JME 2003 3-4
Hala M. Rifaat
The taxonomic analysis of 114 actinomycete strains isolated from water of the River Nile and its bottom sediments showed thatmost of the water isolates belonging the genus Streptomyces. As well as, the majoring of the sediment isolates belongs to the genusMicromonospora. The overwhelming majority of Streptomyces species are Str. antibioticus, Str. aunlatus, Str. violaceus and Str.antimycoticus. M. carbonaceae and M. purpureochromogenes were also identified. Of 68 Streptomyces strains obtained, 11-exhi-bited significant antimycotic activity. Among the test fungi examined, Aspergillus niger and Trichoderma viride proved to be themost susceptible to the active substance present in the fermentation broths of Streptmyces strains. These active substances seem tobe polyenes.
Keywords: Biodiversity, actinomycetes, River Nile, antifungal.
Feliciano Martínez, Raquel G. Laureano & José Merino
The terminal part of the mitochondrial electron pathway, consists of two terminal oxidases: the cytochrome oxidase (sensitive tocyanide) and the alternative oxidase (both resistant to cyanide and sensitive to salicylhidroxamic acid). This study assesses thepresence and importance of these two respiratory branches in the roots of seven Mediterranean Quercus species (4 evergreens and3 deciduous) typical of the South Spain landscapes. The experiments were carried out with seedlings growing under controlledconditions. Determinations were performed using specific inhibitors of both respiration systems (potassium cyanide and sali-cylhydroxamic acid). The results showed that, under the experimental growth conditions, root respiration of all species was sensi-tive to salicylhydroxamic acid, indicating that the alternative oxidase was engaged.Under the experimental growth conditions, the seven woody species studied have a range of cyanide-resistant respiration (37.7 %- 60.9 %) which is in the line of the value published for Q. suber, but lower than those published for herbaceous species. Thissuggests that higher cyanide-resistant respiration might be adaptive in herbaceous species because of their generally higher growthand respiration rates. In the same line, the deciduous species considered in the present study showed a salicylhydroxamic acidsensitive respiration (32 % ± 2.2 %) that is significantly higher than that of the evergreen ones (20.7 % ± 0.8 %), which havegenerally lower growth and respiration rates. Besides, this suggests that the Mediterranean evergreen species are more efficient inthe use of energy than deciduous ones, which is in accordance with the putative low fertility of their habitats.Even not conclusive, the analysis of results shows a general pattern relating faster growth rates, more active tissues, higher respi-ration rates and higher alternative respiration rates; all which is in according with the expected as regards of the recent studies onthe nematode Caenorhabditis elegans.
Keywords: respiration, respiratory pathways, roots, Mediterranean trees, evergreens, deciduous
Mamdouh S. Serag
An ecological study was carried out to throw light on the associated flora, population parameters (mean height, density, number ofsprouts, number of flowering culms/m2) of Cyperus papyrus L in natural and managed stands. Results indicated that papyrusshowed a gaint growth form with an average height up to 4 m in June and August in both natural and managed stands, respectively.The peak of density of the plant was recorded in April and June with a gradual decrease during autumn and winter.The pH of the water where papyrus grows varied from 6.2 to 7.6 with a mean value of 7.5 and from 6.4 to 7.8 with a mean value of7.3 for both natural and managed stands, respectively. Conductivity of water ranged from 340 to 480 µS/cm with a mean value of398 µS/cm for the natural stand and from 280 to 520 µS/cm with a mean value of 475 µS/cm for the managed one.The soil of papyrus is rich in nutrients in particular total phosphorus and nitrogen. Total-P varied from 1.3 to 8.5 mg/100 g dry soilwith a mean value of 5.7 mg/100 g dry soil for the natural stand. For the managed stand the total-P ranged from 3.5 to 8.9 mg/100g dry soil with mean value of 6.3 mg/100 g dry soil. The hydrosoil support the growth of papyrus contained total-N ranged from 5.2to 9.5 mg/100 g dry soil and 3.7 to 9.9 mg/100 g dry soil with a mean value of 7.6 mg/100 g dry soil for both natural and managedstands, respectively.The maximum of about 30 kg/m2 fresh biomass was recorded in June for the above-ground parts for the natural and managedstands. The biomass of papyrus gradually decreased and the minimum values were obtained in winter. During late autumn andwinter the aerial culms of the sedge die and fall off. During December, in both studied stands, below-ground-biomass exhibited anopposite trend than the above-ground culms. The peak of biomass was obtained in June for above-ground parts, however the peakwas obtained for below-ground parts in December.
Keywords: biomass, ecological relations, papyrus, River Nile.
Annalisa Rotondi, Federica Rossi, Corrado Asunis & Carla Cesaraccio
Water appears as the major environmental constraint in Mediterranean climate, and global change effects are likely to provide morefrequent and longer drought periods. Water shortage has significant demographic effects on ecosystem composition, being someplant species thriving in arid environments because of a combination of several anatomical and physiological adaptations.In this study, co-occurring species of a typical thermo-Mediterranean macchia ecosystem were studied to survey the main anatomi-cal features. Observations performed confirmed the presence of several adaptive properties for the macchia ecosystem to couplewith the high temperature and solar radiation and the lack of summer rainfall typical of the Mediterranean climate. Most of thespecies examined show the presence in their internal leaf tissues of ergastic substances, mainly tannins and calcium oxalate, withdefensive functions, crucial in the adaptive resistance of plants to water stress. Nearly all the species present adaptations forprotection against the photo damage possibly induced from the strong UV-B solar irradiance in the summer. The more significantanatomical features are the trichomes, covering the abaxial surfaces of leaves. Such structures are able to regulate the water budgetof the plants both by influencing the diffusion boundary layer of the leaf surface and by regulating leaf optical parameters and,hence, leaf temperature. In many species, when trichomes or wax layers reduce radiation absorbance, two or three layers of palisa-de parenchyma are present, presumably concurring to provide a better efficiency in utilizing the photosynthetic light. In almostevery plant examined, stomata are sunken or well protected.This paper reports also the annual courses of the leaf water potential, net photosynthesis and transpiration rates of the four domi-nant species of the population (Juniperus phoenicea L., Pistacia lentiscus L., Phillyrea angustifolia L. and Chamaerops humilis L.)and the ecosystem flux.
Keywords: Drought, leaf anatomy, histology, ecophysiology, gas exchanges.
Roberto Bianconi, Corrado Battisti & Marzio
The patterns of richness and abundance of four forest interior bird species (Picus viridis, Picoides major, Sitta europaea, Garrulusglandarius), known as sensitive to habitat fragmentation, have been investigated in 12 fragment and 3 large forest sites in a mosaiclandscape of Central Italy using the line transect method. Fragment area and their isolation affected in different ways the patterns ofrichness and abundance of the studied species, except for Picus viridis. Tree mean diameter in the fragments does not seem to explainthe general patterns of the interior species in the study area, even though the uneven aged forest stand management of the fragmentmight, at least locally, sustain the presence of the species. Probably, the populations of the selected species may show a “patchystructure” in the study area and forest fragments could be functionally acting as stepping stones for local dynamics of individuals atlandscape scale. These preliminary results seem to confirm partially previously published data on these forest interior species (poordisperser, area-, isolation- and habitat quality-sensitive). Studied species (particularly, Sitta europaea and Garrulus glandarius) maybe proposed as “target/indicator” of fragmentation process, at least in the hilly fragmented landscape mosaics of Central Italy. Althou-gh, abundance of individual target species could be affected by stochasticity if referred to small sample of forest fragment, totalabundance of these species may be a useful dependent variable able to give rapid quantitative information for landscape planningstrategies at local scale (e.g. selection of nature reserves, Gap analysis, ecological network planning).
Keywords: habitat fragmentation, forest birds, target species, landscape planning.