The time course of photoinactivation of photosystem II in leaves revisited

Since photosystem II (PS II) performs the demanding function of water oxidation using light energy, it is susceptible to photoinactivation during photosynthesis. The time course of photoinactivation of PS II yields useful information about the process. Depending on how PS II function is assayed, however, the time course seems to differ. Here, we revisit this problem by using two additional assays: (1) the quantum yield of oxygen evolution in limiting, continuous light and (2) the flash-induced cumulative delivery of PS II electrons to the oxidized primary donor (P700+) in PS I measured as a ‘P700 kinetics area’. The P700 kinetics area is based on the fact that the two photosystems function in series: when P700 is completely photo-oxidized by a flash added to continuous far-red light, electrons delivered from PS II to PS I by the flash tend to re-reduce P700+ transiently to an extent depending on the PS II functionality, while the far-red light photo-oxidizes P700 back to the steady-state concentration. The quantum yield of oxygen evolution in limiting, continuous light indeed decreased in a way that deviated from a single-negative exponential. However, measurement of the quantum yield of oxygen in limiting light may be complicated by changes in mitochondrial respiration between darkness and limiting light. Similarly, an assay based on chlorophyll fluorescence may be complicated by the varying depth in leaf tissue from which the signal is detected after progressive photoinactivation of PS II. On the other hand, the P700 kinetics area appears to be a reasonable assay, which is a measure of functional PS II in the whole leaf tissue and independent of changes in mitochondrial respiration. The P700 kinetics area decreased in a single-negative exponential fashion during progressive photoinactivation of PS II in a number of plant species, at least at functional PS II contents ≥6 % of the initial value, in agreement with the conclusion of Sarvikas et al. (Photosynth Res 103:7–17, 2010). That is, the single-negative-exponential time course does not provide evidence for photoprotection of functional PS II complexes by photoinactivated, connected neighbours.The support of this study by an Australian Research Council Grant (DP1093827) awarded to W.S.C., a China Scholarship Council Fellowship to J.K., JSPS Postdoctoral Fellowships for Research Abroad (21-674) to R.O. and a Knowledge Innovation Programme of the Chinese Academy of Sciences Grant (KSCX2-EW-J-1) to D.-Y.F. is gratefully acknowledged

Sparse Representation for Wireless Communications:A Compressive Sensing Approach

Sparse representation can efficiently model signals in different applications to facilitate processing. In this article, we will discuss various applications of sparse representation in wireless communications, with a focus on the most recent compressive sensing (CS)-enabled approaches. With the help of the sparsity property, CS is able to enhance the spectrum efficiency (SE) and energy efficiency (EE) of fifth-generation (5G) and Internet of Things (IoT) networks

Comparison of velopharyngeal morphology of two palatoplasty techniques in patients with hard and soft cleft palate

PurposeThe study aims to compare the velopharyngeal morphology of hard and soft cleft palate (HSCP) patients after Furlow and Sommerlad palatoplasty.Patients and methodsA total of 51 patients (20 cases in Furlow palatoplasty group, 16 cases in Sommerlad palatoplasty group and 15 normal children in the control group) were included in our study. Velopharyngeal function and speech outcomes of patients with HSCP who had either Furlow palatoplasty or Sommerlad palatoplasty for cleft palate repair were evaluated by perceptual speech assessment (PSA), lateral cephalometric radiographs and nasopharyngoscopy. To assess velopharyngeal morphology of patients treated with two techqiques, we analyzed measurements such as velar length, pharyngeal depth, and the Adequate ratio (the ratio of velar length to pharyngeal depth). Furthermore, skeletal landmarks including cranial base, cervical vertebrae, posterior nasal spine which were defined as the pharyngeal triangle were measured. Finally, the position of the point U relative to the pharyngeal triangle were compared.ResultsVelopharyngeal closure (VPC) rate in Furlow palatoplasty group accounted for 90%, while that in Sommerlad palatoplasty group was 81.3%. PSA of the former group was significantly better than that of the latter group (P < 0.05). Velar length, pharyngeal depth and the Adequate ratio (1.37 ± 0.14 vs. 1.41 ± 0.15) were comparable between the Furlow group and control group (P > 0.05), while Sommerlad group had a shorter velar length, deeper pharyngeal depth and a smaller Adequate ratio (1.20 ± 0.18) compared to the above two groups (P < 0.05). Furhermore, the point U of Sommerlad group in the pharyngeal triangle was higher than that of the other two groups.ConclusionsIn the treatment modality of patients with HSCP, both Furlow palatoplasty and Sommerlad palatoplasty seem to be effective. Furlow palatoplasty appears to have velopharyngeal morphology similar to normal control group., while Sommerlad group shows a shorter velar length, deeper pharyngeal depth and a smaller Adequate rati

Partially dissecting the steady-state electron fluxes in Photosystem I in wild-type and pgr5 and ndh mutants of Arabidopsis

Cyclic electron flux (CEF) around Photosystem I (PS I) is difficult to quantify. We obtained the linear electron flux (LEFO2) through both photosystems and the total electron flux through PS I (ETR1) in Arabidopsis in CO2-enriched air. Delta Flux = ETR1 - LEFO2 is an upper estimate of CEF, which consists of two components, an antimycin A-sensitive, PGR5 (proton gradient regulation 5 protein)-dependent component and an insensitive component facilitated by a chloroplastic nicotinamide adenine dinucleotide dehydrogenase-like complex (NDH). Using wild type as well as pgr5 and ndh mutants, we observed that (1) 40% of the absorbed light was partitioned to PS I; (2) at high irradiance a substantial antimycin A-sensitive CEF occurred in the wild type and the ndh mutant; (3) at low irradiance a sizable antimycin A-sensitive CEF occurred in the wild type but not in the ndh mutant, suggesting an enhancing effect of NDH in low light; and (4) in the pgr5 mutant, and the wild type and ndh mutant treated with antimycin A, a residual Delta Flux existed at high irradiance, attributable to charge recombination and/or pseudo-cyclic electron flow. Therefore, in low-light-acclimated plants exposed to high light, Delta Flux has contributions from various paths of electron flow through PS I

An Integrated Solution of UAV Push-Broom Hyperspectral System Based on Geometric Correction with MSI and Radiation Correction Considering Outdoor Illumination Variation

The unmanned aerial vehicle (UAV)-borne hyperspectral imaging system has the advantages of high spatial resolution, flexible operation, under-cloud flying, and easy cooperation with ground synchronous tests. Because this platform often flies under clouds, variations in solar illumination lead to irradiance inconsistency between different rows of hyperspectral images (HSIs). This inconsistency causes errors in radiation correction. In addition, due to the accuracy limitations of the GPS/inertial measurement unit (IMU) and irregular changes in flight platform speed and attitude, HSIs have deformation and drift, which is harmful to the geometric correction and stitching accuracy between flight strips. Consequently, radiation and geometric error limit further applications of large-scale hyperspectral data. To address the above problems, we proposed an integrated solution to acquire and correct UAV-borne hyperspectral images that consist of illumination data acquisition, radiance and geometric correction, HSI, multispectral image (MSI) registration, and multi-strip stitching. We presented an improved three-parameter empirical model based on the illumination correction factor, and it showed that the accuracy of radiation correction considering illumination variation improved, especially in some low signal-to-noise ratio (SNR) bands. In addition, the error of large-scale HSI stitching was controlled within one pixel

Obstacles in the quantification of the cyclic electron flux around Photosystem I in leaves of C3 plants

Sixty years ago Arnon and co-workers discovered photophosphorylation driven by a cyclic electron flux (CEF) around Photosystem I. Since then understanding the physiological roles and the regulation of CEF has progressed, mainly via genetic approaches. One basic problem remains, however: quantifying CEF in the absence of a net product. Quantification of CEF under physiological conditions is a crucial prerequisite for investigating the physiological roles of CEF. Here we summarize current progress in methods of CEF quantification in leaves and, in some cases, in isolated thylakoids, of C3 plants. Evidently, all present methods have their own shortcomings. We conclude that to quantify CEF in vivo, the best way currently is to measure the electron flux through PS I (ETR1) and that through PS II and PS I in series (ETR2) for the whole leaf tissue under identical conditions. The difference between ETR1 and ETR2 is an upper estimate of CEF, mainly consisting, in C3 plants, of a major PGR5-PGRL1-dependent CEF component and a minor chloroplast NDH-dependent component, where PGR5 stands for Proton Gradient Regulation 5 protein, PGRL1 for PGR5-like photosynthesis phenotype 1, and NDH for Chloroplast NADH dehydrogenase-like complex. These two CEF components can be separated by the use of antimycin A to inhibit the former (major) component. Membrane inlet mass spectrometry utilizing stable oxygen isotopes provides a reliable estimation of ETR2, whilst ETR1 can be estimated from a method based on the photochemical yield of PS I, Y(I). However, some issues for the recommended method remain unresolved