Chlorophyll (Chl) a fluorescence parameters and rapid light curves of soybean [Glycine max (L.) Merrill] were measured by pulse amplitude modulation fluorometry. Measurements were taken during different stages of soybean growth under field conditions with 20% enhancement in ultraviolet-B (UV-B) radiation. Results showed that supplemental UV-B radiation decreased Chl contents by 5.5% (P=0.048), 8.7% (P=0.046), and 10.5% (P=0.005) in seedling, in branching-flowering, and in pod-setting stages, respectively. In the branching-flowering and pod-setting stages, maximum quantum yield of photosystem (PS) II photochemistry (Fv/Fm) decreased by 6.1% (P=0.001) and 3.0% (P=0.009), respectively. Supplemental UV-B radiation significantly decreased the effective quantum yield (Y). The photosynthetic capacity at light saturation (Pm) also decreased in both the seedling and branching-flowering stages by 28.9% (P=0.007) and 15.5% (P=0.041), respectively. However, Y and Pm showed no significant difference in the trefoil and pod-setting stages with and without the UV treatment. The light saturation parameter (E k) decreased by 21.1% (P=0.000) and 23.2% (P=0.029) in the trefoil and seedling stages, respectively. Moreover, the initial slope (α) decreased by 21.1% (P=0.001) in the branching-flowering stage. Nonphotochemical quenching (NPQ) in the seedling stage and photochemical quenching coefficient (qp) in the
branching-flowering stage decreased significantly under UV-B treatments. The results of the present study suggest that supplemental UV-B radiation adversely affected Chl content and electron transport activity in PSII and consequently decreased the photosynthetic efficiency of soybean plants., Z. Hu ... [et al.]., and Obsahuje bibliografii
In Cistus ladanifer L. the chlorophyll (Chl) concentration differed widely along a latitudinal transect in the Iberian Peninsula [1.15-3.56 g kg-i(d.m.) and 146-655 mg m*2(leaf area)], and Chl a/b ratio and A43o/A^65 showed also a considerable variation (2.79-3.38 and 1.93-3.32, respectively). Chl content on a dry matter basis increased from the top to the base of the plant, especially in individuals with high leaf area index (LAI) values. Young leaves, situated in the periphery of the plant, had lower Chl content per leaf area and higher A43o/A^65 values than mature, more sclerophyllous leaves. Plants ffom higher altitudes, that suffered cold winters, showed generally lower Chl contents than plants from warmer sites. The Chl content and A43o/A^65 index were more sensitive to intemal and environmental changes than the Chl a/b ratio.
Field experiments were conducted in Sicily (south Italy) to assess chlorophyll (Chl) fluorescence parameters in response of potato crop to nitrogen dose, to variation in genotype and in plant age, and to detect relationships between Chl content, fluorescence parameter Fv/Fm, and tuber yield. The experiment included five nitrogen doses (0, 10, 20, 30, and 40 g m-2) and four genotypes (Spunta, Sieglinde, Daytona, and Igea). Chl fluorescence parameters (initial fluorescence, F0, maximum fluorescence, Fm, variable fluorescence, Fv, Fv/Fm, Tmax (the time required to reach Fm), and Chl content were measured weekly between the appearance of the fifth and sixth leaves and the onset of plant senescence. A positive linear relationship was established between nitrogen supply and Chl content, F0, and Tmax. Nitrogen supply up to 10 g m-2 also had a positive effect on Fm and Fv, but above this rate it reduced Fv/Fm. Spunta had the highest Chl content, Fm, Fv, and Fv/Fm, but the lowest F0, whereas Sieglinde had the lowest Chl content, Fv, Fv/Fm, and Tmax and the highest F0. The cvs. Igea and Daytona exhibited intermediate Chl fluorescence parameters. Chl content and Tmax decreased with increasing plant age, whereas F0, Fm, and Fv increased until complete canopy development and thereafter declined until crop maturity. Tuber and plant dry matter yield were significantly correlated with Chl content, F0, and Tmax. Thus Chl fluorescence and content detect differences in the response of potato to N supply, can discriminate between genotypes, predict plant age, and yield performance under field conditions. and G. Mauromicale, A. Ierna, M. Marchese.
We tested whether cheap and quick chlorophyll (Chl) fluorescence can be used in ecophysiological field studies as proxies for
gas-exchange measurements. We measured net photosynthetic rate at saturating irradiance and ambient atmospheric CO2 concentrations (PNsat), maximum carboxylation rate (Vcmax), maximum quantum yield of PSII (Fv/Fm), the performance index (PIabs), leaf nitrogen (Narea), and carbon isotope discrimination (Δ13C) within four herbaceous species along two elevational gradients. We analysed the relationship between Chl fluorescence and gas-exchange parameters and their link to indirect assessment of plant performance via ecophysiological traits. Fv/Fm showed no relationship to PNsat and only weak relationships to Vcmax. PIabs was positively related to PNsat and Vcmax. PIabs, PNsat, and Vcmax were positively associated with Narea and negatively to Δ13C, whereas Fv/Fm showed no relationship to Narea and a positive to Δ13C. Thus, PIabs might be suitable to characterize the photosynthetic activity when aiming on large numbers of samples., S. F. Bucher, M. Bernhardt-Römermann, C. Römermann., and Obsahuje bibliografii
Sun-and shade-adapted plants of Ailanthus altissima utilized thermal-dissipative photoprotection (NPQ) across a range of photosynthetic photon flux densities (PPFD), with higher NPQ and lower maximum quantum yield of photosystem 2 photochemistry (Fv/Fm) in sun-adapted individuals, suggesting increased engagement of antennae-based quenching. Photosynthetic quantum requirements (Qreq; number of photons per CO2) were similar in sun and shade plants, but were low and comparable to forest understory species. Diurnal measurements showed that PPFDs in both habitats were consistently above photosynthetic compensation irradiance, and frequently exceeded saturating values. In addition, sun- and shade-adapted individuals possessed stomata that tracked short-term fluctuations in PPFD. Thus A. altissima may be unique in that it couples high, shade-plant like photosynthetic efficiency with high photosynthetic capacity in high-irradiance, while stomatal attributes that optimize water use efficiency are maintained in the shade. These features may contribute to success of A. altissima in establishing in disturbance-prone urban systems, and facilitate its spread into more PPFD-limited and competitive natural ecosystems.
The effect of water deficit on chlorophyll fluorescence, sugar content, and growth parameters of strawberry (Fragaria×ananassa Duch. cv. Elsanta) was studied. Drought stress caused significant reductions in leaf water potential, fresh and dry masses, leaf area, and leaf number. A gradual reduction of photochemical quenching (qP) and quantum efficiency (ΦPS2) was observed under drought stress while non-photochemical quenching (qN) increased. Maximum efficiency of photosystem 2 (Fv/Fm) was not affected by drought stress. and F. Razavi ... [et al.].
This study examined the utility of the ratio of variable fluorescence to maximum fluorescence (Fv/Fm) to detect freezing injury on buds of two Vitis vinifera cultivars: Pinot noir and Pinot gris. Freezing treatments on buds caused a decrease both in Fv/Fm and percentage of budburst, more severely on Pinot gris than Pinot noir, specifically at the lower temperature (-20°C). Fv/Fm ratio showed a close correlation with percentage of budburst, and a threshold of the lethal Fv/Fm was proposed as an indicator of bud mortality. and L. Zulini, C. Fischer, M. Bertamini.
Chlorophyll (Chl) fluorescence is a subtle reflection of primary reactions of photosynthesis. Intricate relationships between fluorescence kinetics and photosynthesis help our understanding of photosynthetic biophysical processes. Chl fluorescence technique is useful as a non-invasive tool in eco-physiological studies, and has extensively been used in assessing plant responses to environmental stress. The review gives a summary of some Chl fluorescence parameters currently used in studies of stress physiology of selected cereal crops, namely water stress, heat stress, salt stress, and chilling stress.
Acid rain causes damages to forest ecosystems. Here, we reported that acid rain could promote plant growth. From 2006 to 2009, one-year-old Elaeocarpus glabripetalus seedlings were sprayed with simulated acid rain (AR) (pH 2.5, 4.0, and 5.6). The maximum quantum yield efficiency of PSII and the actual photochemical quantum efficiency of PSII increased with rising AR acidity, which facilitated chlorophyll fluorescence and plant growth, as shown by a declining minimal fluorescence yield of dark-adapted state with little damage to the PSII reaction center. After the second experimental year, the plant height and ground diameter were greater at pH 2.5 than those found at pH 4.0 and 5.6. This showed the positive effects of AR on the seedling growth and photosynthesis of E. glabripetalus, revealing that this species exhibited a stronger resistance to acid deposition than some other tree species. This implies that E. glabripetalus is an acid-tolerant species., M.H. Liu, L.T. Yi, S.Q. Yu, F. Yu, X.M. Yin., and Obsahuje bibliografii
Photosynthetic fluorescence emission spectra measurement at the temperature of 77 K (-196°C) is an often-used technique in photosynthesis research. At low temperature, biochemical and physiological processes that modulate fluorescence are mostly abolished, and the fluorescence emission of both PSI and PSII become easily distinguishable. Here we briefly review the history of low-temperature chlorophyll fluorescence methods and the characteristics of the acquired emission spectra in oxygen-producing organisms. We discuss the contribution of different photosynthetic complexes and physiological processes to fluorescence emission at 77 K in cyanobacteria, green algae, heterokont algae, and plants. Furthermore, we describe practical aspects for obtaining and presenting 77 K fluorescence spectra., J. J. Lamb, G. Røkke, M. F. Hohmann-Marriott., and Obsahuje bibliografické odkazy