Water status and water diffusion transport in lupine roots exposed to lead

Water status and diffusion transport were studied in the roots of yellow lupine (Lupinus luteus L., cv. Juno) treated for 48 h with two selected concentrations of Pb(NO₃)₂: 150 mg l⁻¹, which inhibited root growth by about 50% (medium stress intensity), as well as 350 mg l⁻¹, which almost entirely suppressed root elongation (severe stress intensity). Relative water content (RWC), which characterizes the degree of root water saturation, slightly increased at the lower lead concentration and remained unchanged at the higher lead dose. Ultrastructure analyses under a transmission electron microscope revealed that plasmolysis was not evoked by lead in the apical part of the meristem. Moreover, direct observation of meristem cells using Nomarsky optics indicated enhanced vacuolization in the presence of both lead concentrations. These data suggest that the water status of the roots was not affected by the metal. Due to the fact that proline is involved in the maintenance of turgor in the cells, the metabolism of this amino acid was investigated. In the roots, the activity of enzymes involved in proline synthesis, such as pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT), increased at 150 mg l⁻¹ Pb²⁺; nevertheless, proline content was diminished at the lower lead concentration. This effect is likely the result of proline degradation by proline dehydrogenase (PDH), since the activity of this enzyme increased at the lower lead dose. On the other hand, in the presence of 350 mg l⁻¹ Pb²⁺, a low level of proline was correlated with a decrease in the activity of P5CS and OAT, as well as unchanged PDH activity in lupine roots. These data may imply that enzymatic synthesis of proline was strongly damaged by the metal ions. The low level of proline in both experimental variants suggests that proline accumulation is inessential to maintaining the osmotic uptake of water into root cells. NMR spectroscopy showed that exposition of lupine seedlings to lead caused a deceleration in water transport in the roots due to a reduction in the water transfer rate across the membranes (transmembrane transfer) and vacuoles continuum, as well as water diffusion along the root apoplast. Fluorescence staining and immunogold labeling showed the presence of callose strands in cell walls and/or in the vicinity of them. In lead-treated lupine roots, callose was mainly localized in the parenchyma cortex placed lengthwise to the vascular cylinder. Callose deposits in the cell walls may reduce vacuolar transport, as well as increase cell wall resistance to water flow. Deceleration of diffusional water movement to the vascular system, may in turn, influence the rate of long-distance water transport to aerial parts of the plant.     

Influence of slope on root system anchorage of Pinus yunnanensis

In southwestern China, Yunnan pines (Pinus yunnanensis) have been extensively cultivated on barren hills for reforestation and ecological engineering. The objective of this work is to study the influences of slope gradient on anchorage of root systems of P. yunnanensis. Pulling experiments were carried out at low (5–6°), moderate (25–26°) and high gradient (42–43°) by using selected 15-year-old P. yunnanensis. The results showed that the anchorage resistances induced by the slope gradient were significantly (P < 0.01) different from each other and followed in the order of high slope > moderate slope > low slope. Anchorage strength of upslope-grown roots increased with size and length of first-order lateral roots as well as the number of second-order lateral roots. Contributions of upslope-grown roots for preventing plants from overturning varied considerably between those from different slopes. The contribution of roots growing on upslope side on high slope to the anchorage of root system reached 50%, whereas those on moderate and low slopes were about 44% and 37%, respectively. It was concluded that the anchorage resistance was closely related to slope gradient and root distribution, while upslope-grown roots were positively related to anchorage resistance.     

Promotion of Salvia miltiorrhiza hairy root growth and tanshinone production by polysaccharide–protein fractions of plant growth-promoting rhizobacterium Bacillus cereus

This study was to examine the effects of polysaccharides from a plant growth-promoting rhizobacterium (PGPR) Bacillus cereus on the growth and tanshinone production of Salvia miltiorrhiza hairy roots. A polysaccharide fraction designated BPS was isolated from the hot water extract of B. cereus cells by ethanol precipitation. BPS applied to the root culture at 100–400 mg l⁻¹ a few days before the stationary growth phase stimulated the tanshinone accumulation of roots by about 7-fold (1.59 mg g⁻¹ versus 0.19 mg g⁻¹) and also notably promoted the root growth (15% increase in biomass). BPS was a polysaccharide–protein complex containing about 27% protein, which is essential for root growth promotion. BPS was separated by ultrafiltration into two molecular weight (MW) fractions, of which the high MW fraction (∼35.8 kDa) with higher protein content (∼31%) promoted the root growth while the lower MW fraction with lower protein content (∼17%) suppressed the growth. The results suggest that the polysaccharide portion of BPS was responsible for stimulating the tanshinone accumulation while the protein portion was responsible for promoting the hairy root growth. Polysaccharides from PGPR are potential sources of active elicitors and growth-promoting agents for plant roots in culture.     

Iron availability alters ascorbate-induced stress metabolism in Glehnia littoralis root cultures

Our previous study indicated that formation of furanocoumarin phytoalexins could be induced in Glehnia littoralis root cultures by treatment with 10–40 mM ascorbic acid (AsA). This furanocoumarin production is much less evident when G. littoralis roots are treated with AsA under iron-deficient conditions. Instead, two large unknown peaks appeared in the HPLC chromatogram, whose chemical structures were elucidated by spectroscopic methods as being 6, β-dihydroxyphenethyl ferulate (DF) and 6-hydroxyphenethyl ferulate (HF), respectively. Their maximal level of induction was observed at 20 mM AsA, and the production of DF always exceeded that of HF. This is the first report of these compounds in G. littoralis and of the modulation of the phytoalexin biosynthetic pathway in G. littoralis by iron deficiency.     

Cadmium distribution and its effects on molybdate-containing hydroxylases in Phragmites australis

The influence of cadmium (Cd) on physiological and biochemical parameters was studied to elucidate the mechanism of Cd resistance in Phragmites australis. Cadmium concentrations in roots, stems and leaves increased with exogenous Cd concentration, but Cd content in roots was much higher than in shoots. X-ray microanalysis was used to reveal compartments in which Cd accumulated in root cortex. Cadmium concentrations followed a gradient with the sequence: intercellular space > cell wall > vacuole > cytoplasm, indicating that most Cd was immobilized in the apoplast or sequestered into the vacuolar lumen. Sequential extraction of various Cd chelates revealed that more than half of extractable Cd was bound to proteins, whereas 26% was bound to organic acids. Cd-binding protein fractions were found in the roots after gel filtration chromatography, among which a polypeptide with an apparent molecular mass of 14 kDa bound Cd most avidly. One newly synthesized polypeptide of low molecular mass (1 kDa) appeared under Cd pollution, whereas a prominent fraction of 72 kDa disappeared. Four aldehyde oxidase (AO) isoenzyme activities increased significantly in roots under Cd pollution. Cd stress also enhanced xanthine dehydrogenase (XDH) activities in roots. Two AO polypeptides of different molecular sizes were detected in the roots by Western blot assay. The abundance of the 160 kDa subunit correlated with Cd stress, but the amount of the 90 kDa polypeptide did not change under Cd treatment. Enhanced abscisic acid (ABA) contents were observed in roots of P. australis exposed to Cd. The involvement of Cd distribution in plant tissues and subcellular compartments and of AO and XDH enzymatic activities in the acclimation mechanism of P. australis to Cd pollution is discussed herein.     

Thymoquinone causes multiple effects,including cell death,on dividing plant cells

Thymoquinone (TQ) is a major constituent of Nigella sativa oil with reported anti-oxidative activity and anti-inflammatory activity in animal cells. It also inhibits proliferation and induces programmed cell death (apoptosis) in human skin cancer cells. The present study sought to detect the influence of TQ on dividing cells of three plant systems and on expression of Bcl2-associated athanogene-like (BAG-like) genes that might be involved during the process of cell death. BAG genes are known for the regulation of diverse physiological processes in animals, including apoptosis, tumorigenesis, stress responses, and cell division. Synthetic TQ at 0.1 mg/mL greatly reduced wheat seed germination rate, whereas 0.2 mg/mL completely inhibited germination. An Evans blue assay revealed moderate cell death in the meristematic zone of Glycine max roots after 1 h of TQ treatment (0.2 mg/mL), with severe cell death occurring in this zone after 2 h of treatment. Light microscopy of TQ-treated (0.2 mg/mL) onion hairy root tips for 1 h revealed anti-mitotic activity and also cell death-associated changes, including nuclear membrane disruption and nuclear fragmentation. Transmission electron microscopy of TQ-treated cells (0.2 mg/mL) for 1 h revealed shrinkage of the plasma membrane, leakage of cell lysate, degradation of cell walls, enlargement of vacuoles and condensation of nuclei. Expression of one BAG-like gene, previously associated with cell death, was induced 20 min after TQ treatment in Glycine max root tip cells. Thus, TQ has multiple effects, including cell death, on dividing plant cells and plants may serve as a useful system to further investigate the mechanisms underlying the response of eukaryotic cells to TQ.     

Tolerance,accumulation and distribution of zinc and cadmium in hyperaccumulator Potentilla griffithii

In this study, zinc (Zn) and cadmium (Cd) tolerance, accumulation and distribution was conducted in Potentilla griffithii H., which has been identified as a new Zn hyperaccumulator found in China. Plants were grown hydroponically with different levels of Zn²⁺ (20, 40, 80 and 160 mg L^?1) and Cd²⁺ (5, 10, 20 and 40 mg L^?1) for 60 days. All plants grew healthy and attained more biomass than the control, except 40 mg L^?1 Cd treatment. Zn or Cd concentration in plants increased steadily with the increasing addition of Zn or Cd in solution. The maximum metal concentrations in roots, petioles and leaves were 14,060, 19,600 and 11,400 mg kg^?1 Zn dry weight (DW) at 160 mg L^?1 Zn treatment, and 9098, 3077 and 852 mg kg^?1 Cd DW at 40 mg L^?1 Cd treatment, respectively. These results suggest that P. griffithii has a high ability to tolerate and accumulate Cd and Zn, and it can be considered not only as Zn but also as a potential cadmium hyperaccumulator. Light microscope (LM) with histochemical method, scanning electron microscope combined with energy dispersive spectrometry (SEM-EDS) and transmission electron microscope (TEM) were used to determine the distribution of Zn and Cd in P. griffithii at tissue and cellular levels. In roots, SEM-EDS confirmed that the highest Zn concentration was found in xylem parenchyma cells and epidermal cells, while for Cd, a gradient was observed with the highest Cd concentration in rhizodermal and cortex cells, followed by central cylinder. LM results showed that Zn and Cd distributed mainly along the walls of epidermis, cortex, endodermis and some xylem parenchyma. In leaves, Zn and Cd shared the similar distribution pattern, and both were mostly accumulated in epidermis and bundle sheath. However, in leaves of 40 mg L^?1 Cd treatment, which caused the phytotoxicity, Cd was also found in the mesophyll cells. The major storage site for Zn and Cd in leaves of P. griffithii was vacuoles, to a lesser extent cell wall or cytosol. The present study demonstrates that the predominant sequestration of Zn and Cd in cell walls of roots and in vacuoles of epidermis and bundle sheath of leaves may play a major role in strong tolerance and hyperaccumulation of Zn and Cd in P. griffithii.     

Differential tolerance to combined salinity and O2 deficiency in the halophytic grasses Puccinellia ciliata and Thinopyrum ponticum: The importance of K+ retention in roots

Saline environments of terrestrial halophytes are often prone to waterlogging, yet the effects on halophytes of combined salinity and waterlogging have rarely been studied. Either salinity or hypoxia (low O₂) alone can interfere with K⁺ homeostasis, therefore the combination of salinity or hypoxia is expected to impact significantly on K⁺ retention in roots. We studied mechanisms of tolerance to the interaction of salinity with hypoxia in Puccinellia ciliata and Thinopyrum ponticum, halophytic grasses that differ in waterlogging tolerance. Plants were exposed to aerated and stagnant saline (250 mM NaCl) treatments with low (0.25 mM) and high (4 mM) K⁺ levels; growth, net ion fluxes and tissue ion concentrations were determined. P. ciliata was more tolerant than T. ponticum to stagnant-saline treatment, producing twice the biomass of adventitious roots, which accumulated high levels of Na⁺, and had lower shoot Na⁺. After 24 h of saline hypoxic treatment, MIFE measurements revealed a net uptake of K⁺ (∼40 nmol m⁻² s⁻¹) for P. ciliata, but a net loss of K⁺ (∼20 nmol m⁻² s⁻¹) for the more waterlogging sensitive T. ponticum. NaCl alone induced K⁺ efflux from roots of both species, with channel blocker tests implicating GORK-like channels. P. ciliata had constitutively a more negative root cell membrane potential than T. ponticum (−150 versus −115 mV). Tolerance to salinity and hypoxia in P. ciliata is related to increased production of adventitious roots, regulation of shoot K⁺/Na⁺, and a superior ability to maintain negative membrane potential in root cells, resulting in greater retention of K⁺.     

Short-time response in root morphology of Vallisneria natans to sediment type and water-column nutrient

Rooted submerged macrophytes can absorb significant amounts of nutrients from both sediment and water. We investigated root morphology of Vallisneria natans in mesocosm plastic bins, in response to three types of sediment (sandy loam, clay, and a 50:50 (v/v) mixture of the two sediments) and two levels of water-column nutrient (well water and nutrient medium). Compared to the plants grown in the clay or mixed sediments, root diameter decreased (0.39–0.41 versus 0.36–0.37 mm) but total root length per plant increased (0.87–1.27 versus 1.14–1.62 m) when grown in sandy loam. Increase of nutrient availability in water column led to decreased specific root length (306–339 versus 258–281 m g⁻¹). However, both sediment type and water-column nutrient had no impacts on root number (ranged from 19 to 24 number of roots per plant). Root weight ratio, root:leaf mass ratio and root:leaf length ratio generally decreased with enhanced nutrient availability in sediment or water. Plant growth was affected by sediment type alone (P < 0.05), rather than water-column nutrient (P > 0.05). However, plant N and P contents were significantly impacted by both sediment type (P ≤ 0.001) and water-column nutrient (P < 0.05). Increase of nutrient availability in sediment or water led to increased plant N (ranged from 2.47 to 4.77 mg g⁻¹) and P concentrations (ranged from 42.8 to 62.0 mg g⁻¹). These results indicate that considerable variation in root morphology of V. natans exists in response to the fertility of the sediment it is rooted in.     

Expression of serine proteases in egg-parasitic nematophagous fungi during barley root colonization

Nematophagous fungi Pochonia chlamydosporia and P. rubescens colonize endophytically barley roots. During nematode infection, serine proteases are secreted. We have investigated whether such proteases are also produced during root colonization. Polyclonal antibodies against serine protease P32 of P. rubescens cross-reacted with a related protease (VCP1) of P. chlamydosporia, but not with barley proteases. These antibodies also detected an unknown ca. 65-kDa protein, labeled hyphae and appressoria of P. chlamydosporia and strongly reduced proteolytic activity of extracts from fungus-colonized roots. Mass spectrometry (MS) of 32-kDa protein bands detected peptides homologous to VCP1 only in Pochonia-colonized roots. Peptides homologous to barley serine carboxypeptidases were found in 65 kDa bands of all roots. RT-PCR detected expression of VCP1 and a new P. chlamydosporia serine carboxypeptidase (SCP1) genes only in fungus-colonized roots. SCP1 shared limited sequence homology with VCP1 and P32. Expression in roots of proteases from nematophagous fungi could be greatly relevant for nematode biocontrol.     

The impact of heavy metals on the activity of some enzymes along the barley root

Barley seedlings 48 h after the onset of germination on filter paper treated for 24 h by 1 mM cadmium (Cd), 3 mM nickel (Ni) or 0.5 mM mercury (Hg) showed similar approximately 45% root growth inhibition. Although root growth inhibition was similar, loss of cell viability evaluated, as Evans blue uptake was distinct among Cd, Ni and Hg treated roots. While Cd and Hg caused cell death along the whole barley root (0–8 mm), Ni induced significant loss of cell viability only in root cells 6–8 mm distance from the root tip. Our results suggest that different metabolic processes are activated in different parts of barley root in relation to distance from the root tip during heavy metal (HM) treatment. Some of them are characteristic for several HMs such as inhibition of ascorbic acid oxidase or glutathione-S-transferase stimulation, while others are specific for individual HMs, e.g. activation of acid phosphatase and lipoxygenase by Cd and Hg, or inhibition of ascorbate peroxidase by Ni and Hg treatment.     

Response of Vicia faba L. to metal toxicity on mine tailing substrate: Geochemical and morphological changes in leaf and root

Vicia faba L. seeds were grown in a pot experiment on soil, mine tailings, and a mixture of both to mimic field situations in cultivated contaminated areas near mining sites. Metals in the substrates and their translocation in root, stem and leaf tissues were investigated, including morphological responses of plants growing on mine tailings. Metal concentration – and generally bioaccumulation – was in the order: roots > leaves > stems, except Pb and Cd. Translocation was most significant for Zn and Cd, but limited for Pb. Metal concentration in root and leaf was not proportional to that in the substrates, unexpectedly the minimum being observed in the mixed substrate whilst plant growth was retarded by 20% (38% on tailings). Calcium, pH, organic matter and phosphorus were the main influencing factors for metal translocation. The ultrastructure of V. faba L. cells changed a lot in the mine tailings group: root cell walls were thickened with electron dense Pb, Zn and C particles; in chloroplasts, the number of plastoglobuli increased, whereas the thylakoids were swollen and their number decreased in grana. Finally, needle-shaped crystalline concretions made of Ca and P, with Zn content, were formed in the apoplast of the plants. The stratagems of V. faba L. undergoing high concentrations of toxic metals in carbonate substrate, suggest root cell wall thickening to decrease uptake of toxic metals, a possible control of metal transport from roots to leaves by synthesizing phytochelators–toxic metal complexes, and finally a control of exceeded Ca and metal concentration in leaves by crystal P formation as ultimate response to stress defense. The geochemical factors influencing metal availability, guaranty a reduction of metal content in plant growing on mixed tailing/soil substrate as far as carbonate are not completely dissolved.     

Segmental distribution in potentials of lateral root budding and oxygen uptake of plant hairy roots

The positional distributions in potential of lateral root budding and oxygen uptake rate were examined using the segments of madder and horseradish hairy roots with a length of 5.0×10⁻³ m obtained at different mean distances from the root tips of l=7.5×10⁻³–47.5×10⁻³ m. The average rate of lateral root budding and oxygen uptake rate of the roots with smaller l values were higher and both the rates gradually decreased with increase in l value. Positive relations were observed between the rates of lateral root budding and oxygen uptake of both the hairy roots. The relation indicated that the potential of lateral root budding was suppressed at the oxygen uptake rates of 0.15×10⁻⁵ and 0.32×10⁻⁵ mol O₂/(h m) for madder and horseradish hairy roots, respectively.     

Avocado roots treated with salicylic acid produce phenol-2,4-bis (1,1-dimethylethyl), a compound with antifungal activity

We demonstrated the ability of salicylic acid (SA) to induce a compound in avocado roots that strengthens their defense against Phytophthora cinnamomi. The SA content of avocado roots, before and after the application of exogenous SA, was determined by High-Performance Liquid Chromatography (HPLC). After 4 h of SA feeding, the endogenous level in the roots increased to 223 μg g⁻¹ FW, which was 15 times the amount found in control roots. The methanolic extract obtained from SA-treated avocado roots inhibited the radial growth of P. cinnamomi. A thin layer chromatographic bioassay with the methanolic extract and spores of Aspergillus showed a distinct inhibition zone. The compound responsible for the inhibition was identified as phenol-2,4-bis (1,1-dimethylethyl) by gas chromatography and mass spectrometry. At a concentration of 100 μg/mL, the substance reduced germinative tube length in Aspergillus and radial growth of P. cinnamomi. A commercial preparation of phenol-2,4-bis (1,1-dimethylethyl) caused the same effects on mycelium morphology and radial growth as our isolate, confirming the presence of this compound in the root extracts. This is the first report of the induction of this compound in plants by SA, and the results suggest that it plays an important role in the defense response of avocado.     

Nitric oxide protects sour pummelo (Citrus grandis) seedlings against aluminum-induced inhibition of growth and photosynthesis

Limited data are available on the amelioration of nitric oxide (NO) on aluminum (Al)-toxicity. Sour pummelo (Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 0 and 1.2 mM AlCl₃·6H₂O × 0 and 10 μM sodium nitroprusside (SNP, an NO donor). Under Al stress, SNP increased root phosphorus (P) and Al, but decreased shoot Al. Al decreased photosynthesis, maximum quantum yield of primary photochemistry (F_v/F_m) and total performance index (PI_tot,sbs), but increased inactivation of oxygen-evolving complex (OEC), K-band and relative variable fluorescence at I-steps (V_I). SNP alleviated Al-induced changes for all these parameters. SNP stimulated Al-induced secretion of malate and citrate by excised roots from Al-treated seedlings, while Al did not increase their contents in roots. Antioxidant system in leaves and roots was up- and down-regulated by Al, respectively. SNP prevented Al-induced accumulation of malondialdehyde (MDA) in roots and leaves. In conclusion, SNP alleviates Al-induced inhibition of growth and impairment of the whole photosynthetic electron transport chain. This occurs through increasing Al-immobilization and P level in roots and Al-induced secretion of malate and citrate from roots, and decreasing Al accumulation in shoots. Thus, the decrease of photosynthesis is prevented. Increased P level and Al-immobilization in roots through SNP may be effected through enhanced secretion of malate and citrate.     

Alginate embedding and subsequent sporulation of in vitro-produced Conidiobolus thromboides hyphae using a pressurised air-extrusion method

Conidiobolus thromboides is an entomophthoralean fungus with potential as a biological control agent of aphids. However, its application in biological control is limited due to its formulation requirements. The objective of this study was to develop and optimise a novel air-extrusion method to embed C. thromboides hyphae at high density in alginate pellets. An orthogonal experimental design was used to investigate selected combinations of parameters known to affect hyphal density within pellets. The diameter of pellets produced, and the calculated density of hyphae within them, ranged from 0.18 ± 0.09 to 3.17 ± 0.06 mm and from 0.02 to 350.56 mg/mm³ respectively. These data were used to predict the optimal parameter combination to deliver the greatest density of hyphae of C. thromboides per pellet: 1% sodium alginate, a 1:2 ratio of hyphae to sodium alginate, an orifice diameter of 0.232 mm and an air pressure of 0.05 MPa. Pellets made under the optimal conditions predicted produced a mean total of 4.3 ± 0.6 × 10⁵ conidia per pellet at 100% relative humidity which was significantly greater than the mean total number of conidia produced from infected aphid cadavers of comparable size (9.35 ± 0.85 × 10⁴) (p < 0.001). In conclusion, air-extrusion embedding appears to be a promising method for formulating in vitro-produced hyphae of C. thromboides for use in biological control.     

Cadmium uptake by roots: Contribution of apoplast and of high- and low-affinity membrane transport systems

The aim was to measure the respective contributions of apoplast and symplast to the Cd root uptake and to explain the linear component of the symplastic absorption. Two plants were used, maize (Zea mays L.) and two ecotypes of alpine pennycress (Noccaea caerulescens (J. Presl & C. Presl) F.K. Mey.), with contrasted abilities to accumulate Cd. Their roots were exposed to labelled Cd solutions of increasing concentrations. Root Cd was physico-chemically fractioned to obtain the exchanged apoplastic, non-exchanged apoplastic and symplastic pools. For both species, the proportion of Cd retained by the cell walls increased with Cd concentration in the exposure solution (ranging from 0.05 to 50 μmol L^?1), from approximately 30% to 90% of the total root Cd. This was modeled using Freundlich isotherms. The non-exchanged apoplastic Cd was negligible at the highest exposure concentrations, but reached almost 30% of the total root uptake at the lowest ones. The symplastic influx in roots of both species fitted a Michaelis-Menten function associated with a linear one. The linear component of the symplastic influx could reflect absorption through a low-affinity transport system (LATS). The strong adsorption of Cd on root apoplast might act as a driving force to extract the metal from the soil, compete with the symplastic absorption and contribute to the amount of element taken up by the plant, at least in its roots.     

Elevation in liver enzymes is associated with increased IL-2 and predicts severe outcomes in clinically apparent dengue virus infection

The objective of the present study was to assess the circulating TNF-α and IL-2 levels in dengue virus (DENV) infected patients and to correlate these with clinical severity of DENV infections. A single analyte quantitative immunoassay was used to detect TNF-α and IL-2 in 24 dengue fever (DF) and 43 dengue haemorrhagic fever (DHF) patients, 15 healthy adults and 6 typhoid patients. The mean TNF-α and IL-2 levels of DENV- infected patients were higher than that of healthy adults and typhoid patients. No significant difference in TNF-α levels was noted between DF and DHF patients (p = 0.5) but a significant increase in IL-2 levels was observed in DHF compared with DF patients (mean of DF = 59.7 pg/mL, mean of DHF = 166.9 pg/mL; p = 0.02). No significant association of TNF-α or IL-2 levels was noted with packed cell volume (>45), thrombocytopenia, leucopenia or the presence of viraemia. The liver function tests measuring AST (aspartate aminotransferase) (p = 0.01) and ALT (alanine aminotransferase) (p = 0.02) levels were significantly elevated in DENV-infected patients. AST:ALT was significantly elevated in DHF/DSS (dengue shock syndrome) compared with DF patients. A significant positive linear correlation was noted between AST and IL-2 (r = 0.31; p = 0.01) and ALT and IL-2 elevations (r = 0.2; p = 0.02). Thus, AST and ALT levels correlate with both disease severity and circulating IL-2 levels. We suggest a role for circulating IL-2 in liver dysfunction and propose that a combined assessment of AST/ALT in conjunction with IL-2 at the early stages of symptomatic DENV infection may be useful to predict the severe forms of dengue.     

Subcellular distribution and chemical forms of cadmium in Bechmeria nivea (L.) Gaud.

Bechmeria nivea (L.) Gaud. (Ramie) is a promising species for Cd phytoextraction with large biomass and fast growth rate. Nevertheless, little information is available on its tolerance mechanisms towards Cd. Determination of Cd distribution and chemical speciation in ramie is essential for understanding the mechanisms involved in Cd accumulation, transportation and detoxification. In the present study, ramie plants were grown in hydroponics with increasing Cd concentrations (0, 1, 3, 7 mg l^?1). The subcellular distribution and chemical forms of Cd in different tissues were determined after 20 days exposure to this metal. To assess the effect of Cd uptake on plant performance, nitrate reductase activity in leaves and root activity were analyzed during the entire experimental period. Increased Cd level in the medium caused a proportional increase in Cd uptake, and the highest Cd concentration occurred in roots, followed by stems and leaves. Subcellular fractionation of Cd-containing tissues indicated that about 48.2–61.9% of the element was localized in cell walls and 30.2–38.1% in soluble fraction, and the lowest in cellular organelles. Cd taken up by ramie rapidly equilibrated among different chemical forms. Results showed that the greatest amount of Cd was found in the extraction of 1 M NaCl and 2% HAC, and the least in residues in all test tissues. In roots, the subdominant amount of Cd was extracted by d-H₂O and 80% ethanol, followed by 0.6 M HCl. While in stems and leaves, the amount of 0.6 M HCl-extractable Cd was comparable with that extracted by 80% ethanol or d-H₂O. 1 mg l^?1 Cd stimulated nitrate reductase activity in leaves and root activity, while a concentration-dependent inhibitory effect was observed with increasing Cd concentration, particularly at 7 mg l^?1 Cd. It could be suggested that the protective mechanisms evolved by ramie play an important role in Cd detoxification at relatively low Cd concentrations (below 3 mg l^?1 Cd) but become restricted to maintain internal homeostasis with higher Cd stress.     

Response in root morphology and nutrient contents of Myriophyllum spicatum to sediment type

Sediment may play an important role during the submerged macrophyte decline in the eutrophication progress. In order to investigate the response in root morphology and nutrient contents of submerged macrophytes Myriophyllum spicatum to sediment, five sediment types were treated and used (five types of sediment were used in the experiment: treatment 1 was nature sediment + sand, a 50:50 (v/v) mixture, treatment 2 was the studied sediment only, treatment 3 was sediment + nitrogen (N, NH₄Cl 400 mg kg^?1), treatment 4 was sediment + phosphorus (P, NaH₂PO₄ 300 mg kg^?1); treatment 5 was sediment + phosphorus (P, NaH₂PO₄ 600 mg kg^?1)). The results show that the root N content was only significantly affected by adding N in sediments and P was elevated by adding N and P. The root mass and its percentage increased at first, the peak values were reached at 35 d, and then decreased. The root growth was restrained by adding sand and N in sediments, root senescence process was delayed at the later experimental time by adding P in sediments. The increase of root volume showed a similar trend to that of root growth, except for plant with P addition where root volume remained high after 35 d. The root volume decreased while the main root number increased significantly by adding sand in sediments. The mean root length and main root diameter were reduced by adding P in sediments. The compatible sediment nutrient condition is necessary to restore submerged macrophytes in a degraded shallow lake ecosystem, and the effect of sediment on the root morphology and nutrient content is one of the important aspects restricting the restoration of submerged macrophytes.