Abundance and Structure Composition of nirK and nosZ Genes as Well as Denitrifying Activity in Heavy Metal-polluted Paddy Soils

Denitrification is an important microbial process in soils and leads to the emission of nitrous oxide (N₂O). However, studies about the microbial community involved in denitrification processes in polluted paddy fields are scarce. Here, we studied two rice paddies which had been polluted for more than three decades by metal mining and smelter activities. Abundance and community composition were determined using real-time polymerase chain reaction (PCR) assay and denaturing gradient gel electrophoresis of nitrite reductase and nitrous oxide reductase gene amplicons (nirK and nosZ), while denitrifying activities were assessed by measuring potential denitrifier enzyme activity. We found that the community structure of both nirK and nosZ containing denitrifiers shifted under pollution in the two rice paddies. All the retrieved nirK sequences did not group into either α- or β-proteobacteria, while most of the nosZ species were affiliated with α-proteobacteria. While the abundance of both nirK and nosZ was significantly reduced in the polluted soils at “Dexing” (with relatively higher Cu levels), these parameters did not change significantly at “Dabaoshan” (polluted with Cd, Pb, Cu, and Zn). Furthermore, total denitrifying activity and N₂O production and reduction rates also only decreased under pollution at “Dexing.” These findings suggest that nirK and nosZ containing denitrifier populations and their activities could be sensitive to considerable Cu pollution, which could potentially affect N₂O release from polluted paddy soils.     

Net photosynthetic rate,ascorbate peroxidase and glutathione reductase activities of <Emphasis Type="Italic">Erythrina orientalis</Emphasis> in polluted and non-polluted areas

We investigated net photosynthetic rate and antioxidative enzyme activities in Erythrina orientalis grown in three different sites: Makati and Quezon (cities with high levels of air pollution, HP) and La Mesa (a non-polluted area, NP). Photosynthetic activity of E. orientalis was significantly reduced in the HP cities. In contrast, activities of the antioxidative enzymes ascorbate peroxidase and glutathione reductase were significantly higher in HP cities than in the NP area.     

Mechanism of cadmium tolerance in Salicornia europaea at optimum levels of NaCl

• Many saline-alkali soils around the world are polluted by the heavy metal Cd, restricting the development of agriculture and ecology in those regions. The halophyte Salicornia europaea L. is capable of growing healthily in Cd-contaminated saline-alkali soil, suggesting that the species is tolerant to stress caused by both salt and heavy metals. In this study, the mechanism of Cd tolerance in this species was explored under 200 mM NaCl.
• Flame spectrophotometric assays for ions content and spectrophotometric for organic soluble substances, antioxidant enzyme activity, phytochelatins (PCs) content and phytochelatin synthase (PCS) activity, the photosynthetic parameters by portable photosynthesis measurement system, genes expression by qRT-PCR analysis were carried out.
• Cd treatment significantly decreased the dry weight, photosynthetic rate, K⁺, Zn²⁺, and Fe^2+/3+ content, while significantly increasing Na⁺ and Cd⁺, soluble organic matter, and reactive oxygen species (ROS) levels. Compared with Cd treatment at 0 mM NaCl, Cd treatment at 200 mM NaCl significantly increased dry weight and photosynthetic rate while significantly decreasing ROS content through increased antioxidant enzyme activity. When exposed to Cd stress, treatment with 200 mM NaCl significantly increased PCs content and PCS activity and up-regulated the expression of the phytochelatin synthase genes CDA1 and PCS1 were, thereby increasing resistance to Cd.
• NaCl treatment increases the tolerance of S. europaea to the heavy metal Cd by growing rapidly, reducing the quantity of Cd²⁺ from entering the plant shoots, increasing the levels of PCs that chelate Cd²⁺, thereby reducing its toxicity.

     

Efficiency of antioxidant response in Spartina densiflora: An adaptative success in a polluted environment

The effects of different culture conditions, unpolluted and polluted substrates, on an antioxidative system – antioxidant enzymes, such as catalase, ascorbate peroxidase and guaiacol peroxidase, and ascorbic acid – were investigated to establish its relationship with the acclimatization success of Spartina densiflora. Plants of this species growing in the polluted Odiel marshes (Huelva, Spain) showed high levels of catalase, ascorbate and guaiacol peroxidase activities and ascorbate concentration (reduced and oxidized ascorbate). In addition, we found significant oxidation of the ascorbate pool, since only 40% of ascorbate was reduced, and low levels of photosynthetic pigments, suggesting that an oxidative stress was impairing S. densiflora. Transplantation to an unpolluted substrate in the laboratory led to a gradual change in all tested parameters: antioxidative activities and total ascorbate concentration decreased while the percentage of reduced ascorbate and pigment concentrations increased; these data agreed with the hypothesis that oxidative stress conditions in S. densiflora habitat were due to a polluted substrate. After 28 days, the plants were transplanted for a second time to polluted conditions, equivalent to those in their habitats, and a rapid alteration of the antioxidative system was observed. In the first 24 h, catalase and guaiacol peroxidase activities and ascorbate concentration increased greatly and the percentage of reduced ascorbate fell drastically. Regardless of this fact, ascorbate peroxidase activity did not change until the end of the first week, while photosynthetic pigments declined at a constant rate during the whole culture period. Subsequently, we found that the antioxidative system improved its reductive capacity gradually and slowly – over weeks – but this reductive power was rapidly lost within days or even hours. It may be concluded that S. densiflora undergoes oxidative stress in its natural environment and is able to modulate its antioxidative system, based on the degree of pollution, in order to acclimatize successfully to its fluctuating environment.     

Growth characteristics and antioxidant metabolism of moongbean genotypes differing in photosynthetic capacity subjected to water deficit stress

Abstract

Two genotypes (Pusa 9531 and PS 16) of moongbean [Vigna radiata (L) Wilczek], differing in photosynthetic capacity were grown for 30 days in earthen pots at three field capacities (100, 75 and 50%), and the possible role of biochemical alterations and antioxidant metabolism in conferring photosynthetic capacity was determined by measuring Rubisco activity, photosynthetic traits, lipid peroxidation and assaying activities of the central components of antioxidant defence system. Growth, Rubisco activity, photosynthetic traits and soluble protein content decreased significantly with decreasing field capacity (FC) from 100 to 50%. Levels of TBARS, H₂O₂, electrolyte leakage and proline contents increased with decreasing FC. Activities of SOD and GR increased in both genotypes with decreasing FC; the CAT and APX activities over-expressed only at mild (75%) FC but not at severe (50%) FC. There were found genotype-dependent alterations in growth, photosynthetic traits, Rubisco activity and antioxidant metabolism when exposed to water deficit. Decline in efficiency of the H₂O₂-decomposing system at severe drought was responsible for oxidative damage occurring in both the genotypes. The differential responses of antioxidative enzymes in the two genotypes were the result of their ability to protect photosynthetic apparatus and alleviate water deficit stress.     

Changes in gas exchange, proline accumulation and antioxidative enzyme activities in three olive cultivars under contrasting water availability regimes

Changes in photosynthetic performance, osmolyte accumulation and the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and polyphenol oxidase (PPO) were investigated in one-year-old olive cultivars (Chemlali, Meski and Picholine) subjected to contrasting water availability regimes under arid climatic conditions in Tunisia. Shoot elongation rates (SER) and photosynthetic performance were markedly reduced by the water deficit regime (WD) in all cultivars except for Chemlali, which proved to be superior to the other two cultivars with respect to drought tolerance. Higher photosynthetic performance (net photosynthesis (P_n), stomatal conductance (g_s) and transpiration rates (E)) in the Chemlali and Meski cvs. compared to Picholine olive allowed them to maintain better plant water status and shoot elongation rates. Under WD conditions, Chemlali showed a greater capability for proline accumulation. Leaves grown under WD conditions showed signs of oxidative stress such as reduced chlorophyll and carotenoid concentrations. Nevertheless, different cultivars developed certain antioxidative defense mechanisms, including elevated SOD, APX and CAT activities. In contrast, PPO activity decreased under WD circumstances. Comparatively, Chemlali olive displayed better antioxidative enzyme activity, and thus better protection against oxidative stress. These results show that the ability of olive trees to up-regulate the enzymatic antioxidative system might be an important attribute linked to drought tolerance. These findings demonstrate that the association of higher P_n, proline accumulation and antioxidative defenses could be effective in a water-limited environment and may be useful selection criteria in breeding programs with the objective of improving drought tolerance and growth of olive trees, at least under the described environmental conditions.     

Concentration and ecological risk of heavy metal in street dusts of Eslamshahr,Iran

This study was done to evaluate heavy metal concentrations in street dust samples, to compare measured concentrations in samples to background concentrations in order to make evaluations for pollution indices, and to describe the quality of street dust in the studied area in relation to pollution. A total of 30 cumulative samples were collected from the streets of Eslamshahr City. Concentrations of heavy metals were determined using an Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Results determined mean concentrations (mg/kg) of the heavy metals Cd, Cr, Cu, Ni, Pb, and Zn, in collected samples of street dust as 0.34, 35.1, 239, 42.4, 71.3, and 573, respectively. I_geo values for Cd and Cr, Cu, Ni, Pb, and Zn showed level of moderately polluted, unpolluted, moderately to strongly polluted, unpolluted, moderately polluted and moderately to strongly polluted, respectively. The pattern of total metal concentrations in the studied area was ranked as follows: Zn and Cu>Pb>Cd>Ni>Cr. The highest values for the monomial potential ecological risk (E_r) were observed for Cd (114). The mean level of RI for the studied soil samples was 192 (91.3–244), which is classed as presenting a strong potential ecological risk.     

The temporal and species dynamics of photosynthetic acclimation in flag leaves of rice (Oryza sativa) and wheat (Triticum aestivum) under elevated carbon dioxide

In this study, we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO₂] in the flag leaf of two important cereal crops, rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate, we characterized net photosynthesis, g_s, g_m, C_i/C_a, C_i/C_c, V_cmax, J_max, cell wall thickness, content of Rubisco, cytochrome (Cyt) f, N, chlorophyll and carbohydrate, mRNA expression for rbcL and petA, activity for Rubisco, sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion, mid‐anthesis and the late grain‐filling stage. No acclimation was observed for either crop at full flag leaf expansion. However, at the mid‐anthesis stage, photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations, while wheat only had the carboxylation limitation. By grain maturation, the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO₂]; however, the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non‐structural carbohydrates did occur during these later stages, it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather, over time elevated [CO₂] appeared to enhance the rate of N degradation and senescence so that by late‐grain fill, photosynthetic acclimation to elevated [CO₂] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO₂] may be more closely associated with enhanced rates of senescence, and, as a consequence, may be temporally dynamic, with significant species variation.     

土壤铅胁迫对苘麻光合特性及生物量的影响

为明确不同浓度铅污染对苘麻(Abutilon theophrasti)光合特性及生长的影响程度,揭示苘麻对铅胁迫的光合适应能力,在铅污染土壤区域提供潜在物种。该研究设置五个铅浓度梯度(0、500、1 000、1 500、2 000 mg·kg~(-1)),分析了在不同浓度铅污染胁迫下,苘麻的铅积累、气体交换参数、叶绿素荧光特性及生物量的变化。结果表明:当铅浓度在1 000 mg·kg~(-1)以下时,净光合速率(P_n)和气孔导度(G_s)、光化学效率(F_v/F_m)、电子传递速率(ETR)的值分别与空白组的P_n、G_s、F_v/F_m、ETR值相比均不显著(P0.05),表明铅浓度小于1 000 mg·kg~(-1)时,苘麻的光合活性未受到损伤,有很强的光合适应能力。苘麻生物量在500、1 000 mg·kg~(-1)铅胁迫下为空白组的88.6%、106%,苘麻能够正常生长,说明苘麻能够适应铅污染的胁迫。当铅浓度低于1 000 mg·kg~(-1)时,苘麻地上部与地下部对铅富集与转移的效果较好,表明在铅污染区苘麻也具有较强的铅积累能力。根据铅污染土壤区域的实际情况,结合苘麻在低浓度铅污染修复效率高的特点,认为苘麻可以作为铅污染地区修复的潜在物种。     

大气悬浮颗粒物污染对厦门市行道树芒果光合生理指标的影响

随着城市的迅速发展,大气中总悬浮颗粒物(TSP)污染日益严重. 城市植被在吸附和净化TSP的同时,其正常生理生态过程也受到了深刻的影响. 2009年4、5月,对厦门市汀溪清洁对照区、厦大文教区、仙岳商贸区和海沧工业区大气TSP浓度及研究区内行道树芒果(Mangifera indica)的光合生理参数进行监测. 结果表明：汀溪、厦大、仙岳和海沧的日均大气TSP浓度分别为0.061、0.113、0.120和0.205 mg·m^-3;不同功能区行道树芒果受到的胁迫作用为工业区>商贸区>文教区>清洁对照区. 大气TSP污染导致芒果叶片的净光合速率、气孔导度和蒸腾速率显著下降,相关系数均在0.98以上,同时也是胞间CO₂浓度发生变化的重要因素;高浓度的TSP污染通过限制气孔导致芒果的光合强度显著降低.     

Effects of elevated CO2 on life‐history traits of three successive generations of Frankliniella occidentalis and F. intonsa on kidney bean,Phaseolus vulgaris

The objective of this study was to determine how elevated CO₂ impacts on life‐history traits and life table parameters in three successive generations of invasive species Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and its related native species, Frankliniella intonsa (Pergande), fed with kidney bean leaves grown in ambient CO₂. The oviposition period, sex ratio, net reproductive rate (R₀), intrinsic rate of increase (r_m), and finite rate of increase (λ) of F. occidentalis increased in elevated CO₂, and larval duration, survival rate, mean generation time (T), and population doubling time (DT) decreased. For F. intonsa, larval duration, survival rate, oviposition period, longevity of female adults, R₀, r_m, and λ decreased in elevated CO₂, whereas sex ratio, T, and DT increased. These results indicated that the effects of elevated CO₂ would be beneficial to F. occidentalis, whereas it would be detrimental to F. intonsa. However, the effects of elevated CO₂ on F. occidentalis and F. intonsa differed over generations. In elevated CO₂, larval duration, survival rate, oviposition period, sex ratio, r_m, and λ of F. occidentalis increased linearly through successive generations, whereas T and DT decreased linearly, which suggested that the effects of elevated CO₂ on F. occidentalis would be slowly accentuated over time. For F. intonsa, larval duration, survival rate, oviposition period, r_m, and λ decreased linearly over generations, whereas sex ratio, T, and DT increased linearly. This indicated that the effects of elevated CO₂ on F. intonsa would slowly accentuate over time. We conclude that F. occidentalis would be more adapted to elevated CO₂ than F. intonsa.     

Foliar characteristics,cambial activity and wood formation in Azadirachta indica A. Juss. as affected by coal–smoke pollution

This study, aimed at elucidating changes in the foliar and cambial behavior in Azadirachta indica (Neem tree) due to coal-smoke pollution, has revealed inhibitory effects of pollution stress on leaf pigments concentrations, nitrate reductase activity and the contents of reducing sugars and total N content, whereas stimulatory effects were given on stomatal index and nitrate and sulphur contents. Under smoke effects, stomatal conductance was low, leading to a drop in the net photosynthetic rate and a rise in the internal CO₂ concentration of leaf. Cambial reactivation in the stem was delayed at the polluted site. Although the total span of the cambial activity was reduced, greater amount of wood was observed to accumulate in the stem axis under heavy pollution stress. Vessel proportion in the wood increased, whereas size of vessel elements and xylem fibers decreased. “Vulnerability factor” (ratio between mean vessel diameter and mean vessel abundance) and “mesomorphic ratio” (multiplication product of vulnerability factor and mean length of vessel element) of the stem–wood, both declined with increase in the pollution stress, thus indicating a tendency of the species for shifting towards xeromorphy when grown under stress. Given the opposite trends of photosynthetic rate and wood increment, the carbon-partitioning pattern rather than the photosynthetic rate seems to have influenced the accumulation of new wood. The Neem tree proves to be suitable for growing in the polluted areas.     

Seasonal response of photosynthesis to elevated CO2 in loblolly pine (Pinus taeda L.) over two growing seasons

Trees growing in natural systems undergo seasonal changes in environmental factors that generate seasonal differences in net photosynthetic rates. To examine how seasonal changes in the environment affect the response of net photosynthetic rates to elevated CO₂, we grew Pinus taeda L. seedlings for three growing seasons in open-top chambers continuously maintained at either ambient or ambient + 30 Pa CO₂. Seedlings were grown in the ground, under natural conditions of light, temperature nd nutrient and water availability. Photosynthetic capacity was measured bimonthly using net photosynthetic rate vs. intercellular CO₂ partial pressure (A-C_i) curves. Maximum Rubisco activity (Vc_max) and ribulose 1,5-bisphosphate regeneration capacity mediated by electron transport (J_max) and phosphate regeneration (PiRC) were calculated from A-C_i curves using a biochemically based model. Rubisco activity, activation state and content, and leaf carbohydrate, chlorophyll and nitrogen concentrations were measured concurrently with photosynthesis measurements. This paper presents results from the second and third years of treatment. Mean leaf nitrogen concentrations ranged from 13.7 to 23.8 mg g^?1, indicating that seedlings were not nitrogen deficient. Relative to ambient CO₂ seedlings, elevated CO₂ increased light-saturated net photosynthetic rates 60–110% during the summer, but < 30% during the winter. A relatively strong correlation between leaf temperature and the relative response of net photosynthetic rates to elevated CO₂ suggests a strong effect of leaf temperature. During the third growing season, elevated CO₂ reduced Rubisco activity 30% relative to ambient CO₂ seedlings, nearly completely balancing Rubisco and RuBP-regeneration regulation of photosynthesis. However, reductions in Rubisco activity did not eliminate the seasonal pattern in the relative response of net photosynthetic rates to elevated CO₂. These results indicate that seasonal differences in the relative response of net photosynthetic rates to elevated CO₂ are likely to occur in natural systems.     

Effect of hypoxia on photosynthetic activity and antioxidative response in gametophores of <Emphasis Type="Italic">Mnium undulatum</Emphasis>

The effects of hypoxia caused by complete submerging of Mnium undulatum gametophores in water, on their photosynthetic activity and the activity of two antioxidative enzymes: superoxide dismutase (SOD) and catalase (CAT) were investigated. The net photosynthesis was strongly inhibited throughout the experiment, and the strong drop in the maximum quantum yield of the PSII (F_v/F_m) was also observed. Three classes of SOD: MnSOD, FeSOD, Cu/ZnSOD and three isoforms of Cu/ZnSOD were identified. A significant decrease in activity of MnSOD, FeSOD and one Cu/ZnSOD isoform was observed after 24 and 48 h of hypoxia. FeSOD activity decreased already after 1 h of submerging in water and its activity remained at the low level during whole period of the experiment. CAT activity was also strongly inhibited in response to hypoxia stress. The obtained results suggest relationships between photosynthetic activity and antioxidative system in M. undulatum gametophores under oxygen deficiency stress.     

Air pollution effects on structure,proteins and flavonoids in pollen grains of Thuja orientalis L. (Cupressaceae)

Increase in the levels of air pollution due to the increase in industrial and agricultural technology has prompted investigation of mechanisms that contribute to air pollution tolerance in plants. Pollen grains of Thuja orientalis were collected from controlled (less polluted) and polluted areas (mainly SO₂, NO₂, CO, HC and APM). Thuja pollen is considered inaperturate and granulate. The exine is shed during rehydration, leaving the male gametophyte naked. The pollen grains collected from polluted areas are smaller and more fragile compared to control ones. The exine splitting is faster and higher in polluted pollen grains. SDS–PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) pattern do not show significant differences in polluted pollen than those in the control group. HPLC (high pressure liquid chromatography) analysis demonstrates that air pollution induces flavonoids accumulation to significantly higher levels in polluted pollen than in controlled ones. These observations suggest that plants try to respond suitably by adjusting their metabolism so that minimum damage is done due to air pollutants. Their protective responses may include an increase in antioxidant enzymes and metabolites and induction of protection-related secondary metabolite genes especially flavonoids.     

Long-term implications of industrial pollution stress on lipids composition in Scots pine (Pinus sylvestris L.) roots

The influence of pollution stress (SO₂, Cu²⁺, Pb²⁺, Zn²⁺ and fluoride) on composition changes in cellular membranes of roots of three European of Scots pine (Pinus sylvestris L.) populations were examined. Plant material growing in three experimental areas: Kórnik relatively free of air pollution (control), Luboń: SO₂ and HF and Głogów: SO₂ and heavy metals. Analysis of total phospholipids and their composition indicates that the phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were present in lower concentration in the root tissues from both polluted sites (Luboń and Głogów). The difference in PC:PE ratio between control and both polluted sites was greater in root of Scots pine population from Russia than in the population from Slovakia. Under pollution conditions the content of lipid soluble antioxidant α-tocopherol was lower about 220 %, in comparison to the control. The action of pollution stress also lead to lowering of unsaturated:saturated ratio of total fatty acid, and lower content of polyunsaturated fatty acids, linoleic acid (18:2) and eicosatrienoic acid (20:3). We concluded that the long-term pollution stress markedly inhibited lipid biosynthesis in root tissue of Scots pine and it is probably contribute to the reduction of productivity of forests. These results also suggest that lipid composition can be used as an indicator of changes in tissue roots of Scots pine caused by air and/or soil long-term pollution.     

Daily and seasonal trends of gas exchange in Pistacia lentiscus L.

The spring–summer photosynthetic behaviour of Pistacia lentiscus, a spontaneous evergreen bush of the Mediterranean macchia, was followed during two consecutive years. Outdoor measurements were carried out monthly in the period from May to September in the years 2004 and 2005. Mean values of net photosynthesis (P _N) of external tests show a typical daily trend: a rise until the maximum followed by a decline of assimilation with lower values maintained until the end of day. External data were validated by light-response curves, obtained under different thermal regimes in controlled conditions. External trials and measures in controlled conditions confirm an elevated photosynthetic activity below 30°C and a decrease over that limit. The results obtained evidence that the CO₂ assimilation of the P. lentiscus is influenced by stressful temperatures. The ecophysiological response to this limiting factor is an adaptation that concentrates on the photosynthetic activity in the hours of the day and in the periods of the year in which temperatures are more favourable.     

不同种植模式下重金属污染对牧草叶片光合特性和重金属含量的影响

为探索不同种植模式下重金属污染对牧草生理特性的影响,皇竹草(Pennisetum sinese)、黑麦草(Lolium perenne)和龙须草(Juncus effusus)采用单作和间作模式,研究了重金属污染对其叶片光合参数、光合色素和重金属含量的影响.结果表明,与单作相比,间作下皇竹草叶片的叶绿素(Chl)a、C...     

A comparative analysis of photosynthetic characteristics of hulless barley at two altitudes on the Tibetan Plateau

To determine the photosynthetic characteristics of C₃ plants and their sensitivity to CO₂ at different altitudes on the Tibetan Plateau, hulless barley (Hordeum vulgare L. ssp. vulgare) was grown at altitudes of 4,333 m and 3,688 m. Using gas-exchange measurements, photosynthetic parameters were simulated, including the maximum net photosynthesis (P _max) and the apparent quantum efficiency (α). Plants growing at higher altitude had higher net photosynthetic rates (P _N), photosynthesis parameters (P _max and α) and sensitivities to CO₂ enhancement than plants growing at lower altitude on the Tibetan Plateau. The enhancements of P _N, P _max, and α for plants growing at higher altitude, corresponding with 10 μmol(CO₂) mol⁻¹ increments, were approximately 0.20∼0.45%, 0.05∼0.20% and 0.12∼0.36% greater, respectively, than for plants growing at lower altitude, respectively, where CO₂ levels rose from 10 to 170 μmol(CO₂) mol⁻¹. Therefore, on the Tibetan Plateau, the changes in the photosynthetic capacities and the photosynthetic sensitivities to CO₂ observed in the C₃ plants grown above 3,688 m are likely to increase with altitude despite the decreasing CO₂ partial pressure.     

Metalliferous and non-metalliferous populations of Viola tricolor represent similar mode of antioxidative response

Heavy metal-contaminated sites are excellent areas to examine the antioxidative machinery responsible for physiological adaptations of many plant species.Superoxide dismutase (SOD), guaiacol peroxide (GPX), ascorbate peroxide (APX), catalase (CAT) activity and hydrogen peroxide (H₂O₂) content were analyzed in leaves and roots of Viola tricolor (Viola) from contaminated soils (‘Bukowno’, ‘Saturn’, ‘Warpie’ heaps), and non-contaminated soil (‘Zakopane meadow’) to examine the level of oxidative stress and antioxidative response.In leaves, six isoforms of SOD were recognized. Roots possessed two additional bands, named manganese superoxide dismutase (MnSOD)-like form (MnSODI) and Cu/ZnSOD-like form (Cu/ZnSODIV). The H₂O₂ content in leaves ranged from 554 to 5 098 μmol H₂O₂/g f.w. and was negatively correlated with CAT activity. The non-contaminated population was characterized by the lowest CAT activity combined with the highest H₂O₂ concentration. Two isoforms of CAT, CAT-1 and CAT-2, were recognized in leaves of plants from non-contaminated and contaminated sites, respectively. In roots of individuals from two heaps (‘Warpie’ and ‘Saturn’), two distinct bands for each CAT isoform were observed. A slower migrating band may be an aggregate, exhibiting CAT and MnSODs activities. Both peroxidases (APX and GPX) presented the same pattern of activity, depending on the organ, indicating that in leaves and roots APX and GPX were regulated in parallel.Differences in enzyme activities and H₂O₂ content between plants from different contaminated sites were statistically significant, but were tightly maintained at a very similar level. Prolonged and permanent heavy metal stress evoked a very similar mode of antioxidative response in specimens of analyzed metalliferous populations not causing measurable oxidative stress. Thus, our results clearly indicate that V. tricolor is a taxon well adapted to heavy metal-contaminated soils, and that differences in enzyme activities and H₂O₂ content result from adjustment of plants to a variety of conditions.