The concentration of cadmium,lead, copper and zinc inChironomus gr.thummi larvae (Diptera,Chironomidae) with deformedversus normal menta

The concentrations of Cd, Pb, Cu and Zn inChironomus gr.thummi were determined for 4th instar larvae from the polluted Dyle River, tributary of the Scheldt River (Belgium). Comparison was made between larvae with deformed and normal menta. Deformed larvae showed higher overall metal concentrations than normal larvae. Especially Pb and Cu had higher concentrations in deformed larvae (16.22 mg kg^–1 dry weight and 39.66 respectively) than in normal larvae (12.80 mg kg^–1 dry weight and 35.70 respectively). No significant differences were found in the concentrations of Cd and Zn (mean [Cd] = 0.81 mg kg^–1 dry weight and mean [Zn] = 313.12 mg kg^–1 dry weight). There was no difference between the two larval groups as far as total length, dry weight and developmental stage of the imaginal discs are concerned.     

Effects of soil cadmium on Pinus sylvestris L. seedlings

The effects of Cd on the growth and distribution of Cd and mineral nutrients within plant tissues were investigated for Pinus sylvestris L. seedlings grown in mineral forest soil with increasing levels of Cd addition (0–100 mg kg^–1). Approximately 20% of added Cd was found to be extractable from sandy loam forest soil. Root growth was less affected by Cd than shoot growth, which showed a significant reduction in the 100 mg Cd kg^–1 treatment. Cadmium accumulated in roots up to 325 mg kg^–1. Decreased concentrations of K in needles and Ca in stems with increasing Cd levels suggest a disturbance of mineral nutrition as a result of Cd addition.     

Uptake of lead,cadmium and zinc by the fairy shrimp,Branchinecta longiantenna (Crustacea: Anostraca)

Individuals of the fairy shrimp, Branchinecta longiantenna, were subjected to 5 concentrations (0.1 to 15 mg l^–1) of Pb in diluted habitat water at 13 °C. Lead concentrations (mg kg^–1 wet weight) in the animals were determined at 2-day intervals by digestion in nitric acid followed by atomic absorption analysis. The shrimp were also subjected to 0.1 mg l^–1 media of Cd and Zn, separately.Uptake rates by the fairy shrimp for the three metal ions at 0.1 mg l^–1 were: 0.111, 0.0885, and 0.0460 mg kg^–1 day^–1 for Zn, Pb, and Cd, respectively. After 2 days in 1.0 mg l^–1 Cd or Zn, the animals expired; but they surviced for 8 days in a 10 mg l^–1 Pb medium and for 2 days in 25 mg l^–1 Pb. Lead uptake demonstrated a linear dependence on the Pb concentration in the media.Shrimp survived at much higher tissue accumulations of Pb compared to Zn and Cd. Estimated lethal doses were 20, 1.2–2.4, and 0.4–1.4 mg kg^–1 wet weight for Pb, Zn, and Cd, respectively. Pb was found to be at much lower concentration than Cd or Zn in the natural pond water but between Cd and Zn levels in the sediment. Thus Cd and Zn probably present a greater threat to B. longiantenna than Pb, although Pb may be in higher concentration in the environment.Contribution 47, Laboratory of Ecology, The Claremont Colleges, Claremont, CA 91711, USA. Send reprint requests to Clyde Eriksen.     

<Emphasis Type="Italic">Cannabis sativa</Emphasis> L. growing on heavy metal contaminated soil: growth,cadmium uptake and photosynthesis

The effects of different cadmium concentrations [17 mg(Cd) kg⁻¹(soil) and 72 mg(Cd) kg^{− 1}(soil)] on Cannabis sativa L. growth and photosynthesis were examined. Hemp roots showed a high tolerance to Cd, i.e. more than 800 mg(Cd) kg⁻¹(d.m.) in roots had no major effect on hemp growth, whereas in leaves and stems concentrations of 50 – 100 mg(Cd) kg⁻¹(d.m.) had a strong effect on plant viability and vitality. For control of heavy metal uptake and xylem loading in hemp roots, the soil pH plays a central role. Photosynthetic performance and regulation of light energy consumption were analysed using chlorophyll fluorescence analysis. Seasonal changes in photosynthetic performance were visible in control plants and plants growing on soil with 17 mg(Cd) kg⁻¹(soil). Energy distribution in photosystem 2 is regulated in low and high energy phases that allow optimal use of light and protect photosystem 2 from overexcitation, respectively. Photosynthesis and energy dissipation were negatively influenced by 72 mg(Cd) kg⁻¹(soil). Cd had detrimental effects on chlorophyll synthesis, water splitting apparatus, reaction centre, antenna and energy distribution of PS 2. Under moderate cadmium concentrations, i.e. 17 mg(Cd) kg⁻¹(soil), hemp could preserve growth as well as the photosynthesis apparatus, and long-term acclimation to chronically Cd stress occurred.     

Experimental and mathematical simulation of plant growth promoting rhizobacteria and plant interaction under cadmium stress

Bacterial inoculants of the commercially available plant growth promoting rhizobacteria (PGPR) Arthrobacter mysorens 7, Flavobacterium sp. L30, and Klebsiella mobilis CIAM 880 were selected to obtain ecologically safe barley crop production on cadmium (Cd) polluted soils. All the PGPR immobilized 24–68% soluble cadmium from soil suspension. A. mysorens 7 and K. mobilis CIAM 880 were highly resistant to Cd and grew in up to 1 and 3 mmol CdCl₂ on DAS medium respectively. All PGPR were able to fix nitrogen (276–1014 nmol mg^–1 bacterial DW) and to produce indole acetic acid (IAA) (126–330 nmol mg^–1 bacterial DW) or ethylene (4.6–13.5 nmol bacterial DW). All the PGPR actively colonized barley root system and rhizosphere and significantly stimulated root elongation of barley seedlings (up to 25%), growing on soil containing 5 or 15 mg Cd kg^–1 of soil. Created in the simulation mathematical model confirms our hypothesis that PGPR beneficial effect on barley growing under Cd-stress is a complex process. One of mechanisms underlying this effect might be increase of bacterial migration from rhizoplane to rhizosphere, where PGPR bind soluble free Cd ions in biologically unavailable complex forms. Among the studied PGPR K. mobilis CIAM 880 was the most effective inoculant. Inoculation with K. mobilis CIAM 880 of barley plants growing on Cd contaminated soil (5 mg Cd kg^–1 of soil) under field conditions increased by 120% grain yield and 2-fold decreased Cd content in barley grain. The results suggest that the using K. mobilis CIAM 880 is an effective way to increase the plant yield on poor and polluted areas.     

Impact of picolinic acid on the chromium accumulation in fodder radish and komatsuna

Effects of picolinic acid (2-pyridinecarboxylic acid) and chromium(III) picolinate was studied on the chromium (Cr) accumulation of fodder radish (Raphanus sativus L. convar. oleiformis Pers., cv. Leveles olajretek) and komatsuna (Brassica campestris L. subsp. napus f. et Thoms. var. komatsuna Makino, cv. Kuromaru ) grown in a pot experiment. Control cultures, grown in an uncontaminated soil (UCS; humous sand with pH_KCl 7.48, sand texture with 12.4% clay+silt content, organic carbon 0.56%, CaCO₃ 2.2%, CEC 6.2 cmol_c kg^–1, Cr 10.6 mg kg^–1), accumulated low amounts of chromium (less than 5.4 g g^–1) in their roots or shoots. When this UCS was artificially contaminated with 100 mg kg^–1 Cr (CrCl₃) later picolinic acid treatment promoted the translocation of chromium into the shoots of both species. In fodder radish shoots Cr concentration reached 30.4 g g^–1 and in komatsuna shoots 44.5 g g^–1. Application of ethylene diamine tetra-acetic acid (EDTA) to this Cr contaminated soil had similar effect to picolinic acid. When the UCS was amended with leather factory sewage sediment (which resulted in 853 mg kg^–1 Cr in soil), Cr mobilization was observed only after repeated soil picolinic acid applications. From a galvanic mud contaminated soil (brown forest soil with pH_KCl 6.77, loamy sand texture with 26.6% clay+silt content, organic carbon 1.23%, CaCO₃ 0.7%, CEC 24.5 cmol_c kg^–1, Cd 5.0 mg kg^–1, Cr 135 mg kg^–1, and Zn 360 mg kg^–1) the rate of Cr mobilization was negligible, only a slight increase was observed in Cr concentration of fodder radish shoots after repeated picolinic acid treatments of soil. Presumably picolinic acid forms a water soluble complex (chromium(III) picolinate) with Cr in the soil, which promotes translocation of this element (and also Cu) into the shoots of plants. The rate of complex formation may be related to the binding forms and/or concentration of Cr in soil and also to soil characteristics (i.e. pH, CEC), since the rate of Cr translocation was the following: artificially contaminated soil > leather factory sewage sediment amended soil > galvanic mud contaminated soil. Four times repeated 10 mg kg^–1 chromium(III) picolinate application to UCS multiplied the transport of chromium to shoots, as compared to single 10 mg kg^–1 CrCl₃ treatment. This also suggests that chromium(III) picolinate is forming in the picolinic acid treated Cr-contaminated soils, and plants more readily accumulates and translocates organically bound Cr than ionic Cr. Picolinic acid promotes Cr translocation in soil-plant system. This could be useful in phytoextraction (phytoremediation) of Cr contaminated soils or in the production of Cr enriched foodstuffs.     

Heavy metal and PCB contamination of Bryozoan colonies in the River Meuse (Belgium)

In the Meuse River (Liège area, Belgium), large amounts of three species of Bryozoans, Fredericella sultana (BLUM.), Plumatella emarginata ALL. and Plumatella fungosa (PALL.) occur. They cover 3 to 40% of the bank walls and their biomass ranges from 12 to 293 g m^–2 (dry weight). In the heated waters of a nuclear power plant (Tihange) and of industries lined up along the river, colony development occurs 3 to 4 weeks earlier than at an upstream station. The heavy metal content of living colonies ranges from 4 to 21 mg kg^–1 Cd, 45 to 182 mg kg^–1 Cu, 803 to 2232 mg kg^–1 Zn, 150 to 483 mg kg^–1 Pb and 21 to 138 mg kg^–1 Cr (DW). The mean concentration of PCBs was 925 µg kg^–1 (DW). Heavy metal and PCB concentrations in the sediments were close to those of colonies, suggesting that most of the pollutants found in the Bryozoans is in fact in the sediment trapped by the colonies.     

Absence of red-light enhancement of phototropism in pea seedlings at limiting irradiances of blue light

The effect of different light qualities (blue, green, white, red and far-red) on ethylene production in leaf discs and flower petal discs of Begonia × hiemalis cv. Schwabenland Red was studied. All the light qualities, except far-red, reduced the ACC-conversion to ethylene in leaf discs by about 70% at a photosynthetic photon flux density (PPFD) of 20 mol m^–2s^–1.Blue and green light were less inhibitory than white and red light at lower PPFD. In all treatments far-red light at 0.5 mol m^–2s^–1 of photon flux density (PFD) stimulated the ACC-conversion to ethylene in leaf discs by about 60–90% compared to the dark-incubated control. White and red light strongly inhibited the -naphthalene-acetic acid (NAA) stimulated ethylene synthesis in leaf discs. The results may suggest that the ethylene production is controlled by phytochrome in the leaves but not in the petals. Lack of coaction of any light quality with silver ions on ethylene production in leaf and petal discs was also observed.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - EFE ethylene forming enzyme - NAA -naphthalene-acetic acid - PFD photon flux density - PPFD photosynthetic photon flux density - RH relative air humidity - SAM S-adenosylmethionine - STS silver thiosulphate     

Soil washing of Pb, Zn and Cd using biodegradable chelator and permeable barriers and induced phytoextraction by Cannabis sativa

The feasibility of combined phytoextraction and in situ washing of soil contaminated with Pb (1750 mg kg^–1), Zn (1300 mg kg^–1), and Cd (7.2 mg kg^–1), induced by the addition of biodegradable chelator, [S,S] stereoisomere of ethylenediamine discuccinate ([S,S]-EDDS), was tested in soil columns with hemp (Cannabis sativa) as the phytoextracting plant. The addition of [S,S]-EDDS (10 mmol kg^–1 dry soil) yielded concentrations of 1026±442, 330.3±114.7 and 3.84±1.55 mg kg^–1 of Pb, Zn and Cd in the dry above-ground plant biomass, respectively. These concentrations were 1926, 7.5, and 11 times higher, respectively, compared to treatments with no chelator addition. Horizontal permeable barriers, composed of a 3 cm high layer of nutrient enriched sawdust and vermiculite mixture, and a 3 cm layer of soil, vermiculite and apatite mixture, were positioned 20, 30 and 40 cm deep in the soil. In chelator treatments, barriers placed 30 cm deep reduced leaching of Pb, Zn and Cd by 435, 4 and 53 times, respectively, compared to columns with no barrier, where 3.0, 4.3 and 3.3% of total initial Pb, Zn and Cd, respectively, was leached during 6-weeks water irrigation after chelator addition. Lower positioned barriers were almost equally effective in preventing leaching of Pb than barriers positioned closer to the soil surface, less effective for Cd, and did not prevent leaching of Zn. 2.53% of total initial Pb and 2.83% of Cd was washed from the contaminated soil and accumulated into the barrier. Combined method was less effective than simulated ex situ soil washing, where 14.2, 5.5 and 24.5% of Pb, Zn and Cd, respectively, were removed after 1-h extraction, but comparable effective to 48-h extraction. Abbreviations: BCF – bioconcentration factor; EDTA – ethylene diaminetetraacetate; HM – heavy metal; PP – phytoextraction potential; [S,S]-EDDS – [S,S]-ethylenediamine disuccinate.     

Measurement and modelling of photosynthetic response of pearl millet to soil phosphorus addition

There have been no studies of the effects of soil P deficiency on pearl millet (Pennisetum glaucum (L.) R. Br.) photosynthesis, despite the fact that P deficiency is the major constraint to pearl millet production in most regions of West Africa. Because current photosynthesis-based crop simulation models do not explicitly take into account P deficiency effects on leaf photosynthesis, they cannot predict millet growth without extensive calibration. We studied the effects of soil addition on leaf P content, photosynthetic rate (A), and whole-plant dry matter production (DM) of non-water-stressed, 28 d pearl millet plants grown in pots containing 6.00 kg of a P-deficient soil. As soil P addition increased from 0 to 155.2 mg P kg^–1 soil, leaf P content increased from 0.65 to 7.0 g kg^–1. Both A and DM had maximal values near 51.7 mg P kg^–1 soil, which corresponded to a leaf P content of 3.2 g kg^–1. Within this range of soil P addition, the slope of A plotted against stomatal conductance (g_s) tripled, and mean leaf internal CO₂ concentration ([CO₂]_i) decreased from 260 to 92 L L^–1, thus indicating that P deficiency limited A through metabolic dysfunction rather than stomatal regulation. Light response curves of A, which changed markedly with P leaf content, were modelled as a single substrate, Michaelis-Menten reaction, using quantum flux as the substrate for each level of soil P addition. An Eadie-Hofstee plot of light response data revealed that both K_M, which is mathematically equivalent to quantum efficiency, and V_max, which is the light-saturated rate of photosynthesis, increased sharply from leaf P contents of 0.6 to 3 g kg^–1, with peak values between 4 and 5 g P kg^–1. Polynomial equations relating K_M and V_max, to leaf P content offered a simple and attractive way of modelling photosynthetic light response for plants of different P status, but this approach is somewhat complicated by the decrease of leaf P content with ontogeny.     

Role of ethylene in alleviation of cadmium-induced photosynthetic capacity inhibition by sulphur in mustard

Sulphur (S) assimilation leads to the formation of glutathione (GSH) and alleviation of cadmium (Cd) stress. GSH is synthesized from its immediate metabolite cysteine, which also serves as a metabolite for ethylene formation through S‐adenosyl methionine. To assess the role of ethylene in S‐induced alleviation of Cd stress on photosynthesis, the effects of S or ethephon (ethylene source) on GSH and ethylene were examined in mustard (Brassica juncea L. cv. Varuna). Sufficient‐S at 100 mg S kg^?1 soil alleviated Cd‐induced photosynthetic inhibition more than excess‐S (200 mg S kg^?1 soil) via ethylene by increased GSH. Under Cd stress, plants were less sensitive to ethylene, despite high ethylene evolution, and showed photosynthetic inhibition. Ethylene sensitivity of plants increased with ethephon or sufficient‐S, triggering the induction of an antioxidant system, and leading to increased photosynthesis even under Cd stress. The effects of ethephon and S under Cd stress were similar. The effects of S were reversed by ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), suggesting that ethylene plays an important role in S‐induced alleviation of Cd stress on photosynthesis.     

Optimization of glycerol feeding for clavulanic acid production by Streptomyces clavuligerus with glycerol feeding

Glycerol at 10–20 g l^–1 increased clavulanic acid production by Streptomyces clavuligerus in shake-flask culture. The biosynthesis of clavulanic acid continued for longer by feeding glycerol and production increased to 250 mg l^–1 compared with 115 mg l^–1 without feeding. In fermenter batch culture, degradation of clavulanic acid began after 72 h. With glycerol feeding in fed-batch culture, clavulanic acid production was not only increased further to about 280 mg l^–1 but also remained stable up to 130 h.     

Headspace ethylene accumulation on Stizolobium hassjoo hairy root culture producing L-3,4-dihydroxyphenylalanine

The addition of 1-aminocyclopropane-1-carboxylic acid (ethylene precursor), or 2-chloroethylphosphonic acid (ethephon, an ethylene-releasing compound) decreased root dry weight and l-DOPA (l-3,4-dihydroxyphenylalanine) accumulation in hairy root cultures of Stizolobium hassjoo. The inhibition caused by ethephon-mediated ethylene release was alleviated by 0.5 mg CoCl₂ l^–1 as an inhibitor of ethylene biosynthesis. The action of ethylene was inhibited by 1.5 mg AgNO₃ l^–1. Ethylene thus lowers hairy root formation and l-DOPA production; CoCl₂ decreases ethylene formation leading to a considerably improved root dry weight and l-DOPA production.     

Multiple shoot induction and leaf and flower bud abscission of Annonacultures as affected by types of ventilation

Nodal explants of Annona squamosa L. and Annona muricata L. were cultured in vitro under various types of ventilation: airtight vessel (sealed condition; number of air exchange 0.1 h^–1), natural ventilation (via a polypropylene membrane; number of air exchange 1.5 h^–1), and forced ventilation (5.0 cm³ min^–1 in a 60 cm³ vessel; number of air exchange 5.0 h^–1). In both species, numbers of leaves, leaf areas and numbers of nodes per shoot increased with improving standards of ventilation, while leaf abscissions were substantially reduced; all the leaves had abscised in the airtight vessels after 12–15 days, but none had done so with forced ventilation. Flower-bud abscission in A. muricatashowed a similar trend after 21 days. These effects were associated with reductions in the accumulation of ethylene within the culture vessels, produced by increasing the efficiency of ventilation; ethylene was not detected in those fitted with a forced ventilation system. CO₂ concentrations in culture headspaces and the net photosynthetic rates of the plantlets were also evaluated. CO₂ concentrations decreased well below the ambient in the natural and airtight vessels; however, under forced ventilation, CO₂ concentrations were significantly higher during the photoperiod, compared to those of the natural ventilation and airtight vessel treatments. In general, net photosynthetic rates per unit leaf area increased with increasing photosynthetic photon flux (PPF) and rates were highest in plantlets grown under forced ventilation, intermediate under natural ventilation and lowest in the airtight vessels.Eighteen different media were investigated for their effects on multiple shoot induction in both species. The best medium for multiple shoot induction and growth in A. squamosa was Murashige and Skoog medium (MS) + 6-benzylaminopurine (BA; 1.5 mg l^–1) + casein hydrolysate (1.0 g l^–1) and for A. muricata MS + BA (1.0 mg l^–1) + naphthaleneacetic acid (NAA; 0.1 mg l^–1).     

Effects of Cd and Zn on the development of annual xylem rings of young Norway spruce (Picea abies) plants

Three-year-old spruce (Picea abies) saplings were planted and cultivated for 2 years in pots with 3 1 substrate, consisting of a homogenized mixture of sand, peat and forest soil with a high organic content (volume ratio 11.52). This substrate was amended with 10–180 mol Cd [kg soil dry weight (DW)]^–1, 50–7500 mol Zn (kg soil DW)^–1 (determined with 1 M ammonium acetate extracts) or combinations of both elements. Annual xylem growth rings in stems of plants treated with 50 mol Cd (kg soil DW)^–1 or 7500 mol Zn (kg soil DW)^–1 were significantly narrower than in control plants. Growth reductions were more pronounced in the second year of the experiment. The contents of Cd and Zn in stem wood and needles were positively correlated with the substrate concentrations. The Mg contents of the spruce needles were inversely correlated with soil concentrations of Cd and Zn. Root development was impeded at moderate concentrations of Cd (50 mol kg^–1) or Zn (1000 mol kg^–1) in the substrate. The adverse effects of potentially toxic trace elements, like Cd or Zn, on xylem growth of spruce plants are discussed with regard to possible growth reductions in forest trees under field conditions.     

Significance of the Leaf Area Ratio in Hevea brasiliensis Under High Irradiance and Low Temperature Stress

Adjustment in leaf area : mass ratio called leaf area ratio (LAR) is one of the strategies to optimize photon harvesting. LAR was recorded for 10 genotypes of Hevea brasiliensis under high irradiance and low temperature and the genotypes were categorized into two groups, i.e. high LAR and low LAR types. Simultaneously, the growth during summer as well as winter periods, photosynthetic characteristics, and in-vitro oxidative damage were studied. Low LAR (19.86±0.52 m² kg^–1) types, recorded an average of 18.0 % chlorophyll (Chl) degradation under high irradiance and 7.1 % Chl degradation under low temperature. These genotypes maintained significantly higher net photosynthetic rate (P _N) of 10.4 mol(CO₂) m^–2 s^–1 during winter season. On the contrary, the high LAR (24.33±0.27 m² kg^–1) types recorded significantly lower P _N of 4 mol(CO₂) m^–2 s^–1 and greater Chl degradation of 37.7 and 13.9 % under high irradiance and low temperature stress, respectively. Thus LAR may be one of the physiological traits, which are possibly involved in plant acclimation process under both stresses studied.     

Fatty acid production by heterotrophic Chlorella saccharophila

The fatty acid composition of the alga Chlorella saccharophila was investigated under different growth conditions. Using glucose as the sole carbon source, heterotrophically-grown Chlorella saccharophila produced a greater proportion of the polyunsaturated fatty acids (C18: 2 and C18: 3) than photosynthetic cultures, with linoleic acid (C18: 2) predominating. An unexpected discovery was the observation that at the lowest glucose concentration (2.5 gl^–1) the lipid content of the algae increased to between 36–47% of the cell weight, depending on the temperature. At glucose concentrations of 5 g l^–1 or more, the lipid content fell to 10–12% of the cell, although total fatty acid yield was higher due to higher biomass concentrations. Aeration of heterotrophic cultures promoted the production of unsaturated fatty acids compared to non-aerated cultures.     

Cellular responses to increasing Cd concentrations in the freshwater crab,<Emphasis Type="Italic"> Potamonautes warreni</Emphasis>, harbouring microbial gill infestations

We investigated the uptake, transport, storage and defence mechanisms in the freshwater crab, Potamonautes warreni, harbouring microbial gill infestations and exposed to increasing chronic (0.2, 0.5, 1.0 mg l^–1) and acute (2.0 mg l^–1) cadmium (Cd) concentrations under controlled laboratory conditions over a period of 21 days. Transmission electron microscopy and X-ray microanalysis revealed that the microbial gill fauna was eliminated on exposure to 0.2 mg Cd²⁺ l^–1 and that Cd became increasingly adsorbed and incorporated into lamellar crystal deposits and permeated the cuticle of the gills of P. warreni. Degeneration of the apical membrane infoldings and vacuolation of epithelial cells occurred concurrently with pinocytosis, endocytosis and pronounced phagocytotic activity in the epithelia and haemal canal of the gills. Elevated Cd exposures (0.5 or 1.0 mg l^–1) resulted in the swelling and dissociation of mitochondrial outer membranes together with an increase in transport of Cu, Cl and S by haemocytes in the haemal canal to epithelial tissues depleted in these elements. Cd also accumulated in tightly coiled concentric membrane whorls in the haemal canal, whereas the highest concentrations of Cd were found within aggregates of lysosome-like bodies in cuticulin-secreting cells of the gill stem. Chronic exposure to Cd induced increased fatigue and mild uncoordinated motor activity. In contrast, at an acute exposure of 2.0 mg l^–1 over 48 h, P. warreni showed a time-specific rapid loss of motor function, although only mild cellular lesions occurred in the gill tissues. The significance of cellular changes in the gill epithelia and altered motor activity of P. warreni with increased waterborne Cd are discussed as potential biomarker responses in monitoring aquatic pollution.     

铊和镉胁迫对芦竹生长及光合特征的影响

芦竹(Arundo donax)对多种重金属都有较好的耐受性,是植物修复技术较理想的选择,而关于芦竹对Cd和Tl胁迫生理反应的相关研究却较少,为了有效治理Cd和Tl的污染,本研究以芦竹为材料,通过添加不同浓度重金属Tl(4,10和20 mg·kg~(-1))、Cd(50,100和200 mg·kg~(-1))进行芦竹盆栽试验,测定芦竹的株高、分蘖数、叶绿素含量、光合生理指标以及Tl和Cd在芦竹中的累积量,探讨芦竹对Tl和Cd胁迫的响应机制。结果表明:Tl(4~20 mg·kg~(-1))和Cd(50~200 mg·kg~(-1))对芦竹株高、分蘖数以及叶绿素含量均无显著影响(P0.05);芦竹体内Tl和Cd含量随着Tl和Cd浓度的升高呈上升趋势,芦竹体内Tl含量的分布规律为根茎叶,Cd含量的分布规律:Cd浓度50 mg·kg~(-1)时为茎叶根,Cd浓度100和200 mg·kg~(-1)时为根茎叶,表明Tl和Cd主要分布在根部,芦竹对Tl、Cd有一定的富集能力。Cd和Tl处理均显著降低芦竹叶片的胞间CO2浓度,在Tl浓度为10 mg·kg~(-1)时,净光合速率、气孔导度和蒸腾速率得到显著提高,当Cd浓度为50 mg·kg~(-1)时,净光合速率、气孔导度和蒸腾速率得到显著提高。这表明芦竹对重金属Cd和Tl有较强的耐受性,可为Cd和Tl污染土壤的治理和修复提供参考。     

Fungal biotransformation of p-coumaric acid into caffeic acid by Pycnoporus cinnabarinus: an alternative for producing a strong natural antioxidant

Fungal biotransformation of p-coumaric acid into caffeic acid, potentially a strong antioxidant, was evidenced in Pycnoporus cinnabarinus cultures grown with high feeding of p-coumaric acid. Preliminary experiments showed no toxicity of both p-coumaric and caffeic acids at concentrations ranging from 0 to 500 mg l^–1. Feeding 450 mg p-coumaric acid l^–1 into P. cinnabarinus cultures grown on 20 g l^–1 glucose medium resulted in the production of 257 mg caffeic acid l^–1with a molar yield of 21%.