Allelotoxicity of Oudneya africana R. Br. aqueous leachate on germination efficiency of Bromus tectorum L. and Triticum aestivum L.

This present study was conducted to investigate the possible allelopathic effect of Oudneya africana (donor species) on Bromus tectorum (weed species) and Triticum aestivum (cv. Sahel1; crop species) through germination bioassay experiment. B. tectorum is a winter annual grass that grows in winter wheat and other crops and in both disturbed and undisturbed grasslands. The effect of O. africana aqueous leachate (OAAL) on germination and seedling growth of B. tectorum and T. aestivum was investigated. Higher concentrations of the aqueous leachate significantly reduced the germination rate of B. tectorum. Similarly, coleoptile (CL) and radicle (RL) lengths of B. tectorum seeds was significantly inhibited. To go through with this, seedling growth of the weed species was also affected. On the other hand, the germination parameters of wheat seeds were slightly affected with applying different OAAL concentration levels compared to B. tectorum. In conclusion, allelochemicals extracted from the donor species caused a significant reduction in germination and growth parameters of B. tectorum > T. aestivum.Keywords: Aqueous leachate, Oudneya africana, Bromus tectorum, germination rateAfrican Journal of Biotechnology, Vol. 13(10), pp. 1194-1197, 5 March, 201

Carbon isotope signatures from land snail shells: Implications for palaeovegetation reconstruction in the eastern Mediterranean

In this studywecompare carbon isotope values inmodern Helix melanostoma shell carbonate (d13Cshell) from the Gebel al-Akhdar region of Libya with carbon isotope values in H. melanostomabody tissue (d13Cbody), local vegetation (d13Cplant) and soil (d13Csoil). All vegetation in the study area followed the C3 photosynthetic pathway. However, the d13Cplant values of different species formed two distinct isotopic groups. This can be best explained by different water use efficiencies with arid adapted species having significantly more positive d13Cplant values than less water efficient species. The ranges and means of d13Cbody and d13Cplant were statistically indistinguishable from one another suggesting that d13Cbody was primarily a function of local vegetation composition. H. melanostoma d13Cshell reflected the d13Cplant of local vegetation with a positive offset between body/diet and shell of 14.5± 1.4‰. Therefore, in the Gebel al-Akhdar where only C3 plants are present, highermeand13C shell values likely reflect greater abundances ofwater-efficientC3 plants in the snails diet and therefore in the landscape, whilst lower mean d13Cshell values likely reflect the consumption of less water-efficient C3 plants. The distribution of these plants is in turn affected by environmental factors such as rainfall. These findings can be applied to archaeological and geological shell deposits to reconstruct late Pleistocene to Holocene vegetation change in the southeast Mediterranean

Allelopathic effect of Euphorbia guyoniana aqueous extract and their potential uses as natural herbicides

The aim of the present study was to investigate the potential allelopathic effects of Euphorbia guyoniana (donor species) aqueous extract on germination efficiency of two weeds (Bromus tectorum and Melilotus indica) and one crop species (Triticum aestivum) under laboratory conditions. The germination efficiency, plumule and radicle length of Bromus was completely inhibited at the highest concentration of aqueous extracts of the donor species level (10%). The two recipient species exerted weak measures as affected by the highest concentration level of the donor. This inhibition was markedly obvious in B. tectorum than in M. indica indicating that B. tectorum is more sensitive to the tested donor, while the M. indica is more adapted to the aqueous extract than the B. tectorum

Management of the noxious weed; Medicago polymorpha L. via allelopathy of some medicinal plants from Taif region, Saudi Arabia

Germination bioassay was carried out to test the biological activity of Achillea santolina L. (ASAE), Artemisia monosperma Del. (AMAE), Pituranthus tortuosus L. (PTAE) and Thymus capitatus L. (TCAE) aqueous extracts (collected from Taif region, KSA) on germination percentage (GP), plumule (PL) and radicle (RL) lengths (mm) besides seedling dry weight (SDW) (mg/seedlings) of Medicago polymorpha L. The inhibitory effect of P. tortuosus was insignificant compared to the other three donor species which attained the strongest allelopathic potential in the following order: A. santolina > A. monosperma > T. capitatus. Growth experiment using crude powder of the four donor species was conducted to examine their effects on leaf area index (LAI), photosynthetic pigments, total available carbohydrates (TAC) and total protein (TP). It is worth mentioning that each of the four donor species crude powders mixed with clay loam soil appeared to have a great inhibitory allelopathic effect on LAI, total photosynthetic pigment and chlorophyll a (Chl a) while carotenoids exhibited a slight increase with the application of the four donor species crude powders. TAC and TP were significantly decreased with increasing the crude powder concentrations while a slight decrease was recorded for carbon/nitrogen (C/N) ratio. There is possibility of using these allelochemicals directly or as structural leads for the discovery and development of environmentally friendly herbicides to control weeds. The study recommended that these species must be phytochemically examined in future for their allelochemicals in order to provide information on the possibilities of using one or more of these species as bioherbicides. Keywords: Achillea santolina, Artemisia monosperma, Pituranthus tortuosus, Thymus capitatus, Bioherbicide

التكيفات الوظيفية لأشجار الزيتون (Ficus carcia) في النظم البيئي - زراعية لصحراء الساحل الغربي للبحر المتوسط بمصر

The ecophysiological characteristics of fig (Fi'cus carica, L.) trees, growing with maximum activity during the hot and dry summer, were studied in relation to growth, carbon partitioning, nutrient balance and water use. The initiation of growth was dependent on carbohydrate reserves (estimated usage = 62%). The trees enhanced their short growth span by rapid increase in leaf area associated with high photosynthetic rate early in the season, allowing a storage of 20% of net assimilate produced for latter use. High net primary production (3200 kgDM ha~') was the result of a high relative growth rate. About 46% of this production contributes to ligneous structure of the agroecosystem. Fig trees exhibited a positive nitrogen balance, among other nutrients, as a result of withdrawing nutrients prior to leaf abscision except for the excess calcium which is removed through litter. However, large quantities of resources are harvested within fruits, hence fertilizer application is essential for maintenance of yield. Although fig trees exhibited efficient water uptake and water use capacities, yet supplementary irrigation in years of below average rainfall is also important to maintain the relatively high transpiration rate and high annual water output.إستهدف البحث دراسة الصفات البيئي - فسيولوجية لأشجار التين السلطاني والتي تتميز بأقصى نشاط لها أثناء موسم الصيف الجاف والمرتفع في درجة الحرارة . وقد أمكن ربط هذه الصفات بتقديرات النمو ونسبته للأعضاء المختلفة ، إلى جانب ميزانية العناصر المعدنية واستخدام الماء المتاح . وقد تبين إعتماد النبات في بدء ثشاطه على مخزونه من الكربوآيدرات المتاحه ، بينما تميزت المراحل اللاحقة من فترة النمو القصيرة نسبيا لهذه الأشجار بزيادة سريعة لمساحة أوراقها الكلية مصحوبة بإرتفاع معدل البناء الضوئي مبكرا في موسم النمو، ويسمح هذا بتوفير كمية تخترن للاستخدامات اللاحقة تعادل 20% من مجموع إنتاجيتها . وقد كان لإرتفاع معدل النمو النسبي للمجموع الخضري تأثيره الواضح في إرتفاع الإنتاجية الأولية الصافية لأشجار التين . وقد أظهرت الدراسة وجود ميزان موجب للنيتروجين والذي يعزى إلى إعادة توزيعه بسحبه من الأوراق قبل موتها مع العديد من العناصر الأخرى فيما عد ا الكالسيوم الزائد والذي يتخلص منه النبات بتركيزه في النثار . وتبين الدراسة أيضا أن كمية كبيرة من المصادر الغذائية يتم حصادها في الثمار ، ولهذا فإنه من الهام إضافة المخصبات لهذه الزراعات لضمان إنتاجيتها بشكل جيد . ومن ناحية أخرى فإنه بالرغم من أن أشجار التين تبدي كفاءة في إمتصاص وإستخدام الماء إلا أنها تحتاج إلى إضافات مائية مقننة خلال سنوات الجفاف لموازنة إحتياجاتها المائية ، ولمقابلة معدلات النتح المرتفعة وكمية الماء المفقودة سنويا لهذه الأشجا