Showing papers in "Photosynthetica in 2020"
TL;DR: In this article, the authors evaluated the validity of some chlorophyll (Chl) a fluorescence parameters as early indicators of a particular abiotic stress and also to characterize the effect of different abiotic stresses [high light, NaCl, polyethylene glycol (PEG)-induced osmotic stress, and heavy metals] on the electron transport chain of rice seedlings.
Abstract: The aim of this study was to evaluate the validity of some chlorophyll (Chl) a fluorescence parameters as early indicators of a particular abiotic stress and also to characterize the effect of different abiotic stresses [high light, NaCl, polyethylene glycol (PEG)-induced osmotic stress, and heavy metals] on the electron transport chain of rice (Oryza sativa L.) seedlings. The results clearly revealed that Chl a fluorescence parameters differ between abiotic stress types and also allowed us to select some parameters which were specifically and intensively affected under different abiotic stresses. We observed that the performance index is a common sensitive parameter to evaluate the effect of above four different abiotic stresses in rice seedlings. Certain Chl a fluorescence parameters were significant for a specific stress. The ratio between the rate constants of photochemical and nonphotochemical deactivation of excited Chl molecules (FV/F0) was prominently decreasing and the maximum quantum yield of nonphotochemical deexcitation was prominently increasing upon exposure to high light stress. The maximum quantum yield of electron transport and the electron transport from PSII donor side to PSII reaction center was highly reduced under NaCl stress in rice seedlings. Moreover, FV/F0 and PSII structure function index were prominently decreasing and the dissipation per cross section was significantly enhancing under PEG stress. The pool size of reduced plastoquinone on the reducing side of PSII [total complementary area between the fluorescence induction curve and maximal chlorophyll fluorescence (FM)], FM, and the probability by which electrons move from PSII to PSI acceptor side were significantly decreasing under heavy metal stress.
88 citations
TL;DR: The aim of this educative review is to clarify concepts, assumptions, and approximations on which it is based, as well as definitions and terms it uses, reminding that it is meant to evaluate impacts of environmental stresses -factors and/or perturbations - on the photosynthetic structure and function.
Abstract: The aim of this educative review is, by revisiting the JIP-test as introduced and further elaborated and extended by Professor Reto J. Strasser and his research group, to clarify concepts, assumptions, and approximations on which it is based, as well as definitions and terms it uses, reminding that it is meant to evaluate impacts of environmental stresses -factors and/or perturbations - on the photosynthetic structure and function. It analyses how the JIP-test, based on the Theory of Energy Fluxes and adopting Duysens' concept, translates the OJIP polyphasic chlorophyll a fluorescence rise kinetics, emitted by PSII, into biophysical parameters to be compared. The interpretation of the OJIP sequential steps and in-between phases, the definitions/meanings and formulae derivations of quantum yields, probabilities, efficiencies, specific energy fluxes, inactive PSII reaction centres, and performance indexes (PIABS, PItotal) is addressed in detail. OJIP normalizations and subtractions providing semiquantitative information are also discussed.
63 citations
TL;DR: In this article, the effects of different color light-emitting diodes (mixed colors, red, blue, and orange light) on plant growth, gas exchange, and oxidative stress were investigated in Boehmeria nivea L., by means of measuring growth, photosynthesis, chlorophyll (Chl) content, reactive oxygen species (ROS), and activity of antioxidant enzymes under controlled conditions.
Abstract: Light is an important variable affecting the plant growth. In present study, the effects of different color light-emitting diodes (mixed colors, red, blue, and orange light) on plant growth, gas exchange, and oxidative stress were investigated in Boehmeria nivea L., by means of measuring growth, photosynthesis, chlorophyll (Chl) content, reactive oxygen species (ROS), and activity of antioxidant enzymes under controlled conditions. Comparing to the mixed colors light, red light significantly increased shoot and leaf biomass, plant height, number of leaves per plant, and stem diameter by increasing the Chl content and therefore promoting the highest photosynthetic capacity. This might partially be explained by the decrease of malondialdehyde and proline contents as well as the activities of superoxide dismutase and peroxidase under red light, to keep a better internal environment of the cell. However, blue and orange light decreased plant growth, and increased the activities of antioxidant enzymes which suggest an environmental stress on plants. These results suggest that red light can enhance B. nivea growth by activating photosynthesis and reducing ROS accumulation.
41 citations
TL;DR: The initial photochemical quantum efficiency of photosystem II (Fv/Fm) and performance index (PI), describing the ability of the photosynthetic apparatus to collect light energy, have been used to screen tolerance to drought stress by ten maize accessions, monitored by leaf relative water content (RWC) and soilWater content (SWC).
Abstract: The initial photochemical quantum efficiency of photosystem II (Fv/Fm) and performance index (PI), describing the ability of the photosynthetic apparatus to collect light energy, have been used to screen tolerance to drought stress by ten maize accessions, monitored by leaf relative water content (RWC) and soil water content (SWC). The Fv/Fm, PI, and RWC values were significantly reduced in drought-stressed plants. The analysis of chlorophyll a fluorescence induction rise from the basic dark-adapted fluorescence yield to the maximum (OJIP transient), distinguished accession Zea 1006 from Libya and Zea 612 from Italy, as the most tolerant and the least tolerant genotypes. The maize genotypes were classified using the Principal Component Analysis (PCA) and clustering methods, based on Fv/Fm and PI values, leaf RWC and SWC. Genotypes from Egypt and Libya were differentiated from genotypes from Europe, Russia and the USA.
40 citations
TL;DR: The study helps understand the plant tolerance mechanisms of different sweet sorghum genotypes to increasing salinity stress and confirmed that the use of JIP-test is suitable for the identification of sorghu genotypes according to their growth underSalinity stress.
Abstract: The effect of salinity on primary photochemical reactions (using JIP-test) in six sweet sorghum genotypes was tested. An increase in salt concentrations induced significantly the accumulation of proline and caused a decline in leaf osmotic potential. Except for 100 mM NaCl concentration, salinity significantly decreased chlorophyll content and photosynthetic efficiency of plants. Increasing salinity led to a higher accumulation of QB-nonreducing PSII reaction centers. K-step in OJIP fluorescence transient was observed for the most sensitive genotypes under the high NaCl concentration. The studied sorghum genotypes responded differently to salinity stress. Thus, the study helps understand the plant tolerance mechanisms of different sweet sorghum genotypes to increasing salinity stress. The study also confirmed that the use of JIP-test is suitable for the identification of sorghum genotypes according to their growth under salinity stress.
36 citations
TL;DR: In this article, a Petri dish and pot experiment was conducted to investigate the effects of different LEDs, i.e., white light (WL), red light (RL), blue light (BL), and orange light (OL), on morphology, gas-exchange parameters, and antioxidant capacity of Brassica napus.
Abstract: Through its impact on morphogenesis, light is the key environmental factor that alters plant structural development; however, the understanding how light controls plant growth and developmental processes is still poor and needs further research. For this purpose, a Petri dish and pot experiment was conducted to investigate the effects of different LEDs, i.e., white light (WL), red light (RL), blue light (BL), and orange light (OL) on morphology, gas-exchange parameters, and antioxidant capacity of Brassica napus. Compared with WL, RL significantly promoted plant growth and biomass, contents of photosynthetic pigments, and gas-exchange parameters in comparison to BL and OL. However, RL also helped decline malondialdehyde and proline contents and superoxide anion and peroxide production rate. In contrast, BL and OL significantly reduced plant growth and biomass, gas-exchange attributes and increased the activities of superoxide dismutase and peroxidase in Petri dish as well as in pot experiment. These results suggest that red light could improve plant growth in B. napus plants through activating gas-exchange attributes, reduce reactive oxygen species accumulation, and promote antioxidant capacity.
34 citations
TL;DR: In this paper, the response of radish plants to P deficiency throughout stress conditions and recovery period was studied, and the observed decreases in quantum yield and the efficiency of electron transport chain in P-deficient plants could be due to downregulation mechanisms in the photosynthetic apparatus.
Abstract: Phosphorus (P) is an essential nutrient for plant development and its fertilisation efficiency is an important issue in agriculture. Difficulties in diagnosing P deficiency in plants have created a demand for a quick and noninvasive method/tool for assessing plant P status on-site. It has been well documented that chlorophyll fluorescence measurement is a very useful and sensitive tool for screening nutrients deficiency in plants. Although impact of P deficiency on photosynthesis process has been widely examined, its effect/s on photosynthetic electron transport between the two photosystems is still not clear. In this work, we studied the response of radish plants to P deficiency throughout stress conditions and recovery period. Leaf phosphorus content, growth rate, and photosynthetic activity and efficiency were monitored. Under P deficiency, a decrease in all of these physiological features was observed. Moreover, some changes in chloroplast structure were explored, including a reduction in chloroplast grana amount and loose arrangement. Additionally, the I-step disappeared from chlorophyll fluorescence induction curves. This can be linked to the inactivation of PSI and suppression of the cyclic phosphorylation. The observed decreases in quantum yield and the efficiency of electron transport chain in P-deficient plants could be due to downregulation mechanisms in the photosynthetic apparatus. However, both the inhibition of net photosynthetic rate, as well as the severe effect on the I-step were reversible when plants were resupplied with phosphorus. Loss of I-step can be used as a specific bioindicator for early detection of phosphorus deficiency in radish plants.
18 citations
TL;DR: In this article, the authors investigated how the treatment with exogenous Spermidine contributed to the protection against salt stress in rice chloroplasts by enhancing the activities of antioxidant enzymes and decreasing contents of reactive oxygen species and malondialdehyde accumulation.
Abstract: Spermidine (Spd) is a ubiquitous low-molecular-mass aliphatic amine that acts in abiotic stress tolerance in plants. We investigated how the treatment with exogenous Spd contributed to the protection against salt stress in rice chloroplasts. Analysis of the chlorophyll (Chl) fluorescence showed that there were many negative effects of salinity on different sites of the photosynthetic machinery; however, these were alleviated by adding Spd. Spd prevented the damage of structure and function of chloroplasts under salt stress; thylakoid membrane protein components and photosynthetic pigments were not severely affected by salinity in Spd-treated plants. Spd enhanced the activities of antioxidant enzymes and decreased contents of reactive oxygen species and malondialdehyde accumulation, suggesting that Spd may participate in the redox homeostasis in chloroplasts under salt stress. These results highlighted the positive effects of Spd on rice chloroplasts under salt stress through maintaining chloroplast structure stability.
18 citations
TL;DR: In this article, the authors investigated the photosynthesis and growth of lettuce (Lactuca sativa L.) grown under three light/dark cycles in a mini plant factory with artificial illumination.
Abstract: We investigated the photosynthesis and growth of lettuce (Lactuca sativa L.) grown under three light/dark cycles in a mini plant factory with artificial illumination. A relative longer light cycle [12/12 h (light/dark)] increased not only light-response curve parameters, such as light-saturated net photosynthetic rate, light-saturation point, light-compensation point, dark respiration rate, but also upregulated CO2-response curves parameters, such as CO2-saturated net photosynthetic rate, initial carboxylation efficiency, and photorespiration rate, compared to those of the shorter light cycles [6/6 h and 3/3 h (light/dark)]. A longer light cycle enhanced electron transfer potential, increased the chlorophyll amount, leaf area, and biomass and reduced the root/shoot ratio and the specific leaf area. Our results imply that the prolonged light cycle led to the increase in photosynthetic capacity and significantly enhanced the growth rate of lettuce.
18 citations
TL;DR: In this paper, the adaptation of green and purple-leaved Ocimum basilicum varieties, which differ in carotenoid and anthocyanin contents, to high-intensity light have been carried out.
Abstract: Comparative studies of the adaptation of green- and purple-leaved Ocimum basilicum varieties, which differ in carotenoid and anthocyanin contents, to high-intensity light have been carried out. The plants were grown for 21 d under white light-emitting diode providing different light intensities [300, 550, and 1,350 µmol(photon) m-2 s-1]. During the experiment, fresh mass and relative water content, photosynthetic pigment and anthocyanin content, amount of total free phenolic compounds, and the contents of thiobarbituric acid reactive substances and H2O2 were analysed. The fluorescent parameters, which characterized the PSII activity in the leaves (Fv/Fm, Y(II)), as well as the efficiency of dissipation of absorbed energy into heat (Y(NPQ),Y(NO)) and the fraction of the PSII open centres (qL), were determined. The obtained results are consistent with the concept of the important role of not only anthocyanin but also carotenoids in plant adaptation to high-intensity light.
17 citations
TL;DR: In this paper, the combined effect of drought and heat stress on photosynthesis, pigments, and xanthophyll cycle particularly in alfalfa (Medicago sativa L.) is investigated.
Abstract: Climate changes severely influence photosynthetic activity of plants. Studies on the combined effect of drought and heat stress on photosynthesis, pigments, and xanthophyll cycle particularly in alfalfa (Medicago sativa L.) are limited. Thus, this study investigated the combined effects of drought and heat stress in two alfalfa varieties ('Deqin' and 'Algonguin'). Results revealed that the values of the net photosynthetic rate demonstrated a significantly decreasing tendency under stresses. The effect of stresses on ribulose 1,5-bisphosphate carboxylase activity in both varieties showed a trend of first declining and then rising. Meanwhile, phosphoenolpyruvate carboxylase activity showed an increasing tendency. The intensification of stresses led to reduced photochemical efficiency and increased capability of thermal dissipation. A linear correlation was found between nonphotochemical quenching and xanthophyll cycle components. Thus, the change in carotenoids demonstrated an important role in photoprotection, the xanthophyll cycle was the main way of dissipation of excess energy under stress conditions in alfalfa.
TL;DR: This work described and discussed for the first time the dynamics of Chl, anthocyanins, and flavonols combined with photosynthetic efficiency changes during the leaf life in situ.
Abstract: The aim of this study was to examine the development and aging of chosen grapevine leaves in situ during the growing season (130 d) using chlorophyll (Chl) a fluorescence measurements and determining the changes in pigment contents. During the course of photosystems development, the increase of Chl and decrease of anthocyanin contents in leaves was observed simultaneously. On 28th day, the maximum content of Chl and minimum content of anthocyanins was measured. However, the maximal photosynthetic performance was found one week later, when the content of Chl started to diminish. Our study proved that the achievement of maximal photosynthetic performance of each leaf took about quarter of organ life and this state lasted very shortly. In this work, we described and discussed for the first time the dynamics of Chl, anthocyanins, and flavonols combined with photosynthetic efficiency changes during the leaf life in situ.
TL;DR: In this article, the authors used the growth, photosynthetic physiological parameters, and targeted metabolite analysis to evaluate the responses of Eleutherococcus senticosus in different shading treatments.
Abstract: In this investigation, we used the growth, photosynthetic physiological parameters, and targeted metabolite analysis to evaluate the responses of Eleutherococcus senticosus in different shading treatments. The results showed that the moderate shading treatment (Z1) promoted the growth and inhibited photosynthesis of plants. The severe shading treatment (Z2)inhibited both the growth and photosynthesis of the plants. Besides, Z1 had no significant effect on the PSII, while Z2 inhibited the PSII. Most of the eight medicinal metabolites accumulated in the Z1. The C6C1- and C6C3-type phenolics accumulated in the Z1, and the C6C3C6-type in the Z2. In conclusion, the moderate shading treatment accumulated more defensive phenolics; this might be the reason for this shading condition promoting the growth and the accumulation of medicinal metabolites of the plant. The result of this study laid a theoretical foundation for the further study of shading treatments on the secondary metabolism of Eleutherococcus senticosus.
TL;DR: The principal component analyses showed two distinct types of the reaction of the barley genotypes to the mild drought stress at anthesis and the performance index increased from booting to grain filling in most genotypes.
Abstract: This study aimed to explore how ten selected winter barley genotypes responded to variations in environmental conditions during the growth season by using fast chlorophyll a fluorescence and normalized difference vegetation index (NDVI) at the booting, anthesis and early grain-filling stage. Lower amount of rainfall during the anthesis induced instability in the function of PSII, observed as the positive K-band in six and the positive L-band in seven genotypes. At grain filling, all genotypes displayed negative K- and L-bands, suggesting an increase of stability within PSII. The performance index increased from booting to grain filling in most genotypes. Chlorophyll a fluorescence parameters were incorporated into the partial least squares model as explanatory variables of NDVI. After a cross-validation, the model with four latent variables was chosen explaining 75.8% variance (r = 0.870) for NDVI. The principal component analyses showed two distinct types of the reaction of the barley genotypes to the mild drought stress at anthesis.
TL;DR: In this article, a green-to-red conversion (GtR) film was used to increase the dry mass and decrease the petiole length of a sweet pepper (Capsicum annuum L).
Abstract: Although spectrum conversion films are used to improve the photosynthetic efficiency and, ultimately, crop growth, the effects of the modified spectrum on photosynthetic traits in plants have not yet been sufficiently reported. The objective of this study was to investigate the changes in photosynthetic performance and chlorophyll fluorescence of sweet pepper (Capsicum annuum L.) under a green-to-red conversion (GtR) film. The GtR-modified spectrum increased the dry mass and decreased the petiole length. The photosynthetic light-response curves were significantly improved, and the gap of the maximum photosynthetic rates increased over time after covering. The GtR-modified spectrum significantly increased chlorophyll fluorescence parameters in the JIP-test, such as parameters related to the reduction of end electron acceptors on the PSI acceptor side, the efficiency for electron transport in PSII, and the performance indexes. Our data indicated that the GtR-modified spectrum promotes electron transfer around PSI, improving photosynthetic performance and growth.
TL;DR: The study explored three UV-B levels on three contrasting sweet potato cultivars (Beauregard, Hatteras, and Louisiana 1188) using sunlit plant growth chambers at Mississippi State University and showed thatUV-B influenced three cultivars differently.
Abstract: Ground-level UV-B will stay at a high level in the next several decades and influence sweet potato growth and yield because of the remaining chlorofluorocarbons in the atmosphere. The study explored three UV-B (none, ambient, and elevated/projected) levels on three contrasting sweet potato cultivars (Beauregard, Hatteras, and Louisiana 1188) using sunlit plant growth chambers at Mississippi State University. The results showed that UV-B influenced three cultivars differently. Growth, photosynthetic rate, epidermal and leaf structure of Beauregard were negatively influenced under ambient and elevated UV-B. On the contrary, Hatteras was positively influenced, and Louisiana 1188 was influenced by elevated UV-B positively on leaf thickness and waxes content, but negatively on the vine length, dry mass, and leaf area. In summary, Beauregard, Louisiana 1188, and Hatteras were UV-B sensitive, moderately sensitive, and tolerant, respectively. Developing UV-B tolerant cultivars will benefit under both current and projected UV-B exposures.
TL;DR: In this article, the effects of light quality and beneficial microbes (biofertilizer) supply on structural and ecophysiological traits of spinach were investigated, with or without the addition of bio-feedback.
Abstract: In this work, the effects of light quality and beneficial microbes (biofertilizer) supply on structural and ecophysiological traits of spinach were investigated. Plants were grown under four light quality regimens: white light (WL), red-blue (RB), red-green (RG), and red (R) light, with or without the addition of biofertilizer. RG and R plants without biofertilizer showed morphological traits typical of shaded plants as wide leaf lamina and high photosynthetic pigment content. These plants also exhibited a higher photosynthetic capacity compared to WL and RB plants. The improved photosynthesis in RG plants was due to both morphological and physiological adjustments allowing a better utilisation of light energy, whereas in R plants it has been attributed to a reduced photorespiration rate. Biofertilizer application under WL improved plant performance enhancing photosynthesis. The high carbon gain compensates the costs of symbiosis. Biofertilizer application under R light favouring too much the microbial root colonisation, removed the benefits of symbiosis. The interaction of light quality and biofertilization significantly affects the root-microbe relationship.
TL;DR: The results suggested that drought may restrict light harvesting and electron transport in the sunflower lines at various levels and TT317-R and 2478-A were adversely affected by drought when compared to other lines, while 9753-2R exhibited better photosynthetic performance under drought and might be considered as the most tolerant among the lines.
Abstract: The aim of the study was to screen nine inbred lines of sunflower by inducing drought for 10 d and subsequent rewatering for 5 d. Impact of drought was determined by chlorophyll fluorescence and some physiological parameters. Drought led to a decrease in the photosynthetic performance, the quantum yield, and efficiency of electron transport in sunflower lines, while it caused an increase in the absorption flux per reaction centre, dissipation of an active reaction centre, and K-band as well as L-band. Drought also decreased the total chlorophyll contents and water status of the lines, which contributed to photoinhibition. Our results suggested that drought may restrict light harvesting and electron transport in the sunflower lines at various levels. Drought did not cause irreversible membrane damage, since the lines recovered after rewatering. Considering all results, the inbred lines TT317-R and 2478-A were adversely affected by drought when compared to other lines, while 9753-2R exhibited better photosynthetic performance under drought and might be considered as the most tolerant among the lines.
TL;DR: The authors' results revealed that drought significantly affected most of the studied morpho-physiological traits resulting in strong decreases in yield and the studied traits, and the mild stress treatment was considered as the most suitable water level in this study.
Abstract: Drought stress is one of the major constraints limiting the production and productivity of barley. We tried to identify some indicators related to plant productivity by analyzing some agro-morphological and physiological traits in recombinant inbred lines (RILs). Plants were exposed to three water treatments: well-watered at 70% available water content (AWC), mild drought stress at 35% AWC, and severe drought stress at 10% AWC. Our results revealed that drought significantly affected most of the studied morpho-physiological traits resulting in strong decreases in yield and the studied traits. We did not observe a significant difference in water-use efficiency between severe and mild drought conditions. Therefore, the mild stress treatment was considered as the most suitable water level in our study. Genotypes with the most tillers and spikes, the highest 1,000-grain mass, and biological yields achieved higher grain yields under all water stress conditions. Therefore, these traits could be considered as useful tools in breeding programs.
TL;DR: In this paper, the recovery of photosynthetic activity during rehydration of Haberlea rhodopensis from drought-and freezing-induced desiccation was investigated.
Abstract: The recovery of photosynthetic activity during rehydration of Haberlea rhodopensis from drought- and freezing-induced desiccation were investigated The water uptake during the initial 15 h was slow thus preventing cellular damages The results showed faster recovery of quantum efficiency of PSII in plants rehydrated after freezing stress (RAF) compared to plants rehydrated after drought stress (RAD) and the most significant differences between them were evident after 9-15 h of rehydration Following rehydration, PSI activity recovered faster compared to PSII and in contrast to PSII, its activity was higher in RAD compared to RAF plants During the first hours of rehydration, prominent alterations in energy transfer between photosynthetic complexes occurred as revealed by 77 K fluorescence of isolated thylakoids High proportion of thermal energy dissipation in dry plants and during the first hours of rehydration protects them from photooxidation; the role of PSII reaction center quenching during the recovery was suggested
TL;DR: In this paper, a co-author and co-cited reference network in the area of chlorophyll fluorescence research is analyzed. But the authors focus on the research trends in the field.
Abstract: Chlorophyll a fluorescence has been extensively used in studying photosynthesis and overall physiology of plants, algae, and cyanobacteria. As a research hotspot, a large number of papers have been published. This creates a challenge for beginning researchers to gain a holistic view of co-author and co-cited reference network by reading individual publications. Further, these scientists need to understand the research trends in the field. Scientometric analysis, a method for mining publication datasets, was therefore conducted to analyze the co-author and co-cited reference network in the area of chlorophyll fluorescence research. The countries with high-citation-per-paper publications were used as filters to identify the active author communities. The representative author groupings in these representative countries were analyzed by the network-based methods. As authors may have different active periods, their groupings are categorized to analyze their focus areas. Finally, the timeline of knowledge distribution is presented through the use of co-cited reference networks. Although our current analysis was confined to 'plant sciences', several interesting conclusions, including some caveats, are drawn in our paper to provide an overall landscape on co-author and co-cited reference network of this field.
TL;DR: In this article, two homogeneous chitin and chitosan hexamers and one partially acetylated chitosaan hexamer were used to investigate the degree of acetylation (DA) effects of chitooligosaccharides on the growth and photosynthesis of wheat seedlings.
Abstract: In this study, two homogeneous chitin and chitosan hexamers and one partially acetylated chitosan hexamer were used to investigate the degree of acetylation (DA) effects of chitooligosaccharides on the growth and photosynthesis of wheat seedlings. Both chitin and chitosan hexamers showed a significant promoting effect on the growth and photosynthesis of wheat seedlings but the positive effect depended on their DA. The homogeneous chitosan hexamers [(GlcN)6] exhibited the optimal activity compared to other samples. Seven days after (GlcN)6 treatment, the growth parameters of wheat seedlings were all significantly enhanced including fresh mass, dry mass, and length of both shoots and roots, and the contents of soluble sugar were increased by 22.8%. Additionally, (GlcN)6 could significantly promote (by 90.0%) the photosynthetic rate of wheat seedlings. Both Rubisco and fructose-1,6-bisphosphatase activity of photosynthetic carbon metabolism was also found to be significantly improved by (GlcN)6 treatment.
TL;DR: The two studied plane ecotypes showed different tolerance to the elevated temperature, and plants of Italian ecotype showed better adaptivity and developed advantageous photosynthetic characteristics, while Bulgarian ecotype was more affected.
Abstract: Plane (Platanus orientalis) is a popular park tree in Europe but is almost extinct in natural ecosystems, because of climate changes. In our study, two ecotypes of plane tree (Bulgarian and Italian) were submitted to moderately elevated temperature that occurs in summer. Our aim was to compare stress reactions, tolerance, and adaptability of these plants. Leaf age had a significant impact on the stress effects. For correct interpretation of the results, we investigated leaves at different positions from the apical bud, i.e., leaves of different age. We assessed their photosynthetic efficiency at room temperature and after treatment at moderately high temperature by simultaneous measurement of prompt and delayed chlorophyll fluorescence, as well as light reflection at 820 nm. For more precise interpretation of the obtained results we did principal component analysis. The two studied plane ecotypes showed different tolerance to the elevated temperature. Plants of Italian ecotype showed better adaptivity and developed advantageous photosynthetic characteristics, while Bulgarian ecotype was more affected. Plants of both ecotypes recovered from the heat stress.
TL;DR: In this article, the responses of five 10-d old maize hybrids to salinity stress by measuring ChlF parameters, fresh (FM) and dry mass (DM), were incorporated into a penalized regression model to predict biomass traits.
Abstract: Predicting responses to stressful conditions is very important. Chlorophyll a fluorescence (ChlF) can be used to assess effects of various stresses on photosynthetic performance. We tested the responses of five 10-d old maize hybrids to salinity stress by measuring ChlF parameters, fresh (FM) and dry mass (DM). ChlF data were incorporated into a penalized regression model to predict biomass traits. The values of FM and DM significantly decreased under salt stress by 42 and 25%, respectively. Strong responses in ChlF parameters assessing the absorption dissipation and trapping fluxes to NaCl treatment were detected. In penalized regression models, 118 transients showed greater (R2 = 0.663 for FM and R2 = 0.678 for DM), although comparable, predictive abilities as 18 selected JIP-test parameters (R2 = 0.597 for FM and R2 = 0.636 for DM). Genetic assessment of developed models is needed, as they efficiently predict biomass traits and provide physiological context to the obtained predictions.
TL;DR: Changes of photosynthetic activity during natural depletion of nitrogen in a batch culture of Chlorella vulgaris were studied using chlorophyll a fluorescence-based methods and three pivot points were detected in dynamics of the JIP-test parameters during culture growing.
Abstract: Changes of photosynthetic activity during natural depletion of nitrogen in a batch culture of Chlorella vulgaris were studied using chlorophyll a fluorescence-based methods. Complex analysis including JIP-test, multiexponential approximation, and the analysis of differential curves was carried out on the recorded fluorescence transients. Three pivot points were detected in dynamics of the JIP-test parameters during culture growing. We associated these time points with different stages of mineral stress progress. Immediately after nitrogen exhaustion in the cultivation medium, a transient increase in the efficiency of PSII was detected. During this short period, the photosynthetic apparatus acclimated to the stress by reducing the number of PSII reaction centers, simultaneously increasing the effective cross section of the light-harvesting antenna per reaction center. However, prolonged nutrient starvation impaired the structure of the photosynthetic apparatus, deactivating the oxygen-evolving complex and impairing the overall electron transport.
TL;DR: In this article, the effect of thinning of Bertholletia excelsa trees was investigated and the remaining trees increased J-I phase with the formation of a positive K-band which occurred exclusively in unfertilized (no liming or no P) individuals.
Abstract: Phosphorus (P) fertilization and liming can reduce negative effects caused by a sudden increase in light availability after thinning of forest plantations. In this study, immediately after thinning, photochemical performance (quantum yield of PSII and performance index) decreased, however, liming and P fertilization reduced the negative effects caused by thinning and accelerated the recovery of Bertholletia excelsa trees. After thinning, the remaining trees increased J-I phase with the formation of a positive K-band which occurred exclusively in unfertilized (no liming or no P) individuals. Additionally, enhanced effective dissipation (DI0/RC) values (140%) were found in individuals without liming or P after thinning, while plants under liming and P increased DI0/RC values by 47 and 79%, respectively. Photochemical performance of B. excelsa was positively correlated to iron, zinc, and manganese. Thus, P fertilization and liming are recommended for alleviating the stress caused by high irradiance after thinning in B. excelsa plantations.
TL;DR: In this paper, the authors explored photosynthesis and carotenoid-related metabolism under control (CK), low-light (L), and low-temperature and low light (LL) conditions by using the pepper (Capsicum annuum L.) varieties Longjiao 5 and Hangjiao 4.
Abstract: Light and temperature are two major factors for plant growth. Carotenoids are important photoprotective and light-harvesting pigments in photosynthetic organs. Therefore, this study explored photosynthesis and carotenoid-related metabolism under control (CK), low-light (L), and low-temperature and low-light (LL) conditions by using the pepper (Capsicum annuum L.) varieties Longjiao 5 and Hangjiao 4. We found the increased inhibition of plant growth and photosynthetic capacity under both L and LL stress. Meanwhile, carotenoid-related metabolic compounds accumulated in pepper showed different responses to the two stresses. Significantly, zeaxanthin contents were 6.69-8.88 times higher under LL than that of CK, α-carotene contents were 0.9-2.1 times higher under L than that of CK, which may enhance the tolerance to LL and L. Our findings provide a foundation for further research on the molecular mechanism of carotenoid functions regarding L and LL tolerance by regulating photosynthesis.
TL;DR: The result of PCA analysis showed that the genotypes displayed different behavior under the saline conditions and the most discriminating quantitative characters were related to plant biomass production and photosynthesis, especially the mass of fresh root, number of leaves, water-use efficiency, and the substomatal CO2 concentration.
Abstract: In this study, we examined the behavior of six faba bean (Vicia faba L.) genotypes under salinity conditions at the seedling stage. The evaluation was assessed using 21 morphological, physiological, and photosynthetic traits under control, moderate, and severe salinity conditions. The principal component analysis (PCA) was used to identify genotypes of contrasting behavior in response to salt stress and to characterize the important traits for salt tolerance. The result of PCA analysis showed that the genotypes displayed different behavior under the saline conditions. The most discriminating quantitative characters were related to plant biomass production and photosynthesis, especially the mass of fresh root, number of leaves, water-use efficiency, and the substomatal CO2 concentration. The analysis of all parameters by PCA permits us to distinguish cv. Najeh as the most tolerant genotype for salinity conditions and cv. Chourouk as the most sensitive one. These results would be of pertinent tools in faba bean breeding programs.
TL;DR: In this article, the effect of temperature on the fast chlorophyll fluorescence transient (OJIP) and OJIP-derived parameters in Antarctic lichens Xanthoria elegans, Usnea antarctica, and Dermatocarpon polyphyllizum was evaluated.
Abstract: In this study, we evaluated the effect of temperature on the fast chlorophyll fluorescence (ChlF) transient (OJIP) and OJIP-derived parameters in Antarctic lichens Xanthoria elegans, Usnea antarctica, and Dermatocarpon polyphyllizum. Samples were exposed to a range of temperatures (-5 to +45 degrees C) and measured after 15-min equilibration. High temperature (+45 degrees C) caused a decrease of ChlF, an increased J-step, and shortened time to reach peak ChlF (FP). Temperature below +5 degrees C caused the increase of ChlF and J-step. The K-band was identified in X. elegans (above +20 degrees C), U. antarctica (+35 degrees C), and D. polyphyllizum (+45 degrees C). L-band was well distinguishable in X. elegans (+45 degrees C). As indicated by the OJIP-derived parameters, high temperature inhibited photosystem II function. The inhibition was apparent as less effective energetic connectivity. The OJIP transients and auxiliary measurement of ChlF temperature curves suggested that X. elegans had the lowest termostability among the experimental species.
TL;DR: In this article, a forecasting model was designed based on the data of maximal quantum yield of photosystem II (Fv/Fm), efficiency of both photosystems (PIABS), and chlorophyll (Chl) contents of 60-d analysis.
Abstract: The efficiency of chlorophyll (Chl) fluorescence for forecasting plant response to environmental pollution was examined in four wheat cultivars. The plants were irrigated with wastewater from Razi petrochemical complex. A forecasting model was designed based on the data of maximal quantum yield of photosystem II (Fv/Fm), efficiency of both photosystems (PIABS), and Chl contents of 60-d analysis. A comparison of the forecasting model results with the real data of Fv/Fm, PIABS, and Chl in response to wastewater suggested Fv/Fm as an accurate tool for stress forecasting. The high salt concentration in wastewater induced high accumulation of H2O2, lipid peroxidation, inhibition of photosynthesis, and reduction in contents of proteins and carbohydrates, which resulted in growth suppression of all cultivars. Taken together, the negative effect of environmental pollution on crop can be detected at an early stage of stress using Fv/Fm as a fast and accurate tool to prevent irrecoverable damage to plants.