Absorption , fluorescence, delayed emission and photoacoustic spectra were obtained for the green photosynthetic bacterium. Whole cells incorporated in fluid (culture medium, viscous solution of polyvinyl alcohol, glycol) and rigid (isotropic and stretched polyvinyl alcohol film) media were investigated. The polarized absorption spectra of the stretched polyvinyl alcohol sample showed that the Qy transition moments of chlorosomal bacteriochlorophyll с was almost parallel to the film axis. Bacteriochlorophyll (BChl) с degradation occurred in some of the samples during prolonged storage and as a result a pigment absorbing at 670 nm, which was disaggregated BChl с or/and bacteriopheophytin c, was formed. This pigment was unoriented in stretched polyvinyl alcohol. The fluorescence spectrum of native cells can be analyzed using three Gaussian components at 754, 781 and 813 pm. The first component seems to be related to BChl с aggregates and the others to BChl a complexes. The time-resolved delayed luminescence spectra showed that practically all the complexes of green bacteria exhibited delayed emission but the decay times and intensities were different for the different complexes. In the photoacoustic spectra two maxima of the chlorosomal BChl с forms were well resolved and located at 748 and 765 nm. The photoacoustic maximum at 830 nm was probably related to the reaction centre (RC). In the Soret band the largest peak of the photoacoustic spectra was observed at 473 nm which showed that carotenoids absorbing in this range were losing more excitation by heat. The BChl с aggregates attached to chlorosome rods exhibited a peak at 446 nm. The efficient thermal deactivation also showed a BChl a located in RC (peak at 846 nm) and long-wavelength BChl a antenna complexes with a deactivation peak at 884 nm.
Patterns of fluorescence and colony tissue, colour were studied (field observations and epifluorescence microscopy) in six species of the coral genus Madracis over depth from 10 to 60 m at a reef slope in Curaçao. Two functions showed up: (1) Decrease in number of colourmorphs (n = 25) with depth suggests a photo-protective function where short wavelengths (e.g. UV) are transformed to long wavelengths, (2) Green fluorescence, observed in four species over their entire depth range, transforms radiation to wavelengths useful for photosynthesis. The observed patterns in fluorescence between species did not correspond to the current taxonomic classification. Our results do not support the usefulness of fluorescence as a taxonomic tool in corals. and M. J. A. Vermeij ... [et al.].
Life and research results of Pavel Siffel, a talented but untimely deceased Czech scientist in photosynthesis, are reviewed. He studied biophysics and physiology of chlorophyll, its complexes with proteins, their absorption and fluorescence spectra, activities in mutants and transformants, dealt with chlorophyll biosynthesis and protochlorophyllide photoreduction, pigments in plants grown at CO2 deficiency and under simulated acid rain, with changes accompanying leaf and plant development, photobleaching, etc. He participated in construction of specialised spectrofluorometers, finally he built the kinetic spectrophotometer SpeKin. and J. Květoň ... [et al.].
The photosynthetic response of three Arachis hypogaea L. cultivars (57-422, 73-30, and GC 8-35) grown for two months was measured under water available conditions, severe water stress, and 24, 72, and 93 h following re-watering. At the end of the drying cycle, all the cultivars reached dehydration, relative water content (RWC) ranging between 40 and 50 %. During dehydration, leaf stomatal conductance (gs), transpiration rate (E), and net photosynthetic rate (PN) decreased more in cvs. 57-422 and GC 8-35 than in 73-30. Instantaneous water use efficiency (WUEi) and photosynthetic capacity (Pmax) decreased mostly in cv. GC 8-35. Except in cv. GC 8-35, the activity of photosystem 1 (PS1) was only slightly affected. PS2 and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) were the main targets of water stress. After re-watering, cvs. 73-30 and GC 8-35 rapidly regained gs, E, and PN activities. Twenty-four hours after re-watering, the electron transport rates and RuBPCO activity strongly increased. PN and Pmax fully recovered later. Considering the different photosynthetic responses of the studied genotype, a general characterisation of the interaction between water stress and this metabolism is presented. and J. A. Lauriano ... [et al.].
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.