Vol. 1 Issue 1
K.H. Batanouny and Aisha A. Turki
The environment and vegetation of an area in south-western Qatar have been studied. The area comprises different ecogeomorphological systems including: the littoral coastal plain. miocene ridges. rocky and conglomerate hamadas. colian sand formation. depressions. wadis and runnels.
The area lies within the SUbtropical dry zone of the desert. Rainfall is scanty and irregular both in time and space.
The vegetation comprises fifteen plant communities including:
a) Eight xerophytic plant communities dominated by Acacia tortilis-Lycium shawii. Panicum turgidum, Zygophyllum quatarense, Permisetum divisum, Hammada elegans. Rhamerium epapposum, Leptadenia pyrotechnica and Glossonema edule.
b) Seven halophytic plant communities dominated by Halopyrum mucronatum. Halopeplis perfoliata, Halocnemum strobilaceum. Limonium axillare. Anabasis serifera, Aeluropus lagopoides and Suaeda vermiculata.
The communities and their habitats were described. The segetal flora has been investigated.
Loutfy Boulos
Sonchus saudensis Boulos, sp , nov, is described from the western highlands of Saudi Arabia, and is also k.nown from the mounta,ins of Northern Yemen, It is most closely related to S. melanolepis Fresen, and S. obtusilobus R,E, Fries, endemics of the highlands of NE Ethiopia, and represents the only Asiatic element of the African subgenus Origosonchus Boulos.
A. M. A. Ismail
The leguminous tree Prosopis juliflora produces both small and large seeds the donnancy of which appears to be caused by the impenneability of the seed coat to water. Sulphuric acid was found to be the most effective breaker of donnancy. Seed size had no effect on the final gennination percentage prior to breaking of donnancy. After donnancy breaking the small seeds were the faster to germinate during the first five days but the ultimate percentage gennination of both categories of seeds was the same by the end of the experiment. As the donnancy was broken the percentage of seedlings emerging from both types of seeds was higher (and germination more rapid) from shallow sowing and decreased progressively with deeper sowing. Both types of seeds were found to germinate in a wide range of temperatures.
I.C. Hedge and R.A. King
A check-list is given of the known species of Cruciferae in the Arabian peninsula; it includes a selective synonymy and lists the countries of the area where they grow. An illustrated field-key to the 51 genera is followed by a short discussion 00 phytogeography and endemism.
Hussein M. Zeidan
Fluorescence and electron spin (spin labelling) resonance spectroscopy were used to verify the nature of the active site of bovine liver monoamine oxidase B. Fluorescence polarization studies demonstrated that the flavin moiety moves with a certain degree of mobility around the covalent bond.
The ESR spectrum of the enzyme labelled with an N-ethylmaleimide spin label shows components corresponding to weakly and to strongly irrunobilized labels. The binding of the probe to the active site over a temperature range of 5-50°C was studied. From the change of the ESR spectra, it is suggested that the active enzyme is in thermal equilibrium between two conformational states, and this conformational change involves only a short region of the active site of the enzyme. It is also suggested that the two conformational states may involve not only the active site suUhydryl group, but also the environment surrounding the flavine moiety of the enzyme. A model of the two conformational states of the active site of the enzyme is proposed.
Alan R. Katritzky, Azzahra M. EI-Mowafy, and Bernard Leddy
N-Substituted 2,4,6-triphenylpyridinium salts with sodium 2-oxido4,6-diphenylpyridine give olefins by elimination in fair to good yields. Other attempts to prepare olefins from pyridiniums are discussed .
Saboor Ahmad, Mohammad Jahangir and Mohsin Abdul Karim
As a result of continuing search among Saudi Arabian plants for new naturally occurring potential antitumor agents, an ethanolic extract of Euphorbia Iriaculeala Forssk. has met criteria for conflffi1ed activity in PL-388 leukemia system. The active extract has led to the isolation and characterization of a new diterpene, Triaculetin. This paper describes the isolation and structural elucidation of the new diterpene.
Samir Arabi and Patrick Sharrock
The importance of the transition elements in modem chemistry is emphasized with special mention of their role in catalysis. A new copper coordination complex is described, bis(2-methyl, 5-phenyloxazolidine-4carboxylato) copper (11) dihydrate. This compound is isolated as an intermediate in the copper-catalysed condensation reaction of aldehydes on amino-acids and is of importance in the synthesis of food products starting from petroleum derivatives.
John M. Mee
The general chemistry of Saudi Ground water is introduced by way of chemical analysis and parameters such as pH, electrical conductivity (E.C.), total dissolved solids (T.O.S.), and major cations and anions which are of significance to water quality. The frequency distribution of E.C. and T.O.S. in a random group water sample (n=530) with respect to water quality is presented. A new association between E.C. and T.O.S. for Saudi ground water is proposed with a modified formula: T.O.S. = (E.C. x 850) -200, which is subjected to further modification according to each regional ground water characteristics. Range and variation of individual major cations and anions are summarized for comparison via the utilization of RA WRC Water Bank samples which were collected according to E.C. range from 0.8 to 9.0 for the years 1981 and 1982.
Iftikhar Ahmad
The comparative kinetics of the oxidation of DL-valine and isoleucine by hydrogen peroxide in the presence of ferrous sulphate were studied at different temperatures in the acidic medium. The reaction is first order with respect to ferrous sulphate and amino acids , and zero order with respect to hydrogen peroxide. The reaction rate is higher in case of iso-leucine than that of DL-valine. The reaction mechanism for both the amino acids have been proposed and rate laws derived. The energies of activation were calculated to be 14.70 and 19.04 Kcal mol-' for iso-leusine and DL-valine, respectively .