Microbiological Quality and Antibiotic Resistance Analysis of a Brazilian Water Supply Source

Water samples of the Passaúna River, Curitiba/Paraná (Brazil), were analyzed to determine total and thermotolerant coliform counts and Escherichia coli in order to provide information on human impacts on the water supply. Samples were collected and analyzed monthly, from March 2006 to February 2007, at five different locations along the river, and the multiple tube method was used to obtain total and thermotolerant coliform counts. The results varied from 130 MPN/100 mL to 1.6?×?10⁶ MPN/100 mL for total coliforms, while for thermotolerant coliforms the variation was between 40 MPN/100 mL and 5?×?10⁵ MPN/100 mL. The E. coli strains isolated from the samples were tested with 13 different antibiotics to determine their antibiotic resistance. The isolated strains were constantly sensitive to seven of the 13 antibiotics tested, and resistant to at least one of the other antibiotics. The results indicated that two factors could influence the increased contamination on this river, viz., seasonality parameters and domestic wastewater discharges. The determination of antibiotic resistance indices aimed to provide information on the anthropogenic influence. Only one of the locations investigated was considered critical due to the anthropogenic influence, with significant impacts from irregular domestic wastewater discharges.     

Prolonged survival of an environmental Escherchia coli in laboratory soil microcosms

The survival, persistence, and dispersal of bacteria in soil raises serious water quality questions for rural areas of the world especially where podzol-type soils dominate. To determine survival characteristics of an environmentally derived multiple-antibiotic resistant E. coli, it was added to laboratory containers containing sandy-loam podzol soils taken from two different locations (‘Webb’, pH 6.8–8.3 and ‘Rich’, pH 5.5–7.2). This was done in order to study the stability of the tracer bacterium under conditions designed to mimic those that might be encountered during subsequent field mini-plot studies. Sets of microcosms consisting of three replicates of each soil received 10¹² or 10¹³ colony forming units per g of soil and were incubated at four temperatures (5, 10, 20, and 37 °C) and two moisture levels (15% i.e. average field capacity and saturation) for 160 days. The microcosm data gave estimated maximum survical times for the ‘Webb’ soil of 23.3 months at 5 °C under saturating moisture conditions and 20.7 months for the ‘Rich’ soil under the same conditions using exponential regression analysis of the data.     

The Transport of Escherichia coli Through Freeze-Fractured Clay Soil

Little is known about the transport of microorganisms through freeze-fractured clay soils. Normally consolidated clay (NCC) and compacted clay (CC) columns (representing a natural clay barrier and a compacted barrier, respectively) were exposed to six consecutive freeze–thaw cycles and permeated for 21 days with an Escherichia coli cell suspension (approximately 1?×?10⁷ colony forming units (CFU)/mL) containing a 2.1-mM bromide tracer. An unfractured sand column was also examined for comparison with the clay columns. While no E. coli was detected in the effluent of both untreated NCC and CC control clay columns, a relatively low density of E. coli (between 228 and 270 CFU/mL compared to 1?×?10⁷ CFU/mL in the influent) was first detected in the effluent of the freeze-fractured NCC and CC columns at 0.29 and 0.31 pore volumes (or at 5.4 and 4.1 h), respectively. It took 11 min for a full breakthrough of E. coli through the sand column, but only about 0.1% of the influent E. coli density was detected in the effluents of the freeze-fractured NCC and CC columns at day 21. These observations show that despite the high bacterial retention capacity of the freeze-fractured clay columns, the fractures were large enough for the E. coli to flow through. Based on batch sorption tests and the permeation data, it is estimated that 18%, 7%, and 84% of the freeze-fractured NCC, CC, and sand columns would be exposed to the influent, respectively, under a full E. coli breakthrough condition. Our data show that the high bacterial retention capacity of clay barriers can be compromised by freeze–thaw conditions.     

Genetic composition of contemporary proprietary U.S. lettuce (Lactuca sativa L.) cultivars

Pedigree history of 146 lettuce (Lactuca sativa L.) cultivars registered in the U.S. by Plant Variety Protection and/or utility patent of the era from 2000 through 2010 facilitates determination of coefficient of parentage among these cultivars, identification of ancestral parental lines, and their genetic contribution. Principal ancestors of leaf lettuce developed in this era are the cultivars ‘Malibu’, ‘Waldmann’s Green’, and ‘Salad Bowl’ contributing 6.4, 6.1, and 3.5% of the genes, respectively. The cultivars ‘Parris Island Cos’ and ‘Tall Guzmaine’ are major ancestors of romaine lettuce, contributing 25.9 and 23.4% of the genes, respectively. Three crisphead lettuce ancestors identified are the cultivars ‘Vanguard’, ‘Salinas’, and ‘Calmar’, the former two descend from interspecific crosses of L. sativa with Lactuca virosa L. and Lactuca serriola L. Among these three, ‘Vanguard’ is the major ancestor contributing 23.8% of the genes to crisphead lettuce. The crisphead cultivar ‘Salinas’ was frequently crossed with romaine lettuce types and the romaine parental cultivar ‘Parris Island Cos’ was crossed with leaf types contributing to romaine and leaf lettuce genetic diversity, respectively. Genetic similarity was less within leaf cultivars (coefficient of parentage = 0.02) than found within romaine (0.15) and crisphead (0.13) cultivars registered in the U.S. during this era.     

Relationships between intra-aggregate pore structures and distributions of Escherichia coli within soil macro-aggregates

The study evaluated the effects of soil intra-aggregate pore distributions on movement and fate of E. coli (a global indicator of fecal pollution) within soil aggregates. The first objective was to characterize pore structure of intact soil aggregates (4–6 mm in size) using X-ray computed microtomography and to quantify the differences in pore structures of the aggregates from the same soil type but under >18 year contrasting land use and management settings. The studied settings were (i) conventionally plowed row crop (CT), (ii) no-till row crop (NT), and (iii) native succession vegetation (NS) treatments from Long Term Ecological Research site, W.K. Kellogg Biological Station, southwest Michigan. The second objective was to examine spatial distribution of E. coli introduced into the aggregates and the relationships between E. coli distributions and intra-aggregate pores. The results indicated that E. coli distribution in the aggregates was driven by specific configurations of the intra-aggregate pores. When the aggregates’ initial water contents were relatively low, presence of large (>100 μm) pores in the aggregate interiors limited water and thus E. coli entry. Such centrally located large pores were more abundant in the aggregates from NT and NS treatments as compared to CT aggregates. Medium-sized pores (30–60 μm) were more abundant in the aggregates from CT soil and such pores were relatively homogeneously distributed through entire bodies of CT aggregates. Thus, upon entering the aggregate, E. coli became more uniformly distributed through the CT aggregates, while in NT and NS aggregates it more commonly remained in the aggregate exterior parts without reaching the interiors. Implications of these distributional patterns for E. coli survival and re-entering water flow in soil under different land use need to be addressed in further studies.     

Effect of heavy metals on growth population of a fecal coliform bacterium Escherichia coli in aquatic environment

The data on the effects of the concentrations (0.5, l, 2, 5 mg L^?1) of the heavy metals, Hg, As, Pb, Cu, Cd, and Cr on changes in growth population of a fecal coliform bacterium Escherichia coli (in term of number of E. coli per 100 mL water) showed a gradual decline in growth population of the fecal coliform bacterium with the increase of exposure time, as well as concentrations of the metals over control data. The effects were markedly recorded with the treatment of 5 mg L^?1. In general, the harmful effects of the metals on growth population of E. coli were found by the treatments in the order: Cd>Ph>Cu>As>Hg>Cr.     

Thirteen-year survival study of an environmentalEscherichia coli in field mini-plots

A multiple-antibiotic resistantE. coli was applied to rye-grass covered field mini-plots to simulate point-source contamination. Using three mini-plots for testing and a fourth as a control, the ability of the tracer bacterium to survive under field conditions was studied. Three test plots each received separately 10⁷, 10⁸, or 10¹⁰ cfu mL^?1 E. coli grown for 24 h. in 5 L one-third strength Tryptic soy broth. In Phase I of the study, it was determined that the tracer disappeared from leaf surfaces of rye-grass covering the plots after 41 days. In Phase II, determination of the presence of the tracer in the top 2″ (5 cm) of soil after two months elapsed time indicated that tracer cfu/g dry wt. of soil had declined five, three, and three-logs for test plots 1,2, and 3. In Phase III, subsurface soil sampling using a soil auger on the three test minei-plots indicated the tracer had penetrated through the top-soil and into the underlying B horizon (20 to 50 cm down). In Phase IV, detailed sampling by excavation of the subsurface soil Horizons of the third test mini-plot showed that the tracer had also penetrated through the hardpan (C Horizon) located 0.6 m below the surface to enter the groundwater (1.06 m deep) (Phase V).E. coli counts fell precipitously to 10³ cfu g^?1 in soil and then, in the groundwater at the groundwater-soil interface, persisted at a concentration of 10³ cfu 100 mL^?1 for 2 yr. As time past, tracer counts fell to 145 cfu/100 mL in 6 yr. rose to 820 cfu 100 mL^?1 in 1986 (8 yr elapsed time), and then fell to 25 cfu 100 mL^?1 in 1991 after 13 yr. Serotyping of 1986E. coli isolates indicated that 62% were of the original tracer serotype (0.128:B12) while only 43% of the 1991 isolates were of the same serotype. The penetration rate of the tracer down through the mini-plot soil into the groundwater was 0.02 m day^?1 while downslope dispersion occurred at an estimated rate of 1.0 m day^?1. The implications of the above findings are discussed.     

植物汁液化学组成及其与菜心抗性和Cd累积的关系

Sap mixtures of the xylem, phloem, and vacuoles from low and high Cd accumulator varieties of Brassica parachinensis L. H. Bailey were analyzed under Cd stress to understand the biochemical mechanisms of Cd accumulation in plants. Low Cd accumulator （‘Teqing-60＇） and high Cd accumulator （‘Chixin-2＇） plants were grown in Cd-treated soil in pots in a greenhouse. Percentage of cell wall-bound Cd was estimated, pH level and the concentrations of amino acids, organic acids, anions, and cations in both stem and root saps were determined for the calculation of Cd speciations using the computer program GEOCHEM. The results showed that ‘Teqing-60＇ had a significantly higher （P ≤ 0.05） percentage of Cd bound to cell walls in roots and a significantly higher （P ≤ 0.05） pH in the root sap. ‘Teqing-60＇ also contained a higher concentration of total amino acids in both roots and stems compared with the high Cd accumulator variety ‘Chixin- 2＇. However, between the two accumulators, for stems and for roots, there were no significant differences in non-amino organic acids. GEOCHEM calculations showed that Cd in the root sap of ‘Teqing-60＇ mainly combined with amino acids, especially alanine. Compared with ‘Chixin-2＇, in the root sap of ‘Teqing-60＇, much lower levels of Cd as free ions or bound to simple ligands were found, indicating that less ‘Teqing-60＇ is transferred to stems and leaves. Cadmium activity in the shoot sap of ‘Teqing-60＇ was much lower than that in ‘Chixin-2＇; therefore, ‘Teqing-60＇ exhibited higher Cd resistance. However, direct determination of the Cd complexes from xylem and phloem sap is needed to verify these results.     

Transport Of Fecal Bacteria From Poultry Litter and Cattle Manures Applied to Pastureland

Land applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of bacteria in streams. An understanding of the overland transport mechanisms from land applied waste is needed to improve design of best management practices (BMPs) and modeling of nonpoint source (NPS) pollution. Plots were established on pasturelands receiving phosphorus-based livestock waste applications to measure the concentrations of Escherichia coli (E. coli), fecal coliform (FC), and Enterococcus present in overland flow at the edge of the field. The flow-weighted bacteria concentrations were highest in runoff samples from the plots treated with cowpies (1.37×10⁵ colony forming units (cfu)/100 ml of E. coli) followed by liquid dairy manure (1.84×10⁴ cfu/100 ml of E. coli) and turkey litter (1.29×10⁴ cfu/100 ml of E. coli). The temporal distribution of fecal bacterial concentrations appeared to be dependent upon both the animal waste treatment and the indicator species, with peak concentrations occurring either at the beginning of the runoff event or during peak flow rates. BMPs could be selected to reduce peak flows or first flush effects depending upon the litter or manure applied to the land. The commercial Biolog System was used to identify the dominant species of Enterococcus present in the cowpie source manure (Enterococcus mundtii 55%) and in the runoff collected from the transport plots treated with cowpies (Enterococcus faecalis 37%). The identification of predominant species of Enterococcus that are associated with specific sources of fecal pollution could greatly assist with identifying the origins of NPS pollution.     

Wirkungen organischer Substanzen auf Boden- und Düngerphosphat Teil 1: Einfluß von Stroh- und Maiswurzelextrakten auf die Löslichkeit von Boden-und Dünger-P

Effects of organic substances on soil- and fertilizer phosphate Part 1: Influence of straw or maize-root extracts on the solubility of soil and fertilizer P The effects of straw and maize-root extracts on the solubility of soil and fertilizer phosphate were tested in incubation trials. The following results were obtained. 1. Addition of an extract of unrotted straw (10 g straw/100 g soil) to incubate a brown-earth soil, (high or low in P) for 1–14 days did not have any significant effects on the H₂O and CAL P-fraction as compared to a KH₂PO₄ control, but markedly increased transformation of ‘easily soluble’Fe- and Al-phosphates (?15 to ?40 ppm) into ‘less soluble’forms (+15 to +20 ppm). Addition of an extract of rotted straw decreased the amounts of water extractable P and ‘easily soluble’Fe- and Al-phosphates but CAL-extractable P and ‘less soluble’Fe- and Al-phosphates were increased. 2. Incubation of the same soil (P-enriched) with an extract of maize roots (roots: soil = 1:3) for 1 day resulted in a reduction in the fixation of fertilizer phosphate (34 as compared to 42%) and in a decrease of fertilizer P recovered as ‘less soluble’Fe- and Al-P (from 31 to 11%); however, fixation was markedly increased after 14 days.     

Microsatellite analysis of Alpine grape cultivars (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.): alleged descendants of Pliny the Elder’s <Emphasis Type="Italic">Raetica</Emphasis> are genetically related

According to Pliny the Elder and other Greco-Roman geoponics, Raetica was a famous white grape as well as a white wine produced in Raetia, a Province of the Roman Empire. Does Raetica grape have modern descendants? Etymologically and geographically, the white ‘Rèze’ from Valais (Switzerland) would be the best candidate. Using available microsatellite data, we searched for relatives of ‘Rèze’ in our database containing over 1,700 genotypes of grape cultivars from all over the world. Twelve cultivars showing putative first-degree (parent–offspring or full-siblings) or second-degree (grandparent–grandoffspring, uncle–nephew or half-siblings) relationships with ‘Rèze’ were then analysed at 60 microsatellite markers. Calculation of allele sharing and likelihood ratios between competing relationship categories revealed that four cultivars had parent–offspring relationship with ‘Rèze’: ‘Cascarolo Bianco’ (Piedmont, Italy), ‘Arvine Grande’ (Valais, Switzerland), ‘Groppello di Revò’ and ‘Nosiola’ (Trentino, Italy). Given that some of these are also said to be Raetica descendants, we may well be on the tracks of Pliny the Elder’s Raetica grape. However, there is no evidence about the identity of Raetica. Analysis of ancient DNA of grape pips excavated from archaeological sites of the Roman times might provide key information. Our first attempts were unsuccessful, but analysis of additional samples and optimisation of the method could provide groundbreaking results about the identity of the grapes cultivated in classical antiquity.     

Burrowing activity of the earthworms Lumbricus terrestris and Aporrectodea giardi and consequences on C transfers in soil

Two earthworms species, Lumbricus terrestris (epianecic) and Aporrectodea giardi (anecic) were incubated in microcosms with an epigeic ¹³C-labelled litter for 246 d. At the end of the experiment, different soil compartments (surface casts, walls and peripheries of burrows, and surrounding soil) were sampled for ¹³C analysis. Two-dimensional images acquired using X-ray computed tomography allowed to estimate the weight of the ‘burrow wall’ and ‘burrow periphery’ compartments which are required to establish C balance. In the case of L. terrestris, the formed structures were more C litter enriched compared to the other species. The permanent character of the burrow system could lead to a high and constant enrichment of the entire burrow system. As consequence, the percentage of C litter in the ‘burrow wall’ and ‘burrow periphery’ compartments was important in spite of their low volume. The denser system developed by A. giardi resulted in C litter dilution in the whole formed structures. The C litter enrichment decreased with the soil depth, but owing to the intensity of the burrowing activity, the C litter transfers into the ‘burrow walls’ and ‘burrow periphery’ were important and the C litter was homogeneously distributed throughout the whole column.     

Field Evaluation of Colilert 3000 for Ground, Raw and Treated Surface Water and Comparison with Standard Membrane Filtration Method

In the present study, during a period of 16 months Colilert 3000 was validated in laboratory and field tests and compared to standard laboratory methods for monitoring of coliforms and E. coli. No false positive/negative results for coliforms/E. coli were found in 80 potable well water samples monitored with the Colilert 3000 and compared to standard methods. Although usage of Colilert 3000 to monitor raw water is not recommended by the manufacturer, the E. coli results of 100 samples were 100% positive by membrane filtration, Colilert 18 and MPN and only 80% positive by the Colilert 3000. In addition, in all positive samples, Colilert 3000 and Colilert 18 showed higher results of two to three orders of magnitude compared to MF and MPN. This significant difference was probably due to the presence of Aeromonas spp. and Vibrio spp. (natural inhabitants of the raw surface water) known to interfere with the Colilert test. Treated surface water was monitored by Colilert 3000 for the presence of coliforms and E. coli. Among the 100 samples tested in parallel by membrane filtration all were negative, while with Colilert 3000 only 76% were negative. Post-test identification of the positive samples did not reveal the presence of E. coli but interfering microorganisms. The last application was to evaluate Colilert 3000 to monitor accidental or deliberate pollution of drinking water with sewage sources. Among 20 samples spiked with raw sewage (0.1 and 1%) all results were positive for both coliforms and E. coli. The time span required for Colilert 3000 to detect positive samples was 6–10 h compared to 24 h with the standard membrane filtration.     

Concentrations and Exports of Fecal Indicator Bacteria in Watersheds with Varying Densities of Onsite Wastewater Systems

The research goal was to determine if onsite wastewater system (OWS) density had an influence on the concentrations and watershed exports of Escherichia coli and enterococci in urbanizing watersheds. Eight watersheds with OWS densities ranging from <?0.1 to 1.88 systems ha^?1 plus a watershed served by sewer (Sewer) and a mostly forested, natural watershed (Natural) in the Piedmont of North Carolina served as the study locations. Stream samples were collected approximately monthly during baseflow conditions between January 2015 and December 2016 (n?=?21). Median concentrations of E. coli (2014 most probable number (MPN) 100 mL^?1) and enterococci (168 MPN 100 mL^?1) were elevated in streams draining watersheds with a high density of OWS (>?0.77 system ha^?1) relative to watersheds with a low (<?0.77 system ha^?1) density (E. coli: 204 MPN 100 mL^?1 and enterococci: 88 MPN 100 mL^?1) and control watersheds (Natural: E. coli: 355 MPN 100 mL^?1 and enterococci: 62 MPN 100 mL^?1; Sewer: 177 MPN 100 mL^?1 and 130 MPN 100 mL^?1). Samples collected from watersheds with a high density of OWS had E. coli and enterococci concentrations that exceeded recommended thresholds 88 and 57% of times sampled, respectively. Results show that stream E. coli and enterococci concentrations and exports are influenced by the density of OWS in urbanizing watersheds. Cost share programs to help finance OWS repairs and maintenance are suggested to help improve water quality in watersheds with OWS.     

Microsatellite mapping of the genes for sham ramification and extra glume in spikelets of tetraploid wheat

The loci for expression of prolonged spikelet rachilla named ‘sham ramification’ in three tetraploid wheat accessions, two accessions of Triticum jakubzineri Udacz. et Schachm. (2n = 4× = 28, genome BBAA) ‘PI 585014’ and ‘R-101-03’ and one sample of Triticum turgidum L. (2n = 4× = 28, genome BBAA) ‘PI 67339’, were mapped by genotyping F₂ populations using microsatellite markers. The segregation analysis confirmed that sham ramification was controlled by recessive, epistatic genes, shr1 (sham ramification 1) and shr2 (sham ramification 2). The genotypes of ‘sham ramification’ were shr1shr1Shr2Shr2 for T. jakubzineri and Shr1Shr1shr2shr2 for T. turgidum (PI 67339). Normal rachilla was determined by Shr1Shr1Shr2Shr2. The shr1 gene and the gene for extra glume (exg) were completely linked; and, the shr1/exg gene complex was bracketed by the markers Xbarc319 and Xbarc232 on the long arm of chromosome 5A. In the F₂ of PI 67339/LD222 the gene shr2 was bracketed by Xwmc819 and Xwmc794 on the long arm of chromosome 2A.     

A rapid procedure to calculate lime requirements based on single titration with base

The lime requirement (LR) in 39 surface acid soil samples (0–30 cm) from western Greece was calculated using a single-addition titration of successive 3-mL 0.022 M calcium hydroxide [Ca(OH)₂]. Soil pH measurements and titrations were performed in soil/water (1:2) and in a soil/0.01 M CaCl₂ (1:2) suspension while being stirred. The results were referred to as ‘pH data group I’ and ‘pH data group II’, respectively. In each ‘pH data group’, the samples were separated into ‘pH data subgroups’, according to the total volume (mL) of 0.022 M Ca(OH)₂ added to increase the initial pH (pH_a) to a target value of 6.5 (pH_t). The fitted linear regression equation pH_t = b × volume + pH_a was used for each ‘pH data group’ to determine the slope b. The b-weighted mean for each ‘pH data group’ was calculated. The LR was then calculated as follows: Mg CaCO₃ ha^?1 = 0.495 (pH_t – pH_a)/b, where b is the average weighted mean from the two ‘pH data groups’ and is equal to 0.227. The validity of the above equation was confirmed after incubation with Ca(OH)₂ for 72 h. This procedure is simple and gives a rapid and accurate estimation of LR with respect to the environment.     

Heavy metals in the lichen Caloplaca aurantia from urban,suburban and rural regions in Israel (a comparative study)

The content of eight heavy metals: Mn, Zn, Fe, Pb, Ni, Cu, Cr and Cd in the lichen Caloplaca aurantia growing on roof-tiles in urban, suburban and rural settlements in Israel has been evaluated. The data obtained and their statistical analysis indicated the following: (1) The content of all the above listed metals was generally higher in the lichen growing in ‘town’ than in ‘village’ areas; among these metals Ni and Zn were found most suitable for the distinction between ‘town’ and ‘village’ settlements. (2) Comparisons of the coefficient of variation of metal content values in ‘town’ versus ‘village’ furnished indications on the dispersion capacity of the metal particles. (3) Correlation analysis among the metals in ‘town’ and ‘village’ resulted in suggestive information on the emission sources. (4) Leaching tests indicated the tenacity of metal retainment and incorporation efficiency into the lichen tissue. Lichen species like C. aurantia, which grow both in ‘clean’ and metal contaminated areas are suggested as comparative monitors and for assessing periodical changes in metal output and concentrations.     

The effects of suspended ‘red mud’ on mortality,body weight,and growth of the marine planktonic copepod,Calanus helgolandicus

The effect of ‘red mud’ at a dilution of 1:10⁵ to 1:10⁶ on growth, body weight and mortality of juvenile stages of the planktonic copepodCalanus helgolandicus were investigated. In the presence of phytoplanktonC. helgolandicus ingested large amounts of ‘red mud’. In comparison to control copepods growth of ‘red mud’ animals was delayed. Mortality of ‘red mud’ animals was 5 to 8 times higher than that of control animals. The dry body weight of C III, C v, and adults raised from N v/NVI on in ‘red mud’ was far lower than the dry weight of the control animals. All results show that ‘red mud’ at the above mentioned dilutions affects negatively juvenile stages and adults ofCalanus helgolandicus.     

Response of Two Olive Cultivars to Salt Stress and Potassium Supplement

ABSTRACT

The effects of saline water containing 0, 50, 100, and 150 mM sodium chloride (NaCl), and 100 mM NaCl + 100 mM potassium (K) on photosynthesis, water relations, and ion and carbohydrate content of olive (Olea europaea L.) cultivars ‘Koroneiki’ and ‘Mastoidis’ were studied on five-year-old trees. Salinity increased sodium (Na⁺) and chloride (Cl^?) in tissues of both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis.’ Salt-toxicity symptoms were observed at 100 and 150 mM, but not in plants receiving extra K. In salt-stressed plants, leaf water potential declined, whereas turgor potential remained positive due to a rapid decrease in osmotic potential. Salinity increased mannitol content up to 41.3% in ‘Mastoidis’ and 15.8% in ‘Koroneiki’, but reduced starch content in leaves. Photosynthetic rates fell significantly with increasing salinity in both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis’. Potassium supplements reduced the concentration of Na⁺ and increased the concentrations of K⁺ in leaves, but decreased photosynthesis.     

Root cell walls and phytochelatins in low-cadmium cultivar of Brassica parachinensis

‘Lvbao-701’ is a cultivar of Chinese flowering cabbage(Brassica parachinensis) that exhibits low cadmium(Cd) accumulation and high Cd tolerance.In this study, this cultivar was compared with a high-Cd accumulating cultivar, ‘Chixin-4’, to characterize the mechanisms influencing Cd accumulation in B. parachinensis. Root cell walls were isolated by dissolving the cytoplasm with an organic solvent, and root Cd and phytochelatin(PC) contents were analyzed. In addition, a PC synthase gene fragment was cloned and expressed under Cd stress conditions. The proportions of Cd bound to root cell walls were higher in the ‘Lvbao-701’ plants(68.32%–76.80%) than in the ‘Chixin-4’ plants(35.36%–54.18%) after exposure to Cd stress. The proportions of Cd bound to root cell walls measured using cell walls isolated with a non-destructive method were higher than those obtained using a conventional method that required grinding and centrifugation. Exposure to Cd stress induced the PC production and resulted in higher PC contents in the ‘Lvbao-701’ plants than in the ‘Chixin-4’ plants. Cloning and expression analysis of a B. parachinensis PC synthase cDNA fragment indicated that PC synthase gene expression was induced by Cd and occurred mainly in the roots of both ‘Lvbao-701’ and ‘Chixin-4’ plants. However, the PC synthase gene expression level was higher in the‘Lvbao-701’ roots than in the ‘Chixin-4’ roots. Therefore, a higher abundance of Cd in the root cell walls of ‘Lvbao-701’ and up-regulated PC production in the roots are probably the main reasons why ‘Lvbao-701’ exhibits lower Cd translocation to the shoots and higher tolerance to Cd than ‘Chixin-4’.