Potential Role of Phytochromes A and B and Cryptochrome 1 in the Adaptation of Solanum lycopersicum to UV-B Radiation.

UV-B causes both damage to the photosynthetic apparatus (PA) and the activation of specific mechanisms that protect the PA from excess energy and trigger a cascade of regulatory interactions with different photoreceptors, including phytochromes (PHYs) and cryptochromes (CRYs). However, the role of photoreceptors in plants' responses to UV-B radiation remains undiscovered. This study explores some of these responses using tomato photoreceptor mutants (phya, phyb1, phyab2, cry1). The effects of UV-B exposure (12.3 µmol (photons) m-2 s-1) on photosynthetic rates and PSII photochemical activity, the contents of photosynthetic and UV-absorbing pigments and anthocyanins, and the nonenzymatic antioxidant capacity (TEAC) were studied. The expression of key light-signaling genes, including UV-B signaling and genes associated with the biosynthesis of chlorophylls, carotenoids, anthocyanins, and flavonoids, was also determined. Under UV-B, phyab2 and cry1 mutants demonstrated a reduction in the PSII effective quantum yield and photosynthetic rate, as well as a reduced value of TEAC. At the same time, UV-B irradiation led to a noticeable decrease in the expression of the ultraviolet-B receptor (UVR8), repressor of UV-B photomorphogenesis 2 (RUP2), cullin 4 (CUL4), anthocyanidin synthase (ANT), phenylalanine ammonia-lease (PAL), and phytochrome B2 (PHYB2) genes in phyab2 and RUP2, CUL4, ANT, PAL, and elongated hypocotyl 5 (HY5) genes in the cry1 mutant. The results indicate the mutual regulation of UVR8, PHYB2, and CRY1 photoreceptors, but not PHYB1 and PHYA, in the process of forming a response to UV-B irradiation in tomato.

Influence of Light of Different Spectral Compositions on Growth Parameters, Photosynthetic Pigment Contents and Gene Expression in Scots Pine Plantlets.

The photoreceptors of red light (phytochromes) and blue light (cryptochromes) impact plant growth and metabolism. However, their action has been barely studied, especially in coniferous plants. Therefore, the influence of blue (maximum 450 nm), red (maximum 660 nm), white light (maxima 450 nm + 575 nm), far-red light (maximum 730 nm), white fluorescent light and dark on seed germination, growth, chlorophyll and carotenoid contents, as well as the transcript levels of genes involved in reception, photosynthesis, light and hormonal signaling of Scots pine plantlets, was investigated. The highest values of dry weight, root length and photosynthetic pigment contents were characteristic of 9-day-old plantlets grown under red light, whereas in the dark plantlet length, seed vigor, seed germination, dry weight and pigment contents were decreased. Under blue and white lights, the main studied morphological parameters were decreased or close to red light. The cotyledons were undeveloped under dark conditions, likely due to the reduced content of photosynthetic pigments, which agrees with the low transcript levels of genes encoding protochlorophyllide oxidoreductase (PORA) and phytoene synthase (PSY). The transcript levels of a number of genes involved in phytohormone biosynthesis and signaling, such as GA3ox, RRa, KAO and JazA, were enhanced under red light, unlike under dark conditions. We suggest that the observed phenomena of red light are the most important for the germination of the plantlets and may be based on earlier and enhanced expression of auxin, cytokinin, gibberellin and jasmonate signaling genes activated by corresponding photoreceptors. The obtained results may help to improve reforestation technology; however, this problem needs further study.

Investigating the Physiological and Molecular Responses of Solanum lycopersicum hp Mutants to Light of Different Quality for Biotechnological Applications.

The effect of the light of different spectral compositions, white fluorescent light (WFL), red light (RL, 660 nm), blue light (BL, 450 nm), green light (GL, 525 nm), and white LED light (WL, 450 + 580 nm), on the physiological parameters of Solanum lycopersicum 3005 hp-2 (defective for a DET1 gene) and 4012 hp-1w; 3538 hp-1; 0279 hp-1.2 (defective for a DDB1a gene) photomorphogenetic mutants was studied. The parameters of the primary photochemical processes of photosynthesis, photosynthetic and transpiration rates, the antioxidant capacity of low-molecular weight antioxidants, the content of the total phenolic compounds, including flavonoids, and the expression of the genes involved in light signaling and biosynthesis of secondary metabolites were determined. Under BL, the 3005 hp-2 mutant showed the highest nonenzymatic antioxidant activity, which occurred to a greater extent due to the increase in flavonoid content. At the same time, under BL, the number of secretory trichomes on the surface of the leaves of all mutants increased equally. This suggests the accumulation of flavonoids inside leaf cells rather than in trichomes on the leaf surface. The data obtained indicate the possibility of using the hp-2 mutant for biotechnology to increase its nutritional value by enhancing the content of flavonoids and other antioxidants by modulating the spectral composition of light.

24-Epibrassinolide alleviates the toxic effects of NaCl on photosynthetic processes in potato plants.

Brassinosteroids are promising agents for alleviating the negative effects of salinity on plants, but the mechanism of their protective action is far from being understood. We investigated the effect of pretreatment with 24-epibrassinolide (24-EBL) on the photosynthetic and physiological parameters of potato plants under progressive salinity stress caused by root application of 100 mM NaCl. Salinity clearly inhibited primary photosynthetic processes in potato plants by reducing the contents of photosynthetic pigments, photosynthetic electron transport and photosystem II (PSII) maximal and effective quantum yields. These negative effects of salinity on primary photosynthetic processes were mainly due to toxic ionic effects on the plant's ability to oxidize the plastoquinone pool. Pretreatment with 24-EBL alleviated this stress effect and allowed the maintenance of plastoquinone pool oxidation and the efficiency of photosystem II photochemistry to be at the same levels as those in unstressed plants; however, the pretreatment did not affect the photosynthetic pigment content. 24-EBL pretreatment clearly alleviated the decrease in leaf osmotic potential under salinity stress. The stress-induced increases in lipid peroxidation and proline contents were not changed under brassinosteroid pretreatment. However, 24-EBL pretreatment increased the peroxidase activity and improved the K+/Na+ ratio in potato leaves, which were likely responsible for the protective 24-EBL action under salt stress.

Impact of weak water deficit on growth, photosynthetic primary processes and storage processes in pine and spruce seedlings.

We investigated the influence of 40 days of drought on growth, storage processes and primary photosynthetic processes in 3-month-old Scots pine and Norway spruce seedlings growing in perlite culture. Water stress significantly affected seedling water status, whereas absolute dry biomass growth was not substantially influenced. Water stress induced an increase in non-structural carbohydrate content (sugars, sugar alcohols, starch) in the aboveground part of pine seedlings in contrast to spruce seedlings. Due to the relatively low content of sugars and sugar alcohols in seedling organs, their expected contribution to osmotic potential changes was quite low. In contrast to biomass accumulation and storage, photosynthetic primary processes were substantially influenced by water shortage. In spruce seedlings, PSII was more sensitive to water stress than PSI. In particular, electron transport in PSI was stable under water stress despite the substantial decrease of electron transport in PSII. The increase in thermal energy dissipation due to enhancement of non-photochemical quenching (NPQ) was evident in both species under water stress. Simultaneously, the yields of non-regulated energy dissipation in PSII were decreased in pine seedlings under drought. A relationship between growth, photosynthetic activities and storage processes is analysed under weak water deficit.

Influence of photoluminophore-modified agro textile spunbond on growth and photosynthesis of cabbage and lettuce plants.

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 impact of the phytochromes on photosynthetic processes.

This review describes the phytochrome system in higher plants and cyanobacteria and its role in regulation of photosynthetic processes and stress protection of the photosynthetic apparatus. A relationship between the content of the different phytochromes, the changes in the ratios of the physiologically active forms of phytochromes to their total pool and the resulting influence on photosynthetic processes is reviewed. The role of the phytochromes in the regulation of the expression of genes encoding key photosynthetic proteins, antioxidant enzymes and other components involved in stress signaling is elucidated.

Evaluation of new Cu(II) complexes as a novel class of inhibitors against plant carbonic anhydrase, glutathione reductase, and photosynthetic activity in photosystem II.

Increasing inefficiency of production of important agricultural plants raises one of the biggest problems in the modern world. Herbicide application is still the best method of weed management. Traditional herbicides blocking only one of the plant metabolic pathways is ineffective due to the rapid growth of herbicide-resistant weeds. The synthesis of novel compounds effectively suppressing several metabolic processes, and therefore achieving the synergism effect would serve as the alternative approach to weed problem. For this reason, recently, we synthesized a series of nine novel Cu(II) complexes and four ligands, characterized them with different analyses techniques, and carried out their primary evaluation as inhibitors of photosynthetic electron transfer in spinach thylakoids (design, synthesis, and evaluation of a series of Cu(II) based metal-organic complexes as possible inhibitors of photosynthesis, J Photochem Photobiol B, submitted). Here, we evaluated in vitro inhibitory potency of these agents against: photochemistry and carbonic anhydrase activity of photosystem II (PSII); α-carbonic anhydrase from bovine erythrocytes; as well as glutathione reductase from chloroplast and baker's yeast. Our results show that all Cu(II) complexes excellently inhibit glutathione reductase and PSII carbonic anhydrase activity. Some of them also decently inhibit PSII photosynthetic activity.

Reactive oxygen species: re-evaluation of generation, monitoring and role in stress-signaling in phototrophic organisms.

This review provides an overview about recent developments and current knowledge about monitoring, generation and the functional role of reactive oxygen species (ROS) - H2O2, HO2, HO, OH(-), (1)O2 and O2(-) - in both oxidative degradation and signal transduction in photosynthetic organisms including microscopic techniques for ROS detection and controlled generation. Reaction schemes elucidating formation, decay and signaling of ROS in cyanobacteria as well as from chloroplasts to the nuclear genome in eukaryotes during exposure of oxygen-evolving photosynthetic organisms to oxidative stress are discussed that target the rapidly growing field of regulatory effects of ROS on nuclear gene expression.

The Role of Pigments and Cryptochrome 1 in the Adaptation of Solanum lycopersicum Photosynthetic Apparatus to High-Intensity Blue Light.

The effects of high-intensity blue light (HIBL, 500/1000 µmol m-2s-1, 450 nm) on Solanum lycopersicum mutants with high pigment (hp) and low pigment (lp) levels and cryptochrome 1 (cry1) deficiency on photosynthesis, chlorophylls, phenols, anthocyanins, nonenzymatic antioxidant activity, carotenoid composition, and the expression of light-dependent genes were investigated. The plants, grown under white light for 42 days, were exposed to HIBL for 72 h. The hp mutant quickly adapted to 500 µmol m-2s-1 HIBL, exhibiting enhanced photosynthesis, increased anthocyanin and carotenoids (beta-carotene, zeaxanthin), and increased expression of key genes involved in pigment biosynthesis (PSY1, PAL1, CHS, ANS) and PSII proteins along with an increase in nonenzymatic antioxidant activity. At 1000 µmol m-2s-1 HIBL, the lp mutant showed the highest photosynthetic activity, enhanced expression of genes associated with PSII external proteins (psbO, psbP, psbQ), and increased in neoxanthin content. This mutant demonstrated greater resistance at the higher HIBL, demonstrating increased stomatal conductance and photosynthesis rate. The cry1 mutant exhibited the highest non-photochemical quenching (NPQ) but had the lowest pigment contents and decreased photosynthetic rate and PSII activity, highlighting the critical role of CRY1 in adaptation to HIBL. The hp and lp mutants use distinct adaptation strategies, which are significantly hindered by the cry1 mutation. The pigment content appears to be crucial for adaptation at moderate HIBL doses, while CRY1 content and stomatal activity become more critical at higher doses.

Reducing Heavy Metal Contamination in Soil and Water Using Phytoremediation.

The increase in industrialization has led to an exponential increase in heavy metal (HM) soil contamination, which poses a serious threat to public health and ecosystem stability. This review emphasizes the urgent need to develop innovative technologies for the environmental remediation of intensive anthropogenic pollution. Phytoremediation is a sustainable and cost-effective approach for the detoxification of contaminated soils using various plant species. This review discusses in detail the basic principles of phytoremediation and emphasizes its ecological advantages over other methods for cleaning contaminated areas and its technical viability. Much attention has been given to the selection of hyperaccumulator plants for phytoremediation that can grow on heavy metal-contaminated soils, and the biochemical mechanisms that allow these plants to isolate, detoxify, and accumulate heavy metals are discussed in detail. The novelty of our study lies in reviewing the mechanisms of plant-microorganism interactions that greatly enhance the efficiency of phytoremediation as well as in discussing genetic modifications that could revolutionize the cleanup of contaminated soils. Moreover, this manuscript discusses potential applications of phytoremediation beyond soil detoxification, including its role in bioenergy production and biodiversity restoration in degraded habitats. This review concludes by listing the serious problems that result from anthropogenic environmental pollution that future generations still need to overcome and suggests promising research directions in which the integration of nano- and biotechnology will play an important role in enhancing the effectiveness of phytoremediation. These contributions are critical for environmental scientists, policy makers, and practitioners seeking to utilize phytoremediation to maintain the ecological stability of the environment and its restoration.

Influence of Additional White, Red and Far-Red Light on Growth, Secondary Metabolites and Expression of Hormone Signaling Genes in Scots Pine under Sunlight.

The influence of short-term additional white (WL), red (RL) and far-red (FRL) light and combined RL+FRL on the physiological morphological and molecular characteristics of two-year-old Scots pine plants grown in a greenhouse under sunlight was studied. Additional RL and RL+FRL increased the number of xylem cells, transpiration and the expression of a group of genes responsible for the biosynthesis and signaling of auxins (AUX/IAA, ARF3/4, and ARF16) and brassinosteroids (BR-α-RED and BRZ2), while the expression of genes related to the signaling pathway related to jasmonic acid was reduced. Additionally, WL, RL and RL+FRL increased the content of proanthocyanidins and catechins in young needles; however, an increase in the expression of the chalcone synthase gene (CHS) was found under RL, especially under RL+FRL, which possibly indicates a greater influence of light intensity than observed in the spectrum. Additional WL increased photosynthetic activity, presumably by increasing the proportion and intensity of blue light; at the same time, the highest transpiration index was found under RL. The results obtained indicate that the combined effect of additional RL+FRL can accelerate the development of pine plants by increasing the number of xylem cells and increasing the number of aboveground parts but not the photosynthetic activity or the accumulation of secondary metabolites.

The Effect of Short-Term Heating on Photosynthetic Activity, Pigment Content, and Pro-/Antioxidant Balance of A. thaliana Phytochrome Mutants.

The effects of heating (40 °C, 1 and 2 h) in dark and light conditions on the photosynthetic activity (photosynthesis rate and photosystem II activity), content of photosynthetic pigments, activity of antioxidant enzymes, content of thiobarbituric acid reactive substances (TBARs), and expression of a number of key genes of antioxidant enzymes and photosynthetic proteins were studied. It was shown that, in darkness, heating reduced CO2 gas exchange, photosystem II activity, and the content of photosynthetic pigments to a greater extent in the phyB mutant than in the wild type (WT). The content of TBARs increased only in the phyB mutant, which is apparently associated with a sharp increase in the total peroxidase activity in WT and its decrease in the phyB mutant, which is consistent with a noticeable decrease in photosynthetic activity and the content of photosynthetic pigments in the mutant. No differences were indicated in all heated samples under light. It is assumed that the resistance of the photosynthetic apparatus to a short-term elevated temperature depends on the content of PHYB active form and is probably determined by the effect of phytochrome on the content of low-molecular weight antioxidants and the activity of antioxidant enzymes.

Effects of iron oxide nanoparticles (Fe3O4) and salinity on growth, photosynthesis, antioxidant activity and distribution of mineral elements in wheat (Triticum aestivum).

Soil salinisation is one of the main abiotic stresses decreasing crop productivity. Here, we show that the plant treatment with iron oxide (Fe3 O4 ) nanoparticles (NPs) may be a promising solution for reducing the negative impact of soil salinity on plant performance. For this purpose, effects of the NPs on growth, photosynthesis, pro-/antioxidant, redox balance and the content of mineral elements in 19-day-old wheat (Triticum aestivum ) plants under soil salinity were studied. Seed treatment with NPs (200 and 500mg L-1 ) enhanced growth and photosynthetic rate in leaves. Moderate salinity stress (150mMNaCl) led to a decrease in plant biomass as well as the rate of photosynthesis and PSII activity; leaf photosynthetic characteristics were also suppressed by lower (75mMNaCl) salinity treatment. However, seed pre-treatment with the NPs partially eliminated the negative effect of the salt on growth, PSII activity and photosynthesis. Also, we observed a decrease in the content of malondialdehyde (MDA) and an increase in ascorbate and total peroxidase activity in the plant leaves upon combined treatment with NaCl and the NPs compared with treatment with NaCl alone. The combined treatment with the NPs and salinity also led to a noticeable increase in the content of Fe and Mn in the shoot. It was concluded that Fe3 O4 NPs can enhance plant growth by improving photosynthetic characteristics, antioxidant balance and the availability of iron and manganese ions, under conditions of soil salinisation.

Post-Harvest Red- and Far-Red-Light Irradiation and Low Temperature Induce the Accumulation of Carotenoids, Capsaicinoids, and Ascorbic Acid in Capsicum annuum L. Green Pepper Fruit.

Environmental factors, such as light of different spectral compositions and temperature, can change the level of activated photoreceptors which, in turn, can affect the biosynthesis of secondary metabolites in the cells of green fruit. By briefly irradiating the harvested fruit of Capsicum annuum L. hot peppers with red light (RL, maximum 660 nm) and far-red light (FRL, maximum 730 nm) and by keeping them at a low temperature, we attempted to determine whether the state of phytochromes in fruit affects the biosynthesis of secondary metabolites. Using HPLC, we analysed the qualitative composition and quantitative content of the main carotenoids and alkaloids and the chlorophylls and ascorbate, in pepper fruit exposed to the above factors. We measured the parameters characterising the primary photochemical processes of photosynthesis and the transcript levels of genes encoding capsaicin biosynthesis enzymes. The total carotenoids content in the fruit increased most noticeably after 24 h of RL irradiation (more than 3.5 times compared to the initial value), and the most significant change in the composition of carotenoids occurred when the fruit was irradiated with FRL for 72 h. The capsaicin alkaloid content increased markedly after 72 h of FRL irradiation (more than 8 times compared to the initial value). It was suggested that decrease in the activity of phytochromes due to a low temperature or FRL may result in an increase in the expression of the PAL and CAM genes.

Effect of Light of Different Spectral Compositions on Pro/Antioxidant Status, Content of Some Pigments and Secondary Metabolites and Expression of Related Genes in Scots Pine.

The aim of this study was to investigate the effect of light quality (white fluorescent light, WFL, containing UV components), red light (RL, 660 nm), blue light (BL, 450 nm), and white LED light (WL, 450 + 580 nm) on the components of the cellular antioxidant system in Pinus sylvestris L. in needles, roots, and hypocotyls, focusing on the accumulation of key secondary metabolites and the expression of related genes. The qualitative and quantitative composition of carotenoids; the content of the main photosynthetic pigments, phenolic compounds, flavonoids (catechins, proanthocyanidins, anthocyanins), ascorbate, and glutathione; the activity of the main antioxidant enzymes; the content of hydrogen peroxide; and the intensity of lipid peroxidation (MDA and 4-HNE contents) were determined. RL resulted in an increase in the content of hydrogen peroxide and 4-HNE, as well as the total fraction of flavonoids in the needles. It also enhanced the expression of several PR (pathogen-related) genes compared to BL and WL. WFL increased the content of phenols, including flavonoids, and enhanced the overall activity of low-molecular antioxidants in needles and hypocotyls. BL increased the content of ascorbate and glutathione, including reduced glutathione, in the needles and simultaneously decreased the activity of peroxidases. Thus, by modifying the light quality, it is possible to regulate the accumulation of secondary metabolites in pine roots and needles, thereby influencing their resistance to various biotic and abiotic stressors.

The Adaptive Role of Carotenoids and Anthocyanins in Solanum lycopersicum Pigment Mutants under High Irradiance.

The effects of high-intensity light on the pigment content, photosynthetic rate, and fluorescence parameters of photosystem II in high-pigment tomato mutants (hp 3005) and low-pigment mutants (lp 3617) were investigated. This study also evaluated the dry weight percentage of low molecular weight antioxidant capacity, expression patterns of some photoreceptor-regulated genes, and structural aspects of leaf mesophyll cells. The 3005 mutant displayed increased levels of photosynthetic pigments and anthocyanins, whereas the 3617 mutant demonstrated a heightened content of ultraviolet-absorbing pigments. The photosynthetic rate, photosystem II activity, antioxidant capacity, and carotenoid content were most pronounced in the high-pigment mutant after 72 h exposure to intense light. This mutant also exhibited an increase in leaf thickness and water content when exposed to high-intensity light, suggesting superior physiological adaptability and reduced photoinhibition. Our findings indicate that the enhanced adaptability of the high-pigment mutant might be attributed to increased flavonoid and carotenoid contents, leading to augmented expression of key genes associated with pigment synthesis and light regulation.

Impact of varying light spectral compositions on photosynthesis, morphology, chloroplast ultrastructure, and expression of light-responsive genes in Marchantia polymorpha.

Marchantia polymorpha is a convenient model for studying light of different spectral compositions on various physiological and biochemical processes because its photoreceptor system is vastly simplified. The influence of red light (RL, 660 nm), far-red light (FRL, 730 nm), blue light (BL, 450 nm), and green light (GL, 525 nm) compared to white light (high-pressure sodium light (HPSL), white LEDs (WL 450 + 580 nm) and white fluorescent light (WFL) on photosynthetic and transpiration rates, photosystem II (PSII) activity, photomorphogenesis, and the expression of light and hormonal signaling genes was studied. The ultrastructure of the chloroplasts in different tissues of the gametophyte M. polymorpha was examined. FRL led to the formation of agranal chloroplasts (in the epidermis and the chlorenchyma) with a high starch content (in the parenchyma), which led to a reduced intensity of photosynthesis. BL increased the transcription of genes for the biosynthesis of secondary metabolites - chalcone synthase (CHS), cellulose synthase (CELL), and L-ascorbate peroxidase (APOX3), which is consistent with the increased activity of low-molecular weight antioxidants. FRL increased the expression of phytochrome apoprotein (PHY) and cytokinin oxidase (CYTox) genes, but the expression of the phytochrome interacting factor (PIF) gene decreased, which was accompanied by a significant change in gametophyte morphology. Analysis of crosstalk gene expression, and changes in morphology and photosynthetic activity was carried out.

Probing the Influence of Novel Organometallic Copper(II) Complexes on Spinach PSII Photochemistry Using OJIP Fluorescence Transient Measurements.

Modern agricultural cultivation relies heavily on genetically modified plants that survive after exposure to herbicides that kill weeds. Despite this biotechnology, there is a growing need for new sustainable, environmentally friendly, and biodegradable herbicides. We developed a novel [CuL2]Br2 complex (L = bis{4H-1,3,5-triazino[2,1-b]benzothiazole-2-amine,4-(2-imidazole) that is active on PSII by inhibiting photosynthetic oxygen evolution on the micromolar level. [CuL2]Br2 reduces the FV of PSII fluorescence. Artificial electron donors do not rescind the effect of [CuL2]Br2. The inhibitory mechanism of [CuL2]Br2 remains unclear. To explore this mechanism, we investigated the effect of [CuL2]Br2 in the presence/absence of the well-studied inhibitor DCMU on PSII-containing membranes by OJIP Chl fluorescence transient measurements. [CuL2]Br2 has two effects on Chl fluorescence transients: (1) a substantial decrease of the Chl fluorescence intensity throughout the entire kinetics, and (2) an auxiliary "diuron-like" effect. The initial decrease dominates and is observed both with and without DCMU. In contrast, the "diuron-like" effect is small and is observed only without DCMU. We propose that [CuL2]Br2 has two binding sites for PSII with different affinities. At the high-affinity site, [CuL2]Br2 produces effects similar to PSII reaction center inhibition, while at the low-affinity site, [CuL2]Br2 produces effects identical to those of DCMU. These results are compared with other PSII-specific classes of herbicides.

The biomineralization of silica induced stress tolerance in plants: a case study for aluminum toxicity.

Biomineralization in plant roots refers to the process of cell-induced self-assembly to form nanostructures on the root surface. Silicon (Si) is the second most abundant element in soils, and beneficial to plant growth. Meanwhile, silicon is shown to participate in the process of biomineralization, which is useful for improving mechanical strength and alleviating biotic and abiotic stress, for example silicic acid polymerizes to form amorphous silica (SiO2-nH2O) in the process of growing to resist fungi and environmental stress. This process alters physical and chemical properties of cell wall. However, the mechanistic basis of this process remains unclear. Aluminum toxicity is a major constraint affecting plant performance in acid soil. This paper summarizes recent research advances in the field of plant biomineralization and describes the effects of silicon biomineralization on plant aluminum tolerance and its adaptive significance, using aluminum toxicity as a case study.