Note on the bacterial flora of the Egyptian desert in summer

Summary The response of bacterial population to edaphic drought of the Egyptian desert in summer has been investigated. The sporeformers Bacillus subtilis, Bacillus licheniformis, and Bacillus megaterium have predominated in the soil. B. subtilis and B. licheniformis predominated in the rhizosphere of the studied chamaephytes. The total bacterial counts were found to be much higher in the rhizospheres than in the soils apart. Azotobacter sp. and Clostridium sp. have been isolated from rhizospheres but not from soils. The significance of the rhizosphere as constituting a microhabitat in the desert community, has been discussed. The probable contribution of the peritrophic mantle of bacteria for protecting root cells against edaphic drought has also been notified.     

Nubian Complex strategies in the Egyptian high desert

Systematic survey by the Abydos Survey for Paleolithic Sites project has recorded Nubian Complex artifact density, distribution, typology, and technology across the high desert landscape west of the Nile Valley in Middle Egypt. Our work contrasts with previous investigations of Nubian Complex settlement systems in Egypt, which focused on a small number of sites in the terraces of the Nile Valley, the desert oases, and the Red Sea Mountains. Earlier research interpreted the Nubian Complex, in particular, as a radiating settlement system that incorporated a specialized point production. Our high desert data, however, indicate that the Nubian Complex associated with early modern humans in this region of the high desert reflects a circulating, rather than a radiating, settlement system, and that point production has been over-emphasized. Data available from our work, as well as sites investigated by others, do not conclusively identify Nubian Complex behavioral strategies as modern. These data, however, do contribute to the understanding of landscape use by early modern human populations living along the Nile Valley Corridor route out of Africa.     

Leaf and canopy photosynthesis of four desert plants: considering different photosynthetic organs

Photosynthesis Research - Desert plants evolve different photosynthetic organs to adapt to the extreme environment. We studied the leaf and canopy gas exchange, chlorophyll content, fluorescence...     

Phylogenetic diversity and ecological features in the Egyptian flora

Until fairly recently, regional-scale ecological and evolutionarypatterns have tended to be ignored as conservation efforts have been concernedwith species and their habitats. Here we compare frequencies in the Egyptianflora of particular rank sizes (order, family and genus) with patterns ofspecies abundance (classified as very rare, rare, common, or very common) and anarray of life-history attributes. The angiosperm flora of Egypt is representedby 2446 taxa (2088 species), including taxa in 10 subclasses, 51 orders, 120families, and 742 genera. A high degree of monotypism was observed: four ordersare monotypic (each existing as single species), and have very rare overallabundances; 30 families are monotypic (17 of which are very rare or rare); and 354genera are monotypic (over 70% of which are very rare or rare). Fourteenfamilies (in particular the Resedaceae and Zygophyllaceae) have at leastone-fifth of their global species represented in the Egyptian flora. Introducedspecies in general, and tree, aquatic herb and liana life forms all are especially well represented among monotypic genera. Native taxa are highlyrepresented among rare and very rare abundance classes, while introduced taxadid not differ significantly in their abundance patterns, compared to overallflora values. Few large genera (>20 spp.) occur in the flora, with mostspecies concentrated in genera containing 8–19 species per genus.Similarly, few families were highly speciose. Annual and herbaceous species weresignificantly over-represented, mainly among large, speciose genera andfamilies. However, perennials, trees, shrubs, aquatic herbs, lianas and parasiticspecies were found mainly in families and genera having very few taxa.Life-history attributes may have important implications to speciation rates.Taxonomically based results, involving abundances and life-history attributes,are discussed in the context of biodiversity and conservation.     

A chemurgic survey of the desert flora in the American Southwest

While commercial utilization of the desert flora in the American Southwest is still scarcely begun, there are possibilities of obtaining stock feed, alcohol, paper pulp, sugars, starches, resins, gums, alkaloids, oils and other extractives from the xerophytic plants of the region.     

Flexible feeding on cultivated underground storage organs by rainforest-dwelling chimpanzees at Bossou, West Africa

It has been proposed that exploitation of underground storage organs (USOs) played an important role in the evolution of the genus Homo, these items serving as ‘fallback foods’ during periods of low food availability. The use of USOs as food by wild chimpanzees is infrequent and seen mostly in populations inhabiting relatively arid environments, such as the savanna. Here, we specifically test the hypothesis that chimpanzees (Pan troglodytes verus) inhabiting tropical wet forest at Bossou (Republic of Guinea, West Africa) exploit USOs as a fallback food during periods of fruit scarcity. Chimpanzees were never observed feeding on wild USOs, that is, those that were never cultivated, and rarely on other underground plant parts. However, direct observations revealed regular consumption of the USOs of cultivated cassava (Manihot esculenta), a spatially abundant and continuously available plant, although the chimpanzees did not use tools when acquiring and feeding on cassava. In agreement with the fallback foods hypothesis, our results show that chimpanzees exploited cassava USOs more frequently when both wild and cultivated fruits were scarce, and consumption patterns of cassava paralleled those of wild fallback foods. These seasonal extractive USO foraging strategies by chimpanzees can strengthen attempts to construct a clearer picture of the importance of USO feeding in hominoid evolution.     

The ultrastructure of hemocytopoietic organs in the desert scorpion, Paruroctonus

The light and electron microscopes were used to examine possible hemocytopoietic tissue in the desert scorpion, Paruroctonus mesaensis. Results agree with earlier light microscopic studies that cells are released into the blood from the two lateral lymphoid organs and the supraneural gland. The former are sacciform structures attached by their anterior ends to the diaphragm. The supraneural gland forms the thickened wall of the supraneural artery in the mesosoma from the first to the third abdominal ganglia. The lateral lymphoid glands have an acellular stroma in which are embedded granular and agranular cells. The stroma is apparently formed by specialized cells which release membranous cell fragments that become the matrix of the gland. Cells are released into the body cavity from the periphery of the two organs. The supraneural gland has a fibrous stroma in which are embedded a variety of cell types. The cells appear to be released in greatest abundance into the blood in the lumen of the gland. The gland has cells with opaque granules (0.9-1.4 micron diameter) and agranular cells of variable shape. The most abundant cell, possibly the stem-cell for the others, is about 10 micron diameter and often has processes of variable length. In addition, muscle cells at various stages of differentiation are found at the inner margin of the gland. These cells have thick and thin myofilaments (24-32 and 5-8 nm diameter) and dense bodies which sometimes become organized into sarcomeres with Z-bands before the cells are released into the gland lumen. The function of these muscle cells is unknown, but possibly they contribute to the maintenance of blood pressure and the release of cells into the blood from the inner margin of the gland.     

Predator-mediated interactions among the seeds of desert plants

In theory, seed predators are capable of inducing indirect interactions among the seeds they consume. However, empirical evidence of predator-mediated interactions among seeds is rare. Rodents in the Heteromyidae are highly granivorous and therefore likely to induce indirect interactions among the seeds of desert plants. The indirect interactions may be in the form of apparent competition and apparent mutualism between seeds within a patch. Apparent competition exists when the survival of seeds of a focal species is lessened because of the presence of additional seeds of other species in the patch. Apparent mutualism exists when the presence of the other seeds results in an increase in survival of seeds of the focal species. By measuring seed removal from trays placed in the field, apparent competition between the seeds of several plant species was detected. Apparent mutualism might also exist, but there was no strong evidence of it. Apparent competition appeared most likely to occur among the species whose seeds were the most heavily predated. For instance, predation on seeds of Astragalus cicer, Oryzopsis hymenoides, and Sphaeralcea coccinea was substantial with more than 50% of the seeds removed from the trays, on average. The intensity of apparent competition (measured by the indirect effect, IS) between these species and two others was significant; IS ranged from –0.02 to –0.39 on a scale of 0 to –1. This indicates that, in some communities, indirect effects are most likely to exist when direct effects are strong. Received: 5 August 1999 / Accepted: 2 March 2000     

Nematode resistance in plants: the battle underground

Parasitic nematodes infect thousands of plant species, but some plants harbor specific resistance genes that defend against these pests. Several nematode resistance genes have been cloned in plants, and most resemble other plant resistance genes. Nematode resistance is generally characterized by host plant cell death near or at the feeding site of the endoparasitic worm. The timing and localization of the resistance response varies with the particular resistance gene and nematode interaction. Although there is genetic evidence that single genes in the nematode can determine whether a plant mounts a resistance response, cognate nematode effectors corresponding to a plant resistance gene have not been identified. However, recent progress in genetics and genomics of both plants and nematodes, and developments in RNA silencing strategies are improving our understanding of the molecular players in this complex interaction. In this article, we review the nature and mechanisms of plant-nematode interactions with respect to resistance in plants.     

Stable isotope composition of water in desert plants

A survey of the stable isotope content of tissue waters of plants from the Negev desert was conducted. Large differences were observed in the extent of enrichment of the heavy isotopes in leaf water relative to local precipitation among different plants. This is apparently caused by the species-dependent stratagems adopted by the plants to cope with water stress, primarily by differences in the depth of water uptake in the soil and through the timing of stomatal openings during the daily cycle. Salt stressed plants showed extreme variability in the isotopic composition of leaf–water. The results show that plants with adaptation to arid conditions can avoid the transpiration regime, which would lead to the strong isotopic enrichment in their leaf water expected under arid conditions. This has implications for the use of stable isotopes in plants as indicators of either plant ecophysiology or paleoclimate. Responsible Editor: Hans Lambers. G. Goodfriend is deceased.     

Some interesting species of Emericella and Aspergillus from Egyptian desert soil

Emericella desertorum Samson et Mouchacca spec. nov. is described and illustrated. It differs from the other Emericella species by the large ascospores with low crests. An Aspergillus conidial state was not observed. Additional information on the morphology and physiology of Emericella fruticulosa (Raper et Fennell) Malloch et Cain and Aspergillus egyptiacus Moubasher et Moustafa is given. The osmophilic and halophilic properties occurring within the genus Aspergillus are discussed.     

Annual plants in arid and semi-arid desert regions

Annual plants are the main vegetation in arid and semi-arid desert regions.Because of their unique traits,they are the optimal experimental subjects for eco-logical studies.In this article,we summarize annual plants' seed germination strategies,seedling adaptability mechanism to environments,seed dispersal,and soil seed banks.We also discuss the biotic and abiotic factors affecting the composition and dynamics of annual plant populations and communities.Because annual plants have important ecological functions in desert vegetation systems,this study on annual plants will be of great bene-fit to the conservation and restoration of desert ecosys-tems,the rational utilization of resources,and the sustainable development of desert regions.     

Annual plants in arid and semi-arid desert regions

Annual plants are the main vegetation in arid and semi-arid desert regions. Because of their unique traits, they are the optimal experimental subjects for ecological studies. In this article, we summarize annual plants’ seed germination strategies, seedling adaptability mechanism to environments, seed dispersal, and soil seed banks. We also discuss the biotic and abiotic factors affecting the composition and dynamics of annual plant populations and communities. Because annual plants have important ecological functions in desert vegetation systems, this study on annual plants will be of great benefit to the conservation and restoration of desert ecosystems, the rational utilization of resources, and the sustainable development of desert regions. __________ Translated from Chinese Journal of Ecology, 2006, 25(7): 851–856 [译自: 生态学杂志]     

Cold resistance mechanisms in high desert Andean plants

Freezing tolerance and freezing avoidance were studied, during the growing season, in plant species from two different elevations (3200 m and 3700 m) in a desert region of the high Andes (29° 45S, 69° 59W) in order to determine whether there was a relationship between plant height and cold resistance mechanisms. Freezing injury and supercooling capacity were determined in plants of different height, from ground-level (<20 cm tall) to tall shrubs (27–90 cm). All ground-level plants showed freezing tolerance as the main mechanism for resistance to freezing temperatures. Tall shrubs avoided freezing temperatures, mainly through supercooling. Supercooling was only present in plants occupying the lower elevation (i.e., 3200 m). Both avoidance and tolerance mechanisms are present in a single genus (i.e., Adesmia).     

Fungal flora of Egyptian baladi bread with special reference to the mutagenic effects of their toxic metabolites

The fungal flora of wheat flour and baladi bread in upper Egypt were investigated. Most of the isolated fungal species belong to the genus Aspergillus. The presence of non heat resistant fungi of the both flat surfaces of baladi bread, came from contamination after baking and from improper handling at homes. Among the heat resistant fungi, A. fumigatus and A. niger, were recorded to inhabit the spongy crumb although the high temperature of baking process which reached approximately 100 ° C in the center of the bread.The mutagenic effects of the fungal metabolites of the extract of mouldy bread was investigated. Several kinds of aberrations were observed in all stages of mitotic division. The most interesting effect of these fungal metabolites were the induction of tripolar and quadripolar spindle. Multinucleate and polyploid cells were also observed under relatively high concentrations. It was noticed that at either higher concentrations or lower concentrations with long exposure, damaged cells were observed. The hazards involved through the consumption of individuals to such mouldy bread, is accumulation of possible deleterious effects from both long and short term exposure to these toxic metabolites.     

Tolerance of photosynthesis to high temperature in desert plants

Winter- and summertime-active desert annual species were grown at different temperatures to assess their capacity for photosynthetic acclimation. Thermal stability of photosynthesis was determined from responses of chlorophyll fluorescence to increased temperature. Photosynthesis in winter ephemerals grown at 28°C/21°C became unstable close to 41°C in contrast to the summer annuals which were stable up to about 46°C. Growth at higher temperature (43°C/32°C) resulted in increases in thermal stability of 5 to 7°C for the winter annuals and 3 to 4°C for the summer annuals, showing that temperature can provide the primary stimulus for acclimation of the photosynthetic apparatus. The magnitude of these changes was very similar to the range of field values observed for the respective floras, indicating that the thermal acclimation response under field conditions was qualitatively similar to that occurring under controlled growth conditions. Perennial species, co-existing with these annuals in the desert, were on average more thermostable. The cacti were exceptionally heat stable, the threshold for fluorescence increase averaging 55°C.     

Rhizosphere fungal flora of cretain Euphorbiaceous plants

Rhizosphere mycoflora of four euphorbiaceous plants at seedling, flowering and senescent stages have been described. The fungal species were more common in the different rhizospheres in seedling stage when a number of casual forms were recorded. Later on a tendency towards specificity in fungal species was observed. The number of species isolated were generally highest in seedling stage and the least in senescent. The fungi per g of soil were always maximum at the time of maturity.     

黑龙江省木本植物区系分析

黑龙江省有木本植物392种,隶属于42科90属。其中裸子植物4科8属34种,双子叶植物37科81属357种,单子叶植物1科1属1种。本省为大兴安岭植物区、东北植物区和蒙古草原植物区三区汇集之地,木本植物地理成分复杂,具有非常明显的温带性质：温带分布科虽然与热带分布科数目相同,但所含种数多,优势明显;温带分布属占75.86%,以北温带分布比例最高;温带分布种占80.43%,以东北分布居首位,其次是中国—日本分布。该区系木本植物起源古老,有珍稀濒危植物9种,特有植物14种及红松、黄檗等孑遗植物,为第三纪植物区系系统。