Activity Of Photosynthetic Apparatus Research Articles

Phytotoxic Strains of Fusarium commune Isolated from Truffles.

Most Fusarium species are known as endophytes and/or phytopathogens of higher plants and have a worldwide distribution. Recently, information discovered with molecular tools has been also published about the presence of these fungi in the microbiome of truffle fruiting bodies. In the present work, we isolated and identified three Fusarium strains from truffle fruiting bodies. All isolates were assigned to the same species, F. commune, and the strains were deposited in the All-Russian Collection of Microorganisms under accession numbers VKM F-5020, VKM F-5021, and VKM F-5022. To check the possible effects of the isolated strains on the plants, the isolates were used to infect sterile seedlings of Sarepta mustard (Brassica juncea L.). This model infection led to a moderate suppression of the photosynthetic apparatus activity and plant growth. Here, we present characteristics of the F. commune isolates: description of the conidial morphology, pigmentation, and composition of the mycelium fatty acids. Overall, this is the first description of the Fusarium cultures isolated from truffle fruiting bodies. Possible symbiosis of the F. commune strains with truffles and their involvement in the cooperative fatty acid production are proposed.

Effect of growth promotors on morphogenesis, photosynthetic apparatus, productivity and residual substances content in sweet pepper (Capsicum annuum) fruits

The use of plant growth promoting substances in order to optimize crop performance is one of the leading tasks of modern plant physiology. The effect of 0.005% 1-naphthaleneacetic acid (1-NAA), 0.005% gibberellic acid (GA3), 0.005% 6-benzylaminopurine (6-BAP) foliar treatment on morphogenesis, leaf parameters, photosynthetic pigments content, photosynthetic apparatus activity indices, and residual amounts of the used substances in the sweet pepper Capsicum annuum L. variety Antey fruits was investigated. The field experiment was laid on plots of 32 m2. The treatment of plants was carried out at the budding stage. Morphometric indices were determined at the flowering and fruit formation stages. The mesostructure of the middle tier leaves was studied at the fruit formation stage. The content of the chlorophylls was determined in the fresh leaf tissue by the spectrophotometric method. Indices of photosystem II (PSII) activity were determined by registration of chlorophyll fluorescence induction, using a portable single-beam fluorimeter. The assay of the residual content growth of promotors in the fruits was carried out on a Shimadzu GC gas chromatograph with a mass spectrometric detector – GCMS-QP2020 EI. It was revealed that treatment with GA3 increased plant height. All substances increased the number of leaves on the plant, their fresh and dry weight, the leaf area, and the canopy leaf area index. All growth promoting substances thickened leaf laminas due to the growth of chlorenchyma. GA3 and 6-BAP increased the volume of columnar parenchyma cells, and 1-NAA and GA3 increased the size of leaf spongy parenchyma cells. 6-BAP increased the total chlorophyll (a + b) content in the leaves, and under the GA3 treatment this index tended to decrease. 6-BAP increased the chlorophyll index of plants at the fruit formation stage, and GA3 decreased it at the flowering stage. The net photosynthetic rate increased under the influence of 1-NAA and 6-BAP, and decreased under GA3 treatment. GA3 reduced photorespiration and transpiration in leaves, 6-BAP increased transpiration, and 1-NAA decreased it. All substances increased dark respiration. Treatment with GA3 and 6-BAP reliably increased the maximum quantum efficiency of PSII photochemical reactions. 1-NAA and 6-BAP increased the actual quantum efficiency of PSII photochemistry. The coefficient of chlorophyll fluorescence photochemical quenching significantly increased at flowering under the application of 1-NAA, and tended to increase at the stage of fruit formation under the treatment of 1-NAA and 6-BAP. When GA3 was applied, the rate of chlorophyll fluorescence photochemical quenching was significantly reduced. The index of PSII reaction centers fraction that do not reduce the QB acceptor did not change with the use of 1-NAA and GA3 and tended to decrease after the use of 6-BAP. All growth promotors increased the whole plant dry weight. They reduced the net photosynthetic efficiency at the flowering stage, and at the stage of fruit formation it significantly increased under the treatment with 6-BAP. The 6-BAP caused the redistribution of plastic substances into the fruits due to the decrease in the dry weight of vegetative organs. Treatment with 1-NAA increased the proportion of root dry weight. 1-NAA, GA3 and 6-BAP increased the yield of fruits from one plant by 17%, 22% and 20% respectively due to the increase in the number of fruits per plant. The residual amounts of 1-NAA and 6-BAP in ripe sweet pepper fruits did not exceed the maximum permissible sanitary standards.

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity.

Antarctic algae are exposed to prolonged periods of extreme darkness due to polar night, and coverage by ice and snow can extend such dark conditions to up to 10 months. A major group of microalgae in benthic habitats of Antarctica are diatoms, which are key primary producers in these regions. However, the effects of extremely prolonged dark exposure on their photosynthesis, cellular ultrastructure, and cell integrity remain unknown. Here we show that five strains of Antarctic benthic diatoms exhibit an active photosynthetic apparatus despite 10 months of dark-exposure. This was shown by a steady effective quantum yield of photosystem II (Y[II]) upon light exposure for up to 2.5 months, suggesting that Antarctic diatoms do not rely on metabolically inactive resting cells to survive prolonged darkness. While limnic strains performed better than their marine counterparts, Y(II) recovery to values commonly observed in diatoms occurred after 4-5 months of light exposure in all strains, suggesting long recovering times. Dark exposure for 10 months dramatically reduced the chloroplast ultrastructure, thylakoid stacking, and led to a higher proportion of cells with compromised membranes than in light-adapted cells. However, photosynthetic oxygen production was readily measurable after darkness and strong photoinhibition only occurred at high light levels (>800 µmol photons m-2 s-1). Our data suggest that Antarctic benthic diatoms are well adapted to long dark periods. However, prolonged darkness for several months followed by only few months of light and another dark period may prevent them to regain their full photosynthetic potential due to long recovery times, which might compromise long-term population survival.

Morpho-Physiological, Chlorophyll Fluorescence, and Diffuse Reflectance Spectra Characteristics of Lettuce under the Main Macronutrient Deficiency

The aim of the present work was to assess the physiological state of plants and photosynthetic apparatus activity in lettuce (Lactuca sativa L.) by non-invasive methods (leaf diffuse reflectance spectroscopy and chlorophyll fluorescence) under the deficiency of one of the macronutrients (nitrogen, phosphorus, or potassium). Our experiments assessed the deficiency of each of the macronutrients relative to plants vegetating under optimal nutrition. The used methods showed that the deficiency of macronutrients causes changes in the optical characteristics of lettuce plants (cvs. ‘Vitaminnyi’ and ‘Kokarda’), including a decrease in the chlorophyll content (57% and 51%) and a change in metabolism, which leads to a decrease in the efficiency of light energy conversion in photochemical processes of photosynthesis and an increase in the dissipation of excess light energy (19% and 10%). Linear regression equations, describing the relationship between net productivity and spectral characteristics of diffuse leaf reflectance with high accuracy, have been obtained. Changes in all studied indicators of the physiological state of plants under the influence of macronutrient deficiency are more pronounced at the early stages of development than in later periods, when the first symptoms of aging appear (decrease in ChlRI). The observed differences between lettuce cultivars and their response to nitrogen, phosphorus, or potassium deficiency are non-specific and mainly represent quantitative variation. The method for assessing the spectral characteristics of diffuse reflection of leaves seems to be the most promising for monitoring the physiological status of plants and early detection of nitrogen, phosphorus, or potassium deficiency.

Arsenic Soil Contamination and Its Effects on 5-Methylcytosine Levels in Onions and Arsenic Distribution and Speciation.

Arsenic represents a serious health threat in localities with a high arsenic-polluted environment and can easily get into the human food chain through agronomy production in areas affected by arsenic contamination. Onion plants that were grown in controlled conditions in arsenic-contaminated soil (5, 10, and 20 ppm) were harvested 21 days after contamination. Arsenic levels (from 0.43 ± 0.03 µg g-1 to 1761.11 ± 101.84 µg g-1) in the onion samples were high in the roots and low in the bulbs and leaves, which is probably caused by a reduced ability of the onions to transport arsenic from roots to bulbs and leaves. Arsenic species As(V) and As(III) in As(V)-contaminated soil samples were represented strongly in favor of the As(III) species. This indicates the presence of arsenate reductase. Levels of 5-methylcytosine (5-mC) (from 5.41 ± 0.28% to 21.17 ± 1.33%) in the onion samples were also higher in the roots than in the bulbs and leaves. Microscopic sections of the roots were examined, and the most damage was found in the 10 ppm As variant. Photosynthetic parameters pointed to a significant decrease in photosynthetic apparatus activity and the deterioration of the physiological state of plants as arsenic content increased in the soil.

Chlorophyll fluorescence of wheat leaves when infected with <i>Bipolaris sorokiniana</i>, chloride salinity and seed hyperthermia

Results of chlorophyll fluorescence parameters (ChlF) informativity measurement and comparison of 10-d-old spring wheat seedlings under laboratory conditions under separate and combined stressors action are presented. It was found that separate and combined action of chloride salinity (1,3%), infection with cereal root rot pathogen Bipolaris sorokiniana Shoem. (5000 conidia per grain) suppressed light and dark reactions of photosynthesis. The effective quantum yield Y(II), photochemical quenching qP and electron transport ETR decreased significantly in both cultivars, most significantly in the co-activated version (up to 62,7%). The maximum photochemical quantum yield of FS II Fv / Fm was less informative, no significant changes in the parameter were found. Inhibition of light-dependent reactions was accompanied by a significant increase in the values of the parameters of non-photochemical quenching ChlF - coefficient qN and quantum yield of regulated non-photochemical quenching ChlF Y (NPQ) from 24.1 to 72.1% in both varieties, most pronounced in the variety Sibirskaya 12. The parameter Y(NO), the quantum yield of unregulated non-photochemical quenching of ChlF, changed insignificantly relative to the control in both varieties. The positive effect of seed pre-heating (43 °C) on the functional activity of photosynthetic apparatus of seedlings - the reliable (p ≤ 0,05) increase of the parameter Y(II), qP, ETR (by 18,0-59,0%) and decrease of the parameter Y(NPQ), Y(NO) and qN (by 18,8-35,1%) at further infection and chloride salinization in both sorts, mainly in the variety Omskaya 18 was revealed. The informativeness of the parameters ChlF for assessment of varieties stress tolerance was established. Significant intervariety differences (from 1.2-6.2 times) were revealed for almost all parameters (except for Fv / Fm, Y(NO), Fv) for all variants of experiment. The varietal specificity was established - the least changes in ChlF parameters relative to the control were in the stable variety Omskaya 18 in all variants of the experiment. The proposed approach will make it possible to develop a noninvasive method for early diagnosis of stress tolerance (phenotyping) of new wheat genotypes to biotic and abiotic stressors.

Physiological Performance of Mimosa pudica L. under Different Light Quality and Photoperiods

In the present study, we examined the light quality and photoperiod-dependent physiological performance of Mimosa pudica. Plants were grown in pots under white, blue, green and red-light compositions under 12 h per day (12/12 h) and 24 h per day (24/0 h) for 12 days. After 12 days, the physiological parameters’ morphology, fresh weight, chlorophyll fluorescence and biochemical analyses, which include antioxidants, lipid peroxidation, pigment content and carbohydrate content were also measured. Necrosis was found in red, blue and green light and the plant was senesced at the end of the experiment. The blue 24-h light period showed the highest pigment and antioxidant content, whereas the lowest was observed in green light conditions. The OJIP curve was complete in white light, hence it was not completely formed in red, blue and green light. The phenomenological parameters also fluctuated in different light conditions. Photosynthesis ultimately results in starch content, which was highest in blue light and lowest in red light. Different monochromatic light qualities inhibited plant growth by reducing the activity of photosynthetic apparatus in plants. White light was more effective in driving photosynthesis and promoting the plant growth, while green and red light showed a suppressive effect on plants’ growth. The 24 h photoperiod was also accompanied by various spectra to reduce the plants’ growth. The results clearly indicate that the photoperiod and light spectrum must be considered before growing plants in a greenhouse.

Physiological and proteomic analyses of Malus crabapples exposed to long-term warming and short-term heat shock treatments reveal the response characteristics of photosynthetic apparatus

Malus crabapples are precious woody plants with unique ornamental and applied values. Their weak photosynthetic performance in subtropical summer disturbs the normal growth and development, but the underlying mechanism remains unclear. To facilitate their local cultivation, the differences in photosynthetic capacity between six Malus cultivars in subtropical regions from June to September as well as the response characteristics of photosynthetic apparatus in selected cultivar M. ‘Professor Sprenger’ to short-term, extreme heat shock were comprehensively investigated. The results showed that changes in environmental factors, especially the increase in air temperature, limited net photosynthetic rates (Pn) in different cultivars and caused changes in the shapes of the diurnal Pn curves. The utilization range and efficiency of these cultivars for CO2 and light energy also changed under high temperature environment, which resulted in decreased photosynthetic activity and differential photosynthetic adaptability. Interestingly, M. ‘Professor Sprenger’ possessed more activated reaction centers and efficient electron transport chains under heat shock, which ensured the absorption and utilization of light energy; while a series of differentially expressed photosynthesis-related/competitive proteins potentially promoted activity and stability of photosynthetic apparatus. These combined results provided a reasonable explanation for the strong photosynthetic performance of M. ‘Professor Sprenger’ under heat stress.

Physiological and molecular features predispose native and invasive populations of sweet briar (Rosa rubiginosa L.) to colonization and restoration of drought degraded environments

The aim of this study was to determine physiological and molecular grounds for high adaptation potential of invasive populations of Rosa rubiginosa to soil drought. We assume that the invasive populations possess specific and effective adaptive mechanisms making them capable pioneer and nurse plants in dry environments. By colonizing the land, they limit its degradation and initiate revitalization of areas damaged by soil droughts. We analyzed plant water status, the photosynthetic apparatus activity, carbohydrate and phenolic content, the level of non-enzymatic antioxidants and RbcL protein associated with fixation of CO2. The research involved native (Northern Hemisphere: Poland, Spain) and invasive (Southern Hemisphere: Argentine, New Zealand) populations. Contrary to the native population, the invasive one demonstrated soil drought induced specific responses aimed at maintaining high water potential in the leaves, greater content of soluble carbohydrates, and higher osmotic potential. In the invasive population, the accumulation of soluble carbohydrates prevailed over their consumption for the synthesis of phenolic compounds. The invasive plants also maintained high content of assimilation pigments and showed greater level of non-enzymatic antioxidants. Reduced activity of the photosynthetic apparatus was associated both with increased energy amount dissipated from PSII and the efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors. The study results pave the path for further research on the genetic basis of sweet briar response to soil drought in the context of progressive steppe formation and desertification.

Physiological Comparison of Wheat and Maize Seedlings Responses to Water Stresses

The aim of the study was to investigate specific responses of spring wheat (C3 photosynthesis) and maize (C4 photosynthesis) to drought and flooding stress. Analyses of water content, gas exchange intensity, photosynthetic apparatus activity, chlorophyll content, plant height and biological membrane integrity were performed on the 10th day of drought and flooding in both species at the third leaf stage. A specific response of wheat under both drought and flooding conditions involved an increase in ETo/RC ratio, describing electron transport flux converted into a single reaction center in PSII. Correlations between electrolyte leakage and the probability of electron transport beyond the plastoquinone QA, and the amount of energy used for the electron transport were also found. A specific response of maize during flooding was the increase of stomatal conductance. Additionally, a significant correlation between PN/Ci and relative water content was exhibited. Furthermore, the parameters differentiating the studied species only under stressful conditions were rendered. The application of such parameters can be widely used, e.g., for studying the reaction of a potential cultivars to drought and flooding. Providing such information to potential farmers can help better select cultivars for their environmental conditions.

Mitigation effects of selenium on accumulation of cadmium and morpho-physiological properties in rice varieties

Selenium (Se) is a beneficial element, but only when present within its permissible range. Its hyper-accumulation in edible plant parts can cause Se toxicity. This study aimed to develop an agronomic plan for biofortification of rice with Se and reclamation of cadmium (Cd)-contaminated soil, utilizing sodium selenite (Na2SeO3) and cadmium chloride (CdCl2) as soil treatments. Biofortification was performed on two target rice varieties: genotypes 5097A/R2035 and GangYou725, in field trials by applying Cd at a concentration of 0–8 mg kg soil−1 and Se at 0–1 mg kg soil−1. Since these rice varieties have different metabolic specificity, the degree of elemental accumulation, deviations in chlorophyll concentration, activity of photosynthetic apparatus and grain yield were assessed. It was found that application of 1 mg kg−1 Se2O3 decrease Cd content and increased chlorophyll content and photosynthetic activity while grain yield was unaffected by application of the metallic trace-elements. Comparing effects at different stages, we found that the 50% heading stage was most sensitive to metal application. In sum, Se mitigates Cd toxicity, but hyperaccumulation of Se (4 mg kg−1) in polished rice was observed with Cd at 4 and 8 mg kg−1. The elevated level of Cd stress in pot experiments resulted in over-accumulation of Se in the germ and endosperm that poses serious health concerns.

Sulfate-Based Fertilizers Regulate Nutrient Uptake, Photosynthetic Gas Exchange, and Enzymatic Antioxidants to Increase Sunflower Growth and Yield Under Drought Stress

The challenging impact of drought to agricultural productivity requires the adoption of mitigation strategies with a better understanding of underlying mechanisms responsible for drought tolerance. The present study aimed at investigating the effects of sulfur-based fertilizers on mitigation of drought stress in sunflower. Sulfate-containing fertilizers, viz., ammonium sulfate, zinc sulfate, magnesium sulfate, potassium sulfate, and gypsum, were initially evaluated at two different rates (10 and 20 mg kg−1 soil equivalent to 20 and 40 kg ha−1, respectively) for nutrient uptake and growth-promoting traits in sunflower seedlings (cv. Hysun-33). The best performing fertilizer (gypsum) was then selected to evaluate the response of sunflower under drought stress imposed at flowering stage for three weeks (25–30% water holding capacity). Results indicated significant amelioration of drought stress with higher activity of photosynthetic apparatus, upregulation of antioxidative enzymes, and increased achene yield by gypsum application. In comparison to control, gypsum-treated plants (20 mg kg−1 soil) exhibited higher water status (32%), leaf photosynthetic rate (29%), transpiration rate (67%), and stomatal conductance (118%) under drought stress. The antioxidant enzyme activities of catalase, guaiacol peroxidase, and superoxide dismutase were also increased by 67%, 62%, and 126%, respectively, resulting in higher achene yield (19%) under water-deficit conditions. This study indicates that the application of sulfur-based fertilizers (gypsum) can be used to induce drought tolerance and obtain high sunflower yields under drought stress, and furthermore, it is a cost-effective strategy resulting in high benefit–cost ratio with respect to no gypsum application.

Influence of Nanoparticles of Metals and Their Oxides on the Photosynthetic Apparatus of Plants

A comparative survey of the published data concerning the effects of the most frequently used metal nanoparticles and their oxides on the main parameters of the photosynthetic apparatus activity and the chloroplast ultrastructure of higher plants is presented. It is demonstrated that metal nanoparticles are capable of both stimulating and suppressing activities towards the photosynthetic apparatus. Possible mechanisms of the effects of metal nanoparticles on the plant organism are discussed.

Some special features of the water regime and the photosynthetic apparatus activity in Feijoa sellowiana (O. Berg) O. Berg plants under the water stress

When assessing the drought tolerance of Feijoa sellowiana cultivars and forms, the total water content in leaf tissues and their waterretaining and regenerative capacity were determined, and the parameters of chlorophyll fluorescence induction were measured at different water content in leaves. Current-year leaves were characterized by a higher sensitivity to drought. According to the complex of water regime parameters and characteristics of the chlorophyll fluorescence induction (CFI), it was found that the cultivar Aromatnaya Fantazia and the form 3/1 are characterized by a relatively high drought tolerance. It has been demonstrated that the common method for assessing plant tolerance by the index of their water-retaining forces, in relation to Feijoa sellowiana genotypes, does not allow determining the critical level of water deficit. It has been found that in the cultivars and forms with low water stress tolerance, with the water loss of 20-25% from the leaf tissues complete hydration, irreversible irregularities in the PS II structures occurred. The most sensitive to the lack of water in the leaves were such parameters as variable fluorescence, rate constants of the photochemical and non-photochemical deactivation of the excitation, as well as the processes of Qa reduction in the reaction centers of PS II.

Флуоресценция хлорофилла в оценке воздействия соединений тяжёлых металлов на водные организмы

Fluorescent methods allow to improve the bioassays because of time effectiveness. These methods give information on chlorophyll concentration and plant photosynthetic apparatus activity in a short period of time. The aim of this study was to estimate the sensitivity of aquatic organisms to heavy metals using chlorophyll fluorescent methods. The test-organisms of different taxonomic categories were used, including thermophilic strain Chlorella vulgaris Beijer, aquatic plants Elodea сanadensis Michx. and Lemna minor L., crustacean Daphnia magna Straus. Fluorimeter “Foton 10” developed in SibFU was employed to measure prompt and delayed fluorescence (PF and DF respectively). The experiments revealed that copper ions affected DF of chlorella in 30 minutes, resulting in a 50% decrease of relative indicator of DF (RIDF) in the range of concentrations 0.005-0.01 mg/l of Cu2+. Measuring the DF of duckweed was less time-consuming compared to registration the changing of morphological parameters when the plants were exposed to heavy metals. Copper, cadmium, and nickel exposures were found to decrease the RIDF of duckweed by more than 50% at the concentrations of 0.17, 0.31, and 1.89 mg/l respectively. However, zinc had no significant effect on the RIDF of Lemna minor in the range of 0.1-8 mg/l of Zn2+ within 24 h of exposure time. The analysis of fluorescent parameters of Canadian elodea showed the possibility of using the plant as a sorbent during the bioremediation of aquatic environments from heavy metals. Registration of chlorophyll fluorescence allowed revealing the toxic effects of negligible concentrations of heavy metals in experiments with the feeding rate of daphnids. The median effective concentrations (EC50) were 0.002, 0.02, 0.4, and 0.25 mg/l of Cd2+, Cu2+, Zn2+, and potassium dichromate respectively. This makes it possible to obtain information on the effects of pollution in the early stages of exposure and in a shorter time. Thus, the use of chlorophyll fluorescence in biomonitoring the state of the aquatic environment makes it possible to more quickly respond to changes in the ecological situation in water bodies.

Boronic Acids of Pharmaceutical Importance Affect the Growth and Photosynthetic Apparatus of Cyanobacteria in a Dose-Dependent Manner.

The dynamic increase in the commercial application of antimicrobial derivatives of boronic acids, and potential impact of their presence in aquatic systems, supports the necessity to study the toxicity of these substances towards microorganisms of crucial meaning in the environment. One example of the mentioned derivatives is tavaborole (5-fluoro-substituted benzoxaborole), a pharmaceutical agent with antifungal activity. Cyanobacteria were used as model organisms, which are photoautotrophic prokaryotes, as representative aquatic bacteria and photoautotrophs associated with the plant kingdom. To the best of our knowledge, we investigated this issue for the first time. In order to recognize the under-stress response of those microorganisms, the concentration of photopigments—a key factor in the activity of photosynthetic apparatus—was measured spectrophotometrically. We found that the 3-piperazine bis(benzoxaborole) significantly suppressed the growth of halophilic and freshwater cyanobacteria, at a concentration 3.0 mM and 0.3 mM, respectively. Our results also showed that the tested substances at micromolar concentrations stimulated the growth of cyanobacteria, particularly in the freshwater strain Chroococcidiopsis thermalis. The tested substances acted with various strengths, depending on their structure and concentration; nevertheless, they had a greater influence on the synthesis of phycobiliproteins (e.g., lowered their concentration) than on the formation of chlorophyll and carotenoids.

Physiological and biochemical parameters of apricot cultivars under drought conditions on the Southern Coast of the Crimea

In order to determine special features of the photosynthetic apparatus activity and the content of thread compounds in various apricot cultivars during the period of maximum drought probability on the Southern Coast of the Crimea, we studied the concentration of proline, phenolic compounds and chlorophylls, as well as the parameters of chlorophyll fluorescence induction (CFI) in some apricot cultivars ( Prunus armeniaca Lam.), characterized by various degree of drought tolerance (‘Alupkinsky’, ‘Krymskiy Amur’) are weakly resistant; Khurmai cultivar is characterized by labile resistance, and the cultivars Kazachok, Professor Smykov, Nagycorosi Orias are drought tolerant cultivars). It has been found out that drought-resistant cultivars are characterized by a relatively low content of proline in their leaves. It is supposed that this amino acid is involved in the protective reactions of apricot plants under water stress. The results of the photosynthetic apparatus studies in the presented cultivars demonstrated that in leaves, water loss less than 20% caused reversible changes in the parameters of CFI. An increase in the water deficit up to 25-30% caused the destruction of PS2 in weakly drought-resistant cultivars. The most stable photosynthetic apparatus activity was noticed in the cultivar Nagycorosi Orias. Deviations in photosynthesis processes were most pronounced during the period of water restoration in leaves.

Growth, Yield and Quality of Sweet Pepper Fruits Fertilized with Polyphosphates in Hydroponic Cultivation with LED Lighting

The aim of this study was to investigate the effect of phosphorus application in the form of polyphosphates on the yield and quality of sweet pepper fruits grown with LED (light-emitting diodes) assimilation lighting. Phosphorus is absorbed by the root system of plants mainly in the form of orthophosphates ions. The availability of phosphorus depends, among other things, on the pH of the substrate and the temperature. Two cultivars of sweet pepper with red fruits were tested in hydroponic cultivation on a mineral wool substrate. The plants were fertilized with one of three schedules, each of the same concentration of components, but differing only in the form of the applied phosphorus: polyphosphates (PP) and orthophosphates (OP). In the experiment, stem length extensions and number of leaves, chlorophyll concentration in leaves and fluorescence of the chlorophyll in a leaf were measured. The number and weight of fruits in total as well as marketable and non-commercial fruits with symptoms of dry rot (BER—blossom end rot) were studied. The concentration of dry matter and selected chemical components in fruits were examined and the sensory quality of fruits was evaluated using the QDA (Quantitative Description Analysis) method. The nutrient status of the pepper plants was also examined. Polyphosphates used in the medium increase the activity of photosynthetic apparatus of leaves and have a positive effect on the share of marketable yield of the total yield in the cultivar susceptible to BER. Fertigation in hydroponic cultivation with medium containing 30% phosphorus in the form of polyphosphates increased the uptake of calcium in pepper plants growing with LED lighting. The pepper cultivars tested differ in, among other things, the susceptibility to BER and the quality attributes of the fruit.

Influence of drought on the photosynthetic apparatus activity, senescence rate, and productivity in wheat plants

Effects of soil drought at flowering stage on the functional state of photosynthetic apparatus and chloroplast enzymatic antioxidant defense systems in flag leaf during reproductive period, and the productivity of winter wheat plants of high-protein Natalka variety and drought-tolerant Podolyanka variety were studied in pot experiment. Until flowering and for the control plants during the entire vegetation, the soil moisture content was maintained at a level of 60—70 % of field capacity (FC). Drought treatment (soil moisture 30 % FC) was applied for 7 days covering flowering—early kernel watery ripe period (BBCH 61—71). After that, watering of plants was resumed to a control level which was maintained until the end of the growing season. The estimation of the chlorophyll and Rubisco content, the chloroplast antioxidant enzymes activity, and the net CO2 assimilation and transpiration rates was carried out on flag leaves. The measurements were taken on the third day of watering cessation (the first day the soil moisture reached 30 % FC, BBCH 61), at the end of the drought period (seventh day at 30 % FC, BBCH 71), and after watering resumed at the medium milk (BBCH 75) and late milk (BBCH 77) stages. The components of plant grain productivity were determined by weighing air-dry material at grain full ripeness. It was revealed, that drought stress during flowering inhibited CO2 assimilation and accelerated induction of senescence processes in wheat plants associated with degradation of photosynthetic apparatus and manifested in quicker ontogenetic drop in chlorophyll and Rubisco contents and loss of leaf photosynthetic activity. This exacerbated the drought impact on the plant organism so that after optimal watering return, the physiological and biochemical parameters were not restored to the values of control plants that were all time under optimal moisture supply. Stress-induced premature senescence reduced the supply of plants with assimilates and ultimately led to a decrease in their grain productivity. Impact of drought on flag leaf photosynthetic activity and especially on senescence induction were much more pronounced in the high-protein wheat variety Natalka with a genetically programmed earlier start of the nitrogen-containing compounds remobilization from leaves than in Podolyanka variety. The drought-tolerant variety Podolyanka keep ability to maintain much higher CO2 assimilation activity during drought period and to preserve photosynthetic apparatus from early induction of senescence due to likely more efficient chloroplast antioxidant defense systems, thereby gaining a better assimilates supply for yield formation.

Analysis of Aldo–Keto Reductase Gene Family and Their Responses to Salt, Drought, and Abscisic Acid Stresses in Medicago truncatula

Salt and drought stresses are two primary abiotic stresses that inhibit growth and reduce the activity of photosynthetic apparatus in plants. Abscisic acid (ABA) plays a key role in abiotic stress regulation in plants. Some aldo–keto reductases (AKRs) can enhance various abiotic stresses resistance by scavenging cytotoxic aldehydes in some plants. However, there are few comprehensive reports of plant AKR genes and their expression patterns in response to abiotic stresses. In this study, we identified 30 putative AKR genes from Medicago truncatula. The gene characteristics, coding protein motifs, and expression patterns of these MtAKRs were analyzed to explore and identify candidate genes in regulation of salt, drought, and ABA stresses. The phylogenetic analysis result indicated that the 52 AKRs in Medicago truncatula and Arabidopsis thaliana can be divided into three groups and six subgroups. Fifteen AKR genes in M. truncatula were randomly selected from each group or subgroup, to investigate their response to salt (200 mM of NaCl), drought (50 g·L−1 of PEG 6000), and ABA (100 µM) stresses in both leaves and roots. The results suggest that MtAKR1, MtAKR5, MtAKR11, MtAKR14, MtAKR20, and MtAKR29 may play important roles in response to these stresses.