Neuroprotective effects of Tradescantia spathacea tea bioactives in Parkinson's disease: In vivo proof-of-concept.

Background and aim: Tradescantia spathacea (T. spathacea) is a traditional medicinal plant from Central America and its tea, obtained by infusion, has been recognized as a functional food. The aim of this work was to investigate the effects of dry tea containing biocompounds from T. spathacea tea on motor and emotional behavior, as well as tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP) expression in 6-hydroxydopamine (6-OHDA)-lesioned rats. Experimental procedure: Bioactives were identified by Ultra Performance Liquid Chromatography (UPLC) and an in vivo study in male Wistar rats was run as proof of concept of neuroprotective effects of DTTS. Results and conclusion: We found 15 biocompounds that had not been previously reported in T. spathacea: the UPLC-QTOF-MS/MS allowed identification five phenolic acids, one coumarin, two flavonoids, one iridoid, one phenylpropanoid glycoside, and six fatty acid derivatives. The dry tea of T. spathacea (DTTS) presented significant antioxidant activity and high contents of phenolic compounds and flavonoids. Doses of 10, 30, and 100 mg/kg of DTTS were protective against dopaminergic neurodegeneration and exhibited modulatory action on the astrocyte-mediated neuroinflammatory response. Behavioral tests showed that 30 mg/kg of DTTS counteracted motor impairment, while 100 mg/kg produced an anxiolytic effect. The DTTS could be, therefore, a promising strategy for the management of Parkinson's disease.

Antioxidant isolation and characterization from the plant Tradescantia spathacea Sw. of the Commelinaceae family.

A novel bioactive flavan glycoside was isolated by solvent extraction method with the help of Soxhlet apparatus from the methanolic extract of Tradescantia spathacea Sw. Flavan glycoside having molecular formula C20H22O10, melting point 175-1780C, molecular weight by ESI-MS m/z (M + H]+ 423, optical rotation was[α]21D-45.1(c 0.20 methanol). Its structure was determined (-)-epicatechin 7-O-alpha-L-arabinopyranoside. Various color reactions, chemical degradation (like acid hydrolysis, permethylation, and enzymatic hydrolysis), UV-Visible spectrophotometry, Fourier transforms infrared spectroscopy, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy were used to establish the structure of compound (-)-(-)-epicatechin 7-O-alpha-L-arabinopyranoside.. A flavan glycoside was also tested with a DPPH assay method for antioxidant activity by using Ascorbic acid as standard. DPPH radical scavenging test data demonstrate that a flavan glycoside possesses potent antioxidant activity so this flavan glycoside can be utilized as a potent antioxidant agent.

Staminal hairs increase pollinator attraction and pollination accuracy in Tradescantia fluminensis (Commelinaceae).

Staminal hairs are the particular appendages of stamens, which may affect pollinator foraging behaviour and pollen transfer. However, experimental evidence of the functions of staminal hairs in pollination remains scarce. Here, we conducted staminal hair manipulation experiments in Tradescantia fluminensis (Commelinaceae) to investigate their effects on visitation and pollen transfer by bees. Our observations revealed that both visitation rates and visit duration of honeybees (Apis cerana) to control flowers were significantly higher than that of hairless flowers. Moreover, removing the staminal hairs significantly decreased pollen deposition by honeybees (A. cerana), but did not affect pollen removal. The staminal hair was similar in length to the stamen and the pistil of T. fluminensis. The staminal hairs provide more footholds for honeybees, and they lay prone on the staminal hairs to collect pollen, which increased the accuracy of pollination through the consistent pollen placement and pick-up on the ventral surface of honeybees. These results showed that the staminal hairs in T. fluminensis may represent an adaptation to attract pollinators and enhance pollination accuracy.

Assessment of the antidiabetic potential of extract and novel phytoniosomes formulation of Tradescantia pallida leaves in the alloxan-induced diabetic mouse model.

Diabetes inflicts health and economic burdens on communities and the present antidiabetic therapies have several drawbacks. Tradescantia pallida leaves have been used as a food colorant and food preservative; however, to our knowledge antidiabetic potential of the leaves of T. pallida has not been explored yet. The current study aimed to investigate the antidiabetic potential of T. pallida leaves extract and its comparison with the novel nisosome formulation of the extract. The leaves extract and phytoniosomes of T. pallida in doses of 15, 25 and 50 mg/kg were used to assess the oral glucose loaded, and alloxan-induced diabetic mice models. The biological parameters evaluated were; change in body weight, blood biochemistry, relative organ to body weight ratio and histopathology of the liver, pancreas and kidney. Results revealed that the extract 50 mg/kg and phytoniosomes 25 and 50 mg/kg remarkably reduced the blood glucose level in all hyperglycemic mice by possibly inhibiting α-amylase and α-glucosidase production. Body weight and blood biochemical parameters were considerably improved in phytoniosomes 50 mg/kg treated group. The relative body weight was similar to those of healthy mice in extract 50 mg/kg, phytoniosomes 25 mg/kg, and phytoniosomes 50 mg/kg treated groups. Histopathology showed the regeneration of cells in the CHN50 treated group. Hyphenated chromatographic analysis revealed potent metabolites, which confirmed the antidiabetic potential of the extract by inhibiting α-amylase and α-glucosidase using in silico analysis. The present data suggested that phytoniosomes have shown better antidiabetic potential than crude extract of these leaves.

Phenolic compounds from Tradescantia pallida ameliorate diabetes by inhibiting enzymatic and non-enzymatic pathways.

Diabetes is a chronic metabolic disorder marked by postprandial hyperglycemia due to several etiologies including abnormal carbohydrate digestion and glycation of hemoglobin. The prolong use of synthetic drugs results in characteristic side effects which necessitates the discovery of safe and cost-effective substitutes. The aim of the current study is to isolate and evaluate the antidiabetic potential of the phenolic compounds from the leaves of Tradescantia pallida. Syringic acid, p-coumaric acid, morin and catechin (compounds 1-4) were isolated and characterized from Tradescantia pallida leaves using column chromatography and spectroscopic techniques. The in vitro antidiabetic potential of the phenolic compounds were assessed using α-amylase and non-enzymatic glycosylation of hemoglobin protein assays. A mechanistic insight of interactions between phenolic compounds and human α-amylase and hemoglobin protein were scrutinized by employing molecular docking method. Prime Molecular Mechanics/Generalized Born Surface Area (MM-GBSA) calculations were carried out to find the binding energies of the ligand-protein complexes. Morin and catechin were further analyzed to find the dynamic and thermodynamic constraints of the complexes under specific biological conditions using molecular dynamic simulation trajectories. The stability and flexibility of the complexes were justified by fluctuation of α-carbon chain, Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF) and type of interactions involved which authenticated the in vitro inhibitory potential of morin and catechin against enzymatic and non-enzymatic pathways. The current study could be fruitful in rational designing of safe antidiabetic drugs of natural origin.Communicated by Ramaswamy H. Sarma.

Prediction of α-Glucosidase Inhibitory Activity of LC-ESI-TQ-MS/MS-Identified Compounds from Tradescantia pallida Leaves.

Diabetes is a chronic disease that leads to abnormal carbohydrate digestion and hyperglycemia. The long-term use of marketed drugs results in secondary infections and side effects that demand safe and natural substitutes for synthetic drugs. The objective of this study is to evaluate the antidiabetic potential of compounds from the leaves of Tradescantia pallida. Thirteen phenolic compounds were identified from the ethyl acetate fraction of leaves of Tradescantia pallida using liquid chromatography-mass spectrometry. The compounds were then studied for the type of interactions between polyphenols and human α-glucosidase protein using molecular docking analysis. Prime Molecular Mechanics/Generalized Born Surface Area (MM-GBSA) calculations were performed to measure the binding free energies responsible for the formation of ligand-protein complexes. The compounds were further investigated for the thermodynamic constraints under a specified biological environment using molecular dynamic simulations. The flexibility of the ligand-protein systems was verified by Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF) and molecular interactions. The results authenticated the antidiabetic potential of polyphenols identified from the leaves of Tradescantia pallida. Our investigations could be helpful in the design of safe antidiabetic agents, but further in vitro and in vivo investigations are required.

Antioxidant, Cytotoxic, and Antimicrobial Potential of Silver Nanoparticles Synthesized using Tradescantia pallida Extract.

Silver nanoparticles have received much attention, due to their wide range of biological applications as an alternative therapy for disease conditions utilizing the nanobiotechnology domain for synthesis. The current study was performed to examine the antioxidant, anticancer, antibacterial, and antifungal potential of biosynthesized silver nanoparticles (TpAgNPs) using plant extract. The TpAgNPs were produced by reacting the Tradescantia pallida extract and AgNO3 solution in nine various concentration ratios subjected to bioactivities profiling. According to the current findings, plant extract comprising phenolics, flavonoids, and especially anthocyanins played a critical role in the production of TpAgNPs. UV-visible spectroscopy also validated the TpAgNP formation in the peak range of 401-441 nm. Further, the silver ion stabilization by phytochemicals, face-centered cubic structure, crystal size, and spherical morphology of TpAgNPs were analyzed by FTIR, XRD, and SEM. Among all TpAgNPs, the biosynthesized TpAgNP6 with a medium concentration ratio (5:10) and the plant extract had effective antioxidant potentials of 77.2 ± 1.0% and 45.1 ± 0.5% free radical scavenging activity, respectively. The cytotoxic activity of TpAgNP6 in comparison to plant extract for the rhabdomyosarcoma cell line was significantly the lowest with IC50 values of 81.5 ± 1.9 and 90.59 ± 1.6 µg/ml and cell viability % of 24.3 ± 1.62 and 27.4 ± 1.05, respectively. The antibacterial and antifungal results of TpAgNPs revealed significant improvement in comparison to plant extract, i.e., minimum inhibition concentration (MIC) 64 µg/ml against Gram-negative Pseudomonas aeruginosa while, in the case of antifungal assay, TpAgNP6 was active against Candida parapsilosis. These TpAgNPs play a crucial role in determining the therapeutic potential of T. pallida due to their biological efficacy.

Migration of repetitive DNAs during evolution of the permanent translocation heterozygosity in the oyster plant (Tradescantia section Rhoeo).

Due to translocation heterozygosity for all chromosomes in the cell complement, the oyster plant (Tradescantia spathacea) forms a complete meiotic ring. It also shows Rabl-arrangement at interphase, featured by polar centromere clustering. We demonstrate that the pericentromeric regions of the oyster plant are homogenized in concert by three subtelomeric sequences: 45S rDNA, (TTTAGGG)n motif, and TSrepI repeat. The Rabl-based clustering of pericentromeric regions may have been an excellent device to combine the subtelomere-pericentromere sequence migration (via inversions) with the pericentromere-pericentromere DNA movement (via whole arm translocations) that altogether led to the concerted homogenization of all the pericentromeric domains by the subtelomeric sequences. We also show that the repetitive sequence landscape of interstitial chromosome regions contains many loci consisting of Arabidopsis-type telomeric sequence or of TSrepI repeat, and it is extensively heterozygous. However, the sequence arrangement on some chromosomal arms suggest segmental inversions that are fully or partially homozygous, a fact that could be explained if the inversions started to create linkages already in a bivalent-forming ancestor. Remarkably, the subterminal TSrepI loci reside exclusively on the longer arms that could be due to sharing sequences between similarly-sized chromosomal arms in the interphase nucleus. Altogether, our study spotlights the supergene system of the oyster plant as an excellent model to link complex chromosome rearrangements, evolution of repetitive sequences, and nuclear architecture.

A Review on Tradescantia: Phytochemical Constituents, Biological Activities and Health-Promoting Effects.

Tradescantia is a genus of herbaceous and perennial plants belonging to the Commelinaceae family and organized into three infrageneric classifications and 12 sections. More than 80 species within the genus have been used for centuries for medicinal purposes. Phytochemical compounds (from various species of the genus) such as coumarins, alkaloids, saponins, flavonoids, phenolics, tannins, steroids and terpenoids have recently been characterized and described with antioxidant, cytotoxic, anti-inflammatory, anticancer or antimicrobial properties. The objective of this review is to describe the different aspects of the genus Tradescantia, including its botanical characteristics, traditional uses, phytochemical composition, biological activities, and safety aspects.

The noninvasive monitoring of the redox status of photosynthetic electron transport chains in Hibiscus rosa-sinensis and Tradescantia leaves.

We present an approach to the noninvasive determination of the electron capacity of the intersystem pool of electron carriers in chloroplasts in situ. As apt experimental models, we used the leaves of Hibiscus rosa-sinensis and Tradescantia species. Electron paramagnetic resonance and optical response of P700 (the primary electron donor in Photosystem I) were applied to measuring electron transport in chloroplasts. Electron capacities of the intersystem electron transport chain (ETC) were determined from redox transients of P700 upon chromatic transitions (white light → far-red light). During the induction period, we observed the nonmonotonic changes in the number of electron equivalents in the intersystem ETC per P700 (parameter Q). In Hibiscus rosa-sinensis, the light-induced rise of Q from ≈2.5 (in the dark) to Q ≈ 12 was followed by its decrease to Q ≈ 6. The data obtained are discussed in the context of pH-dependent regulation of electron transport in chloroplasts, which provides the well-balanced operation of the intersystem ETC. The decay of Q is explained by the attenuation of Photosystem II activity due to the lumen acidification and the acceleration of plastoquinol re-oxidation as a result of the Calvin-Benson cycle activation. Our computer model of electron and proton transport coupled to ATP synthesis in chloroplasts was used to analyze the up and down feedbacks responsible for pH-dependent regulation of electron transport in chloroplasts. The procedures introduced here may be important for subsequent works aimed at defining the plastoquinone participation in regulation of photosynthetic processes in chloroplasts in situ.

Structural and functional changes in the fungal community of plant detritus in an invaded Atlantic Forest.

BACKGROUND: Changes in the fungal community in the litter decomposition by invasive plants can negatively impact nutrient cycling in natural ecosystems. One still does not know the dimension of this hypothesis, but apparently, it is not despicable. This study evaluated the assemblage composition of fungi during litter decomposition in areas of Atlantic Forest invaded or not invaded by Tradescantia zebrina using Illumina MiSeq and metabarcoding analysis. RESULTS: The invaded sample showed significantly higher richness and a difference in the species dominance than the invaded litter. Ascomycota was the first most abundant phylum in both areas. Even so, the dissimilarity between areas can be evidenced. The fungal from Basidiomycota were very representative in the non-invaded areas (ranged from an abundance of 43.29% in the non-invaded to 2.35% in the invaded sample). The genus Lepiota can indicate the primary functional group related to biomass degradation and showed the might difference about the invaded areas due to its essential reduction by the invader. In the invaded sample, there was a total absence of the endophyte-undefined saprotroph guild. Also, some genera not taxonomically characterized were eliminated in the invaded sample, revealing that the fungal biodiversity of areas has not yet been thoroughly characterized. CONCLUSIONS: Hence, makes impossible the real interpretation of the invasive plant impact, showing the importance of continuing research on fungal biodiversity. It is important to emphasize that the replacement of the native species by T. zebrina may be responsible for the elimination of fungal groups that have not yet been identified.

Assessment of allelopathic activity of Tradescantia spathacea Sw. for weed control.

Tradescantia spathacea Sw. (Commelinaceae) is widely cultivated as an ornamental and medicinal plant in Southeast Asia, and its pharmacological properties are well known. On the other hand, this plant species is classified as an invasive weed in some countries. As a noxious weed, T. spathacea has been reported to disrupt the growth of native plants. However, no study has reported on its allelopathic activity. Thus, we investigated the allelopathic property and inhibitory substance of T. spathacea. The extracts of T. spathacea significantly inhibited the shoots and roots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), Italian ryegrass (Lolium multiflorum Lam.), and timothy (Phleum pratense L.) at concentrations ≥ 3 mg dry weight (D.W.) equivalent extract/mL. As the extract concentration increased, the growth of the shoots and roots decreased. The I50 values of the test plant shoots and roots were 11.6-72.4 and 5.4-19.5 mg D.W. equivalent extract/mL, respectively. The extracts were purified by column chromatography, and an inhibitory substance was separated, which inhibited the shoots and roots of cress to 18.8 and 11.6% of control growth, respectively. The results of present findings indicate that T. spathacea extracts possess an allelopathic property, and its inhibitory substance may contribute this activity.

Pericentromere clustering in Tradescantia section Rhoeo involves self-associations of AT- and GC-rich heterochromatin fractions, is developmentally regulated, and increases during differentiation.

A spectacular but poorly recognized nuclear repatterning is the association of heterochromatic domains during interphase. Using base-specific fluorescence and extended-depth-of-focus imaging, we show that the association of heterochromatic pericentromeres composed of AT- and GC-rich chromatin occurs on a large scale in cycling meiotic and somatic cells and during development in ring- and bivalent-forming Tradescantia spathacea (section Rhoeo) varieties. The mean number of pericentromere AT-rich domains per root meristem nucleus was ca. half the expected diploid number in both varieties, suggesting chromosome pairing via (peri)centromeric regions. Indeed, regular pairing of AT-rich domains was observed. The AT- and GC-rich associations in differentiated cells contributed to a significant reduction of the mean number of the corresponding foci per nucleus in relation to root meristem. Within the first 10 mm of the root, the pericentromere attraction was in progress, as if it was an active process and involved both AT- and GC-rich associations. Complying with Rabl arrangement, the pericentromeres preferentially located on one nuclear pole, clustered into diverse configurations. Among them, a strikingly regular one with 5-7 ring-arranged pericentromeric AT-rich domains may be potentially engaged in chromosome positioning during mitosis. The fluorescent pattern of pachytene meiocytes and somatic nuclei suggests the existence of a highly prescribed ring/chain type of chromocenter architecture with side-by-side arranged pericentromeric regions. The dynamics of pericentromere associations together with their non-random location within nuclei was compared with nuclear architecture in other organisms, including the widely explored Arabidopsis model.

Molecular Characterization and Identification of Calnexin 1 As a Radiation Biomarker from Tradescantia BNL4430.

Calnexin (CNX) is an integral membrane protein that functions as a chaperone in the endoplasmic reticulum for the correct folding of proteins under stress conditions, rendering organisms tolerant under adverse conditions. Studies have investigated the cytogenetic effects of gamma irradiation (Ɣ-IR) on plants, but information on the molecular response under Ɣ-IR remains limited. Previously, we constructed a cDNA library of an irradiation-sensitive bioindicator plant, Tradescantia BNL4430 (T-4430) under Ɣ-IR, in which the Calnexin-1 gene was highly upregulated at 50 mGy treatment. TrCNX1 encodes a 61.4 kDa protein with conserved signature motifs similar to already reported CNX1s. TrCNX1 expression was evaluated by semiquantitative reverse transcriptase PCR and quantitative real-time PCR and was ubiquitously expressed in various tissues and highly upregulated in flower petals under 50 mGy Ɣ-IR stress. The protective function of TrCNX1 was investigated by overexpression of TrCNX1 in an Escherichia coli BL21(DE3) heterologous system. Using plate assay, we showed that TrCNX1 increased the viability of E. coli transformants under both UV-B and Ɣ-IR compared with the control, demonstrating that TrCNX1 functions under irradiation stress. TrCNX1 may enhance irradiation stress tolerance in crops and act as a radio marker gene to monitor the effects of radiation.

Tradescantia pallida extract inhibits biofilm formation in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is capable of biofilm formation. In this study, we investigated the effects of aqueous Tradescantia pallida extract on Pseudomonas aeruginosa growth and biofilm formation. Aqueous Tradescantia pallida extracts significantly inhibited both bacterial growth and biofilm formation. However, methanolic Tradescantia pallida extracts inhibited neither. Aqueous Tradescantia pallida extracts were deactivated by heating but were not deactivated by light exposure. The ingredients retained the inhibitory effect on the bacterial growth and biofilm formation after ultrafiltration of aqueous Tradescantia pallida extract. Furthermore, polyphenol-rich Tradescantia pallida extracts inhibited bacterial growth, thus, polyphenols are possible to be an active ingredient. We observed the biofilm by scanning electron microscopy, and quantitative and qualitative differences in the biofilm and cells morphology. Interestingly, the biofilm treated aqueous Tradescantia pallida extracts remained premature. We postulated that premature biofilm formation was due to the inhibition of swarming motility. Indeed, aqueous Tradescantia pallida extracts inhibited swarming motility. These results demonstrate that Peudomonas aeruginosa growth and biofilm formation are inhibited by aqueous Tradescantia pallida extracts.

Phytochemical Investigation of Tradescantia Albiflora and Anti-Inflammatory Butenolide Derivatives.

Phytochemical investigation of the whole plant of Tradescantia albiflora Kunth led to the isolation and characterization of a butanolide, rosmarinosin B (1), that was isolated from natural sources for the first time, a new butenolide, 5-O-acetyl bracteanolide A (2), and a new apocarotenoid, 2ß-hydroxyisololiolide (11), together with 25 known compounds (compounds 3-10 and 12-28). The structures of the new compounds were elucidated by analysis of their spectroscopic data, including MS, 1D, and 2D NMR experiments, and comparison with literature data of known compounds. Furthermore, four butenolides 4a-4d were synthesized as novel derivatives of bracteanolide A. The isolates and the synthesized derivatives were evaluated for their preliminary anti-inflammatory activity against lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production in RAW 264.7 cells. Among them, the synthesized butenolide derivative n-butyl bracteanolide A (4d) showed enhanced NO inhibitory activity compared to the original compound, with an IC50 value of 4.32 ± 0.09 µg/mL.

Micronucleus Assay with Tetrad Cells of Tradescantia.

The Tradescantia micronucleus assay has been used since 50 years for the detection of genotoxins (including carcinogens) in the environment. A large database concerning the effects of individual chemicals and complex environmental mixtures (soil, air and waters) has accumulated. In contrast to other mutagenicity test systems, the effects of low concentrations of heavy metals, radionuclides, certain herbicides, pesticides and gaseous mutagens can be detected and it is also possible to conduct in situ biomonitoring studies with plant. The test system has been validated and standardized protocols have been developed for laboratory experiments and for field studies which are described in this chapter.

Slow induction of chlorophyll a fluorescence excited by blue and red light in Tradescantia leaves acclimated to high and low light.

Tradescantia is a good model for assaying induction events in higher plant leaves. Chlorophyll (Chl) fluorescence serves as a sensitive reporter of the functional state of photosynthetic apparatus in chloroplasts. The fluorescence time-course depends on the leaf growth conditions and actinic light quality. In this work, we investigated slow induction of Chl a fluorescence (SIF) excited by blue light (BL, λmax = 455 nm) or red light (RL, λmax = 630 nm) in dark-adapted leaves of Tradescantia fluminensis acclimated to high light (~ 1000 µmol photons m-2 s-1; HL) or low light (~ 100 µmol photons m-2 s-1; LL). Our special interest was focused on the contribution of the avoidance response to SIF kinetics. Bearing in mind that BL and RL have different impacts on photoreceptors that initiate chloroplast movements within the cell (accumulation/avoidance responses), we have compared the SIF patterns during the action of BL and RL. The time-courses of SIF and kinetics of non-photochemical quenching (NPQ) of Chl a fluorescence revealed a certain difference when leaves were illuminated by BL or RL. In both cases, the yield of fluorescence rose to the maximal level P and then, after the lag-phase P-S-M1, the fluorescence level decreased toward the steady state T (via the intermediate phases M1-M2 and M2-T). In LL-acclimated leaves, the duration of the P-S-M1 phase was almost two times longer that in HL-grown plants. In the case of BL, the fluorescence decay included the transient phase M1-M2. This phase was obscure during the RL illumination. Non-photochemical quenching of Chl a fluorescence has been quantified as [Formula: see text], where [Formula: see text] and [Formula: see text] stand for the fluorescence response to saturating pulses of light applied to dark-adapted and illuminated samples, respectively. The time-courses of such a formally determined NPQ value were markedly different during the action of RL and BL. In LL-grown leaves, BL induced higher NPQ as compared to the action of RL. In HL-grown plants, the difference between the NPQ responses to BL and RL illumination was insignificant. Comparing the peculiarities of Chl a fluorescence induced by BL and RL, we conclude that the avoidance response can provide a marked contribution to SIF and NPQ generation. The dependence of NPQ on the quality of actinic light suggests that chloroplast movements within the cell have a noticeable impact on the formally determined NPQ value. Analyzing kinetics of post-illumination decay of NPQ in the context of solar stress resistance, we have found that LL-acclimated Tradescantia leaves are more vulnerable to strong light than the HL-grown leaves.

Three phases of energy-dependent induction of [Formula: see text] and Chl a fluorescence in Tradescantia fluminensis leaves.

In plants, the short-term regulation (STR, seconds to minute time scale) of photosynthetic apparatus is associated with the energy-dependent control in the chloroplast electron transport, the distribution of light energy between photosystems (PS) II and I, activation/deactivation of the Calvin-Benson cycle (CBC) enzymes, and relocation of chloroplasts within the plant cell. In this work, using a dual-PAM technique for measuring the time-courses of P700 photooxidation and Chl a fluorescence, we have investigated the STR events in Tradescantia fluminensis leaves. The comparison of Chl a fluorescence and [Formula: see text] induction allowed us to investigate the contribution of the trans-thylakoid pH difference (ΔpH) to the STR events. Two parameters were used as the indicators of ΔpH generation: pH-dependent component of non-photochemical quenching of Chl a fluorescence, and pHin-dependent rate of electron transfer from plastoquinol (PQH2) to [Formula: see text] (via the Cyt b6f complex and plastocyanin). In dark-adapted leaves, kinetics of [Formula: see text] induction revealed three phases. Initial phase is characterized by rapid electron flow to [Formula: see text] (τ1/2 ~ 5-10 ms), which is likely related to cyclic electron flow around PSI, while the outflow of electrons from PSI is restricted by slow consumption of NADPH in the CBC. The light-induced generation of ΔpH and activation of the CBC promote photooxidation of P700 and concomitant retardation of [Formula: see text] reduction (τ1/2 ~ 20 ms). Prolonged illumination induces additional slowing down of electron transfer to [Formula: see text] (τ1/2 ≥ 30-35 ms). The latter effect is not accompanied by changes in the Chl a fluorescence parameters which are sensitive to ΔpH generation. We suggest the tentative explanation of the latter results by the reversal of Q-cycle, which causes the deceleration of PQH2 oxidation due to the back pressure of stromal reductants.

Light acclimation of shade-tolerant and sun-resistant Tradescantia species: photochemical activity of PSII and its sensitivity to heat treatment.

In this work, we have compared photosynthetic characteristics of photosystem II (PSII) in Tradescantia leaves of two contrasting ecotypes grown under the low light (LL) and high light (HL) regimes during their entire growth period. Plants of the same genus, T. fluminensis (shade-tolerant) and T. sillamontana (sun-resistant), were cultivated at 50-125 µmol photons m-2 s-1 (LL) or at 875-1000 µmol photons m-2 s-1 (HL). Analyses of intrinsic PSII efficiency was based on measurements of fast chlorophyll (Chl) a fluorescence kinetics (the OJIP test). The fluorescence parameters Fv/Fm (variable fluorescence) and F0 (the initial level of fluorescence) in dark-adapted leaves were used to quantify the photochemical properties of PSII. Plants of different ecotypes showed different sustainability with respect to changes in the environmental light intensity and temperature treatment. The sun-resistant species T. sillamontana revealed the tolerance to variations in irradiation intensity, demonstrating constancy of maximum quantum efficiency of PSII upon variations of the growth light. In contrast to T. sillamontana, facultative shade species T. fluminensis demonstrated variability of PSII photochemical activity, depending on the growth light intensity. The susceptibility of T. fluminensis to solar stress was documented by a decrease in Fv/Fm and a rise of F0 during the long-term exposition of T. fluminensis to HL, indicating the loss of photochemical activity of PSII. The short-term (10 min) heat treatment of leaf cuttings caused inactivation of PSII. The temperature-dependent heating effects were different in T. fluminensis and T. sillamontana. Sun-resistant plants T. sillamontana acclimated to LL and HL displayed the same plots of Fv/Fm versus the treatment temperature (t), demonstrating a decrease in Fv/Fm at t ≥ 45 °C. The leaves of shadow-tolerant species T. fluminensis grown under the LL and HL conditions revealed different sensitivities to heat treatment. Plants grown under the solar stress conditions (HL) demonstrated a gradual decline of Fv/Fm at lower heating temperatures (t ≥ 25 °C), indicating the "fragility" of their PSII as compared to T. fluminensis grown at LL. Different responses of sun and shadow species of Tradescantia to growth light and heat treatment are discussed in the context of their biochemical and ecophysiological properties.