Chlorophyll (Chl) a fluorescence transient and 820-nm transmission kinetic were investigated to explore the development of photosynthetic apparatus in grapevine leaves from emergence to full expansion. In this study, all leaves at various developing stages exhibited typical Chl a fluorescence transient. In newly initiating leaves, the maximum quantum yield of primary photochemistry (ϕP0) was slightly lower (<10 %) than that in fully expanded leaves. Nevertheless, the fluorescence rise from O to J step was clearly speeded up in young leaves compared with that in fully expanded leaves. Additionally, a distinct K step appeared in young leaves at high irradiances. With leaf development, the efficiency that a trapped exciton can move an electron into the electron transport chain further than QA - (Ψ0), the quantum yield of electron transport beyond QA (ϕE0), electron transport flux per excited cross section (ET0/CS0), the amount of active photosystem (PS) 2 reaction centres per excited cross section (RC/CS0), and the performance index on cross section basis (PICS) increased gradually and rapidly. Young leaves had strikingly lower amplitude of transmission at 820 nm. A linear relationship between Ψ0 and the transmission at 820 nm (I30/I0) was evident. Based on these data, we suggest that (1) the primary photochemistry of PS2 may be not the limiting step of the photosynthetic capacity during leaf growth under natural irradiance; (2) oxygen evolving complex (OEC) might be not fully connected to PS2 at the beginning of leaf growth; (3) though there are a few functional PS1 and PS2 at the early stages of leaf development, they match perfectly. and C.-D. Jiang ... [et al.].
Irradiation of etiolated leaves leads to their greening. Although this problem has a long history, the question of whether the intermittent irradiation (IMI) grown plants have fully functional reaction centres as well as the oxygen clock, before exposure to continuous irradiation (CI), had not been resolved. To answer this question, as well as to analyze the development of the two photosystems, the following parallel measurements were made: (1) Emission spectra at 77 K; (2) OJIP chlorophyll (Chl) a fluorescence transient; (3) period 4 oscillation in the flash number dependence of initial fluorescence F0 (at 50 µs) and FJ (at 2 ms); and (4) P700. In the 1-ms-flash (FL) grown pea, that has a different biogenesis of the photosynthetic apparatus, delayed light emission (DLE) and Chl a fluorescence transient were measured in parallel. Quantitative analysis of Chl a fluorescence values provided the following conclusions: (1) IMI, not FL, plants have almost fully developed reaction centres and the oxygen clock. (2) Further greening of IMI plants under CI involves two phases: (a) during 3-4 h of CI, the number of PS2 units and connectivity between them increase, and then (b) light-harvesting antenna increases. (3) In FL, 10 min CI activates fully the oxygen clock. and A. Srivastava, R. J. Strasser, Govindjee.
Meteorological parameters inside and outside an open-top chamber (OTC) fumigation facility were recorded and the primary photosynthetic response of four tree species measured with chlorophyll (Chl) a fluorescence emission. Parameters extracted from the Chl a fluorescence transient were used to calculate photosynthetic activity of the leaves using a performance index. Measurements were made during the night throughout a single growing season. The seasonal primary photosynthetic performance in all species was significantly altered by growth in the OTCs, and the degree of response was dependent upon the species. Wind was an important effectual component of the altered environment. The average temperature was consistently 1.94±0.70 °C higher within the OTCs, whereas wind speed fluctuated substantially more between inside and outside the OTCs (0 to 8 m -1). There was a correlation between the photosynthetic performance index and wind speed in Fagus sylvatica, Fraxinus excelsior, and Prunus serotina. The response to wind was also particular to each species; the photosynthetic performance of F. sylvatica increased with wind speed (1 to 7 m s-1), decreased with F. excelsior (0 to 6.5 m s-1) and P. serotina (0 to 5.5 m s-1). Abies alba, in contrast, was almost insensitive to wind. A model was proposed and tested for the conversion of the photosynthetic performance values collected in OTCs to predict the photosynthetic performance outside OTCs. The wide variety of responses to wind and temperature of the four species conformed to linear functions that describe the relationship of the wind speed and temperature responses with the difference in photosynthetic performance between the OTC and open environments. Specific coefficients for wind and temperature were proposed. The photosynthetic response to wind of each species depends on its ecophysiological specialisation. and A. J. Clark ... [et al.].
The effect of water on the primary photosynthetic activity of purple bacterium Rhodospirillum rubrum was studied in Hexadecane-Tween-Spane (HTS)- and phospholipid (PLC)-reverse micelles. Reverse micelles offer the possibility of modulating the amount of water to which enzymes and multienzymatic complexes are exposed. Fast bacteriochlorophyll (BChl) fluorescence induction kinetics and reaction centre absorption changes at 820 nm were used as an assay for the functional transfer of bacterial cells into HTS-reverse micelles and bacterial photosynthetic complexes (BPC) into PLC-reverse micelles. Both the bacterial cells and BPC showed an increase in the rate of primary photosynthetic activity by increasing the concentration of water in the reverse micelles. The bacterial cells could be kept viable for many hours in HTS-reverse micelles in presence of 6% (v/v) water. NMR studies indicated that the photosynthetic activity was affected by the availability of water in reverse micelles. The bacterial cells in HTS or BPC in PLC reverse micelles could be used to further understand the influence of water on the organisation and function of photosynthetic complexes. and A. Srivastava, A. Darszon, R. J. Strasser.
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 effects of submergence on chlorophyll (Chl) a fluorescence were compared in seven Oryza sativa (L.) cultivars, namely FR 13A, Khoda, Khadara, Kalaputia (tolerant), Sabita, and Hatipanjari (avoiding type), and IR 42 (susceptible). Seedlings were submerged for 4 d under complete darkness. Oxygen concentration of flood water decreased with the period of submergence with concomitant increase in concentration of carbon dioxide. Submergence caused diminution in the amount of total Chl. Genotypic differences were observed for Chl content and survival percentage. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of photosystem 2 (PS2) to submergence. The kinetics of Chl a fluorescence rise showed complex changes in the magnitudes and rise of O-J, J-I, and I-P phases caused by submergence. The selective suppression of the J-I phase of fluorescence especially after 2 d of submergence provided evidence for weakened electron donation from the oxygen evolving complex whereas under severe submergence stress (4 d) both O-J and J-I steps were suppressed greatly with highly suppressed P-step, which resulted in lowering of variable fluorescence. Grouping probability or energetic connectivity between PS2 obtained through JIP-test from the data after 2 d of submergence showed a direct relation with survival percentage, i.e. fluorescence measurements contained the information of the survival chance of a plant under submerged conditions. The information could be used in identifying the submergence tolerant cultivars when the damage is not very severe. and D. Panda ... [et al.].