Typical chestnut thylakoid extracts isolated by mechanical disruption of leaf tissues had an equivalent of 0.28 kg m-3 chlorophyll (Chl) which is six times less than in thylakoids obtained from spinach, although Chl content in leaves was only half as small. According to optical microscopy, the vesicles showed a good integrity, exhibiting at 21 °C a high capacity of photon-induced potential membrane generation, which was demonstrated by the almost full 9-amino-6-chloro-2-methoxyacridine fluorescence quenching in a hyper-saline medium containing 150 mM KCl and having osmotic potential of -1.5 MPa. The half-time of the thylakoid potential generation was 11.7 s with the time of dissipation around 8.9 s. In such conditions, spinach thylakoids showed an increased swelling and also differences in the half-time generation which was almost four times faster than was observed in chestnut. However, when spinach thylakoids were incubated in a typical hypo-saline medium without KCl with osmotic potential -0.8 MPa, no additional swelling was observed. Consequently the half-time of potential dissipation was 35 s. Studies with nigericin suggested a chestnut thylakoid ΔpH significantly smaller than that observed in spinach, which was confirmed by the measurements of the ATP driven pumping activity. and J. Gomes-Laranjo ... [et al.].
In the epiphytic tillandsioids, Guzmania monostachia, Werauhia sanguinolenta, and Guzmania lingulata (Bromeliaceae), juvenile plants exhibit an atmospheric habit, whereas in adult plants the leaf bases overlap and form water-holding tanks. CO2 gas-exchange measurements of the whole, intact plants and δ13C values of mature leaves demonstrated that C3 photosynthesis was the principal pathway of CO2 assimilation in juveniles and adults of all three species. Nonetheless, irrespective of plant size, all three species were able to display features of facultative CAM when exposed to drought stress. The capacity for CAM was the greatest in G. monostachia, allowing drought-stressed juvenile and adult plants to exhibit net CO2 uptake at night. CAM expression was markedly lower in W. sanguinolenta, and minimal in G. lingulata. In both species, low-level CAM merely sufficed to reduce nocturnal respiratory net loss of CO2. δ13C values were generally less negative in juveniles than in adult plants, probably indicating increased diffusional limitation of CO2 uptake in juveniles., J. D. Beltrán ... [et al. ]., and Obsahuje bibliografii
Extreme conditions, such as drought, high temperature, and solar irradiance intensity, are major factors limiting growth and productivity of grapevines. In a field experiment, kaolin particle film application on grapevine leaves was examined during two different summer conditions (in 2012 and 2013) with the aim to evaluate benefits of this practice against stressful conditions hindering photochemical processes. We used chlorophyll a fluorescence to investigate attached leaves. Two months after the application, during the hottest midday, the kaolin-treated plants showed by the JIP test significantly higher quantum yield of PSII photochemistry, flux ratios, maximum trapped excitation flux of PSI, absorption flux, electron transport flux, maximum trapped energy flux per cross section, and performance index than plants under control conditions in the warmer year. On the contrary, the treated plants showed a lower initial slope of relative variable fluorescence and a decrease in the absorption and electron transport per cross section. The JIP test showed higher efficiency of PSII in the plants treated with kaolin mainly in 2013 (higher temperature and drought). Our results supported the hypothesis that the accumulation of active PSII reaction centres was associated with decreased susceptibility to photoinhibition in the kaolin-treated plants and with more efficient photochemical quenching. Grapevines in the Douro Region seems to profit from the kaolin application., L.-T. Dinis, H. Ferreira, G. Pinto, S. Bernardo, C. M. Correia, J. Moutinho-Pereira., and Obsahuje seznam literatury
In this study, the effects of lanthanum were investigated on contents of pigments, chlorophyll (Chl) fluorescence, antioxidative enzymes, and biomass of maize seedlings under salt stress. The results showed that salt stress significantly decreased the contents of Chl and carotenoids, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching (qP), and quantum efficiency of PSII photochemistry (ΦPSII), net photosynthetic rate (P N), and biomass. Salt stress increased nonphotochemical quenching (qN), the activities of ascorbate peroxidase, catalase, superoxide dismutase, glutathione peroxidase, and the contents of malondialdehyde and hydrogen peroxide compared with control. Pretreatment with lanthanum prior to salt stress significantly enhanced the contents of Chl and carotenoids, Fv/Fm, qP, qN, ΦPSII, P N, biomass, and activities of the above antioxidant enzymes compared with the salt-stressed plants. Pretreatment with lanthanum also significantly reduced the contents of malondialdehyde and hydrogen peroxide induced by salt stress. Our results suggested that lanthanum can improve salt tolerance of maize seedlings by enhancing the function of photosynthetic apparatus and antioxidant capacity., R. Q. Liu, X. J. Xu, S. Wang, C. J. Shan., and Obsahuje seznam literatury
We investigated the lead (Pb) effect on chlorophyll (Chl) fluorescence and photosynthetic electron transport system in Talinum triangulare (Jacq.) Willd. Plants were exposed to different concentrations of Pb(NO3)2 (i.e. 0, 0.25, 0.5, 0.75, 1.0, and 1.25 mM) for seven days in hydroponic experiments. Pb-treated leaves exhibited a relative decrease in Chl fluorescence induction curve, which resulted in the decrease of maximal fluorescence yield, maximal quantum yield, and effective quantum yield of PSII, while nonphotochemical quenching, quantum yield of regulated and nonregulated energy dissipation of PSII significantly increased during Pb stress. Furthermore, Pb concentrations also caused a decrease in maximal P700 change, photochemical quantum yield, nonphotochemical quantum yield, and ETR of PSI. We suggested that the changes in these parameters were a manifestation of Pb interference in the electron transport chain in both PSII and PSI. The sensitivity of PSII was greater than that of PSI in T. triangulare leaves., A. Kumar, M. N. V. Prasad., and Obsahuje bibliografii