This work aimed to evaluate if chilling stress may be mitigated by elevated CO2 (EC) in Beta vulgaris L. plants. Photosynthetic rate was measured at 21% and 2% O2 after a short-term exposure of 5 h at four different treatments: 360 μmol(CO2) mol-1/25°C (AC); 360 μmol(CO2) mol-1/4°C (AC+LT); 700 μmol(CO2) mol-1/25°C (EC); 700 μmol(CO2) mol-1/4°C (EC+LT). Compared to AC+LT, EC+LT plants showed higher values of CO2 fixation, photochemical activity, and Rubisco amount. These latter invest a higher portion of photosynthetic electron flow to O2, differently from AC+LT plants that promote the regulated thermal dissipation processes. In EC+LT plants, the photosynthetic electron flow to O2 acts as a safety mechanism against the excess of absorbed light, upon return to prechilling conditions, allowing photosynthetic apparatus to maintain its efficiency. In AC+LT plants, the increase of thermal dissipation processes was not adequate to guarantee the PSII photoprotection and the photosynthetic recovery after chilling., C. Arena, L. Vitale., and Obsahuje bibliografii
Photosystem II (PSII) photochemistry was examined by chlorophyll (Chl) a fluorescence analysis in high-yield rice LYPJ flag leaves during senescence. Parameters deduced from the JIP-test showed that inhibition of the donor side of PSII was greater than that of the acceptor side in hybrid rice LYPJ. The natural senescence process was accompanied by the increased inactivation of oxygen-evolving complex (OEC) and a lower total number of active reaction centers per absorption. It indicated that the inhibition of electron transport caused by natural senescence might be caused partly by uncoupling of the OEC and/or inactivation of PSII reaction centers. Chl fluorescence parameters analyzed in this study suggested that energy dissipation was enhanced in order to protect senescent leaves from photodamage. Nevertheless, considerably reduced PSI electron transport activity was observed at the later senescence. Thus, natural senescence inhibited OEC-PSII electron transport, but also significantly limited the PSII-PSI electron flow., Y. W. Wang, C. Xu, C. F. Lv, M. Wu, X. J. Cai, Z. T. Liu, X. M. Song, G. X. Chen, C. G. Lv., and Seznam literaruty
Alhagi sparsifolia Shap. is exposed to a high-irradiance environment as the main vegetation found in the forelands of the Taklamakan Desert. We investigated chlorophyll a fluorescence emission of A. sparsifolia seedlings grown under ambient (HL) and shade (LL) conditions. Our results indicated that the fluorescence intensity in the leaves was significantly higher for LL-grown plants than that under HL. High values of the maximum quantum yield of PSII for primary photochemistry (φPo) and the quantum yield that an electron moves further than QA - (φEo) in the plants under LL conditions suggested that the electron flow from QA - (primary quinone electron acceptors of PSII) to QB (secondary quinone acceptor of PSII) or QB - was enhanced at LL compared to natural HL conditions. The efficiency/probability with which an electron from the intersystem electron carriers was transferred to reduce end electron acceptors at the PSI acceptor side and the quantum yield for the reduction of end electron acceptors at the PSI acceptor side were opposite to φPo, and φEo. Thus, we concluded that the electron transport on the donor side of PSII was blocked under LL conditions, while acceptor side was inhibited at the HL conditions. The PSII activity of electron transport in the plants grown in shade was enhanced, while the energy transport from PSII to PSI was blocked compared to the plants grown at HL conditions. Furthermore, PSII activity under HL was seriously affected in midday, while the plants grown in shade enhanced their energy transport., L. Li, X. Y. Li, F. J. Zeng, L. S. Lin., and Seznam literatury
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
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
Graft union development in plants has been studied mainly by destructive methods such as histological studies. The aim of this work was to evaluate whether the chlorophyll fluorescence imaging (CFI) technique is sensitive enough to reflect changes at the cellular level in different Solanaceae grafted plants 30 d after grafting, when both grafted partners were well fused and strong enough in all plant combinations. The pepper cultivar ‘Adige’ was grafted onto different Capsicum spp. accessions typified with different compatibility degrees; eggplant was grafted on Solanum torvum and pepper homografts as compatible unions; pepper was grafted on S. torvum and on tomato as incompatible unions. ‘Adige’/’Adige’ and ‘Adige’/pepper A25 showed a higher maximum quantum efficiency of PSII associated with higher values of actual quantum efficiency of PSII and photochemical quenching as well as with vascular regeneration across the graft interface. Our results highlighted that CFI changes reflected histological observations in grafted Solanaceae plants., C. Penella, A. Pina, A. San Bautista, S. López-Galarza, Á. Calatayud., and Obsahuje seznam literatury
Chlorophyll a fluorescence analysis (CFA) has been accepted to study postharvest activity and stability of photosynthesis of vegetables and salad greens, and some fruits. Commercial chlorophyll fluorescence imaging (CFI) systems may provide additional insight into spatial and temporal dynamics of photosynthesis. This yields valuable information on the effects of postharvest handling and processing (sorting, cutting, packaging, etc.) on physiological activity and 'internal quality' of green produce, and its changes. Here, meaning and physiological basics of relevant fluorescence parameters is briefly summarised, while major focus is on recent applications of CFI to evaluate quality and quality maintenance during postharvest handling and minimal processing of fresh fruits and vegetables. CFI is given surprisingly little attention in the monitoring of postharvest quality, although it is suitable for adjusting and/or optimising innovative postharvest techniques. Knowledge of the physiological base and the limit of interpretation is indispensable for meaningful interpretations of results to draw correct consequences., W. B. Herppich., and Obsahuje bibliografické odkazy
The objective of this study was to use nondestructive measurements as the precise irrigation indices for potted star cluster (Pentas lanceolata). Drought stress was imposed on plants for 0, 3, 5, 7, 12, and 16 d by withholding water. Measurements were conducted on the third leaf counted from the apex (upper leaves) and on the third leaf from the bottom (lower leaves). Within the range of soil water content (SWC) from 10 to 45%, leaf water potential (WP), SWC, and soil matric potential (SMP), chlorophyll fluorescence, photochemical reflectance index (PRI), adjusted normalized difference vegetation index (aNDVI), and the reflectance (R) at 1950 nm (R1950) were measured. The plants reached the temporary wilting point at -3.87 MPa of leaf WP; the maximal fluorescence yield of the light-adapted state (Fm′) ratio of upper-to-lower leaves was 1.7. When the Fm′ ratio was 1.3, it corresponded to lower-leaf WP < -2.27 MPa, SWC < 21%, SMP < -20 kPa, PRI < 0.0443, aNDVI < 0.0301, and R1950 > 8.904; it was the time to irrigate. In conclusion, the Fm′ ratio of upper-to-lower leaves was shown to be a nondestructive predictor of leaf WP and can be used to estimate irrigation timing., C. W. Wu, M. C. Lee, Y. L. Peng, T. Y. Chou, K. H. Lin, Y. S. Chang., and Obsahuje seznam literatury
We examined effects of late-season heat stress (L-SHS) on chlorophyll (Chl) fluorescence parameters and yield of bread wheat as well as roles of phosphate bio-fertilizer (PB-F) and Zn and B to compensate for the likely effects of heat stress. Factors were planting date (21 November and 5 January to coincide with grain filling to L-SHS) as the main factor, no inoculation (control) and inoculation of the seeds with PB-F as the sub-factor, and foliar application of water (control), Zn, B, and Zn + B as 3 L ha-1 as
sub-sub factor. Results revealed that L-SHS reduced maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, efficiency of PSII in the light-adapted state, and the grain yield. Moreover, L-SHS increased the nonphotochemical quenching. The PB-F mitigated the effects of L-SHS on Chl fluorescence, yield, and yield components. Among nutrients, the combined Zn + B was more effective in reducing the effects of L-SHS than that of Zn and B alone. Nevertheless, there was an interaction between foliar nutrients application and PB-F, suggesting that Zn application alone had a profound influence on improving Chl fluorescence parameters and increased yield in combination with PB-F., H. R. Eisvand, H. Kamaei, F. Nazarian., and Obsahuje bibliografii