Industrial chicory, Cichorium intybus L., is cultivated for the production of inulin. Most varieties of industrial chicory exhibit rather poor early growth, which limits further yield improvements in their European cultivation area. The poor early growth could be due to suboptimum adaptation of the gene pool to growth at low temperatures, sometimes in combination with high light intensities, which is typical of early-spring mornings. We have used chlorophyll (Chl) a fluorescence to evaluate the response of young plants of the cultivar 'Hera' to low temperatures and high light intensities. Plants were grown at three temperatures: 16°C (reference), 8°C (intermediate), and 4°C (cold stress). Light-response measurements were carried out at different light intensities in combination with different measurement temperatures. Parameters that quantify the photosystem II (PSII) operating efficiency (including PSII maximum efficiency and PSII efficiency factor) and nonphotochemical quenching (NPQ) are important to evaluate the stress in terms of severity, the photosynthetics processes affected, and acclimation to lower growth temperatures. The results clearly demonstrate that in young industrial chicory plants the photosynthetic system adapts to lower growth temperatures. However, to fully understand the plant response to the stresses studied and to evaluate the long-term effect of the stress applied on the growth dynamics, the subsequent dark relaxation dynamics should also be investigated. and S. Devacht ... [et al.].
Simultaneous measurements of leaf gas exchange and chlorophyll fluorescence for Koelreuteria paniculata Laxm. at 380 ± 5.6 and 600 ± 8.5 μmol mol-1 were conducted, and the photosynthetic electron flow via photosystem II (PSII) to photosynthesis, photorespiration, and other electron-consuming processes were calculated. The results showed that the photosynthetic electron flow associated with carboxylation (Jc), oxygenation (Jo), and other
electron-consuming processes (Jr) were 72.7, 45.7, and 29.4 μmol(e-) m-2 s-1 at 380 μmol mol-1, respectively; and 86.1, 35.3, and 48.2 μmol(e-) m-2 s-1 at 600 μmol mol-1, respectively. Our results revealed that other aspects associated with electronconsuming processes, except for photosynthesis and respiration, were neither negligible nor constant under photorespiratory conditions. Using maximum net photosynthetic rate (Pmax), day respiration (R), photorespiration rate (Rl), and maximum electron flow via PSII
(Jmax), the use efficiency of electrons via PSII at saturation irradiance to fix CO2 was calculated. The calculated results showed that the use efficiency of electrons via PSII to fix CO2 at 600 μmol mol-1 was almost as effective as that at 380 μmol mol-1, even though more electrons passed through PSII at 600 μmol mol-1 than at 380 μmol mol-1., Z. P. Ye, Q. Yu, H. J. Kang., and Obsahuje bibliografii
The effectiveness of eight spectral reflectance indices for estimating chlorophyll (Chl) content in leaves of Eugenia uniflora L., a tropical tree species widely distributed throughout the world and a key species for ecosystem restoration projects, was evaluated. Spectral reflectance indices were tested using sun and shade leaves with a broad variation in leaf mass per area (LMA). Shortly after plants were exposed to chilling temperatures, there was a dramatic visible change in some sun leaves from green to red. Prior to testing Chl-related reflectance indices, the green and red leaves were separated according to the anthocyanin reflectance index (ARI). Slightly green to dark green leaves corresponded to an ARI value less than 0.11 (n = 107), whereas slightly red to red leaves corresponded to an ARI value greater than 0.11 (n = 35). To estimate leaf Chl, two simple reflectance indices (SR680 and SR705), two normalized difference indices (ND680 and ND705), two modified reflectance indices (mSR705 and mND705), a modified Chl absorption ratio index (mCARI705) and an index insensitive to the presence of anthocyanins (CIre) were evaluated. Good estimates of leaf Chl content were obtained using the reflectance indices tested regardless of the presence of anthocyanins and changes in LMA. Based on the coefficients of determination (r2) and the root mean square errors (RMSɛc) the best results were obtained with reflectance indices measured at wavelengths of 750 and 705 nm. Considering the performance of the models the best reflectance indices to estimate Chl contents in E. uniflora leaves with a broad variation in LMA and anthocyanin contents was SR705 and mCARI705., M. S. Mielke, B. Schaffer, A. C. Schilling., and Obsahuje bibliografii
Epigenetická regulace aktivity genů může významnou měrou ovlivňovat fenotypovou variabilitu organismů. Vzhledem k tomu, že některá indukovaná epigenetická variabilita může být děděna po mnoho generací, je možné, že epigenetická variabilita ovlivňuje jak ekologii, tak i evoluční trajektorie organismů. V článku popisuji některé poslední poznatky úlohy epigenetické variability v ekologii a evoluci rostlin., Phenotypic variation can be driven by epigenetic regulation of genes' activity. It is possible that induced epigenetic variation can alter the ecology and evolutionary trajectories of organisms because some induced epigenetic variation can be faithfully heritable among several generations. In the article, I discuss some recent information about the role of epigenetic variation in the ecology and evolution of plants., and Vít Latzel.
Excitation kinetics based on feedback regulation of chlorophyll (Chl) fluorescence of leaves measured with the chlorophyll fluorometer, FluoroMeter Modul (FMM), are presented. These kinetics showed the variation of excitation light (laser power, LP) regulated by the feedback mechanism of the FMM, an intelligent Chl fluorometer with embedded computer, which maintains the fluorescence response constant during the 300-s transient between the dark- and light-adapted state of photosynthesis. The excitation kinetics exhibited a rise of LP with different time constants and fluctuations leading to a type of steady state. The variation of excitation kinetics were demonstrated using the example of primary leaves of etiolated barley seedlings (Hordeum vulgare L. cv. Barke) during 48 h of greening in the light with gradual accumulation of Chl and development of photosynthetic activity. The excitation kinetics showed a fast rise followed by a short plateau at ca. 30 s and finally a slow constant increase up to 300 s. Only in the case of 2 h of greening in the light, the curve reached a stable steady state after 75 s followed by a slight decline. The final LP value (at 300 s of illumination) increased up to 12 h of greening and decreased with longer greening times. The active feedback mechanism of the FMM adjusted the excitation light during the measurement to the actual photosynthetic capacity of the individual leaf sample. In this way, the illumination with excessive light was avoided. The novel excitation kinetics can be used to characterize health, stress, disease, and/or product quality of plant material., C. Buschmann ... [et al.]., and Obsahuje bibliografii
The hypothesis that application of exogenous glycine betaine (GBEX) may attenuate the effects of mild water deficit in leaf gas exchange and lipid peroxidation in Carapa guianensis was examined. For this reason, 110-d old plants were sprayed with 0, 25, and 50 mM GBEX and then subjected to two watering regimes. In the first, irrigation was continuously performed to maintain the soil near to field capacity (watered plants). In the second, irrigation was withheld and water deficit resulted from progressive evapotranspiration (water-stressed plants). Treatment comparisons were assessed when predawn leaflet water potential (Ψpd) of stressed plants reached -1.28 ± 0.34 MPa. Regardless of the watering regime, significant (P<0.05) increases in foliar glycine betaine (GBLeaf) concentration were observed in response to increasing GBEX; however, such increases were more expressive in stressed plants. The net photosynthetic rate, stomatal conductance to water vapor, and intercellular to ambient CO2 concentration ratio were significantly lower in water-stressed plants independently of GBEX concentration sprayed on leaves. The application of 25 and 50 mM GBEX caused significant (P<0.05) increases in ascorbate peroxidase (APX) activity in stressed plants, while significant (P<0.05) increases in catalase activity was observed just in the stressed plants treated with 50 mM GBEX. Malondialdehyde concentrations did not differ between watered and stressed plants regardless of GBEX concentration. In conclusion, C. guianensis was able to incorporate GBEX through their leaves and the resulting increases in GBLeaf attenuated lipid peroxidation in stressed plants through positive modulation of APX and CAT activities., F. J. R. Cruz ...[et al.]., and Obsahuje bibliografii