Coral reef bleaching is a global phenomenon poorly understood today. We investigated during 7 d the photosynthetic behaviour of symbionts of coral reef and temperate foraminifers in hospite, by means of the JIP-test. By this screening test the fast fluorescence rise O-J-I-P, measured by a Plant Efficiency Analyser (PEA) with 10 µs time resolution and 12 bit signal resolution, was analysed. It informs about the structure and function of photosystem 2 being at different physiological states established by adaptation to different irradiance and temperature. The test needs a measuring time in vivo of only 1 to 5 s, and thus many samples can be analysed. The measurements can be done continuously even on a single cell in a test tube or on the reef. The reef foraminifers tested here were Amphistegina and Amphisorus, freshly collected in Mauritius. As a temperate foraminifer, Sorites from the Mediterranean Sea was tested. The cells are very sensitive to slight temperature changes (25 to 32 °C). The comparison showed that the more the foraminifers live in an environment with constant temperature the less they are able to respond to temperature changes and, thus, the less they can adapt. Rising the temperature increases in general the sensitivity to different stress factors, such as high irradiance, pH, CO2, etc. After the test series, the cells recovered fully and were kept in an aquarium for long time observation. and R. J. Strasser, M. Tsimilli-Michael, M. Pêcheux.
The chloroplast development in maize (Zea mays L.) is retarded at low growth temperatures. The composition of thylakoid membranes isolated from fiiliy-expanded leaves of plants grown at 17/14 or 14/12 “C (day/night) differed markedly from that of 25/22 "C-grown plants dne to a deficiency of chloroplast-encoded gene products. Appreciable net synthesis of thylakoid proteins in vivo was observed in a 3-h labelling period with p^SJ-methionine at 14/12 “C, but the ratio of accumuiated chloroplast- to nuclear-encoded products was lesser than at 25/22 °C. The protein synthesis by chloroplasts in vitro demonstrated that the accumulation of thylakoid membrane proteins was markedly temperature-dependent. Both the protein assembly into thylakoids and its subsequent breakdown took plače more rapidly at higher temperatures. Extensive differences in nuclear protein composition were observed between maize leaves grown at 14/12 and 25/22 "C, suggesting a possible role for nuclear factors in suppressing the expression of genes for chloroplast proteins at temperatures which inhibit thylakoid assembly.
We investigated the effects of long-term acclimation of Eucalyptus nitens seedlings to ultraviolet-A (UV-A) irradiation (320-400 nm) on phenolic compounds (gallotannins, stilbenes, and flavonols), photochemical efficiency, and chlorophyll and carotenoid contents. Seedlings were raised under four nutrient regimes, ranging from low to high application rates, in an environment that included or excluded UV-A irradiance. Our aims were: to classify phenolic compounds that absorb in the UV-A and their relative contribution to total UV-A absorption; to identify how phenolic compounds respond to UV-A exposure and exclusion, and to determine how plant nutrient status affects acclimation of photo-and pigment-chemistry to UV-A exposure and exclusion. Gallotannins contributed to only a minor fraction of total absorption within the lower range (320-360 nm) of the UV-A spectrum. Stilbene and flavonol compounds dominated absorption within the 320-360 and 360-400 nm ranges, respectively. Contents of gallotannin were generally high in UV-A-exposed seedlings. Although there was a significant effect of UV-A on contents of stilbenes, a general response (across nutrient treatment comparisons) was not evident. Contents of flavonols were not affected by UV-A exposure. Contents of gallotannin, stilbene, and flavonols decreased from low to high nutrient-application treatments. There were no effects of UV-A on photochemical efficiency or pigment-chemistry. and D. C. Close ... [et al.].