Phosphene is the experience of light without natural visual stimulation. It can be induced by electrical stimulation of the retina, optic nerve or cortex. Induction of phosphenes can be potentially used in assistive devices for the blind. Analysis of phosphene might be beneficial for practical reasons such as adjustment of transcranial alternating current stimulation (tACS) frequency and intensity to eliminate phosphene perception (e.g., tACS studies using verum tACS group and sham group) or, on the contrary, to maximize perception of phosphenes in order to be more able to study their dynamics. In this study, subjective reports of 50 healthy subjects exposed to different intensities of retinal tACS at 4 different frequencies (6, 10, 20 and 40 Hz) were analyzed. The effectiveness of different tACS frequencies in inducing phosphenes was at least 92 %. Subject reported 41 different phosphene types; the most common were light flashes and light circles. Changing the intensity of stimulation often induced a change in phosphene attributes. Up to nine phosphene attributes changed when the tACS intensity was changed. Significant positive correlation was observed between number of a different phosphene types and tACS frequency. Based on these findings, it can be concluded that tACS is effective in eliciting phosphenes whose type and attributes change depending on the frequency and intensity of tACS. The presented results open new questions for future research.
The oxygen-evolving complex (OEC) of Zostera marina is prone to deactivation under visible light, which results in a formation of the long-lived radical P680+. The mechanism to prevent damage caused by P680+ remains unclear. In this study, following light exposure, the upregulation in ascorbate (AsA) content and the presence of PSII cyclic electron flow (PSII-CEF) provide evidence that AsA and PSII-CEF donate electrons to PSII. Furthermore, a factorial design experiment with different combinations of inhibition of AsA and PSII-CEF demonstrates that both inhibition treatments lead to decreases in maximal photochemical yield of PSII, increases in relative variable fluorescence at the K-step, as well as the net loss of PSII reaction center proteins and further degradation of OEC peripheral proteins. These results suggest that AsA and PSII-CEF play photoprotective roles by providing electrons to efficiently prevent damage to PSII from the highly oxidizing radical P680+ in Z. marina.
Elements not usually included in culture medium formulations, such as selenium (Se), may have beneficial effects on micropropagated plants. We evaluated the effects of Se on the physiological and anatomical responses of Alcantarea imperialis during in vitro culture. Plants were cultured in a medium containing a gradient of Se concentrations (0, 4, 8, 16, or 32 µM Se). After 56 d, the growth traits, chlorophyll a fluorescence, and root and leaf anatomy were analyzed. The fresh mass declined at the highest Se concentration. Higher Se concentrations induced bigger stomata, while the stomatal density decreased. Plants cultured with Se had improved PSII and PSI electron transport. This led to higher values of the total performance index. Thus, Se-induced plants showed a higher electron transport dynamics and energy conservation from water to PSI and developed anatomical traits that can favor tolerance to water deficit.
Alterations in photosynthetic performance of lutein-deficient mutant lut2 and wild type (wt) of Arabidopsis thaliana were followed after treatment with low temperature and high light for 6 d. The obtained results indicated lower electrolyte leakage, lower excitation pressure, and higher actual photochemical efficiency of PSII in lut2 plants exposed to combined stress compared to wt plants. This implies that lut2 is less susceptible to the applied stress conditions. The observed lower values of quantum efficiency of nonphotochemical quenching and energy-dependent component of nonphotochemical quenching in lut2 suggest that nonphotochemical quenching mechanism(s) localized within LHCII could not be involved in the acquisition of higher stress tolerance of lut2 and alternatives to nonphotochemical quenching mechanisms are involved for dissipation of excess absorbed light. We suggest that the observed enhanced capacity for cyclic electron flow and the higher oxidation state of P700 (P700+), which suggests PSI-dependent energy quenching in lut2 plants may serve as efficient photoprotective mechanisms, thus explaining the lower susceptibility of lut2 to the combined stress treatments.
This study aimed to determine the photosynthetic performance and differences in chlorophyll fluorescence (ChlF) parameters between Eulophia dentata and its companion species Bletilla formosana and Saccharum spontaneum when subjected to different photosynthetic photon flux density (PPFDs). Leaf surfaces were then illuminated with 50, 100 (low PPFDs), 300, 500, 800 (moderate PPFDs); 1,000; 1,500; and 2,000 (high PPFDs) μmol m-2.s-1, and the ChlF parameters were measured during the whole process. Increasing nonphotochemical quenching of ChlF and decreasing potential quantum efficiency of PSII, actual quantum efficiency of PSII, and quantum efficiency ratio of PSII in dark recovery from 0-60 min were observed in all leaves. A significant and negative relationship was detected between energy-dependent quenching (qE) and photoinhibition percent in three species under specific PPFD conditions, whereas a significant and positive relationship was detected between photoinhibitory quenching (qI) and photoinhibition percent. The qE and qI can be easily measured in the field and provide useful ecological indexes for E. dentata species restoration, habitat creation, and monitoring.
Selected light wavebands promote plant development and/or the biosynthesis of targeted metabolites. This work offers new insights on the effects of red (R), green (G), blue (B), and white (W - R:G:B; 1:1:1) LED light supplementation on physiochemical traits of strawberry leaves. Gas exchange and chlorophyll fluorescence parameters, photosynthetic pigments, and superoxide anion (*O2-) content were analysed in plants grown for 1 (T1) and 17 (T17) d with light supplementations. At T1, light supplementations resulted in the enhancement of the de-epoxidation state of xanthophylls and nonphotochemical quenching, but no changes were observed in maximal photosynthetic rate (PNmax), irrespective of light spectra. At T17, xanthophyll contents remained higher only in R-supplemented plants. Overall, W light resulted in higher photosynthesis, whilst R and B light depressed PNmax values and promoted *O2- formation at T17. G light did not induce variations in photosynthetic traits nor induced oxidative stress at both T1 and T17.
Hybrid photoelectrodes containing biological pigment-protein complexes can be used for environmentally friendly solar energy conversion, herbicide detection, and other applications. The total number of scientific publications on hybrid bio-based devices has grown rapidly over the past decades. Particular attention is paid to the integration of the complexes of PSII into photoelectrochemical devices. A notable feature of these complexes from a practical point of view is their ability to obtain electrons from abundant water. The utilization or imitation of the PSII functionality seems promising for all of the following: generating photoelectricity, photo-producing hydrogen, and detecting herbicides. This review summarizes recent advances in the development of hybrid devices based on PSII. In a brief historical review, we also highlighted the use of quinone-type bacterial reaction centers in hybrid devices. These proteins are the first from which the photoelectricity signal was detected. The photocurrent in these first systems, developed in the 70s-80s, was about 1 nA cm-2. In the latest work, by Güzel et al. (2020), a stable current of about 888 μA cm-2 as achieved in a PSII-based solar cell. The present review is inspired by this impressive progress. The advantages, disadvantages, and future endeavors of PSII-inspired bio-photovoltaic devices are also presented.
Extracellular vesicles are small membrane particles (30-1000 nm) released by Bacteria, Eukaryotes and Archaea. They have been shown to play an important role in intracellular and intercellular communication, within and between kingdoms via transport of bioactive molecules. Thus, they can be involved in altering gene expression and regulation of physiological and pathological processes of the recipient. Their unique properties make extracellular vesicles a perfect candidate vector for targeted drug delivery or a biomarker. For a long time, animal and mainly mammal extracellular vesicles have been used in research. But for plants, there had been speculations about the existence of nanovesicles due to the presence of a cell wall. Today, awareness of plant extracellular vesicles is on the rise and their research has proved they have various functions, such as protein secretion, transport of bioactive molecules or defense against pathogens. Further potential of plant extracellular vesicles is stressed in this review.
Plant volatiles can synergize the response to moth pheromone. Synthetic pheromone analogs, in turn, have the opposite effect in reducing pheromone attractiveness. To determine how these two types of stimuli interact and influence male moth behaviour, we performed wind tunnel experiments on the grapevine moth, Lobesia botrana. We noticed that a blend of host plant volatiles [(E)-β-caryophyllene, 1-hexanol, (Z)-3-hexenyl acetate and 1-octen-3-ol in a 100:20:10:5 ratio] significantly increased the response of males to an optimized blend of sex pheromone [(7E,9Z)-dodeca-7,9-dienyl acetate (E7,Z9-12:Ac), (7E,9Z)- dodeca-7,9-dienol (E7,Z9-12:OH) and (Z)-9-dodecenyl acetate (Z9-12:Ac)] in a 100:10:2 ratio. However, the response of males to the natural attractant was significantly reduced by two analogs [(9E,11Z)-tetradeca-9,11-dien-2-one (MK 2) and [(9E,11Z)-1,1,1-trifluoro-tetradeca-9,11-dien-2-one (TFMK 3)], of the major component of the sex pheromone of the insect (E7,Z9-12:Ac). When both stimuli were tested on males at pheromone:analog:plant volatile blend 1:100:1000 ratio, the plant blend offset the inhibitory effect induced by TFMK 3 but not that of MK 2. Our results show for the first time that under laboratory conditions plant volatiles can prevent inhibition by a pheromone analog., Albert Sans, Miguel Morán, Magí Riba, Ángel Guerrero, Jaume Roig, César Gemeno., and Obsahuje bibliografii
Výzkumná práce se zaměřuje na analýzu oblasti podpůrných opatření ve vzdělávání žáků se speciálními vzdělávacími potřebami. Hlavní oblastí studie je navyšování časové dotace na práci žáků se specifickými poruchami učení, což je jedna z nejčastěji volených forem podpory pro tyto žáky. Byla provedena kvantitativní analýza výkonu žáků 9. tříd základních škol. Výzkumný soubor obsahoval žáky se SPU (N=31) a intaktní žáky (N=188). Žáci pracovali na Testu struktury inteligence I-S-T 2000 R a jejich výkony byly následně statisticky zpracovány. Žáci se SPU měli k dispozici o 25 % na práci více, než žáci intaktní, ale byli hodnoceni také v základním čase. Pracovalo se s jejich výkonem v podobě hrubých skórů (tedy fakticky správně vyplněných položek), hrubé skóre se nepřevádělo na inteligenční kvocient. Statisticky významné výsledky byly zjištěny v následujících oblastech. Žáci se SPU podali v rámci své skupiny statisticky významně lepší výkon, pokud pracovali s navýšením času (než v čase základním), a to ve všech hodnocených škálách i subtestech. Při hodnocení rozdílu mezi žáky se SPU a intaktní skupinou žáků dosahovali žáci se SPU s přidaným časem navíc statisticky významně lepších výkonů ve figurální škále testu a v subtestu Výběr obrazců; statisticky významně horší výkon podali v numerickém subtestu Číselné řady. Pokud pracovali žáci se SPU a intaktní skupina žáků ve stejném (základním) čase, pak byli intaktní žáci statisticky významně úspěšnější v numerické škále. V rámci verbální škály nebyly zjištěny žádné statisticky významné rozdíly ve výkonech, což je překvapivým zjištěním. and The research focuses on the analysis of support measures in the education of pupils with special educational needs. The main area of the study is to increase the time allowance for the work of pupils with specific learning disabilities, which is one of the most frequently chosen forms of support for these pupils. The research is a quantitative analysis of the performance of 9 th -grade elementary school students. The research group included pupils with SPU (N = 31) and intact pupils (N = 188). The students worked on the I-S-T 2000 R Intelligence Structure Test and their performance was statistically processed. Pupils with SPU had 25% more time for work available than intact pupils, but they were also evaluated in basic time. We worked with their performance in the form of gross scores (that is correctly filled in items), the gross scores were not converted into intelligence quotients. Statistically significant results were found in the following areas. Pupils with SPU performed statistically significantly better within their group in all evaluated scales and subtests if they worked with increasing time (than in basic time). When we are evaluating the difference between pupils with SPU and an intact group of pupils, pupils with SPU with added extra time achieved statistically significantly better performances in the figural test scale and the Pattern Selection subtest. Statistically significantly worse performance was given in the numerical subtest of the Number Series. If students with SPU and an intact group of students worked at the same (base) time the intact students were statistically significantly more successful on the numerical scale. The surprising finding is that there are no statistically significant differences in performance within the verbal scale.