Winter wheat (Triticum aestivum L. cv Norin No. 61) was grown at 25°C until the third leaves reached about 10 cm in length and then at 15°C, 25°C, or 35°C until full development of the third leaves (about 1 week at 25°C, but 2-3 weeks at 15°C or 35°C). In the leaves developed at 15°C, 25°C, and 35°C, the optimum temperature for CO 2 -saturated photosynthesis was 15°C to 20°C, 25°C to 30°C, and 35°C, respectively. The photosystem II (PS II) electron transport, determined either polarographically with isolated thylakoids or by measuring the modulated chlorophyll a fluorescence in leaves, also showed the maximum rate near the temperature at which the leaves had developed. Maximum rates of CO 2 -saturated photosynthesis and PS II electron transport determined at respective optimum temperatures were the highest in the leaves developed at 25°C and lowest in the leaves developed at 35°C. So were the levels of chlorophyll, photosystem I and PS II, whereas the level of Rubisco decreased with increasing temperature at which the leaves had developed. Kinetic analyses of chlorophyll a fluorescence changes and P700 reduction showed that the temperature dependence of electron transport at the plastoquinone and water-oxidation sites was modulated by the temperature at which the leaves had developed. These results indicate that the major factor that contributes to thermal acclimation of photosynthesis in winter wheat is the plastic response of PS II electron transport to environmental temperature.Photosynthesis in plants native to areas with large seasonal variations in temperature during their growth exhibits an ability to acclimate to growth temperature (Berry and Bjö rkman, 1980). Plants that are grown at cold temperature regimes show maximum rates of photosynthesis at lower temperatures than do plants grown under warm temperature regimes, and an increase in growth temperature results in an increase in optimal temperature for photosynthesis. This enables plants to perform a high rate of photosynthesis at the growth temperature, provided that a shift in optimum temperature is not accompanied with counteracting changes in the photosynthetic capacity. The acclimation potential of photosynthesis to temperature greatly varies with the plant species and ecotypes. Although a shift in the optimum temperature for photosynthesis is generally less than one-half that in the growth temperature (Berry and Bjö rkman, 1980), several plants show dramatic changes in the temperature-response curve of photosynthesis. The optimum temperature for photosynthesis in winter wheat (Triticum aestivum L. cv Norin No. 61) grown at different seasons of the year increased with increase in the mean air temperature at a rate of about 3°C increase for each 4°C increase in the growth temperature (Sawada, 1970). A 15°C increase in the growth temperature resulted in a 15°C increase in optimum temperature for photosynthesis in Pinus taeda (Strain et al., 1976) and acclimation of Saxifraga cernua to a 10°C higher temperature was accompanied with about a 10°C upw...

One-pot sequences of hydrogenation/hydroamination to form indoles from (2-nitroaryl)alkynes and hydrogenation/reductive amination to form aniline derivatives from nitroarenes and aldehydes were catalyzed by Au nanoparticles supported on Fe(2)O(3). Nitro group selective hydrogenations and successive reactions were efficiently catalyzed under the conditions.

High-temperature effects on Photosystem II and plasma membranes, temperature dependence of growth, and acclimation to the growth temperature were studied in a mesophilic cyanobacterium, Synechocystis sp. PCC6803. The following results were obtained. (1) Small but distinct temperature acclimation of the PSII reaction center activity was shown for the first time when the activity was measured at inhibitory high temperatures. However, the reaction center activity showed no apparent acclimation when it was measured at growth temperatures after heat stress. (2) Oxygen-evolving activity and the permeability of plasma membranes showed higher resistance to heat when PCC6803 cells were grown at higher temperatures. (3) Acclimation of photosynthesis to the growth temperature seemed to occur so as to maintain photosynthesis activity not at a maximum level but in a certain range at the growth temperatures. (4) Neither sensitivity to high-temperature-induced dissociation of phycobilisomes from the PSII reaction center complexes nor degradation of phycocyanin were altered by changes in the environmental temperature. (5) A close relationship between the viability of cells and the structural changes of plasma membranes (but not the inactivation of photosynthesis) was observed. The denaturation process of PSII complexes and the relationship between the temperature dependence of the growth of Synechocystis PCC6803 cells and that of the photosynthetic activity are also discussed.

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Effects of high-temperature treatments on a thermophilic cyanobacterium, Synechococcus vulcanus, were studied, and the following results were obtained. (1) Oxygen evolution and the PSII photochemical reaction were the most sensitive sites and started to be inactivated at temperatures slightly higher than the cultivating temperature. (2) The decrease in the fluorescence Fv value reflected the inactivation of the charge separation reaction of PSII as well as that of the oxygen evolution reaction. (3) The dark fluorescence level, Fo, showed an increase at around 70 degrees C, which was partially reversed by further incubation at 50 degrees C. This increase reflected the inactivation of PSII reaction centers and probably dissociation of phycobilisomes from the PSII reaction center complexes. (4) At higher temperatures, phycobiliproteins disassembled and denatured in a pH-dependent manner, causing a large Fo decrease. (5) Cell membranes became leaky to low-molecular-weight substances at around 72 degrees C. (6) Inhibition of growth of the cells was recognized when the cells were pretreated at temperatures higher than 72 degrees C. Reversibility of the high-temperature effects and relationship between viability of the cells and the degradation of the cell membranes are discussed.