Changes of metal-induced toxicity by H2O 2/NO modulators in Scenedesmus quadricauda (Chlorophyceae).

Effect of nitric oxide donor (sodium nitroprusside, SNP, 500 µM) or hydrogen peroxide scavenger (dithiothreitol, DTT, 500 µM) on cadmium (Cd) or copper (Cu) uptake (150 µM solutions) and toxicity using Scenedesmus quadricauda was studied. Combined treatments (Cd or Cu + DTT or SNP) usually ameliorated metal-induced toxicity at the level of pigments, proteins, and mineral nutrients in comparison with respective metal alone. Viability tests (MTT and TTC) showed the lowest values preferentially in Cu treatments, indicating higher toxicity in comparison with Cd. Cd showed low impact on amino acids while strong Cu-induced depletion was mitigated by DTT and SNP. Amount of ROS and NO showed the most pronounced responses in SNP variants being rather reciprocal than parallel and regulated ascorbate peroxidase activity. Blot gel analyses of hsp70 protein did not reveal extensive changes after given exposure period. Phenols were elevated by DTT alone while all Cu treatments revealed depletion. Total Cu content decreased while total Cd content increased in metal + SNP or metal + DTT. Subsequent experiment using lower Cd, SNP or DTT doses (10 and 100 µM) revealed concentration-dependent impact on Cd uptake. Overall, DTT was found to be more suitable for the amelioration of metal-induced toxicity.

Physiological responses of Tillandsia albida (Bromeliaceae) to long-term foliar metal application.

The impact of 2-month foliar application of cadmium, nickel and their combination (10 µM) on Tillandsia albida was studied. Cadmium caused damage of tissue but assimilation pigments were depressed in Cd+Ni variant only. Stress-related parameters (ROS and peroxidase activities) were elevated by Cd and Cd+Ni while MDA content remained unaffected. Free amino acids accumulated the most in Ni alone but soluble proteins were not influenced. Among phenolic acids, mainly vanillin contributed to increase of their sum in all variants while soluble phenols even decreased in Cd+Ni and flavonols slightly increased in Cd variants. Phenolic enzymes showed negligible responses to almost all treatments. Mineral nutrients (K, Ca, Na, Mg, Fe, and Zn) were not affected by metal application but N content increased. Total Cd or Ni amounts reached over 400 µg g(-1) DW and were not affected if metal alone and combined treatment is compared while absorbed content differed (ca. 50% of total Cd was absorbed while almost all Ni was absorbed). These data indicate tolerance of T. albida to foliar metal application and together with strong xerophytic morphology, use for environmental studies is recommended.

Modulation of copper uptake and toxicity by abiotic stresses in Matricaria chamomilla plants.

The impact of salinity (S) or nitrogen deficiency (-N) on copper (Cu) uptake and changes to metabolism were studied in the combined treatments after 7 days of exposure. S suppressed growth, water content, soluble proteins, and reducing sugars more negatively than -N. ROS (hydrogen peroxide and superoxide) were differentially but relatively slightly affected while peroxidase activities were strongly elevated mainly in Cu+NaCl variant. Total soluble phenols and individual phenolic acids (free and cell wall-bound fraction) were accumulated the most in Cu-N while, among free amino acids, proline sharply increased in Cu+NaCl; this suggests a compensatory mechanism between the syntheses of antioxidants aimed to maintain antioxidative protection because numerous root phenolic acids were even depressed by S. Salinity also suppressed accumulation of coumarin herniarin, but its glucosidic precursors ((Z)- and (E)-2-ß-D-glucopyranosyloxy-4-methoxycinnamic acids) increased. Activities of selected phenolic enzymes were rather suppressed by S after a given exposure period while lignin content increased, suggesting different time dynamics if S and -N variants are compared. Selected mineral nutrients (K, Fe, and partially Mg) were more reduced by S than by -N. Shoot and root Cu amounts were depressed by -N but elevated by S. Significance and possible role of observed metabolic changes in relation to Cu accumulation are discussed.

Effect of metabolic regulators on aluminium uptake and toxicity in Matricaria chamomilla plants.

Phenolic metabolism of Al-exposed Matricaria chamomilla plants was modulated with four regulators: 2-aminoindane-2-phosphonic acid (AIP), salicylic acid (SA), sodium nitroprusside (SNP) and dithiothreitol (DTT). Physiological parameters (tissue water content, soluble proteins, reducing sugars, K+ content), root lignin content and free amino acids (increase in root proline and alanine) were the most affected in SA + Al variant, indicating negative impact of SA on Al-induced changes. SNP showed the least visible impact, suggesting protective effect of nitric oxide. Complex comparison between Al alone and combined treatments revealed that SA and DTT stimulated increase in shoot phenolic acids (mainly vanillic acid), sum of flavonols and soluble phenols but decreased the levels of coumarin-related compounds (Z- and E-2-ß-D-glucopyranosyloxy-4-methoxycinnamic acids), leading to elevation of shoot Al. Positive correlation between phenolic acids (mainly ferulic and chlorogenic acids), soluble phenols and total Al was found in the roots of SA and DTT variants. These events were not observed in AIP and SNP treatments. These data, to our knowledge for the first time, exactly confirm that phenolic metabolites may affect shoot Al uptake and this relation is rather positive in terms of simple phenols (and negative in terms of coumarin-related compounds).

Prey-induced changes in the accumulation of amino acids and phenolic metabolites in the leaves of Drosera capensis L.

Effect of prey feeding (ants Formica fusca) on the quantitative changes in the accumulation of free amino acids, soluble proteins, phenolic metabolites and mineral nutrients in the leaves of carnivorous plant Drosera capensis was studied. Arginine was the most abundant compound in Drosera leaves, while proline was abundant in ants. The amount of the majority of amino acids and their sum were elevated in the fed leaves after 3 and 21 days, and the same, but with further enhancement after 21 days, was observed in ants. Accumulation of amino acids also increased in young non-fed leaves of fed plants. Soluble proteins decreased in ants, but were not enhanced in fed leaves. This confirms the effectiveness of sundew's enzymatic machinery in digestion of prey and suggests that amino acids are not in situ deposited, but rather are allocated within the plant. The content of total soluble phenols, flavonoids and two selected flavonols (quercetin and kaempferol) was not affected by feeding in Drosera leaves, indicating that their high basal level was sufficient for the plant's metabolism and prey-induced changes were mainly N based. The prey also showed to be an important source of other nutrients besides N, and a stimulation of root uptake of some mineral nutrients is assumed (Mg, Cu, Zn). Accumulation of Ca and Na was not affected by feeding.

Sensitivity of Xanthoria parietina to UV-A: role of metabolic modulators.

Effects of methyl jasmonate (MeJA), salicylic acid (SA) or 2-aminoindane-2-phosphonic acid (AIP) pre-treatments on the sensitivity of Xanthoria parietina exposed to UV-A were studied. UV decreased chlorophylls and stimulated increase in hydrogen peroxide and superoxide level. Accumulation of soluble phenols and flavonoids increased in response to UV treatment. Metabolic modulators had negligible impact on these UV-induced changes. Within free amino acids, AIP (-UV variant) and SA and MeJA (+UV variants) altered their accumulation. AIP had no effect on the amount of phenylalanine. Benzoic and cinnamic acids were elevated by UV and mainly MeJA influenced their accumulations. Among lichen specific metabolites, vulpinic acid and ergosterol increased while usnic acid and atranorin decreased after exposure to UV; accumulation of parietin was not affected. Applied modulators showed a different effect on these lichen metabolites but biosynthetic pathway-specific trend of alteration was visible. Overall, MeJA showed the most pronounced effect among studied parameters. Accumulation of selected phenolics in response to UV-A seems to be an important feature of Xanthoria tolerance. Present finding in the context of phenolic metabolism in non-vascular plants and with respect to limited data about effect of studied modulators on non-vascular plants are discussed.

Nitrate deficiency reduces cadmium and nickel accumulation in chamomile plants.

The effect of nitrogen (nitrate) deficiency (-N) on the accumulation of cadmium (Cd) and nickel (Ni) in chamomile ( Matricaria chamomilla ) plants was studied. Elimination of N from the culture medium led to decreases in N-based compounds (free amino acids and soluble proteins) and increases in C-based compounds (reducing sugars, soluble phenols, coumarins, phenolic acids, and partially flavonoids and lignin), being considerably affected by the metal presence. Proline, a known stress-protective amino acid, decreased in all -N variants. The activity of phenylalanine ammonia-lyase was stimulated only in -N control plants, whereas the activities of polyphenol oxidase and guaiacol peroxidase were never reduced in -N variants in comparison with respective +N counterparts. Among detected phenolic acids, chlorogenic acid strongly accumulated in all N-deficient variants in the free fraction and caffeic acid in the cell wall-bound fraction. Mineral nutrients were rather affected by a given metal than by N deficiency. Shoot and total root Cd and Ni amounts decreased in -N variants. On the contrary, ammonium-fed plants exposed to N deficiency did not show similar changes in Cd and Ni contents. The present findings are discussed with respect to the role of phenols and mineral nutrition in metal uptake.

COMPARISON OF METHYL JASMONATE AND CADMIUM EFFECT ON SELECTED PHYSIOLOGICAL PARAMETERS IN SCENEDESMUS QUADRICAUDA (CHLOROPHYTA, CHLOROPHYCEAE)(1).

Effect of methyl jasmonate (MeJA) in the concentrations of 10 or 100 µM on selected physiological parameters in Scenedesmus quadricauda (Turp.) Bréb. after 24 h of exposure was studied. Results were compared with the application of general toxic metal (cadmium, Cd) to identify MeJA-specific responses. Accumulation of reactive oxygen species (ROS; hydrogen peroxide and superoxide) was the most elevated by 10 µM MeJA and 100 µM Cd, while total chls showed decrease (Cd) and increase (MeJA) in these variants. The amount of carotenoids and cell viability were affected neither by MeJA nor by Cd application. The sum of free amino acids was considerably elevated by 10 µM Cd (increase in histidine, threonine, arginine, leucine, and lysine mainly) but depleted by 100 µM MeJA (14 from 17 compounds decreased), while accumulation of soluble proteins was unaffected by Cd and enhanced by MeJA. Cadmium application reduced the amount of Ca and also Mg in the case of 100 µM Cd, while MeJA had no effect on the content of mineral nutrients. Total Cd content reached 557 and 1,334 µg · g(-1) dry weight (dwt) in 10 and 100 µM Cd variant, respectively. Intracellular Cd uptake was ca. 55% from total Cd content in both Cd variants. The present findings are discussed in the context of the available literature, and possible explanations are suggested.

Physiological responses of root-less epiphytic plants to acid rain.

Selected physiological responses of Tillandsia albida (Bromeliaceae) and two lichens (Hypogymnia physodes and Xanthoria parietina) exposed to simulated acid rain (AR) over 3 months were studied. Pigments were depressed in all species being affected the most in Tillandsia. Amounts of hydrogen peroxide and superoxide were elevated and soluble proteins decreased only in AR-exposed Hypogymnia. Free amino acids were slightly affected among species and only glutamate sharply decreased in AR-exposed Xanthoria. Slight increase in soluble phenols but decrease in flavonoids in almost all species suggests that the latter are not essential for tolerance to AR. Almost all phenolic acids in Tillandsia leaves decreased in response to AR and activities of selected enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, ascorbate- and guaiacol-peroxidase) were enhanced by AR. In lichens, considerable increase in metabolites (physodalic acid, atranorin and parietin) in response to AR was found but amount of ergosterol was unchanged. Macronutrients (K, Ca, Mg) decreased more pronouncedly in comparison with micronutrients in all species. Xanthoria showed higher tolerance in comparison with Hypogymnia, suggesting that could be useful for long-term biomonitoring.