2,591 research outputs found
Resolving the ‘Nitrogen Paradox’ of arbuscular mycorrhizas : fertilization with organic matter brings considerable benefits for plant nutrition and growth
Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilisation has been shown to elicit strong mutualism, characterised by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a 15N‐labelled, nitrogen‐rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Moreover, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant
Blurring Borders: Innate Immunity with Adaptive Features
Adaptive immunity has often been considered the
penultimate of immune capacities. That system is now being
deconstructed to encompass less stringent rules that govern its
initiation, actual effector activity, and ambivalent results.
Expanding the repertoire of innate immunity found in all
invertebrates has greatly facilitated the relaxation of
convictions concerning what actually constitutes innate and
adaptive immunity. Two animal models, incidentally not on the line
of chordate evolution (C. elegans and
Drosophila), have contributed enormously to defining
homology. The characteristics of specificity and
memory and whether the antigen is pathogenic or nonpathogenic
reveal considerable information on homology, thus
deconstructing the more fundamentalist view. Senescence, cancer,
and immunosuppression often associated with mammals that possess
both innate and adaptive immunity also exist in invertebrates
that only possess innate immunity. Strict definitions become
blurred casting skepticism on the utility of creating rigid
definitions of what innate and adaptive immunity are without
considering overlaps
A new sdO+dM binary with extreme eclipses and reflection effect
We report the discovery of a new totally-eclipsing binary (RA=06:40:29.11;
Dec=+38:56:52.2; J=2000.0; Rmax=17.2 mag) with an sdO primary and a strongly
irradiated red dwarf companion. It has an orbital period of
Porb=0.187284394(11) d and an optical eclipse depth in excess of 5 magnitudes.
We obtained two low-resolution classification spectra with GTC/OSIRIS and ten
medium-resolution spectra with WHT/ISIS to constrain the properties of the
binary members. The spectra are dominated by H Balmer and He II absorption
lines from the sdO star, and phase-dependent emission lines from the irradiated
companion. A combined spectroscopic and light curve analysis implies a hot
subdwarf temperature of Teff(spec) = 55 000 +/- 3000K, surface gravity of log
g(phot) = 6.2 +/- 0.04 (cgs) and a He abundance of log(nHe/nH) = -2.24 +/-
0.40. The hot sdO star irradiates the red-dwarf companion, heating its
substellar point to about 22 500K. Surface parameters for the companion are
difficult to constrain from the currently available data: the most remarkable
features are the strong H Balmer and C II-III lines in emission. Radial
velocity estimates are consistent with the sdO+dM classification. The
photometric data do not show any indication of sdO pulsations with amplitudes
greater than 7mmag, and Halpha-filter images do not provide evidence of the
presence of a planetary nebula associated with the sdO star.Comment: 13 pages, 5 figures; accepted for publication in Ap
Impact of European Integration on the Functioning of the Insurance Market in Poland
The transformation process, that has begun 20 years ago, generated significant changes in the structure and organization of Polish economy. It stimulated development of particular market's segments, especially of the insurance sector. Poland's accession to the European Union required conformity to Its regulations, fulfillment of several conditions connected with the membership in the European Community. The purpose of this article is to present the main consequences of Poland's integration with EU in the field of insurance market. Joining the common market was an important challenge for this sector in our country.Rok 1990 stanowił początek procesu transformacji systemu społeczno - gospodarczego i ustrojowego. Ostatnie 20 lat to okres intensywnych przemian o charakterze strukturalnym i organizacyjnym, w wyniku których ukształtowały się warunki rozwoju poszczególnych segmentów systemu finansowego państwa, zwłaszcza sektora ubezpieczeń. Przystąpienie Polski do Unii Europejskiej wymagało wprowadzenia szeregu zmian, dostosowujących polski porządek prawny do uregulowań wspólnotowych regulujących funkcjonowanie rynku ubezpieczeń. Celem artykułu jest zaprezentowanie szans i zagrożeń, jakie wynikają dla tego segmentu gospodarki z przystąpienia Polski do UE. Niewątpliwie proces integracji stanowił poważne wyzwanie dla polskiego rynku ubezpieczeń
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