This study was designed to test the hypothesis that the spectral composition of incident radiation, as defined by the relative proportions of blue (B; λmax = 455 nm) and red (R; λmax = 625 nm) photons, can affect photosynthetic induction, since B photons stimulate stomatal opening and are more effectively absorbed by leaves than R photons. Different stages of photosynthetic induction, primarily determined by the photo-modulation of Rubisco activity and stomata opening, were investigated in dark-adapted leaves of Fagus sylvatica transferred to saturating irradiance [800µmol(photon) m-2 s-1] at B/R ratios of 1/3, 1/1, or 3/1.
In agreement with our hypothesis, photosynthesis was induced faster by irradiance with a high B/R ratio (3/1); as demontrated by a higher IS60 (induction state 60 s after leaf illumination) and lower T 90 (the time period required to reach 90 % of maximum steady-state photosynthesis). However, there were no differences in induction between leaves receiving equal (1/1) and low (1/3) B/R ratios. Electron transport was highly sensitive to radiation quality, exhibiting faster induction kinetics with increasing B/R ratio. Such stimulation of carbon-assimilatory processes corresponds with faster activation of Rubisco and lower non-photochemical quenching (NPQ) as the proportion of B photons is increased. In contrast, the kinetics of stomatal opening was independent of the spectral composition of incoming radiation. Since slightly higher absorption efficiency of high B/R radiation does not fully explain the changes in induction kinetics, the other possible mechanisms contributing to the stimulation of electron transport and Rubisco activity are discussed. and M. Košvancová-Zitová ... [et al.].
The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 µmol(photon) m-2 s-1]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660- 710 nm). Non-photochemical quenching of maximal (NPQ) and minimal fluorescence (SV0), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2 (LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660-710 nm) led to pronounced increase of NPQ, SV0, and the PS2 photochemical efficiencies (FV/FM and FV'/FM'), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %. and M. Štroch ... [et al.].
In vivo reflectance and fluorescence spectra from berry skins of a white (Riesling) and red (Cabernet Sauvignon) grapevine variety were measured during a ripening season with a new CMOS radiometer instrument. Classical reference measurements were also carried out for a sugar content of the berry juice [°Brix] and pigment contents (chlorophyll a and b, carotenoids, anthocyanins) from methanol extracts of the berry skin. We showed that the colours and the spectra analysed from them could be taken as an unambiguous indicator of grapevine ripening. Reflectance spectra, which were affected by the content of pigments (chlorophylls and anthocyanins), effects of surface (wax layers), and tissue structure (cell size) of the berries well correlated (R2 = 0.89) with the °Brix measurements of the berries. The fast data acquisition of both reflectance and fluorescence spectra in one sample with our radiometer instrument made it superior over the time-consuming, traditional, and mostly destructive chemical analysis used in
vine-growing management., M. Navrátil, C. Buschmann., and Obsahuje seznam literatury
Plants of Nicotiana benthamiana (Gray) (60 d old) were mechanically inoculated by a spreading of the fourth and fifth leaves with inoculum with or without plum pox potyvirus (PPV). Changes in growth parameters and selected photosynthetic characteristics were followed in control and inoculated plants in the locally affected leaves (LA) during 11 d after inoculation (DAI), in systemically affected leaves immature at time of inoculation (SAI) during 14-25 DAI, and in systemically affected leaves developed after the inoculation (SAD) during 28-39 DAI. The pure mechanical damage caused by inoculation induced a decrease in the net photosynthetic rate (PN) in LA and SAD leaves, and an increase in the steady-state value of the non-photochemical chlorophyll (Chl) fluorescence quenching qN. The qN increase appeared in certain time intervals in all measured leaves on plants, so it could be regarded as indication of a systemic reaction of plant to the local mechanical injury. The viral infection developed in LA leaves and spread to SAI and SAD leaves was documented by the ELISA-DASI method. The plant height and area of SAI and SAD leaves were lower in infected plants. The combined effect of mechanical damage and viral infection caused a decrease in PN only in LA and SAD leaves. In SAD leaves, an increased relative height of the J step (VJ) in the O-J-I-P Chl fluorescence transient together with a lower B/A band ratio of thermoluminescence glow curves reflected a damage to the acceptor side of photosystem 2 (PS2) caused by the viral infection, and a faster kinetics of the induction of the photochemical quenching coefficient qP of Chl fluorescence indicated a faster QA- re-oxidation in the remaining undamaged centres of PS2. and V. Hlaváčková ... [et al.].
Pro včasnou diagnostiku maligních chorob je důležité všímat si časných příznaků a včas zahájit širší diagnostický proces, jedině tak lze diagnostikovat nádor v počátečním stadiu, což povede k lepšímu léčebnému výsledku. Následující přehled uvádí výčet jak systémových (paraneoplastických projevů maligních chorob ? vzdálených projevů nádoru), tak vyjmenovává některé příznaky způsobené lokální expanzí nádoru. Cílem přehledu je připomenout všechny časné signály přítomnosti maligních chorob u nemocného a přispět k časné diagnostice a léčbě., Zdeněk Adam, G. Chlupová, J. Tomášek, and Lit. 34
Mechanical behavior of biological structures under dynamic loading generally depends on elastic as well as viscous properties of biological materials. The significance of “viscous” parameters in real situations remains to be elucidated. Behavior of rheological models consisting of a combination of inertial body and two Voigt’s bodies were described mathematically with respect to inverse problem solution, and behavior in impulse and harmonic loadings was analyzed. Samples of walls of porcine and human aorta thoracica in transverse direction and samples of human bone (caput femoris, substantia compacta) were measured. Deformation responses of human skin in vivo were also measured. Values of elastic moduli of porcine aorta walls were in the interval from 102 kPa to 103 kPa, values of viscous coefficients were in the interval from 102 Pa.s to 103 Pa.s. The value of shear stress moduli of human caput femoris, substantia compacta range from 52.7 to 161.1 MPa, and viscous coefficients were in the interval from 27.3 to 98.9 kPa.s. The role of viscous coefficients is significant for relatively high loading frequencies - in our materials above 8 Hz in aorta walls and 5 Hz for bones. In bones, the viscosity reduced maximum deformation corresponding to short rectangular stress., M. Kuchařová, S. Ďoubal, P. Klemera, P. Rejchrt, M. Navrátil., and Obsahuje bibliografii