Early development of the coccidium Sarcocystis muriviperae Matuschka, Heydom, Mehlhom, Abd-Al-Aal, Diesing et Bichler, 1987 is described from experimentally infected white mice fed sporocysts from naturally infected Vipera palaestinae and Coluber jugularis. Although the course of infection was similar, mice infected with the sporocysts from the first host survived an inoculum of up to 200,000 sporocysts, while others infected with the second, succumbed to inocula exceeding 40,000 sporocysts in 7-10 days post infection (p,i,). Histological and ultrastructural studies revealed merogony in the hepatocytes during days 7-10 p.i. and onset of sarcocyst development by days 19-21 p.i. The livers of infected mice are grossly enlarged and of a mottled whitish colour due to severe neutrophil inflammatory infiltration, apparently stimulated by host cell residues or from defunct disaggregating meronts at the end of the merogony cycle. Early sarcocysts undergo a further division by endopolygeny before proceeding to division by endodyogeny.
Six-year-old Scots pine (Pinus sylvestris L.) seedlings were grown in open top chambers (OTCs) at ambient (AC) or elevated (ambient + 400 µmol mol-1; EC) CO2 concentration for three years (1996-1998). Chlorophyll (Chl) a fluorescence of current and one-year-old needles was measured in the field at two-weekly intervals in the period July-October 1998. In addition, Chl, carbon (C), and nitrogen (N) concentrations in both needle age classes were determined monthly during the same period. Chl fluorescence parameters were not significantly affected by EC, suggesting there was no response of the light reactions and the photochemical efficiency of photosystem 2. Chl concentrations were not significantly different but a reduced N concentration was observed in needles of EC treatment. Significant differences between needle age classes were observed for all parameters, but were most apparent under EC and toward the end of the growing season, possibly due to an acclimation process. As a result, significant interactions between CO2 treatment, needle age class, and season were found. This study emphasizes the importance of repeated measures including different leaf/needle age classes to assess the photosynthetic response of trees under EC. and B. Gielen, M. E. Jach, R. Ceulemans.
a1_The effect of a wide range of temperatures (-15 and 60°C) in darkness or under strong irradiation [1,600 μmol(photon) m-2 s-1] on quantum yield of photosystem II photochemistry and xanthophyll cycle pigments was investigated in a tropical fruit crop (Musa sp.) and a temperate spring flowering plant (Allium ursinum L.). In darkness within the nonlethal thermal window of A. ursinum (from -6.7 to 47.7°C; 54.5 K) and of Musa sp. (from -2.2°C to 49.5°C; 51.7 K) maximal quantum yield of PSII photochemistry (Fv/Fm) was fairly unaffected by temperature over more than 40 K. At low temperature Fv/Fm started to drop with ice nucleation but significantly only with initial frost injuries (temperature at 10% frost damage; LT10). The critical high temperature threshold for PSII (Tc) was 43.8°C in A. ursinum and 44.7°C in Musa sp. Under strong irradiation, exposure to temperatures exceeding the growth ones but being still nonlethal caused photoinhibition in both species. Severity of photoinhibition increased with increasing distance to the growth temperature range. ΔF/Fm′ revealed distinctly different optimum temperature ranges: 27-36°C for Musa sp. and 18-27°C for A. ursinum exceeding maximum growth temperature by 2-7 K. In both species only at temperatures > 30°C zeaxanthin increased and violaxanthin decreased significantly. At nonlethal low temperature relative amounts of xanthophylls remained unchanged. At temperatures > 40°C β-carotene increased significantly in both species. In Musa sp. lutein and neoxanthin were significantly increased at 45°C, in A. ursinum lutein remained unchanged, neoxanthin levels decreased in the supraoptimal temperature range. In darkness, Fv/Fm was highly temperature-insensitive in both species., a2_Under strong irradiation, whenever growth temperature was exceeded, photoinhibition occurred with xanthophylls being changed only under supraoptimal temperature conditions as an antiradical defence mechanism., A. Dongsansuk, C. Lütz, and G. Neuner., and Obsahuje bibliografii
After some general remarks, a few observed time-scale in stars discussed in this colloquium are presented. Characteristic times in stellar models for the internal structure and the outerlayers are
reviewed. Examples of mode Identification are discussed. In the low frequency domain, the situation is quite simple. But the high frequency region is more difficult to decipher as many phenomena occupy the same domain: orbital motion, rotation of a non-uniform body, spheroidal g modes and Rossby waves. The linear framework is not always relevant and the nonlinear dynamic is more difficult to characterise. In general timescales alone cannot permit a mode idenfitication. Additional informations on energy content, amplitudes, coherence, multiplicity, stationarity are necessary to discriminate among the different possibilities.