Effects of cadmium and enhanced UV radiation on the physiology and the concentration of UV-absorbing compounds of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia

Tree Physiological Variables as a Proxy of Heavy Metal and Platinum Group Elements Pollution in Urban Areas

Physiological variables (the content of chlorophyll, flavonoids and nitrogen, together with Fv/Fm) and the content of ten heavy metals (As, Cd, Cu, Hg, Mn, Ni, Pb, Sb, V and Zn) and two platinum group elements (PGEs: Pd and Rh) were measured in the leaves of 50 individuals of Ligustrum lucidum trees regularly distributed in the city of Logroño (Northern Spain). Three of these variables increased with increasing physiological vitality (chlorophyll, nitrogen and Fv/Fm), whereas flavonoids increased in response to different abiotic stresses, including pollution. Our aim was to test their adequacy as proxies for the pollution due to heavy metals and PGEs. The three vitality indicators generally showed high values typical of healthy plants, and they did not seem to be consistently affected by the different pollutants. In fact, the three vitality variables were positively correlated with the first factor of a PCA that was dominated by heavy metals (mainly Pb, but also Sb, V and Ni). In addition, Fv/Fm was negatively correlated with the second factor of the PCA, which was dominated by PGEs, but the trees showing Fv/Fm values below the damage threshold did not coincide with those showing high PGE content. Regarding flavonoid content, it was negatively correlated with PCA factors dominated by heavy metals, which did not confirm its role as a protectant against metal stress. The relatively low levels of pollution usually found in the city of Logroño, together with the influence of other environmental factors and the relative tolerance of Ligustrum lucidum to modest atmospheric pollution, probably determined the only slight response of the physiological variables to heavy metals and PGEs.

Bryophyte ultraviolet-omics: from genes to the environment

Ultraviolet (UV) radiation has contributed to the evolution of organisms since the origins of life. Bryophytes also have evolutionary importance as the first clearly identified lineage of land plants (embryophytes) colonizing the terrestrial environment, thus facing high UV and water scarcity, among other new challenges. Here we review bryophyte UV-omics, the discipline relating bryophytes and UV, with an integrative perspective from genes to the environment. We consider species and habitats investigated, methodology, response variables, protection mechanisms, environmental interactions, UV biomonitoring, molecular and evolutionary aspects, and applications. Bryophyte UV-omics shows convergences and divergences with the UV-omics of other photosynthetic organisms, from algae to tracheophytes. All these organisms converge in that UV damage may be limited under realistic UV levels, due to structural protection and/or physiological acclimation capacity. Nevertheless, bryophytes diverge because they have a unique combination of vegetative and reproductive characteristics to cope with high UV and other concomitant adverse processes, such as desiccation. This interaction has both evolutionary and ecological implications. In addition, UV effects on bryophytes depend on the species and the evolutionary lineage considered, with mosses more UV-tolerant than liverworts. Thus, bryophytes do not constitute a homogeneous functional type with respect to their UV tolerance.

Antioxidant and Antibacterial Properties of Extracts and Bioactive Compounds in Bryophytes

Today global health problems such as increased risks of oxidative stress-related diseases and antibiotic resistance are issues of serious concern. Oxidative stress is considered to be the underlying cause of many contemporary pathological conditions such as neurological disorders, ischemia, cancer, etc. Antibiotic-resistant bacteria are a concerning issue in clinical practice, causing an increase in deadly infections. Bryophytes synthesize an outstanding number of secondary metabolites that have shown several potential therapeutic and nutraceutical applications. Research in the field has led to the isolation and characterization of several compounds (flavonoids, terpenoids, and bibenzyls). Some of these compounds have shown promising in vitro antibacterial activities and antioxidant potential comparable to known natural antioxidants such as ascorbic acid and α-tocopherol. However, the process of developing new drugs from naturally occurring molecules is often an impervious path. In this paper, the current state of research of bryophytic antioxidant and antibacterial applications is discussed.

Simultaneously monitoring UVC-induced DNA damage and photoenzymatic repair of cyclobutane pyrimidine dimers by electrochemical impedance spectroscopy

Cyclobutane pyrimidine dimers (CPDs) are the major DNA photoproducts of thymine-thymine dinucleotides upon ultraviolet (UV) irradiation. Failure in the repair of damaged DNA may lead to DNA replication errors, DNA mutations, and even cell death. Photoreactivation can mediate the repair of UV-induced DNA lesions by photolyases upon UVA (315-400 nm) or blue light (400-500 nm) irradiation. Herein, the UVC (254 nm)-induced DNA damage and photoenzymatic repair of the CPD products were simultaneously monitored by electrochemical impedance spectroscopy (EIS). The UVC-damaged dT₂₀ was first immobilized on the gold electrode, and the specific recognition by the anti-CPD antibody leads to significantly increased EIS signals. The electron transfer resistance (R_et) values were linearly proportional to the concentrations of damaged dT₂₀ ranging from 0.005 to 0.1 μM, and a detection limit of 3.06 nM was achieved. Using surface plasmon resonance, the equilibrium dissociation constant (K_D) between the CPDs in dT₂₀ and anti-CPD antibody was estimated to be (3.32 ± 0.31) × 10^-12 M, indicating the strong binding affinity. Evidenced by EIS, the CPDs in the damaged dT₂₀ could be repaired by the attached DNA photolyase under UVA (365 nm) photoexcitation, and the detachment of the photolyase from the DNA strand was accomplished after completion of the repair process. The repair efficiency was calculated to be 70.0% by EIS, being consistent with that of 71.4% by UV spectroscopy. The electrochemical method is simple, sensitive and straightforward, holding great potential for assaying other types of DNA lesions and their repair processes.

Acclimation of Bryophytes to Sun Conditions, in Comparison to Shade Conditions, Is Influenced by Both Photosynthetic and Ultraviolet Radiations

We studied the acclimation modalities of bryophytes to sun and shade under ambient or close-to-ambient conditions, measuring variables usually influenced by photosynthetically active (PAR) and ultraviolet (UV) radiations. Our aim was to elucidate to what extent the responses to changing radiations were influenced by PAR and UV wavelengths. For this aim, we used three taxonomically and structurally different species: the thalloid liverwort Marchantia polymorpha subsp. polymorpha, the leafy liverwort Jungermannia exsertifolia subsp. cordifolia, and the moss Fontinalis antipyretica. In the field, liverworts were more radiation-responsive than the moss, and the thalloid liverwort was more responsive than the leafy liverwort. Sun plants of M. polymorpha showed, in comparison to shade plants, higher sclerophylly, lower Chl a + b contents, higher Chl a/b ratios, higher (antheraxanthin + zeaxanthin)/(violaxanthin + antheraxanthin + zeaxanthin) ratios (xanthophyll index), lower F v/F m values, higher contents of methanol-soluble vacuolar UV-absorbing compounds (soluble UVACs), higher values of the ratio between the contents of methanol-insoluble cell wall-bound UVACs (insoluble UVACs) and soluble UVACs, higher contents of soluble luteolin and apigenin derivatives and riccionidin A, and higher contents of insoluble p-coumaric and ferulic acids. Overall, these responses reduced light absorption, alleviated overexcitation, increased photoprotection through non-photochemical energy dissipation, increased UV protection through UV screening and antioxidant capacity, and denoted photoinhibition. J. exsertifolia showed moderate differences between sun and shade plants, while responses of F. antipyretica were rather diffuse. The increase in the xanthophyll index was the most consistent response to sun conditions, occurring in the three species studied. The responses of soluble UVACs were generally clearer than those of insoluble UVACs, probably because insoluble UVACs are relatively immobilized in the cell wall. These modalities of radiation acclimation were reliably summarized by principal components analysis. Using the most radiation-responsive species in the field (M. polymorpha), we found, under close-to-ambient greenhouse conditions, that sclerophylly and Chl a + b content were only influenced by PAR, F v/F m, and luteolin and apigenin derivatives were only determined by UV, and xanthophyll index was influenced by both radiation types. Thus, responses of bryophytes to radiation can be better interpreted considering the influence of both PAR and UV radiation.

Photosynthetically-active radiation, UV-A and UV-B, causes both common and specific damage and photoprotective responses in the model liverwort Marchantia polymorpha subsp. ruderalis

We studied the effects of different radiation treatments on the physiology and UV-absorbing compounds of the model liverwort Marchantia polymorpha subsp. ruderalis. Starting from gemmae, samples were exposed to five radiation treatments: low photosynthetically active radiation (PAR), low PAR+ UV-A, low PAR + UV-B, low PAR + UV-A + UV-B, and high PAR. After 35 days, the maximum quantum yield of photosystem II was similar between treatments, which suggested comparable photoinhibition and physiological vitality, also supported by results showing an unchanged chlorophyll a/b ratio and only slight changes in growth. However, the total contents of both chlorophylls and carotenoids decreased in the UV radiation treatments and, more strongly, in the high-PAR samples, suggesting mainly PAR-dependent damage to the photosynthetic pigments. The xanthophyll index (antheraxanthin + zeaxanthin)/(violaxanthin + antheraxanthin + zeaxanthin) was only increased in the high-PAR samples, indicating an increase in photoprotection through nonphotochemical dissipation of the excess energy. The sclerophylly index (the ratio between the thallus dry mass and surface area) was increased in the UV-B-exposed samples, suggesting a UV-induced structural protection. Only the UV-B-exposed samples showed DNA damage. Several apigenin and luteolin derivatives were found in the methanol-soluble vacuolar fraction of the liverwort and p-coumaric and ferulic acids in the methanol-insoluble cell wall-bound fraction. Most individual soluble compounds, the bulk level of soluble compounds, and chalcone synthase expression increased in UV-B-exposed samples, whereas individual insoluble compounds increased in the samples exposed to only PAR. Principal components analysis summarized these responses, showing the strong influence of both UV-B and PAR levels on the physiology and UV protection of the samples.

Spatial variability of ultraviolet-absorbing compounds in an aquatic liverwort and their usefulness as biomarkers of current and past UV radiation: a case study in the Atlantic-Mediterranean transition

The spatial variability of ultraviolet-absorbing compounds (UVACs) in the freshwater liverwort Jungermannia exsertifolia subsp. cordifolia was studied in mid-latitudes (the Atlantic-Mediterranean transition) across a wide lati-altitudinal gradient, with the aim of testing the usefulness of UVACs as biomarkers of current ambient levels of UV radiation. We analysed 17 samples from streams located in the main mountain ranges of the Iberian Peninsula, differentiating methanol-soluble (SUVACs, mainly located in the vacuoles) and methanol-insoluble (IUVACs, bound to cell walls) compounds, since they represent different manners to cope with UV radiation. In both fractions, the bulk level of UVACs and the concentrations of several individual compounds were measured. In addition, we measured Fv/Fm, DNA damage and sclerophylly index (SI) as possible additional UV biomarkers. UVACs showed a high variability, probably due not only to the gradients of macroenvironmental factors (UV radiation, PAR, and water temperature), but also to microenvironmental factors inherent to the dynamic nature of mountain streams. Two soluble coumarins were positively correlated with UV levels and could be used for ambient UV biomonitoring in the spatial scale. In contrast to the variability in UVACs, the relatively homogeneous values of Fv/Fm and the lack of any DNA damage made these variables useless for ambient UV biomonitoring, but suggested a strong acclimation capacity of this liverwort to changing environmental conditions (in particular, to UV levels). Finally, UVACs of fresh samples of the liverwort were compared to those of herbarium samples collected in the same lati-altitudinal gradient. SUVACs were significantly higher in fresh samples, whereas IUVACs generally showed the contrary. Thus, IUVACs were more stable than SUVACs and hence more adequate for retrospective UV biomonitoring. In conclusion, UVAC compartmentation should be taken into account for bryophyte-based UV biomonitoring in future studies.

Effects of UV exclusion on the physiology and phenolic composition of leaves and berries of Vitis vinifera cv. Graciano

BACKGROUND

Ultraviolet (UV) radiation induces adaptive responses that can be used for plant production improvement. The aim of this study was to assess the effect of solar UV exclusion on the physiology and phenolic compounds of leaves and berry skins of Vitis vinifera L. cv. Graciano under field conditions. Phenolic compounds were analyzed globally and individually in both the vacuolar fraction and, for the first time in grapevine, the cell wall-bound fraction. These different locations may represent diverse modalities of phenolic response to and protection against UV.

RESULTS

UV exclusion led to a decrease in Fv /Fm in leaves, revealing that solar UV is needed for adequate photoprotection. Only p-caffeoyl-tartaric acid from the soluble fraction of leaves and myricetin-3-O-glucoside from the soluble fraction of berry skins were significantly higher in the presence of UV radiation, and thus they could play a role in UV protection. Other hydroxycinnamic acids, flavonols, flavanols and stilbenes did not respond to UV exclusion.

CONCLUSION

UV exclusion led to subtle changes in leaves and berry skins of Graciano cultivar, which would be well adapted to current UV levels. This may help support decision-making on viticultural practices modifying UV exposure of leaves and berries, which could improve grape and wine quality.

Dynamic response of UV-absorbing compounds, quantum yield and the xanthophyll cycle to diel changes in UV-B and photosynthetic radiations in an aquatic liverwort

We studied the diel responses of the liverwort Jungermannia exsertifolia subsp. cordifolia to radiation changes under laboratory conditions. The samples were exposed to three radiation regimes: P (only PAR), PA (PAR+UV-A), and PAB (PAR+UV-A+UV-B). The day was divided in four periods: darkness, a first low-PAR period, the high-PAR plus UV period, and a second low-PAR period. After 15 days of culture, we measured photosynthetic pigments, chlorophyll fluorescence and UV-absorbing compounds in the four periods of the day on two consecutive days. With respect to UV-absorbing compounds, we analyzed their global amount (as the bulk UV absorbance of methanolic extracts) and the concentration of seven hydroxycinnamic acid derivatives, both in the soluble (mainly vacuolar) and insoluble (cell wall-bound) fractions of the plant extracts. PAB samples increased the bulk UV absorbance of the soluble and insoluble fractions, and the concentrations of p-coumaroylmalic acid in the soluble fraction and p-coumaric acid in the cell wall. Most of these variables showed significant diel changes and responded within a few hours to radiation changes (more strongly to UV-B), increasing at the end of the period of high-PAR plus UV. F(v)/F(m), Φ(PSII), NPQ and the components of the xanthophyll cycle showed significant and quick diel changes in response to high PAR, UV-A and UV-B radiation, indicating dynamic photoinhibition and protection of PSII from excess radiation through the xanthophyll cycle. Thus, the liverwort showed a dynamic protection and acclimation capacity to the irradiance level and spectral characteristics of the radiation received.

Effects of UV radiation on aquatic ecosystems and interactions with climate change

The health of freshwater and marine ecosystems is critical to life on Earth. The impact of solar UV-B radiation is one potential stress factor that can have a negative impact on the health of certain species within these ecosystems. Although there is a paucity of data and information regarding the effect of UV-B radiation on total ecosystem structure and function, several recent studies have addressed the effects on various species within each trophic level. Climate change, acid deposition, and changes in other anthropogenic stressors such as pollutants alter UV exposure levels in inland and coastal marine waters. These factors potentially have important consequences for a variety of aquatic organisms including waterborne human pathogens. Recent results have demonstrated the negative impacts of exposure to UV-B radiation on primary producers, including effects on cyanobacteria, phytoplankton, macroalgae and aquatic plants. UV-B radiation is an environmental stressor for many aquatic consumers, including zooplankton, crustaceans, amphibians, fish, and corals. Many aquatic producers and consumers rely on avoidance strategies, repair mechanisms and the synthesis of UV-absorbing substances for protection. However, there has been relatively little information generated regarding the impact of solar UV-B radiation on species composition within natural ecosystems or on the interaction of organisms between trophic levels within those ecosystems. There remains the question as to whether a decrease in population size of the more sensitive primary producers would be compensated for by an increase in the population size of more tolerant species, and therefore whether there would be a net negative impact on the absorption of atmospheric carbon dioxide by these ecosystems. Another question is whether there would be a significant impact on the quantity and quality of nutrients cycling through the food web, including the generation of food proteins for humans. Interactive effects of UV radiation with changes in other stressors, including climate change and pollutants, are likely to be particularly important.

Acute exposure to UV-B sensitizes cucumber, tomato, and Arabidopsis plants to photooxidative stress by inhibiting thermal energy dissipation and antioxidant defense

To characterize a change in NPQ upon exposure to ultraviolet-B (UV-B), the xanthophyll cycle-dependent and -independent NPQs were compared in Cucumis sativus, Lycopersicum esculentum, and Arabidopsis thaliana leaves. The xanthophyll cycle-dependent NPQ was dramatically but reversibly suppressed by UV-B radiation. This suppression was correlated more strongly with a marked decrease in photosynthetic electron transport rather than changes in xanthophyll cycle enzymes such as violaxanthin de-epoxidase and zeaxanthin epoxidase. Accordingly, the UV-B-induced suppression of NPQ cannot be attributed to changes in expressions of VDE and ZEP. However, suppression of the xanthophyll cycle-dependent NPQ could only account for the 77 K fluorescence emission spectra of thylakoid membranes and the increased level of (1)O(2) production, but not for the decreased levels of •O(2)(-) production and H(2)O(2) scavenging. These results suggest that a gradual reduction of H(2)O(2) scavenging activity as well as a transient and reversible suppression of thermal energy dissipation may contribute differentially to increased photooxidative damages in cucumber, tomato, and Arabidopsis plants after acute exposure to UV-B radiation.

Molecular mechanisms of ultraviolet radiation-induced DNA damage and repair

DNA is one of the prime molecules, and its stability is of utmost importance for proper functioning and existence of all living systems. Genotoxic chemicals and radiations exert adverse effects on genome stability. Ultraviolet radiation (UVR) (mainly UV-B: 280-315 nm) is one of the powerful agents that can alter the normal state of life by inducing a variety of mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs), 6-4 photoproducts (6-4PPs), and their Dewar valence isomers as well as DNA strand breaks by interfering the genome integrity. To counteract these lesions, organisms have developed a number of highly conserved repair mechanisms such as photoreactivation, base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). Additionally, double-strand break repair (by homologous recombination and nonhomologous end joining), SOS response, cell-cycle checkpoints, and programmed cell death (apoptosis) are also operative in various organisms with the expense of specific gene products. This review deals with UV-induced alterations in DNA and its maintenance by various repair mechanisms.

Effects of enhanced UV-B radiation on hydroxycinnamic acid derivatives extracted from different cell compartments in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia

We examined the responses of ultraviolet-absorbing compounds (UVAC) to enhanced UV-B radiation in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia for 31 days under laboratory conditions. Samples were exposed to three radiation regimes: P (only photosynthetic radiation), PA (photosynthetic + UV-A radiation) and PAB (photosynthetic + UV-A + UV-B radiation). We measured both the bulk UV absorbance of the methanolic extracts and the levels of individual UVAC. In both cases, the methanol-soluble and the methanol-insoluble, alkali-extractable cell wall-bound fractions were analyzed. The bulk UV absorbance of the soluble fraction was higher than that of the cell wall-bound fraction. The bulk UV absorbances of both fractions increased under enhanced UV-B (PAB regime). Five different hydroxycinnamic acid (HCA) derivatives were found in the soluble fraction and two additional ones in the cell wall-bound fraction, among which only p-coumaroylmalic acid in the soluble fraction and p-coumaric acid in the cell wall-bound fraction increased under enhanced UV-B. The maximum quantum yield of PSII (F(v) /F(m)) decreased and DNA damage (amount of thymine dimers) strongly increased under enhanced UV-B, showing UV-B-induced damage. We conclude that methanol-soluble and cell wall-bound fractions of the liverwort studied have different UVAC, and each individual compound may respond in a different way to UV-B radiation. Thus, the analysis of individual UVAC in both the methanol-soluble and cell wall-bound fractions is advisable to better evaluate the protection mechanisms of liverworts against UV-B radiation. In particular, p-coumaric acid and p-coumaroylmalic acid seem to be especially UV-B responsive and merit further investigation.

Acclimation to ultraviolet irradiation affects UV-B sensitivity of Daphnia magna to several environmental toxicants

Phototoxicity of several environmental contaminants by UV light has been reported in many studies. Nevertheless, field observations suggest the presence of certain defense mechanisms that would protect aquatic organisms against phototoxic damages. The current study was conducted to understand the responses of aquatic receptors to phototoxic chemicals in a natural environment where low dose UV light is present and long-term acclimation to UV might have been taken place. For this purpose, the water flea Daphnia magna was acclimated to a non-lethal, environmentally relevant level of UV-B light for >20 successive generations. The differences in toxicity response were evaluated between the UV-B acclimated and the non-acclimated daphnids when they were exposed to phototoxic compounds such as polynuclear aromatic hydrocarbons (fluoranthene and pyrene), a pharmaceutical (sulfathiazole), or metals (Cd and Cu) under UV-B light. Following the UV-B acclimation, toxicity of metals under UV-B light significantly decreased (P<0.1) suggesting the defense/repair system which might be developed through acclimation. For PAHs and sulfathiazole, however the acclimation rendered organisms more susceptible (P<0.05). The metabolic cost incurred during the acclimation to UV-B stress may in part explain the organisms' reduced capacity to deal with other stressors. Addition of vitamin C significantly increased the resistance of UV-B acclimated individuals against Cu, while no change was observed for the other chemicals, suggesting that the mode of Cu phototoxicity is different from those of the other phototoxicants under UV-B light. Two-dimensional gel electrophoresis analyses showed that long-term acclimation to UV-B lead to notable changes in protein expression, which may be further evaluated to explain varying susceptibilities of the acclimated daphnids to different phototoxicants.

Seasonal variations in UV-absorbing compounds and physiological characteristics in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia over a 3-year period

Temporal physiological variations in relation to environmental factors, in particular to ultraviolet (UV) radiation, have been studied in bryophytes from circumpolar latitudes, but not in mid-latitudes with longer growing seasons. In addition, seasonal and interannual changes in individual UV-absorbing compounds (UVAC) have not been previously studied in bryophytes. To fill these gaps, samples of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia were collected on a monthly basis during 3 years from a mountain stream in northern Spain. Sclerophylly index, chlorophyll fluorescence, DNA damage, the bulk UV absorbance of methanolic extracts and the concentration of five UVAC (hydroxycinnamic acid derivatives) were measured. Interannual changes were little marked, probably because the 3 years studied were environmentally similar. In summer-autumn, with respect to seasonal variations, newly grown tender young shoots with high F(v)/F(m) accumulated higher amounts of several hydroxycinnamic acid derivatives than in winter-spring. DNA damage was not detected in any of the samples analyzed. p-Coumaroylmalic acid was the compound best associated with radiation changes, and the best model explaining UV-B took into consideration the concentration of this compound and the ozone level. The specific effects of UV radiation could not be separated from the effects caused by other environmental factors, such as global radiation or temperature, because all these variables were correlated. However, indirect evidence strongly suggests that seasonal changes in bulk UV absorbance and p-coumaroylmalic acid are mainly driven by UV radiation. This compound may be a promising physiological variable to be used for UV bioindication.

Dichromate effect on energy dissipation of photosystem II and photosystem I in Chlamydomonas reinhardtii

In this study, we investigated the energy dissipation processes via photosystem II and photosystem I activity in green alga Chlamydomonas reinhardtii exposed to dichromate inhibitory effect. Quantum yield of photosystem II and also photosystem I were highly decreased by dichromate effect. Such inhibition by dichromate induced strong quenching effect on rapid OJIP fluorescence transients, indicating deterioration of photosystem II electron transport via plastoquinone pool toward photosystem I. The decrease of energy dissipation dependent on electron transport of photosystem II and photosystem I by dichromate effect was associated with strong increase of non-photochemical energy dissipation processes. By showing strong effect of dichromate on acceptor side of photosystem I, we indicated that dichromate inhibitory effect was not associated only with PSII electron transport. Here, we found that energy dissipation via photosystem I was limited by its electron acceptor side. By the analysis of P700 oxido-reduction state with methylviolagen as an exogenous PSI electron transport mediator, we showed that PSI electron transport discrepancy induced by dichromate effect was also caused by inhibitory effect located beyond photosystem I. Therefore, these results demonstrated that dichromate has different sites of inhibition which are associated with photosystem II, photosystem I and electron transport sink beyond photosystems.

Effects of supplemental ultraviolet-B and cadmium on growth, antioxidants and yield of Pisum sativum L

The impact of supplemental UV-B irradiation (sUV-B) and cadmium (Cd, 68 micromol kg(-1) soil) singly and in combination was studied on growth, pigments, enzymatic and non-enzymatic antioxidants, lipid peroxidation (LPO), uptake and translocation of Cd and yield of pea plants under field condition. Compared to the control, both the stresses individually and in combination led to in reductions in growth, photosynthetic pigments, ascorbic acid, catalase (CAT) activity and yield, whereas a reverse trend was observed for flavonoids, thiols and proline contents, superoxide dismutase (SOD) and peroxidase (POD) activities, and LPO. The uptake and translocation of Cd increased in different plant parts with duration of its treatment and also when applied with sUV-B. Combined treatment of sUV-B and Cd inhibited the growth and various metabolic processes antagonistically except the CAT activity which showed additive response. Further, CAT activity may be used as a bioindicator parameter to evaluate the individual and interactive effects of both the stresses.

In vitro radiation induced alterations in heavy metals and metallothionein content in Plantago ovata Forsk

Proton Induced X-ray emission (PIXE) and fluorescence-activated cell sorting (FACS) have been used to study the effects of gamma irradiation on heavy metal accumulation in callus tissue of Plantago ovata-an important cash crop of India. PIXE analysis revealed radiation-induced alteration in trace element profile during developmental stages of the callus of P. ovata. Subsequent experiments showed antagonism between Fe and Cu and also Cu and Zn and synergistic effect between Fe and Zn. FACS analysis showed significant induction of the metallothionein (MT) protein following gamma-irradiation, and maximum induction was noted at the 50-Gy absorbed dose. This indicated a progressive increment of MTs as a measure for protection against gamma-rays, to combat alteration in the homeostasis of heavy metals like Fe, Cu, Zn, and Mn.