We provide here a general introduction on chlorophyll (Chl) a fluorescence, then we present our measurements on fast (< 1 s) induction curves (the so-called OJIP transients) on dark-adapted intact leaves of Arabidopsis thaliana, under five different light intensities [in the range of ~ 500 to ~ 3,000 µmol(photons) m‒2 s‒1] using two different instruments: Handy PEA (Hansatech Instruments, UK; excitation light, 650 nm) and FluorPen (model FP-110; Photon Systems Instruments, The Czech Republic; excitation light, 470 nm). We then discuss the observed differences in the OJIP curves, as well as in Fo (F20μs, F50μs, or the extrapolated Ft→0), FP (the peak), and the ratios FP/Fo, and Fv (= FP ‒ Fo)/FP in terms of differences in excitation light intensity and absorptance (or absorbance) of the excitation light by the leaves, and other factors, as well as the data available in the literature. We suggest that such measurements be accompanied, in the future, by parallel measurements on Chl a fluorescence imaging, an area pioneered by Hartmut K. Lichtenthaler., B. Padhi, G. Chauhan, D. Kandoi, A. Stirbet, B. C. Tripathy, G. Govindjee., and Obsahuje bibliografické odkazy
In stressful environments, invasive plants acclimate more efficiently than native plants and hybridization mainly contributes to this process. We examined changes in the morphological characteristics, photosynthetic characteristics, and antioxidant capacity of Sphagneticola trilobata and its hybrids in a low-light environment to explore their invasiveness, with Sphagneticola calendulacea serving as the control. The morphological plasticity of S. trilobata was not dominant, the maximal photochemical efficiency of PSII, actual quantum yield of PSII, and electron transport rate of PSⅡ increased and nonphotochemical quenching decreased, while S. calendulacea and the hybrid produced opposite results. S. trilobata showed fewer spots stained for reactive oxygen species in tissues, with an increase in superoxide dismutase activity. Although S. trilobata is a heliophilous plant, we found that the shade tolerance of S. trilobata and the hybrid were stronger than that of S. calendulacea, which may be one important mechanism of invasion.
Active control of photosynthetic activities is important in plant physiological study. Although models of plant photosynthesis have been built at different scales, they have not been fully examined for their application in plant growth control. However, we do not have an infrastructure to support such experiments since current plant growth chambers usually use fixed control protocols. In our current paper, an open IoT-based framework is proposed. This framework allows a plant scientist or agricultural engineer, through an application programming interface (API), in a desirable programming language, (1) to gather environmental data and plant physiological responses; (2) to program and execute control algorithms based on their models, and then (3) to implement real-time commands to control environmental factors. A plant growth chamber was developed to demonstrate the concept of the proposed open framework.
Shade treatment was applied to tall fescue with 30% full light. The results showed that shade increased chlorophyll (Chl) content per unit leaf mass, decreased the Chl a/b ratio in the mature leaves, and decreased effective quantum yield based on Chl fluorescence compared to the full light treatment. Shade stress did not cause increased contents of malondiadehyde at the early stages of leaf development. However, normalized vegetation indices were able to detect shade stress. Chloroplasts in the shaded leaves are arranged tightly against the periclinal cell wall and are in a spindle shape. There were no differences in the number of grana per chloroplast or grana size (thylakoids per granum) between shade and full light treatment. In conclusion, tall fescue leaves showed unique ultrastructure changes. Turfgrass managers could use vegetation indices developed from the leaf light reflection spectrum as an effective tool to assess shade stress levels and make management decisions.
Mesembryanthemum crystallinum is an annual succulent plant that is being used as an emerging healthy leafy vegetable. To investigate the growth and physiological response of M. crystallinum to artificial lighting, five different light treatments were applied at 150 µmol(photon) m-2 s-1, which were white (W), different rations of red/blue (B) (15, 40, and 70%B), and blue (100%B), respectively. Our results showed that plants could gain as much as edible leaf area and dry mass with a certain ratio of blue (40%) in comparison with W. Plants grown under 100%B resulted in reduced photosynthetic rate, leaf area, and fresh mass compared with W. Adding blue fraction in the light regime enhanced the photosynthetic performance by influencing the amount of chlorophyll (Chl), Chl a/b, and specific leaf area. Under red/blue treatments, the electron transport rate and effective quantum yield of both PSII and PSI increased, while the nitrate content was reduced and flavonoids and total antioxidant capacity were unaffected.
Chlorophyll fluorescence has developed into a well-established noninvasive technique to study photosynthesis and by extension, the physiology of plants and algae. The versatility of the fluorescence analysis has been improved significantly due to advancements in the technology of light sources, detectors, and data handling. This allowed the development of an instrumention that is effective, easy to handle, and affordable. Several of these techniques rely on point measurements. However, the response of plants to environmental stresses is heterogeneous, both spatially and temporally. Beside the nonimaging systems, low- and high-resolution imaging systems have been developed and are in use as real-time, multi-channel fluorometers to investigate heterogeneous patterns of photosynthetic performance of leaves and algae. This review will revise in several paragraphs the current status of chlorophyll fluorescence imaging, in exploring photosynthetic features to evaluate the physiological response of plant organisms in different domains. In the conclusion paragraph, an attempt will be made to answer the question posed in the title., R. Valcke., and Obsahuje bibliografické odkazy
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
Our research aimed to study the correlation between the SPAD-502 readings and the color space CIE L*a*b* values in two cultivars of Alstroemeria sp. during leaf senescence and to evaluate the statistical criteria used in the selection of the best fit calibration functions. We demonstrate the importance of the Akaike information criterion and the parsimonious function besides the coefficient of determination. The reliability of the functions was tested by Student's t-test comparison between the chlorophyll (Chl) estimated from SPAD readings and their chemical concentrations. Polynomial and Hoerl function described well the changes in Chl a and total Chl (a+b) during senescence, but calibration functions are required to perform for each cultivar. We demonstrated that CIE L*a*b* system is reliable to estimate SPAD reading at stages of leaf senescence of Alstroemeria sp. and can be used instead of SPAD-502.
Little data on the role played in vivo by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation via disulphide bridges by AtDeg2 acting as a holdase. To reach this goal, we performed analyses which involved comparative diagonal electrophoreses of lysates of chloroplasts isolated from wild type (WT) plants and transgenic plants 35S:AtDEG2ΔPDZ1-GFP which expressed AtDeg2 lacking its chaperone activity but retaining the protease activity. The results of the analyses indicate that AtDeg2 acting as a holdase prevents a single chloroplast protein, i.e., the γ1 subunit of ATP synthase from long-term high irradiance-induced homodimerization mediated by disuplhide bridges and this allows us to better understand a complexity of physiological significance of AtDeg2 - the chloroplast protein of dual protease/chaperone activity.
The content of chlorophylls (Chl) (a+b), total carotenoids (x+c), and the pigment ratios of Chl a/b and Chls to carotenoids (a+b)/(x+c) of green leaves of five C4 plants were determined and compared to those of C3 plants. The C4 plants were: Pacific and Chinese silvergrass (Miscanthus floridulus and Miscanthus sinensis), sugar cane (Saccharum officinarum) as well as feed and sugar maize (Zea mays). The three C3 plants were beech, ginkgo, and oak. C4 plants possess higher values for the ratio Chl a/b (3.4-4.5) as compared to the C3 plants (2.6-3.3). Sugar maize had the highest values for Chl a/b (4.04-4.70) and exceptionally high contents of total carotenoids and consequently lower values for the ratio of (a+b)/(x+c) (mean: 3.75 ± 0.6). During autumnal senescence also C4 plants showed a faster decline of Chl b as compared to Chl a yielding high values for Chl a/b of 6 to 8. Chlorophylls declined faster than carotenoids yielding low (a+b)/(x+c) values below 1.0.
The occurrence of shade and drought stress either individually or simultaneously causes altered morphophysiological and molecular responses in crops. Nevertheless, responses of crop plants to combined shade and drought stress are unique as compared to those of individually occurring stress which urges need to study and identify distinctions, commonalities, and the interaction between responses of plants to these concurrent stress factors. In the present review, we outlined currently available knowledge on responses of plants to shade and drought stress on a shared as well as the unique basis and tried to find a common thread potentially underlying these responses. Then, we briefly described some plausible mitigation strategies to cope with these stresses along with future perspectives. A deeper insight into plant responses to co-occurring shade and drought stress will help us to generate crops with broad-spectrum stress tolerance and increased resilience to such stresses in high planting densities or intercropping systems, thus, ensuring food security.
In our earlier works, we have identified rate-limiting steps in the dark-to-light transition of PSII. By measuring chlorophyll a fluorescence transients elicited by single-turnover saturating flashes (STSFs) we have shown that in diuron-treated samples an STSF generates only F1 (< Fm) fluorescence level, and to produce the maximum (Fm) level, additional excitations are required, which, however, can only be effective if sufficiently long Δτ waiting times are allowed between the excitations. Biological variations in the half-rise time (Δτ1/2) of the fluorescence increment suggest that it may be sensitive to the physicochemical environment of PSII. Here, we investigated the influence of the lipidic environment on Δτ1/2 of PSII core complexes of Thermosynechococcus vulcanus. We found that while non-native lipids had no noticeable effects, thylakoid membrane lipids considerably shortened the Δτ1/2, from ~ 1 ms to ~ 0.2 ms. The importance of the presence of native lipids was confirmed by obtaining similarly short Δτ1/2 values in the whole T. vulcanus cells and isolated pea thylakoid membranes. Minor, lipid-dependent reorganizations were also observed by steady-state and time-resolved spectroscopic measurements. These data show that the processes beyond the dark-to-light transition of PSII depend significantly on the lipid matrix of the reaction center.
Large amounts of antibiotics and microplastics are used in daily life and agricultural production, which affects not only plant growth but also potentially the food safety of vegetables and other plant products. Fast detection of the presence of antibiotics and microplastics in leafy vegetables is of great interest to the public. In this work, a method was developed to detect sulfadiazine and polystyrene, commonly used antibiotics and microplastics, in vegetables by measuring and modeling photosystem II chlorophyll a fluorescence (ChlF) emission from leaves. Chrysanthemum coronarium L., a common beverage and medicinal plant, was used to verify the developed method. Scanning electron microscopy, transmission electron microscopy, and liquid chromatograph-mass spectrometer analysis were used to show the presence of the two pollutants in the samples. The developed kinetic model could describe measured ChlF variations with an average relative error of 0.6%. The model parameters estimated for the chlorophyll a fluorescence induction kinetics curve (OJIP) induction can differentiate the two types of stresses while the commonly used ChlF OJIP induction characteristics cannot. This work provides a concept to detect antibiotic pollutants and microplastic pollutants in vegetables based on ChlF.
To understand growth limitations of photosynthetic microorganisms, and to investigate whether batch growth or certain photosynthesis-related parameters predict a turbidostat (continuous growth at constant biomass concentration) growth rate, five green algal species were grown in a photobioreactor in batch and turbidostat conditions and their susceptibilities to photoinhibition of photosystem II as well as several photosynthetic parameters were measured. Growth rates during batch and turbidostat modes varied independently of each other; thus, a growth rate measured in a batch cannot be used to determine the continuous growth rate. Greatly different photoinhibition susceptibilities in tested algae suggest that different amounts of energy were invested in repair. However, photoinhibition tolerance did not necessarily lead to a fast growth rate at a moderate light intensity. Nevertheless, we report an inverse relationship between photoinhibition tolerance and minimum saturating irradiance, suggesting that fast electron transfer capacity of PSII comes with the price of reduced photoinhibition tolerance.
Apple rootstock seedling M.9-T337 was selected to explore the effect of drought stress. The findings indicated that the relative water content of both the leaf and soil gradually decreased with an increase in drought stress. The water-use efficiency of the leaves increased gradually but decreased sharply after 20 d of drought. Changes in the gas-exchange parameters and chlorophyll fluorescence parameters reflected the gradual decrease in the photosynthetic capacity of the plants with drought stress duration. Infrared thermal imaging showed significant temperature differences between the drought-stressed and control plants after 15 d of drought treatment. When irreversible damage occurred under drought stress, the crop water-stress index and relative water content of the leaf and soil were 0.7, 60.5, and 17.8%, respectively. Based on the results, we formulated a drought stress-grade standard. Further, we established that the best time for irrigation is when drought stress reaches grade 3., D. T. Gao, C. Y. Shi, Q. L. Li, Z. F. Wei, L. Liu, J. R. Feng., and Obsahuje bibliografické odkazy
At a three-leaf stage, two Fe treatments [0 mg kg-1 (Fe-) and 20 mg.kg-1 (Fe+) in the form of FeCl3] were used in the soil of the pot and then two concentrations of α-ketoglutaric acid [0 mg L-1 (A-) and 50 mg L-1 (A+)] were sprayed to the rice plants of Meixiangzhan and Yuxiangyouzhan cultivars. We showed that seedlings exhibited an increased length and fresh and dry mass of shoots and roots with treatments Fe+A- and Fe-A+, as well as the Fe content increased greatly. Both treatments increased the morphological characteristic values of roots and promoted photosynthesis. Interestingly, Fe+A+ notably affected the photosynthesis of fragrant rice seedlings; however, it exerted no significant differences on other parameters. Overall, Fe and α-ketoglutaric acid had the potential for improving the growth of fragrant rice seedlings. The interaction between Fe and α-ketoglutaric acid regulated photosynthesis in seedling leaves, which provided evidence for further improvement of rice cultivation.
The effects of different light-emitting diode (LED) lights on saffron growth and photosynthetic characteristic were explored. Physiological mechanisms were explained by chlorophyll a fluorescence transient curves (OJIP) and JIP-test parameters. A decrease in the red to blue light ratio resulted in negative effects, particularly for monochromatic blue (B) LED light; saffron seedlings showed reduced chlorophyll accumulation, inhibited leaf elongation, and decreased photosynthetic performance. In the OJIP curve, the higher positive K-band observed for B LED light indicated that oxygen-evolving complex activation significantly decreased. B LED light inhibited the electron transport between primary quinone acceptor and secondary quinone acceptor as well as the existence of reducing plastoquinone centers, and increased energy dissipation of reaction centers. Otherwise, the red to blue light ratio of 2:1 had a positive effect on saffron cultivation, resulting in the longest leaf lengths, highest chlorophyll content, and photosynthetic characteristics. This study provides theoretical guidance for saffron agricultural practices.
Anticipating warming related to climate change, commercial mango plantations in China have been shifting from lower to higher elevations. Such a practice may expose mangoes to climatic conditions that could affect photosynthesis. Photosynthesis research on mango has previously examined mature plantations but exploring adequate functions before the time of fruit production is necessary for later crop success. Therefore, we established two main commercial mango cultivars, Tainong No. 1 and Jinhuang, at 450 m and 1,050 m and examined their photosynthetic performance. Our results showed that photosynthetic capacity parameters, including maximum photosynthetic rate, apparent quantum yield, maximum carboxylation rate, and photosynthetic electron transport rate, were significantly different between cultivars due to elevation and positively correlated with leaf nitrogen per area. Moreover, the seasonal gas exchange of the two cultivars showed variations due to elevation, particularly during the warmer seasons. Therefore, elevation affects the photosynthetic performance of these mango cultivars.
Alkaline stress is important abiotic stress that restricts the growth and physiological activity of sorghum (Sorghum bicolor L. Moench). We aimed to investigate the effects of alkaline stress on alkali-tolerant SX44B and alkali-sensitive 262B sorghum inbred lines. The results showed that alkaline stress decreased the content of chlorophyll, activity of photosystem II, net photosynthetic rate, and destroyed chloroplast morphology. These changes were less pronounced in SX44B, possibly owing to its higher antioxidant enzyme activity and nonphotochemical quenching. Alkaline stress decreased water content, transpiration rate, and stomatal conductance while increasing the leaf temperature, with the effect being more pronounced in 262B. A significant correlation was observed between leaf-air temperature difference (ΔT) and relative water content and gas-exchange parameters, especially in 262B. Therefore, ΔT is an effective indicator for monitoring changes in sorghum leaves under alkaline stress and evaluating the alkali tolerance of different sorghum germplasm.
The frequent occurrence of monsoon winds usually leads to the formation of inverted soybean leaves. However, the effect of leaf inversion on photosynthetic capacity remains unclear. The responses of leaf anatomical traits, chlorophyll fluorescence induction kinetics parameters, photosynthetic capacity, and nonstructural carbohydrates of fully expanded leaves to inversion of leaves in two soybean cultivars were studied. Leaf inversion decreased the stomatal size and thickness of developed leaves. The net photosynthetic rate was significantly reduced under leaf inversion, which resulted from reduced excitation energy trapping and electron transport of PSII reaction center. Leaf inversion increased leaf temperature 10 d after leaf inversion but reduced the instantaneous water-use efficiency compared to normally oriented leaves. Due to the decreased light-saturated net photosynthetic rate, the soluble sugars of light-sensitive cultivar decreased significantly. In summary, leaf inversion deactivated the PSⅡ reaction centers, reduced photosynthesis and nonstructural carbohydrates in upper canopy soybean leaves.
Secondary soil salinization causes plant stress, which can be relieved by different ratios of red to far-red light (R:FR). Our study aimed to elucidate the role of low R:FR ratios treatments on photosynthesis and growth of tomato seedlings in salinized soils. Tomato seedlings were treated under three R:FR ratios and calcium nitrate was applied simultaneously. The results showed that the treatments under low R:FR ratios stimulated growth parameters of tomato seedlings under calcium nitrate stress, the best impact being achieved at the R:FR ratio of 0.7 in this experiment. Low R:FR ratios treatments increased proline content as well as PSII maximum efficiency, actual electron transport operating efficiency, and photochemical quenching of tomato seedlings under calcium nitrate stress but decreased the value of nonphotochemical quenching. Moreover, low R:FR ratios treatments promoted net photosynthetic rate and increased the expression of a Rubisco gene. In conclusion, low R:FR ratios treatments could improve the salt resistance of greenhouse tomato plants.
The formation of economic yield and fruit quality of Roxburgh rose (Rosa roxburghii Tratt.) depends essentially on its source-sink interaction. Thus, a pruning experiment was conducted to assess the effects of source-sink regulation on photosynthetic physiology and fruit yield of Roxburgh rose, which was of great significance to production. Cutting off vegetative branches reduced physiological fruit loss and malformed fruits but increased single fruit quality and yield. Results revealed that the stomatal characteristics, the composition of mesophyll tissue, and photosynthesis of leaves on reproductive branches were significantly affected by the ratio of the vegetative and reproductive shoots. Our data indicated that the source-sink ratio could reflect the balance between vegetative growth and reproductive growth of the tree during the whole fruit period. Fruit tree pruning had guiding significance for improving the fruit yield of Roxburgh rose.
Low temperature has negative effects on apple photosynthesis by inhibiting the accumulations of photosynthates and nitrogen. The interactive effects of low temperature and nitrogen application on photosynthetic parameters and the absorption and distribution of carbon and nitrogen in different organs were assessed to investigate if nitrogen application can relieve the low-temperature stress on gas exchange and the accumulations of carbon and nitrogen inside the apple plants. No matter under normal or low-temperature conditions, nitrogen application both improved the photosynthetic parameters including net photosynthetic rate, intercellular CO2 concentration, and quantum yield of regulated energy dissipation of PSII as well as the absorption of carbon and nitrogen in roots, stems, and leaves. Thus, we conclude that nitrogen application can relieve the effects of low-temperature stress on photosynthesis and is of benefit for the accumulations of carbon and nitrogen in multiple organs of apple seedlings.
Handy Plant Efficiency Analyser (Handy PEA) provides a method for the high-throughput screening of photosynthetic germplasm. However, the large number of chlorophyll a fluorescence parameters (CFPs) from PEA and the inconsistency of CFP applications among studies greatly limit the accuracy of photosynthesis analyses. In this study, all 53 CFPs of 186 upland cotton cultivars (strains) were measured at 12:00 and 17:00 h. Thirty-two CFPs were selected according to biological importance, and the CFP relationships were determined. Differences in the response ability of cotton cultivars (strains) to high light intensity stress were demonstrated by the distribution of CFPs. Furthermore, the classification and evaluation of photosynthetic characteristics of cotton cultivars (strains) were carried out by Principal Component Analysis and Cluster Analysis. Finally, ten cotton cultivars (strains) with good photosynthetic performance were selected. This study provides a high-throughput method how to identify cotton germplasm resources with high photosynthetic efficiency.
We recently developed a chlorophyll a fluorescence method (activated F0 rise) for estimating if a light wavelength preferably excites PSI or PSII in plants. Here, the method was tested in green microalgae: Scenedesmus quadricauda, Scenedesmus ecornis, Scenedesmus fuscus, Chlamydomonas reinhardtii, Chlorella sorokiniana, and Ettlia oleoabundans. The Scenedesmus species displayed a plant-like action spectra of F0 rise, suggesting that PSII/PSI absorption ratio is conserved from higher plants to green algae. F0 rise was weak in a strain of C. reinhardtii, C. sorokiniana, and E. oleoabundans. Interestingly, another C. reinhardtii strain exhibited a strong F0 rise. The result indicates that the same illumination can lead to different redox states of the plastoquinone pool in different algae. Flavodiiron activity enhanced the F0 rise, presumably by oxidizing the plastoquinone pool during pre-illumination. The activity of plastid terminal oxidase, in turn, diminished the F0 rise, but to a small degree.
Increasing the efficiency of photosynthesis in sugarcane canopies is the key for improving crop yield. Herein, we evaluated the photosynthetic performance along the canopy of ten sugarcane cultivars and three Saccharum species. Canopy morphological traits were evaluated, and leaf gas exchange was measured in the first (sun-exposed, +1) and the fourth (shaded, +4) fully expanded leaves and under low- and high-light conditions. Similar photosynthetic capacity was found in leaves +1 and +4 under high light in genotypes with a high leaf area index and a high fraction of the sky blocked by the foliage (> 85%). Interestingly, such canopy characteristics cause low light availability to leaves +4, suggesting the photosynthetic acclimation of these leaves to self-shading in some genotypes. We highlight IACCTC06-8126 and CTC4 as those genotypes with higher canopy photosynthetic capacity, presenting high leaf area, high photosynthetic rates in sun-exposed leaves, and high responsiveness of shaded leaves to increasing light availability.
Foliar anthocyanins shape a peculiar shade in a red leaf's interior leading to uneven energy distribution between the two photosystems. Accordingly, a readjustment of PSII/PSI stoichiometry could restore excitation balance. To test this hypothesis, 77 K fluorescence emission spectra of thylakoids from green and red leaves of seven species with different pigment profiles were compared. The ratio of F686/F736 served as an indication of the PSII/PSI functional ratio. To avoid possible species-dependent differences in the measured parameters, plants showing intra-individual, intra-species, or intra-leaf variation in the expression of the anthocyanic character were used. Red leaves or red leaf areas displayed higher PSII/PSI ratio, irrespectively of species and anthocyanin accumulation pattern. PSII/PSI ratio declined in parallel with anthocyanin decrease. In five species, red leaves displayed also a lower Chl a/b ratio. We conclude that red leaves growing in full sunlight develop adaptive adjustments in their chlorophyll and photosystem ratios, compatible with the shade-acclimation syndrome.
EGY1 (ethylene-dependent gravitropism-deficient and yellow-green 1) is an intramembrane metalloprotease located in chloroplasts, involved in many diverse processes including chloroplast development, chlorophyll biosynthesis, and the ethylene-dependent gravitropic response. Plants deprived of this protease display pleiotropic effects such as the yellow-green early senescence phenotype and a poorly developed thylakoid system membrane in the mature chloroplasts. We applied the GC/MS technique to analyze the changes in fatty acid composition in two egy1 mutant lines. We used DAPI staining and transmission electron microscopy methods to establish the number of nucleoids and the amount of chloroplast DNA. Our results indicated that the lack of EGY1 protease led to a dramatic overaccumulation and a dramatic decrease in the content of linolenic acid C18:3 and hexadecatrienoic acid C16:3, respectively. The amount of chloroplast DNA and the number of nucleoids were severely reduced in egy1 mutant lines. Similarly, a reduced correlation between DAPI and autofluorescence signal was observed, which may indicate some perturbations in nucleoid anchoring.
We present here our adventures in research in photosynthesis with George C. Papageorgiou (1933-2020) focusing on George's initiative in the discovery of the protective effects of glycine betaine on the oxygen-evolving photosystem II complex. We end with a brief description of research on glycine betaine-synthesizing transgenic cyanobacteria. Two of us, Norio Murata (in Japan) and Kostas Stamatakis (in Greece), and all our collaborators, have the highest respect for George, and we miss him and our intense discussions with him on various topics of photosynthesis research.
This study was conducted to assess whether silicon (Si) supply can alleviate the harmful effects of severe salinity in barley (Hordeum vulgare). Plants were grown on non-saline (0 mM NaCl) or saline (200 mM NaCl) nutrient media supplemented or not with 0.5 mM Si. Salinity impacted plant morphology and induced sodium and chloride accumulation within plant tissues. It significantly affected almost all measured parameters. Interestingly, Si supply alleviated salt stress effects on plant morphology, growth (up to +59%), water status (up to +74%), membrane integrity (up to +35%), pigment contents (up to +121%), and the activity of the two photosystems (PSI and PSII) by improving their yields, and by reducing their energy dissipation. Si beneficial effect was more pronounced on PSI as compared to PSII. As a whole, data inferred from the present study further confirmed that silicon application is an effective approach to cope with salinity.
Acid rain is a serious environmental problem and has obvious impacts on the growth, reproduction, and photosynthesis of terrestrial plants. Ulva prolifera, a main blooming species of green tides, was studied on its physiological response to acid rain. The photosynthetic parameters were determined under different conditions (salinity: 1, 10, 30‰; pH: 3.0, 3.5, 4.5; duration: 0.5, 1.0, 2.0 h) followed by 24-h recovering under natural conditions. Results showed 1-h treatment with pH 3.5 caused 50-70% reduction in the maximal quantum yield of PSII photochemistry (Fv/Fm) and effective quantum yield of PSII photochemistry (ФPSII) at normal salinity but when the low pH was combined with a salinity of 10‰ or lower, PSII activity was almost completely inhibited. Moreover, the low salinity (1‰ and 10‰) reduced the degree of photoprotection under low pH (3.5) conditions. Finally, we speculated if the pH of acid rain ≤ 3.5, with 1‰ salinity and 2-h rainfall time, the amount of U. prolifera and the scale of green tides would decrease.
Wheat yellow-green mutant Jimai5265yg has a more efficient photosynthetic system and higher productivity than its wild type under N-deficient conditions. To understand the relationship between photosynthetic properties and the grain yield, we conducted a field experiment under different N application levels. Compared to wild type, the Jimai5265yg flag leaves had higher mesophyll conductance, photosynthetic N-use efficiency, and photorespiration in the field without N application. Chlorophyll a fluorescence analysis showed that PSII was more sensitive to photoinhibition due to lower nonphotochemical quenching (NPQ) and higher nonregulated heat dissipation. In N-deficient condition, the PSI acceptor side of Jimai5265yg was less reduced. We proposed that the photoinhibited PSII protected PSI from over-reduction through downregulation of electron transport. PCA analysis also indicated that PSI photoprotection and electron transport regulation were closely associated with grain yield. Our results suggested that the photoprotection mechanism of PSI independent of NPQ was critical for crop productivity.
We honor here Hartmut Karl Lichtenthaler, a pioneer of plant physiology, plant biochemistry, plant biophysics, plant molecular biology, and stress physiology. His contributions to the ingenious use of chlorophyll a fluorescence imaging in understanding the physiological processes in leaves stand out. We wish him many happy and productive years of research and educating others., G. Govindjee., and Obsahuje bibliografické odkazy
Photosynthesis can be affected by nanoparticles (NPs) both negatively (e.g., through decreasing the chlorophyll content and electron transport rate, damages to chloroplast components, etc.) or positively (e.g., via enhancing chlorophyll content, the activity of Rubisco enzyme, the performance of PSII, and CO2 harvesting, as well as broadening the chloroplast photoabsorption spectrum). Enhanced photosynthetic efficiency could be a possible impact of NPs on photosynthetic organisms of major economic and ecological significance (e.g., crops and algae), which warrants an in-depth understanding of NPs interactions with chloroplast and its structural components (e.g., thylakoid membranes), signaling molecules, and pathways involved in photosynthesis. In this review, we comprehensively explore the potential effects of NPs on photosynthesis in different photosynthetic organisms (terrestrial plants, aquatic plants, and algae), and highlight research limitations and possible practical implications.
Climate change impacts environmental conditions that affect photosynthesis. This review examines the effect of combinations of elevated atmospheric CO2, long photoperiods, and/or unfavorable nitrogen supply. Under moderate stress, perturbed plant source-sink ratio and redox state can be rebalanced but may result in reduced foliar protein content in C3 plants and a higher carbon-to-nitrogen ratio of plant biomass. More severe environmental conditions can trigger pronounced photosynthetic downregulation and impair growth. We comprehensively evaluate available evidence that microbial partners may be able to support plant productivity under challenging environmental conditions by providing (1) nutrients, (2) an additional carbohydrate sink, and (3) regulators of plant metabolism, especially plant redox state. In evaluating the latter mechanism, we note parallels to metabolic control in photosymbioses and microbial regulation of human redox biology.
The ability to modulate photosynthesis is essential for plants to adapt to fluctuating growing conditions. Populus species show high tolerance to various and highly variable environments. To understand their response strategies against fluctuating environments, this study investigated the morphological and physiological differences of white poplar (Populus alba) leaves when grown in a phytotron, glasshouse, and field. Our results show that the palisade cells were elongated in the field, which would enhance intercellular CO2 exchange. Photosynthetic capacity was the highest in the field leaves, as shown by higher electron transport rates (1.8 to 6.5 times) and carbon assimilation rates (2.7 to 4.2 times). The decrease of PSI acceptor-side limitation and increase of PSI donor-side limitation suggests changes in PSI redox status may contribute to photoprotection. This plasticity of white poplar allows adjusting its structure and photosynthesis under fluctuating conditions, which may partly enable its outstanding tolerance against environmental changes.
Oxygenic photosynthesis takes place in thylakoid membranes (TM) of cyanobacteria, algae, and higher plants. It begins with light absorption by pigments in large (modular) assemblies of pigment-binding proteins, which then transfer excitation energy to the photosynthetic reaction centers of photosystem (PS) I and PSII. In green algae and plants, these light-harvesting protein complexes contain chlorophylls (Chls) and carotenoids (Cars). However, cyanobacteria, red algae, and glaucophytes contain, in addition, phycobiliproteins in phycobilisomes that are attached to the stromal surface of TM, and transfer excitation energy to the reaction centers via the Chl a molecules in the inner antennas of PSI and PSII. The color and the intensity of the light to which these photosynthetic organisms are exposed in their environment have a great influence on the composition and the structure of the light-harvesting complexes (the antenna) as well as the rest of the photosynthetic apparatus, thus affecting the photosynthetic process and even the entire organism. We present here a perspective on 'Light Quality and Oxygenic Photosynthesis', in memory of George Christos Papageorgiou (9 May 1933-21 November 2020; see notes a and b). Our review includes (1) the influence of the solar spectrum on the antenna composition, and the special significance of Chl a; (2) the effects of light quality on photosynthesis, measured using Chl a fluorescence; and (3) the importance of light quality, intensity, and its duration for the optimal growth of photosynthetic organisms.
Haberlea rhodopensis Friv. is unique with its ability to survive desiccation to an air-dry state during periods of extreme drought and freezing temperatures. To understand its survival strategies, it is important to examine the protective mechanisms not only during desiccation but also during rehydration. We investigated the involvement of alternative cyclic electron pathways during the recovery of photosynthetic functions after freezing-induced desiccation. Using electron transport inhibitors, the role of PGR5-dependent and NDH-dependent PSI-cyclic electron flows and plastid terminal oxidase were assessed during rehydration of desiccated leaves. Recovery of PSII and PSI, the capacity of PSI-driven cyclic electron flow, the redox state of plastoquinone pool, and the intersystem electron pool were analyzed. Data showed that the effect of alternative flows is more pronounced in the first hours of rehydration. In addition, the NDH-dependent cyclic pathway played a more determining role in the recovery of PSI than in the recovery of PSII.
Chloroplast PSII photochemical efficiency is upregulated more rapidly than CO2 assimilation during photosynthesis induction, suggesting the existence of other electron sinks than that of CO2 assimilation. We hypothesized that the mitochondrial alternative oxidase (AOX) pathway could be such a sink. Inhibition of the AOX restricted light activation of the malate-oxaloacetate shuttle and caused an excessive reduction of PSI acceptor side and substantial accumulation of QA-, hindering the photosynthetic linear electron transport rate (ETR) and leading to an imbalance between light energy absorption and exploitation during photosynthetic induction. ETR limitation also restricted the formation of thylakoid pH gradient, evidenced by a decreased de-epoxidation of the xanthophyll cycle, thus preventing nonphotochemical quenching. Delayed CO2 assimilation due to thylakoid pH gradient restriction was partially reversed by exogenous ATP application. The AOX pathway acts as a photosynthetic electron sink, protecting the photosynthetic apparatus against photoinhibition and accelerating the induction of CO2 assimilation during photosynthetic induction in Rumex K-1 leaves.
Water deficit (WD) at the start of the flowering stage can negatively affect the productivity of plants. The aim was to investigate the morphophysiological strategies of two crambe lineages (FMS CR 1326 and 1307) submitted to WD during the flowering stage and their connection with the progeny's germination. Plants were submitted to WD at the start of flowering for 12 d and then were irrigated again (water resumption, WR). As a control, plants were cultivated with uninterrupted daily irrigation. Under WD, reductions were observed in the stomatal conductance, the number of xylem vessels, and the mass of grains. Positive K- and L-bands occurred, indicating lower stability and efficiency in the use of energy under WD. In the WR period, plants presented photochemical recovery. WD induced less vigorous seeds. FMS CR 1307 had the highest capacity to maintain its photochemical performance, due to alterations in water conductivity, resulting in greater seed production and vigor.
a1_Imaging the four fluorescence bands of leaves, the red (F690) and far-red (F740) chlorophyll (Chl) fluorescence as well as the blue (F440) and green (F520) fluorescence of leaves and the corresponding fluorescence ratios is a fast and excellent nondestructive technique to detect the photosynthetic activity and capacity of leaves, of gradients over the leaf area as well as the effect of various strain and stress parameters on plants. This review primarily deals with the first and pioneering multi-colour fluorescence imaging results obtained since the mid-1990s in a cooperation with French colleagues in Strasbourg and in my laboratory in Karlsruhe. Together we introduced not only the joint imaging of the red and far-red Chl fluorescence but also of the blue and green fluorescence of leaves. The two instrumental setups composed for this purpose were (1) the Karlsruhe-Strasbourg UV-Laser Fluorescence Imaging System (Laser-FIS) and (2) the Karlsruhe Flash-Light Fluorescence Imaging System (FL-FIS). Essential results obtained with these instruments are summarized as well as the basic principles and characteristics of multi-colour fluorescence imaging. The great advantage of fluorescence imaging is that the fluorescence yield in the four fluorescence bands is sensed of several thousand up to 200,000 pixels per leaf area in one image. The multi-colour FIS technique allows to sense many physiological parameters and stress effects in plants at an early stage before a damage of leaves is visually detectable. Various examples of plant stress detection by the multi-colour FIS technique are given. Via imaging the Chl fluorescence ratio F690/F740 it is even possible to determine the Chl content of leaves. The FIS technique also allows to follow the successive uptake of diuron and loss of photosynthetic function and to screen the ripening of apples during storage., a2_Particularly meaningful and of high statistical relevance are the fluorescence ratio images red/far-red (F690/F740), blue/red (F440/F690), and blue/green (F440/F520) as well as images of the fluorescence decrease ratio RFd, which is an indicator of the net CO2 assimilation rates of leaves., H. K. Lichtenthaler., and Obsahuje bibliografické odkazy
Two japonica rice cultivars with different panicle trait index (PTI), HP917 (a high-PTI cultivar) and DP128 (a low-PTI cultivar) were used to investigate the effects of the nitrogen (N) rate and plant density on the grain distribution of secondary branches on the panicle axis, leaf photosynthetic characteristics, and grain yield by a split plot design. The main plots were assigned to four N rates (0, 140, 200, and 260 kg ha-1), and the subplots were assigned to two plant densities: (D20, 15 plants m-2; D10, 30 plants m-2). Results showed that the grain yield was increased by increasing N rate and plant density, reaching a peak at N200 with D10. Compared with N0 treatment, the PTIs of HP917 and DP128 increased with an increase in the N rate, respectively. The PTIs of HP917 and DP128 increased by 4% with increasing plant density from D20 to D10. The leaf capacity was significantly affected by N rate and plant density. The grain distribution characteristics of secondary branches on the panicle axis was closely related to yield. Correlation analysis showed the PTI was positively correlated with grain yield and net photosynthetic rate. These results suggested the improvement in PTI from 0.15 to 0.52 was beneficial to increase the grain yield, which might contribute to the increased grain number of secondary branches of the middle and bottom panicle.
To study the light intensity suitable for Bletilla ochracea Schltr., morphology, photosynthetic parameters, and polysaccharide content of seedlings were evaluated under different light intensities. All shade treatments promoted plant growth and net photosynthetic rate while having no significant effect on transpiration rate. The maximum photochemical efficiency and potential photochemical efficiency reached the lowest values under full sunlight. The electron transport rate and photochemical quenching under shade were significantly higher than those under full light, while nonphotochemical quenching was the highest under full light. This indicated that the shade alleviated photoinhibition in summer and improved the utilization of light. B. ochracea could adapt to different light intensities, enhancing photosynthetic efficiency under low light by improving the electron transport and the degree of opened PSⅡ reaction centers, and adapting to high light by increasing heat dissipation. Plant growth, photosynthesis, and polysaccharide accumulation of B. ochracea greatly increased under 76.4% shade.
Two light treatments [ambient sunlight (L1) during the entire growth period and 40% shade (L2) from 40 d after sowing until 24 d after flowering] and two phosphate fertilizer treatments [no phosphate fertilizer application (P0) and a conventional phosphate fertilizer application (P1)] were used to determine how phosphate fertilizer regulates soybean [Glycine max (L.) Merr.] photosynthesis under shading. We showed that phosphorus significantly increased chlorophyll content and grain yield under shading. The light-saturated net photosynthetic rate, apparent quantum yield, maximum electron transport rate, and maximum Rubisco carboxylation rate in P1 under L2 significantly increased. Moreover, phosphate fertilizer significantly improved the electron transfer and PSII reaction center performance under shading. Therefore, phosphate fertilizer increases low light-utilization efficiency by improving PSII performance, promoting ribulose-1,5-bisphosphate regeneration, ensuring a source of carboxylate substrates, and coordinating the balance between photochemical reaction and Calvin cycle under shading.
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.