- acrylic yamino acid methyl esters (XXXII- XXXV) have been carried out by the condensation of the corresponding acids (I or XXV or XXXI) with amino acid methyl ester hydrochlorides in THF-Et3N medium using DCC procedure. Hydrazinolysis of the methyl esters (II-IX and XXXII-XXXV) in methanol or ethanol gave the corresponding hydrazides (X-XVII and XXXVI- XXXIX), respectively. The azides from (XI- XVII) on coupling with gamma- TyrOme gave the desired dipeptides (XVIII-XXIV). Beta- (2-quinolyl)- acryloyl-gamma- Leu- OMe (V) and beta- (2-quinolyl)- alpha, beta-dibromo acryloyl- Gly-OMe (XXVI) were found to be active against a number of microorganisms.

Saleh Mohamed Okla
A complete section of the Tuwaiq Mountain Limestone (upper Jurassic) was measured along a new road cut through the Tuwaiq Mountain escarpment between Riyadh and Al Mizahmia to the west. The section is 193 meters thick. The lower 103.3 meters of the section are designated as the Lower Tuwaiq Mountain Limestone, and the upper 89.7 meters are designated as the Upper Tuwaiq Mountain Limestone. Incomplete sections in the Upper Tuwaiq Mountain Limestone were also measured at the Old Darb Al Hijaz to the north of the main complete section and at Wadi Nisah to the south. These are 49.3 m and 27 m thick, respectively. The Lower Tuwaiq Mountain Limestone is characterized by alternating light yellow, spicular biomicrites and light gray, pelletiferous biomicrites. The Upper Tuwaiq Mountain Limestone comprises light gray, hard, ledge forming biomicrites with abundant corals, stromatoporoids and algae. The microfacies of the Tuwaiq Mountain Limestone are the product of carbonate deposition in two major carbonate environments that prevailed successively over the flooded Arabian Platform. The first represented a calm and sheltered seafloor that was subject to periodic agitation, whereas the second had more open marine conditions. The final phase of deposition was particularly characterized by abundant blue green and dasycladacean algae