We compared the sensitivity to cold stress, in terms of photosynthetic capacity and changes in chlorophyll fluorescence of photosystem 2 (PS2), of an evergreen and a deciduous oak species, which co-occur in the southeastern United States. We predicted that the evergreen species, Quercus virginiana, which must endure winter, is likely to have an inherently greater capacity for energy dissipation and to be less susceptible to chilling stress than the deciduous species, Quercus michauxii. Short-term cold stress in both species lead to greater than 50 % reduction in maximum photosynthetic rates, 60-70 % reduction in electron transport, and irreversible quenching of PS2 fluorescence. The kinetics of recovery in the dark after exposure to 1 h high irradiance (1000 µmol m-2 s-1) and chilling (5 °C) showed that the evergreen Q. virginiana exhibited more protective qE and less irreversible quenching (qI) than the deciduous Q. michauxii. The large qE which we observed in Q. virginiana suggests that the capacity for photoprotection at low temperatures is not induced by a long-term acclimation to cold but preexists in evergreen leaves. This capacity may contribute to the ability of this species to maintain leaves during the winter. and J. Cavender-Bares ... [et al.].
This work aimed to evaluate if chilling stress may be mitigated by elevated CO2 (EC) in Beta vulgaris L. plants. Photosynthetic rate was measured at 21% and 2% O2 after a short-term exposure of 5 h at four different treatments: 360 μmol(CO2) mol-1/25°C (AC); 360 μmol(CO2) mol-1/4°C (AC+LT); 700 μmol(CO2) mol-1/25°C (EC); 700 μmol(CO2) mol-1/4°C (EC+LT). Compared to AC+LT, EC+LT plants showed higher values of CO2 fixation, photochemical activity, and Rubisco amount. These latter invest a higher portion of photosynthetic electron flow to O2, differently from AC+LT plants that promote the regulated thermal dissipation processes. In EC+LT plants, the photosynthetic electron flow to O2 acts as a safety mechanism against the excess of absorbed light, upon return to prechilling conditions, allowing photosynthetic apparatus to maintain its efficiency. In AC+LT plants, the increase of thermal dissipation processes was not adequate to guarantee the PSII photoprotection and the photosynthetic recovery after chilling., C. Arena, L. Vitale., and Obsahuje bibliografii
Fourteen predatory species of ladybirds (Coleoptera: Coccinellidae) were collected from May to October 2008 from mountain ash (Sorbus aucuparia) infested with the scale insect Chionaspis salicis at 31 localities in the Ore Mountains, northern Bohemia, Czech Republic. Chilocorus renipustulatus, usually a rare species, made up 85% of the individuals collected (1690). Other abundant species were Coccinella septempunctata, Calvia quatuordecimguttata, Adalia bipunctata and Adalia decempunctata. The invasive alien Harmonia axyridis was present but made up less than one per cent of the individuals collected. Niche overlap between pairs of ladybird species measured in terms of the coefficient of community, Morisita's index and cluster analysis showed that microhabitat preferences were similar and hence the possibility of competition was high in two pairs of congeneric species (Chilocorus and Calvia). Larvae of Ch. renipustulatus were abundant from mid-June through August and were still present in October. and Emanuel Kula, Oldřich Nedvěd.
Chimaerula bonai sp. n. is described from the small Intestine of Phimosus infuscatus (Lichtenstein) in Paraguay. The new species differs from the other two species of Chimaerula Bona, 1994, i.e., Chimaerula woodlandi (Prudhoe, 1960) and Chimaerula leonovi (Belogurov et Zueva, 1968), mainly by the intermediate number of rostellar hooks (30-34 compared to 42-46 in the former and 20-22 in the latter), longer rostellar hooks (31-34 pm versus 26 pm and 19-21 pm, respectively), shorter cirrus sac (58-82 pm versus 158-201 pm and 134-183 pm, respectively) and the absence of rosethorn spines in the cirrus armament. Modifications in the generic diagnosis of Chimaerula are proposed in order to conform it with some peculiarities of the new species (i.e., the relatively small and thin cirrus, the absence of rosethom spines in its armament and the small cirrus sac).