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The relationship between photosynthesis, pigment accumulation, and the expression of key light-regulated genes in Solanum lycopersicum hp-1, hp-2 and hp-1.2 photomorphogenetic mutants under conditions of high-intensity light (2000 μm (photons) m−2s−1) was studied. The hp-2 mutant (LA3006) and the hp-1 mutants (LA4012 and LA3538) are deficient in DET1 (De-etiolated 1 and DDB1 (DNA DAMAGE-BINDING PROTEIN 1), respectively, which are components of the CDD complex (COP10, DDB1, DET1). HP mutants are superproducers of various pigments and are sensitive to light. We have shown that HIL (high-intensity light) causes a decrease in PSII activity after 24 and 72 h of irradiation, which was partially restored after 72 h in the WT. The photosynthetic rate noticeably decreased only in LA4012 and LA3538 after 24 h of irradiation. After 72 h, the photosynthetic rate decreased in all mutants, with the exception of hp-1.2 LA0279, but the decrease was most noticeable in LA4012, yet significant changes in the respiration rate were absent. The LA0279 mutant was more capable of accumulating anthocyanin in the cells of the subepidermal parenchyma and chlorenchyma, as well as in the cells at the base of large multicellular glandular trichomes and in the mesophyll. Another important difference was the accumulation of increased amounts of antheraxanthin and phenolic compounds in the leaves of LA0279 after 72 h of HIL irradiation. Unlike LA4012, LA3006, LA0279, and LA3538 sowed a significant increase in the expression levels of CHS, HY5, and FLS genes after 24 h, which may be one of the reasons for the higher adaptive potential of those three mutants. In addition to that in LA3538, strong light-induced stress led to an increased level of flavonol synthase (FLS) expression in the LA3006, LA0279, and LA4012 mutants. We hypothesize that the photosynthetic apparatus (PA) of the LA0279 mutant, which is deficient in the DET1 and DDB1 genes, is most adapted to prolonged HIL. Most likely, the resistance of PA mutants to HIL is due to a variety of factors, which, in addition to the redistribution of carotenoids, may include morphological features associated with the accumulation of anthocyanin in the epidermis, subepidermal layer, mesophyll and trichomes of leaves and with an increase in leaf thickness.

The effects of the quality of light on the content of phytochrome interacting factors (PIFs) such as PIF3, PIF4 and PIF5, as well as the expression of various light-dependent microRNAs, in adult Arabidopsis thaliana pif mutant plants (pif4, pif5, pif3pif5, pif4pif5, pif3pif4pif5) were studied. We demonstrate that under blue light, the pif4 mutant had maximal expression of most of the studied microRNAs (miR163, miR319, miR398, miR408, miR833) when the PIF4 protein in plants was reduced. This finding indicates that the PIF4 protein is involved in the downregulation of this group of microRNAs. This assumption is additionally confirmed by the fact that under the RL spectrum in pif5 mutants, practically the same miRNAs decrease expression against the background of an increase in the amount of PIF4 protein. Unlike the WT and other mutants, the pif4 mutant responded to the BL spectrum not only by activating the expression of light-dependent miRNAs, but also by a significant increase in the expression of transcription factors and key light signalling genes. These molecular reactions do not affect the activity of photosynthesis but may be involved in the formation of a light quality-dependent phenotype.

The effect of red (RL, 660 nm) and blue (BL, 450 nm) light on phy mutant tomato plants was studied. The rates of photosynthesis (Pn) and transpiration, the efficiency of the primary photochemical processes of photosynthesis, the contents of flavonoids and phenolic compounds, the low-molecular-weight antioxidant capacity (Trolox equivalent antioxidant capacity (TEAC)) of leaf extracts, and the expression of light-dependent genes were evaluated. Under RL, BL, and white fluorescent light (WFL), the Pn values decreased in the order: WT > phyb2 > phyaphyb2 > phyaphyb1phyb2, except for the Pn in phyb2 on BL. Phyb2 also had a larger number of stomata under BL and, as a result, it reached maximum transpiration. The noticeable accumulation of flavonoids and phenolic compounds was observed only in the phyb2 and phyaphyb2 mutants upon irradiation with BL, which agrees with the increased TEAC in the leaf extracts. We suggest that the increased antioxidant activity under PHYB2 deficiency and the maintenance of high photosynthesis under BL are based on an increase in the expression of the early signaling transcription factors genes BBX, HY5. The largest decrease in the content of flavonoids and TEAC was manifested with a deficiency in PHYB1, which is probably the key to maintaining the antioxidant status in BL plants.

During the tidal cycle, Fucus vesiculosus L. lost moisture (up to 30% of wet weight) and was characterized by a sinusoidal pattern in photosynthetic activity. Three peaks in the photosynthesis capacity were observed at the beginning and middle of low tide and at the beginning of high tide. There were no structural changes in the photosynthetic apparatus. When analyzing the curves of CO2 gas exchange, the processes of photosynthesis in the algae exposed to the air was limited by the activity of the light and dark phases of photosynthesis. The increase in the content of lipid peroxidation products, catalase activity, and accumulation of proline in F. vesiculosus thalli indicated the presence of reversible oxidative stress during low tide.

The relationship is studied between the physiological and biochemical characteristics of different ecological halophyte groups and their adaptive strategies (determined by the type of adaptation to soil salinity, type of photosynthesis, and life form). It is found that the key parameters that determine the formation of different adaptation strategies of halophytes are the rate of CO2 gas exchange, content of chlorophylls a + b, and cell membrane permeability. At the same time, different adaptation strategies of halophytes significantly differ in the pattern and range of variation in their physiological and biochemical characteristics, which indicates different manifestations of adaptation mechanisms and deeper ecological differentiation of individual halophyte species and groups.

Dynamics of the photosynthetic apparatus' (PA) structural and functional parameters during the day was investigated in euhalophyte Salicorniaperennans Willd., crynohalophyte Limoniumgmelinii (Willd.) O. Kuntze, and glycohalophyte Artemisiasantonica L. The greatest PA activity judging from the rate of СО2 consumption/release by the leaves was observed in the morning. In salt-accumulating (S. perennans) and salt-eliminating (A. santonica) species, the rate of photosynthesis was greater than in L. gmelinii plants possessing the systems of salt excretion. In A. santonica and S. perennans, the content of green pigments decreased during the day, while it remained permanent in L. gmelinii. During the day, the ratio between plastid lipids and pigments increased in A. santonica and S. perennans. In chloroplast lipids from S. perennans, a decrease in the relative content of monogalactosyldiacylglycerol (MGDG) was compensated for by a rise in relative content of digalactosyldiacylglycerol (DGDG), with the contribution of sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) remaining the same. In the chloroplasts from L. gmelinii, the proportion of neutral lipids MGDG and DGDG did not change in contrast to the level of anionic lipids SQDG and PG. In A. santonica, we detected changes in both neutral and anionic lipids. A high proportion of unsaturated FA (UFA) (over 70%) in the total pool of FA was mainly accounted for by α-linolenic acid. It was found that the proportion of saturated FA tended to increase in the evening. All the revealed structural and functional reorganizations of PA associated with fluctuation of pigment-lipid resources of thylakoid membranes were adaptive and aimed at optimization of photosynthesis under specific environmental conditions.

This work focuses on developing light environments for the effective regulation of morphogenesis and ex vitro conditions adaptation in micropropagated raspberry plants on the basis of photomorphogenetic control of physiological processes using light-emitting diodes (LEDs). In experiments with cloned plants growing ex vitro in stressful conditions during acclimation, the effects of optical radiation of various spectral combinations from different photosynthetically active radiation (PAR) spectral regions were studied. The data on the plant development and state of the photosynthetic apparatus, features of photosynthetic gas exchange and transpiration, accumulation of photosynthetic pigments, light curves of photosynthesis, and data on growth processes in light modes using combined quasimonochromatic radiation (either mixture of red, green, and blue light or red, far-red, and blue light) with various ratio of the distinct spectral regions were obtained. Photosynthetic apparatus functional activity under different light conditions was studied with chlorophyll fluorescence determination, and plant stress responses to growing under artificial spectral light conditions were characterized. The experiments were accompanied by detailed plant phenotyping at the structural and functional levels. Plant acclimation and photosynthetic improvements in response to added far-red and green light wavelengths to the main red-blue spectrum have been elucidated.

The impacts of high-intensity light (HIL) (4 h) and UV-B radiation (1 h) on the photosynthetic activity, content of photosynthetic and UV-absorbing pigments (UAPs), activity of antioxidant enzymes (ascorbate peroxidase (APX) and guaiacol-dependent peroxidase (GPX)), content of thiobarbituric acid reactive substances (TBARs), expression of some light-regulated genes in 25-day-old wild type (WT) and the cryptochrome 1 (Cry1) hy4 mutant of A. thaliana Col-0 plants grown under blue light (BL) were studied. HIL and UV-B treatments led to decreases in the photosynthetic rate (Pn), photochemical activity of PSII (FV/FM) and PSII performance index (PIABS) of WT and mutant plants grown under high-intensity BL (HBL) and moderate intensity BL (MBL). However, in HBL plants, the decrease in the photosynthetic activity in hy4 plants was significantly greater than that in WT plants. In addition, hy4 HBL plants demonstrated lowered UAP and carotenoid contents as well as lower activity of APX and GPX enzymes. The difference in the decline in the photosynthetic activity of WT and hy4 plants grown at MBL in response to HIL was nonsignificant, while that in response to UV-B was small. We assume that the deficiency in cryptochrome 1 under HIL irradiation disrupts the interaction between HY5 and HFR1 transcription factors and photoreceptors, which affects the transcription of light-induced genes, such as CAB1, PSY and PAL1 linked to carotenoid and flavonoid biosynthesis. It was concluded that PA stress resistance in WT and hy4 plants depends on the light intensity and reduced stress resistance of hy4 at HBL, is likely linked to low UAP and carotenoid contents as well as lowered APX and GPX enzyme activities in hy4 mutants.

Engineered nanoparticles (NPs) are considered potential agents for agriculture as fertilizers and growth enhancers. However, their action spectrum differs strongly, depending on the type of NP, its concentrations, and plant species per se, ranging from growth stimulation to toxicity. This work aimed to investigate effects of iron oxide (Fe3O4) NPs on growth, photosynthesis, respiration, antioxidant activity, and leaf mineral content of wheat plants. Wheat seeds were treated with NP for 3 h and plants were grown in the soil at two light intensities, 120 and 300 μmol (photons) m−2·s−1, followed by physiological assessment at several time points. High NP treatment (200 and 500 mg·L−1) enhanced plant growth, photosynthesis and respiration, as well as increasing the content of photosynthetic pigments in leaves. This effect depended on both the light intensity during plant growth and the age of the plants. Regardless of concentration and light intensity, an effect of NPs on the primary photochemical processes was not observed. Seed treatment with NP also led to increased activity of ascorbate peroxidase and reduced malondialdehyde (MDA) content in roots and leaves. Treatment with Fe3O4 also led to noticeable increases in the leaf Fe, P, and K content. It is concluded that iron oxide (Fe3O4)-based NP could enhance plant growth by improving photosynthetic performance and the availability of Fe and P.

The photosynthetic acclimation of extremophile Eutrema salsugineum plants to red light (RL) (14 days, 150 μmol photons m−2 s-1, 660 nm) and the expression of the key photoreceptor apoprotein genes, transcription factors (TFs) and associated with phytochrome system MIR (microRNA) genes were studied. RL exposure induced an increase in the content of anthocyanin and total phenolic compounds and the level of Chls was decreased. The photosystem 2 electron transport rate and the number of open reaction centres (qL) were not changed in RL plants, however, the levels of non-photochemical quenching (NPQ) and the regulated quantum yield of non-photochemical quenching Y(NPQ) were significantly higher in the RL plants. The rate of CO2 uptake was decreased by almost 1.4-fold but the respiration and transpiration rates, as well as the stomatal conductance were not changed in the RL plants. An increase in the expression of the photoreceptor apoprotein genes PHYA, PHYB and PHYC, the TF genes PIF4, PIF5 and miR395, miR408, miR165 and decreases in the levels of the transcripts of the TF gene HY5 and miR171, miR157, and miR827 were detected. The acclimation effect of photosynthetic apparatus to RL was accompanied by an increase of pigment content such as total phenolic compounds and carotenoids and it is due to the changes in the expression of the apoprotein phytochrome genes PHYA, PHYB, PHYC and phytochrome signalling TFs (PIF4, PIF5 and HY5) as well as MIR genes associated with phytochrome system.

Structural and molecular parameters of photosynthetic apparatus in plants with different strategies for the accumulation of salts were investigated. CO2 gas exchange rate, content of pigments, mesostructure, chloroplast ultrastructure and the biochemical composition of the membrane structural components in leaves were measured. The objects of the study were euhalophytes (Salicornia perennans, Suaeda salsa, Halocnemum strobilaceum), crynohalophyte (Limonium gmelinii), glycohalophyte (Artemisia santonica). Euhalophytes S. perennans and S. salsa belong to the plants of the halosucculent type, three other species represent the xerophilic type. The highest photosynthetic activity estimated by the average parameters of CO2 gas exchange rate in the leaves was observed in S. perennans plants. Plants of the xerophyte type including both H. strobilaceum euhalophyte and cryno- and glycohalophytes are described by lower values of these characteristics. Larger cells with a great number of chloroplasts and a high content of membrane glycerolipids and unsaturated C18:3 fatty acid, but with smaller pigment and light-harvesting complexes size characterise the features of euhalophytes with a succulent leaf type. Thus, features of the mesostructure, ultrastructure, and supramolecular interactions of the halophyte PA were closely related to the functional parameters of gas exchange, and were characterised by the strategy of species in relation to the accumulation of salts, the life form of plants, and the attitude to the method of water regulation.

Light-converting polypropylene spunbond was first used in the study of the key physiological parameters of plants. A comparative study of the functioning of the photosynthetic apparatus and the dynamics of growth in late cabbage plants (Olga variety) and leaf lettuce (Emerald variety) was conducted using the ordinary nonwoven polypropylene fabric (spunbond) (density 30 g·m-2) and the spunbond containing a photoluminophore (PL) (1.6% yttrium oxysulfide doped with europium). The plants were grown in a glass greenhouse without spunbond and under the spunbond containing and not containing the PL that transforms a part of UV-radiation into red light radiation. The use of the spunbond led to a decrease in the rate of photosynthesis, activity of the photosystem 2, and the accumulation of plant biomass and to an increase in the stomatal conductance. By contrast to unmodified spunbond, the application of the spunbond containing the PL led to an increase in the rate of photosynthesis, the water-use efficiency (WUE), and the accumulation of the total biomass of plants by 30-50% but to a decrease in the transpiration rate and the stomatal conductance. It is assumed that the positive effect of the PL is associated with an increase in the fraction of fluorescent red light, which enhances photosynthetic activity and accelerates plant growth.

The effects of high-intensity light (HIL, 4 and 24 h) and UV-B (1 h) on the net photosynthesis rate, activity of photosystem II (PSII), content of photosynthetic pigments, anthocyanin and UV-absorbing pigments as well as the expression of certain light-responsive genes (HY5,CAB1) chalcone synthase (CHS) and main antioxidants enzyme genes (APX1, GPX and GR) in the leaves of phyB and phyA mutant A. thaliana plants were studied. Both UV-B and 4 and 24 h HIL decreased the PSII maximum quantum yield (Fv/Fm), PSII performance index (PIABS), photosynthesis and respiration rates in plants. Moreover, all stress treatments increased the dissipation of the absorbed energy (DI0/RC) as well as the flux of absorbed energy per RC (ABS/RC). The maximal changes in photosynthesis and chlorophyll fluorescence parameters were observed in the phyB mutant. The WT and the phyA mutant showed similar responses. In addition, the phyB mutant exhibited decreases in the expression of genes encoding enzyme CHS, the transcription factor HY5 and the antioxidant enzymes APX1 and GPX. One of the possible mechanisms protecting the photosynthetic apparatus from light excess or UV radiation is the elevated content of various pigments that can act as antioxidants or optical filters. We assume that the greater decrease in photosynthetic activity in the phyB mutant under HIL and UV-B conditions was due to the decreased content of carotenoids and UV-absorbing pigments in this mutant.

The effect of UV-A radiation (365 nm) and the protective effect of preillumination with red light (RL, 664 nm, 10 min) or with a combination of red and far-red light (FRL, 727 nm, 10 min) on the activity of the PSII as well as the expression levels of selected genes, especially those encoding chloroplast proteins (sAPX, tAPX, CAB1, and D1), were studied in leaves of the 26-d-old hy3 mutant of Arabidopsis thaliana, which is deficient in the phytochrome B apoprotein. The effects were compared with corresponding effects observed in the hy2 mutant of A. thaliana, which is deficient in the phytochrome chromophore. Illumination with UV-A decreased the photosynthetic pigment content, the maximum photochemical quantum yield of PSII (Fv/Fm), and the effective quantum yield of PSII (ΦPSII). The reduction of the Fv/Fm ratio and ΦPSII was more pronounced in the mutants as compared to wild-type plants (WT). The preillumination of the leaves with RL caused a significant reduction in the inhibitory effect of UV-radiation on the PSII activity in the WT plants, but it caused only a small decrease in the hy3 mutant. The preillumination of leaves with RL and FRL combination compensated the protective effect of RL on the UV-induced decrease of the fluorescence parameters in the WT. Such reversibility is typical for involvement of red/far-red reversible phytochromes at low intensity light. The results suggest an important role of red/far-red reversible phytochromes (phytochrome B) in the resistance of PSII to UV-A radiation caused by changes in contents of either carotenoids or other UV-absorbing pigments probably through biosynthesis of these pigments. The data also demonstrated that phytochrome B and other phytochromes can affect the PSII stress resistance by the fast regulation of the expression of genes encoding antioxidant enzymes and transcription factors at the step of gene transcription.

The effects of high-intensity light (HIL) on the activity of photosystem II (PSII) and photosynthesis in wild-type (WT) and single (phyB2, phyB1, phyA and cry1), double (phyB1B2, phyAB2 and phyAB1) and triple (phyAB1B2 and cry1phyAB1) mutants of Solanum lycopersicum were studied. In addition, changes in the activity of the antioxidant enzymes ascorbate peroxidase, glutathione reductase and guaiacol peroxidase as well as the photosynthetic pigment and anthocyanin contents in the leaves of phyB2 and cry1phAB1 mutants under HIL were examined. When plants were irradiated with HIL (2 h), the PSII resistance of the cry1phyAB1 mutant was the lowest, while the resistance of WT and single mutants excluding cry1 was the highest. The effect of HIL on PSII activity in all double mutants and the phyAB1B2 mutant was intermediate between the effects on the WT and the cry1phyAB1 mutant. The intensity of oxidative processes in the cry1phyAB1 mutant was higher than that in WT and phyB2, but in cry1phyAB1, the activity of antioxidant enzymes and the anthocyanin content were lower. The low resistance of the cry1phyAB1 mutant to HIL may be due to the low antioxidant activity of key enzymes and the reduced pigment content, which are consistent with the reduced expression of CHS and sAPX genes in the cry1phyAB1 mutant.

Study of the functional state of the photosynthetic apparatus in winter triticale under conditions of salinity (120 mM NaCl) has been carried out. It is shown that the initial stress response (up to 24–48 hours) is characterized by a 35% reduction in stomatal conductance, an increase in the RuBisCo activity (up to 37 μmol NADH/min g), and a high rate of electron transport (up to 502 μmol DCPIP/mg Chl h). The response of plants after 48 hours of salinity is associated with a significant increase in stomatal conductance (up to 68.3 nmol/m2 s), as well as the decline in rate of electron transport (up to 222 μmol DCPIP/mg Chl h), the RuBisCo activity (up to 22 μmol NADH/min g), and the rate of photosynthesis (up to 10.96 μmol CO2/m2 s). In addition, plants preserve their functional photosynthetic apparatus under conditions of continuous salinity (lasting for more than 48 h) reducing the efficiency of photosynthesis.

The influence of phytochrome B overproduction in 50- to 60-day-old transgenic potato plants (Solanum tuberosum L., lines Dara 5 and Dara 12 with moderate and intense expression of PHYB, respectively) on the resistance of photosynthetic apparatus to UV-B irradiation was investigated. In plants unexposed to UV-B, there was no significant difference in photosynthetic rates (P n) and fluorescence parameters (F v/F m, qN, qP) between the nontransformed (NT) line and Dara-5 and Dara-12 lines, whereas the content of photosynthetic pigments per 1 cm2 leaf area was higher in the transgenic plants. Irradiation with UV-B resulted in the decrease in photosynthetic rate in NT plants by 35–45%, whereas in Dara-12 line this rate was lowered by only 20–25%. Exposure to UV-B reduced the amplitudes of both fast and slow components of delayed fluorescence (DF), which indicated the diminished efficiency of photosystem II (PSII). The decrease in the maximum amplitude of the slow DF component was markedly lower in Dara-12 (19%) than in NT line (33%). The maximal photochemical quantum yield of PSII (F v/F m ratio) in plants exposed to UV-B was also suppressed stronger in NT line than in Dara-12. The line Dara-5 had intermediate position among other lines in terms of UV-B resistance of photosynthesis and PSII activity, but it was closer to NT than to Dara-12. Thus, the potato plants actively expressing the gene of Arabidopsis phytochrome B apoprotein (PHYB) demonstrated a higher resistance of photosynthetic apparatus to UV-B radiation compared to nontransformed plants. The elevated UV-B tolerance is most likely related to the increased leaf content of chlorophyll, carotenoids, and flavonoids.

Improving the efficiency of growing plants in phytotrons is largely linked to the introduction of advanced technologies, providing the optimization of the light conditions. The use of modern light sources such as light emitting diodes (LEDs) or induction lamps can reduce the energy consumption for growing plants due to the high light output, long work and control of the spectrum of irradiation. Comparative studies of growth processes and activity of the photosynthetic apparatus of plants of Basil (Ocimum basilicum L.) variety Ararat, when using LEDs and induction lamps with an energy capacity of 64 and 150 W, respectively were done. The light intensity was 80-85 μmol photons• m-2•s-1 under LEDs white light and 240-260 μmol photons•m-2•s-1 under induction lamps. CO2 gas exchange, the content of pigments and growth processes in plants grown in hydroponic conditions were estimated. The rate of photosynthesis under induction lamp was more than 2 times higher than under LEDs (2.6±0.4 and 1.2±0.3 μmol CO2•m-2•s-1, respectively), although there was a slight decrease in the content of the chlorophylls (a + b) to 0.71±0.01 mg/g dry weigh compared to 0.83±0.03 for LEDs. More than twofold increase in the rate of photosynthesis did not result in the same increase in the accumulation of plant biomass that may be connected with different light saturation of growth processes and photosynthesis. The efficiency of biomass accumulation per 1 W of energy power for a period of 40 days under LEDs was 1.7 times higher than under the irradiation of induction lamp. Significant difference in photosynthetic efficiency was not detected. At elevated concentrations of CO2 the rates of photosynthesis were comparable as a result of higher values of the quantum yield of photosynthesis, activity ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO) and the efficiency of carboxylation in LEDs plants. The investigation of structural and functional parameters of the photosynthetic apparatus and growth processes under the action of different light intensity showed the complex nature of the changes of some processes during long-term exposure to light of different intensity and spectral composition.

Structural and functional parameters and redox homeostasis in leaves of Artemisia santonica L. under environment conditions of Elton lake (the southeast region of the European part of Russia) were measured. The highest photosynthetic apparatus (PA) activity in A. santonica leaves on CO2 gas exchange as well as the highest content of green pigments was observed in the morning. Maximum share of violaxanthin cycle key pigments – zeaxanthin (Zx) and antheraxanthin (Ax) was observed in the afternoon and decreased in the evening. Lipids/chlorophyll (Chl) ratio increased in the evening due to the decrease in Chl concentration, and content of linolenic acid (С18:3n3) was decreased in the middle of the day. The content of TBA-reacting products increased 1.4-fold in the middle of the day, and decreased approximately 2-fold in the evening. The decrease of the activity was observed in diurnal dynamics of superoxide dismutase (SOD) and polyphenol oxidase (PPO). Increased accumulation of phenols and flavonoids, as well as free amino acids (FAA) in A. santonica leaves was observed in the middle of the day. Thus, the ability of A. santonica plants to resist the soil salinization, high levels of solar illumination and temperature consists of a number of protectively-adaptive reactions of metabolic and photosynthetic control.