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Different Biotic (different + biotic)
Selected AbstractsOyster greening by outdoor mass culture of the diatom Haslea ostrearia Simonsen in enriched seawaterAQUACULTURE RESEARCH, Issue 10 2001V Turpin Abstract Oyster greening was first described in the seventeenth century as a natural phenomenon. However, it has recently been discovered that the diatom Haslea ostrearia Simonsen causes greening by synthesis of a blue pigment designated as ,marennine'. This phenomenon, which involves massive proliferation of H. ostrearia in oyster ponds, was not understood or controlled by oyster farmers in the Marennes-Oléron region (Atlantic coast of France). As greening oysters improved their market value, they tried to develop empirical methods to guarantee oyster fattening and improve profits. In this context, the present study investigated the feasibility of mass culture of diatoms outdoors in 10-m3 ponds, using enriched seawater. Different biotic and abiotic parameters were monitored daily to determine the influence of the day,night temperature range. After 8 days, H. ostrearia was the dominant diatom species (66%), reaching a mean cell concentration of 2 × 105 cell mL,1 and a marennine concentration of 3.4 mg L,1. Although intensive greening was obtained, further studies are required to optimize the production stages before this technology can be transferred to oyster farmers. [source] Temporal, spatial and biotic variations in extrafloral nectar secretion by Macaranga tanariusFUNCTIONAL ECOLOGY, Issue 6 2000Heil M. Abstract 1Many plants produce extrafloral nectar (EFN) to nourish ants and other animals which defend them against herbivores. We aimed to find reasons for the high variability in amounts of EFN produced by most plant species. We investigated the influence of several biotic and abiotic factors (time of day, leaf age, nectar removal and leaf damage) on secretion rates of EFN in the common south-east Asian pioneer tree species, Macarangatanarius (L.) Muell. Arg. 2In most experiments leaves were washed with pure water and bagged in nets to protect them against nectar-collecting insects, and nectar was collected and quantified 24 h later. Six soluble sugars and up to eight amino acids were detected in nectar samples derived from untreated, field-grown plants. Total amounts of soluble substances varied more than the relative composition of EFN. 3Nectar secretion rates were highest on young, expanded leaves. A diurnal pattern with a secretion peak in the first 2 h after dusk was detected in the field. Nectar removal had a positive effect and its accumulation a negative effect on further EFN production. Artificial leaf damage (punching leaves with a needle or removing parts of the leaf blade with scissors) led to a significant induction of EFN production for the next 3 days. 4Extrafloral nectar of M. tanarius was secreted in complex patterns influenced by different biotic and abiotic factors; its production appeared to be adapted temporally and spatially in order to ensure optimal use of invested resources. [source] Growth in length and in body depth in young-of-the-year perch with different predation riskJOURNAL OF FISH BIOLOGY, Issue 3 2004C. Magnhagen Body shape of young-of-the-year (YOY) perch Perca fluviatilis, and number and size of potential predators (perch and pike Esox lucius) were compared across five lakes in northern Sweden. Body depth and dorsal fin ray length of YOY perch differed between lakes, with high relative body depth and long dorsal fin rays found in the lakes where the number of large piscivores was the highest. The most slender fish were found in the lake where the perch population had the smallest individuals and pike occurred in very low numbers. The average body mass in YOY perch from the two lakes with highest and lowest body depth, respectively, were the same, which indicates a difference between lakes in the relation between growth in length and in depth. Both body depth and fin ray length were correlated with predation risk by pike. Fin ray length was also correlated with number of piscivorous perch. Selection for different body shapes can be caused by different biotic and abiotic factors, singly or in combination, and the results from this study indicates that predation risk is one of these factors affecting body depth and fin ray length in perch. [source] The relative role of dispersal and local interactions for alpine plant community diversity under simulated climate warmingOIKOS, Issue 8 2007Kari Klanderud Most studies on factors determining diversity are conducted in temperate or warm regions, whereas studies in climatically harsh and low productivity areas, such as alpine regions, are rare. We examined the relative roles of seed availability and different biotic and abiotic factors for the diversity of an alpine plant community in southern Norway. Furthermore, because climate warming is predicted to be an important driver of alpine species diversity, we assessed how the relative impacts of dispersal and local interactions on diversity might change under experimental warming (open top chambers, OTCs). Addition of seeds from 27 regional species increased community diversity. The establishment of the species was negatively related both to the diversity of the existing system and the cover of the abundant dwarf shrub Dryas octopetala. These results show that both species dispersal limitation and local biotic interactions are important factors for alpine plant community diversity. Despite relatively harsh environmental conditions and low productivity, competition from the resident vegetation appeared to have a greater role for species establishment and diversity than facilitation and experimental warming. Higher temperature appeared to increase the negative relationship between resident species diversity and species establishment. This may suggest that climate warming can increase the role of interspecific competition for alpine plant community structure, and thus alter the long-term effects of biotic interactions on diversity. [source] Oxidative gating of water channels (aquaporins) in Chara by hydroxyl radicalsPLANT CELL & ENVIRONMENT, Issue 9 2004T. HENZLER ABSTRACT Hydroxyl radicals (*OH) as produced in the Fenton reaction (Fe2+ + H2O2 = Fe3+ + OH, + *OH) have been used to reversibly inhibit aquaporins in the plasma membrane of internodes of Chara corallina. Compared to conventional agents such as HgCl2, *OH proved to be more effective in blocking water channels and was less toxic to the cell. When internodes were treated for 30 min, cell hydraulic conductivity (Lp) decreased by 90% or even more. This effect was reversed within a few minutes after removing the radicals from the medium. In contrast to HgCl2, radical treatment reduced membrane permeability of small lipophilic organic solutes (ethanol, acetone, 1-propanol, and 2-propanol) by only 24 to 52%, indicating some continued limited movement of these solutes across aquaporins. The biggest effect of *OH treatment on solute permeability was found for isotopic water (HDO), which largely used water channels to cross the membrane. Inhibition of aquaporins reduced the diffusional water permeability (Pd) by about 70%. For the organic test solutes, which mainly use the bilayer to cross the membrane, channel closure caused anomalous (negative) osmosis; that is, cells had negative reflection coefficients (,s) and were transiently swelling in a hypertonic medium. From the ratio of bulk (Lp or osmotic permeability coefficient, Pf) to diffusional (Pd) permeability of water, the number (N) of water molecules that align in water channels was estimated to be N = Pf/Pd = 46 (on average). Radical treatment decreased N from 46 to 11, a value still larger than unity, which would be expected for a membrane lacking pores. The gating of aquaporins by *OH radicals is discussed in terms of a direct action of the radicals when passing the pores or by an indirect action via the bilayer. The rapid recovery of inhibited channels may indicate an easy access of cytoplasmic antioxidants to closed water channels. As hydrogen peroxide is a major signalling substance during different biotic and abiotic stresses, the reversible closure of water channels by *OH (as produced from H2O2 in the apoplast in the presence of transition metals such as Fe2+ or Cu+) may be downstream of the H2O2 signalling. This may provide appropriate adjustments in water relations (hydraulic conductivity), and a common response to different kinds of stresses. [source] | |||||||||||||