Control of Cortaderia selloana with a glyphosate-based herbicide led to a short-term stimulation of soil fungal communities.

In the north of Spain, Cortaderia selloana plants have invaded ecosystems of high ecological value. Control of this species is carried out with the application of glyphosate-based formulations. The aim of this work was to determine, under microcosm conditions, the short-term (2 months) effects of the application of a glyphosate-based herbicide (Roundup®) on C. selloana rhizosphere microbial communities. To this purpose, before and after the application of Roundup®, several parameters that provide information on the biomass, activity and diversity of rhizosphere fungal and bacterial communities (enzyme activities, basal and substrate-induced respiration, potentially mineralizable nitrogen, nitrification potential rate, ergosterol content and community-level profiles with Biolog™ plates and ARISA) were determined. We observed a stimulation of some microbial parameters, in particular those related to fungal communities. Further research is needed to determine the long-term consequences of this short-term fungal stimulation for soil functioning.

Lemna minor tolerance to metal-working fluid residues: implications for rhizoremediation.

For the first time in the literature, duckweed (Lemna minor) tolerance (alone or in combination with a consortium of bacteria) to spent metal-working fluid (MWF) was assessed, together with its capacity to reduce the chemical oxygen demand (COD) of this residue. In a preliminary study, L. minor response to pre-treated MWF residue (ptMWF) and vacuum-distilled MWF water (MWFw) was tested. Plants were able to grow in both residues at different COD levels tested (up to 2300 mg·l(-1) ), showing few toxicity symptoms (mainly growth inhibition). Plant response to MWFw was more regular and dose responsive than when exposed to ptMWF. Moreover, COD reduction was less significant in ptMWF. Thus, based on these preliminary results, a second study was conducted using MWFw to test the effectiveness of inoculation with a bacterial consortium isolated from a membrane bioreactor fed with the same residue. After 5 days of exposure, COD in solutions containing inoculated plants was significantly lower than in non-inoculated ones. Moreover, inoculation reduced ß+γ-tocopherol levels in MWFw-exposed plants, suggesting pollutant imposed stress was reduced. We therefore conclude from that L. minor is highly tolerant to spent MWF residues and that this species can be very useful, together with the appropriate bacterial consortium, in reducing COD of this residue under local legislation limits and thus minimise its potential environmental impact. Interestingly, the lipophilic antioxidant tocopherol (especially the sum of ß+γ isomers) proved to be an effective plant biomarker of pollution.

Evaluation of the Effect of 1,3-Bis(4-Phenyl)-1H-1,2,3-Triazolyl-2-Propanolol on Gene Expression Levels of JAK2-STAT3, NF-κB, and SOCS3 in Cells Cultured from Biopsies of Mammary Lesions.

Breast cancer is the most frequent neoplasia in women and is responsible for approximately 13.8% of deaths per year for this gender. It has been suggested that JAK2, STAT3, and NF-κB gene expression is involved in this type of cancer. The objective of the present study was to determine the effect of bistriazole in these signaling pathways in patients with breast cancer and benign mammary lesions. The inhibitory concentration 50 of bistriazole was calculated in cell cultures of patients with benign lesions, Probit = 4.6 µM with IC = 95%. The study was performed by examining 63 women who submitted to mammary biopsies. Biopsies of the mammary lesions were performed, gene expression was determined, and cells were cultured in the presence of 4.6 µM bistriazole. We found that breast cancer is related to age greater than 50 (P ≤ 0.01), being overweight (P ≤ 0.023) and having a waist circumference larger than 80 cm (P ≤ 0.01). The gene expression of JAK2, STAT3, and NF-κB was higher in groups of patients with breast cancer, while SOCS3 expression was lower. After being exposed to bistriazole, the expression of JAK2 and STAT3 decreased, and the expression of SOCS3 and NF-κB increased. In conclusion, this molecule in development has an effect on the gene expression of JAK3 and STAT3; nevertheless, the lack of change in NF-κB indicates that it is not a regulator of inflammation, and therefore, more studies should be performed.

THE ACHES THAT TAKE YOUR BREATH (AND TEARS) AWAY.

An 80-year-old man presented with a complaint of three months of fatigue and aching of his shoulders and hips, as well as pain, swelling, and stiffness in bilateral fingers that was worse in the morning but improved with movement. Associated symptoms included worsening dry mouth and eyes, dysphagia, exertional dyspnea, and right foot drop. Physical exam was significant for edematous and tender bilateral proximal interphalangeal joints, metacarpophalangeal joints and wrists with decreased grip, extension and flexion, as well as bilateral pulmonary crackles. Laboratory analysis revealed Anti-Ro (SSA) and Anti-La (SSB) positivity with elevated erythrocyte sedimentation rate (70mm/hr) and C-reactive peptide (13mg/L). Pulmonary function testing was notable for a forced vital capacity (FVC) of 64% and carbon monoxide diffusing capacity (DLCO) of 44%. High resolution chest computed tomography demonstrated fibrotic changes consistent with nonspecific interstitial pneumonitis. The patient was started on mycophenolate mofetil, hydroxychloroquine, and prednisone for Sjögren's syndrome (SjS). Symptoms improved and repeat FVC revealed a 20 percent improvement, however subsequent tapering of prednisone resulted in worsening dyspnea and increase of FVC to 60 prcent. Prednisone was restarted and rituximab 2g divided in two doses was administered with overall symptom improvement. Symptoms and FVC continued to wax and wane over the following 18 months requiring re-dosing of rituximab with most recent FVC improved to 71 percent and DLCO 41 percent.

Does plant colour matter? Wax accumulation as an indicator of decline in Juniperus thurifera.

The photosynthesis in evergreen trees living in Mediterranean ecosystems is subjected to multiple climatic stresses due to water shortage and high temperatures during the summer and to low temperatures during the winter. Mediterranean perennials deploy different photoprotective mechanisms to prevent damage to the photosynthetic system. Wax accumulation in leaves is a primary response which by enhancing light scattering in the leaf surface reduces incident radiation in the mesophyll. The existence of high variability in wax accumulation levels between coexisting individuals of a species has a visual effect on colour that provides distinguishable green and glaucous phenotypes. We explored this variability in a Mediterranean evergreen tree Juniperus thurifera (L.) to evaluate the impact of epicuticular wax on optical and ecophysiological properties and on the abundance of photoprotective pigments throughout an annual cycle. Because of light attenuation by waxes, we expected that glaucous phenotypes would lower the need for photoprotective pigments. We evaluated the effect of phenotype and season on reflectance, defoliation levels, photochemical efficiency and photoprotective pigment contents in 20 green and 20 glaucous junipers. Contrary to our expectations, the results showed that glaucous trees suffered from a diminution in photochemical efficiency, but there was no reduction in photoprotective pigments. Differences between glaucous and green phenotypes were greater in winter, which is the most stressful season for this species. Glaucous individuals also showed the highest levels of leaf defoliation. The lower photochemical efficiency of glaucous trees, together with higher defoliation rates and equal or greater number of physiological photoprotective mechanisms, suggests that in spite of wax accumulation, glaucous trees suffer from more severe stress than green ones. This result suggests that changes in colouration in Mediterranean evergreens may be a decline indicator.

Plant tolerance to diesel minimizes its impact on soil microbial characteristics during rhizoremediation of diesel-contaminated soils.

Soil contamination due to petroleum-derived products is an important environmental problem. We assessed the impacts of diesel oil on plants (Trifolium repens and Lolium perenne) and soil microbial community characteristics within the context of the rhizoremediation of contaminated soils. For this purpose, a diesel fuel spill on a grassland soil was simulated under pot conditions at a dose of 12,000 mg diesel kg(-1) DW soil. Thirty days after diesel addition, T. repens (white clover) and L. perenne (perennial ryegrass) were sown in the pots and grown under greenhouse conditions (temperature 25/18 °C day/night, relative humidity 60/80% day/night and a photosynthetic photon flux density of 400 µmol photon m(-2) s(-1)) for 5 months. A parallel set of unplanted pots was also included. Concentrations of n-alkanes in soil were determined as an indicator of diesel degradation. Seedling germination, plant growth, maximal photochemical efficiency of photosystem II (F(v)/F(m)), pigment composition and lipophylic antioxidant content were determined to assess the impacts of diesel on the studied plants. Soil microbial community characteristics, such as enzyme and community-level physiological profiles, were also determined and used to calculate the soil quality index (SQI). The presence of plants had a stimulatory effect on soil microbial activity. L. perenne was far more tolerant to diesel contamination than T. repens. Diesel contamination affected soil microbial characteristics, although its impact was less pronounced in the rhizosphere of L. perenne. Rhizoremediation with T. repens and L. perenne resulted in a similar reduction of total n-alkanes concentration. However, values of the soil microbial parameters and the SQI showed that the more tolerant species (L. perenne) was able to better maintain its rhizosphere characteristics when growing in diesel-contaminated soil, suggesting a better soil health. We concluded that plant tolerance is of crucial importance for the recovery of soil health during rhizoremediation of contaminated soils.

Native plant communities in an abandoned Pb-Zn mining area of northern Spain: implications for phytoremediation and germplasm preservation.

Plants growing on metalliferous soils from abandoned mines are unique because of their ability to cope with high metal levels in soil. In this study, we characterized plants and soils from an abandoned Pb-Zn mine in the Basque Country (northern Spain). Soil in this area proved to be deficient in major macronutrients and to contain toxic levels of Cd, Pb, and Zn. Spontaneously growing native plants (belonging to 31 species, 28 genera, and 15 families) were botanically identified. Plant shoots and rhizosphere soil were sampled at several sites in the mine, and analyzed for Pb, Zn and Cd concentration. Zinc showed the highest concentrations in shoots, followed by Pb and Cd. Highest Zn concentrations in shoots were found in the Zn-Cd hyperaccumulator Thlaspi caerulescens (mean = 18,254 mg Zn kg(-1) DW). Different metal tolerance and accumulation patterns were observed among the studied plant species, thus offering a wide germplasm assortment for the suitable selection of phytoremediation technologies. This study highlights the importance of preserving metalliferous environments as they shelter a unique and highly valuable metallicolous biodiversity.

Dehydration-mediated activation of the xanthophyll cycle in darkness: is it related to desiccation tolerance?

The development of desiccation tolerance by vegetative tissues was an important step in the plants' conquest of land. To counteract the oxidative stress generated under these conditions the xanthophyll cycle plays a key role. Recent reports have shown that desiccation itself induces de-epoxidation of xanthophyll cycle pigments, even in darkness. The aim of the present work was to study whether this trait is a common response of all desiccation-tolerant plants. The xanthophyll cycle activity and the maximal photochemical efficiency of PS II (F(v)/F(m)) as well as ß-carotene and α-tocopherol contents were compared during slow and rapid desiccation and subsequent rehydration in six species pairs (with one desiccation-sensitive and one desiccation-tolerant species each) belonging to different taxa. Xanthophyll cycle pigments were de-epoxidised in darkness concomitantly with a decrease in F(v)/F(m) during slow dehydration in all the desiccation-tolerant species and in most of the desiccation-sensitive ones. De-epoxidation was reverted in darkness by re-watering in parallel with the recovery of the initial F(v)/F(m). The stability of the ß-carotene pool confirmed that its hydroxylation did not contribute to zeaxanthin formation. The α-tocopherol content of most of the species did not change during dehydration. Because it is a common mechanism present in all the desiccation-tolerant taxa and in some desiccation-sensitive species, and considering its role in antioxidant processes and in excess energy dissipation, the induction of the de-epoxidation of xanthophyll cycle pigments upon dehydration in the dark could be understood as a desiccation tolerance-related response maintained from the ancestral clades in the initial steps of land occupation by plants.

Phytostabilization of metal contaminated soils.

The contamination of soils with heavy metals represents a worldwide environmental problem of great concern. Traditional methods for the remediation of metal contaminated soils are usually very expensive and frequently induce adverse effects on soil properties and biological activity. Consequently, biological methods of soil remediation like phytoremediation (the use of green plants to clean up contaminated sites) are currently receiving a great deal of attention. In particular, chemophytostabilization of metal contaminated soils (the use of metal tolerant plants together with different amendments like organic materials, liming agents, or phosphorus compounds and such) to reduce metal mobility and bioavailability in soils appears most promising for sites contaminated with high levels of several metals when phytoextraction is not a feasible option. During chemophytostabilization processes, one must at all times be cautious with a possible future reversal of soil metal immobilization, with concomitant adverse environmental consequences.

Unravelling the roles of desiccation-induced xanthophyll cycle activity in darkness: a case study in Lobaria pulmonaria.

Desiccation-tolerance ability in photosynthetic organisms is largely based on a battery of photoprotective mechanisms. Xanthophyll cycle operation induced by desiccation in the absence of light has been previously proven in the desiccation-tolerant fern Ceterach officinarum. To understand the physiological function of xanthophyll cycle induction in darkness and its implication in the desiccation tolerance in more detail, we studied its triggering factors and its photochemical effects in the lichen Lobaria pulmonaria. We found that both the drying rate and the degree of desiccation play a crucial role in the violaxanthin de-epoxidase activation. De-epoxidation of violaxanthin to zeaxanthin (Z) occurs when the tissue has lost most of its water and only after slow dehydration, suggesting that a minimum period of time is required for the enzyme activity induction. Fluorescence analysis showed that Z, synthesised during tissue dehydration in the absence of light, prevents photoinhibition when rewatered tissues are illuminated. This is probably due to Z implication in both non-photochemical quenching and/or antioxidative responses.

Phytoextraction potential of two Rumex acetosa L. accessions collected from metalliferous and non-metalliferous sites: effect of fertilization.

Metal tolerance and phytoextraction potential of two common sorrel (Rumex acetosa L.) accessions, collected from a Pb/Zn contaminated site (CS, Lanestosa) and an uncontaminated site (UCS, Larrauri), were studied in fertilized and non-fertilized pots prepared by combining soil samples from both sites in different proportions (i.e., 0%, 33%, 66% and 100% of Lanestosa contaminated soil). The original metalliferous mine soil contained 20480, 4950 and 14 mg kg(-1) of Zn, Pb and Cd, respectively. The microcosm experiment was carried out for two months under greenhouse controlled conditions. It was found that fertilization increased mean plant biomass of both accessions as well as their tolerance. However, only the CS accession survived all treatments even though its biomass decreased proportionally according to the percentage of contaminated mine soil present in the pots. This metallicolous accession would be useful for the revegetation and phytostabilization of mine soils. Due to its high concentration and bioavailability in the contaminated soil, the highest values of metal phytoextracted corresponded to Zn. The CS accession was capable of efficiently phytoextracting metal from the 100% mine soil, indeed reaching very promising phytoextraction rates in the fertilized pots (6.8 mg plant(-1) month(-1)), similar to the ones obtained with hyperaccumulator plants. It was concluded that fertilization is certainly worth being considered for phytoextraction and revegetation with native plants from metalliferous soils.

Chromium (VI) adsorption on boehmite.

Boehmite was synthesized and characterized in order to study the adsorption behavior and the removal of Cr(VI) ions from aqueous solutions as a function of contact time, initial pH solution, amount of adsorbent and initial metal ion concentration, using batch technique. Adsorption data of Cr(VI) on the boehmite were analyzed according to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293, 303, 313 and 323K temperatures. The kinetic values and thermodynamic parameters from the adsorption process show that the Cr(VI) ions adsorption on boehmite is an endothermic and spontaneous process. These results show that the boehmite could be considered as a potential adsorbent for chromium ions in aqueous solutions.

Short- and long-term modulation of the lutein epoxide and violaxanthin cycles in two species of the Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana Mill.).

Short- and long-term responses of the violaxanthin (V) and lutein epoxide (Lx) cycles were studied in two species of Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana L.). The Lx content exceeded the V content in shade leaves of both species. Both Lx and V were de-epoxidised on illumination, but only V was fully restored by epoxidation in low light. Violaxanthin was preferentially de-epoxidised in low light in L. nobilis. This suggests that Lx accumulates with leaf ageing, partly because its conversion to lutein is limited in shade. After exposure to strong light, shade leaves of avocado readjusted the total pools of alpha- and beta-xanthophyll cycles by de novo synthesis of antheraxanthin, zeaxanthin and lutein. This occurred in parallel with a sustained depression of F(v)/F(m). In Persea indica, a closely related but low Lx species, F(v)/F(m) recovered faster after a similar light treatment, suggesting the involvement of the Lx cycle in sustained energy dissipation. Furthermore, the seasonal correlation between non-reversible Lx and V photoconversions and pre-dawn F(v)/F(m) in sun leaves of sweet bay supported the conclusion that the Lx cycle is involved in a slowly reversible downregulation of photosynthesis analogous to the V cycle.

Use of nanofiltration for potable water from an aquifer recharged with wastewater.

This paper presents the comparison of nine nanofiltration membranes to treat water coming from an aquifer recharged with wastewater and used as municipal supply in the Tula Valley, Mexico. The comparison was made based on (a) the amount of water produced; (c) the capability to produce a <1 mg TOC/L effluent without entirely eliminating salts, (b) the removal of specific organic and microbiological pollutants, and (c) the reduction of toxicity and mutagenicity from water. From the tested membranes, only four produce an effluent with <1 TOC mg/L, and three totally retained dibutyl phthalate, diethyl phthalate and hydroxytoluene butylate. Influent mutagenicity (Ames test) was negative but these was a certain degree of toxicity when Tetrahymena pyriformis was used as indicator. Toxicity was partially reduced by some of the NF membranes. The best membrane had a flux of 95 L m(-2)h(-1) and removal efficiencies of 98% for TOC, 92% for AUV(254), and 92% for TDS. The permeate had a final hardness of 76 mg/L and an alkalinity of 124 mg/L. Additionally, this membrane removed totally specific organic compounds, total and fecal coliforms and almost all the somatic coliphages.

Plasticity of photoprotective mechanisms of Buxus sempervirens L. leaves in response to extreme temperatures.

Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.

Synthesis of low molecular weight thiols in response to Cd exposure in Thlaspi caerulescens.

In this study, we investigated the accumulation of phytochelatins (PCs) and other low molecular weight (LMW) thiols in response to Cd exposure in two contrasting ecotypes differing in Cd accumulation. Using a root elongation test, we found that the highly accumulating ecotype Ganges was more tolerant to Cd than the low Cd-accumulation ecotype Prayon. L-buthionine-(S,R)-sulphoximine (BSO), a potent inhibitor of the gamma-glutamylcysteine synthetase gamma-ECS) (an enzyme involved in the PC biosynthetic pathway), increased the Cd sensitivity of Prayon, but had no effect on Ganges. Although PC accumulation increased in response to Cd exposure, no significant differences were observed between the two ecotypes. Cd exposure induced a dose-dependent accumulation of both Cys and a still unidentified LMW thiol in roots of both ecotypes. Root accumulation of Cys and this thiol was higher in Ganges than in Prayon; the ecotypic differences were more pronounced when the plants were treated with BSO. These findings suggest that PCs do not contribute to the Cd hypertolerance displayed by the Ganges ecotype of Thlaspi caerulescens, whereas Cys and other LMW thiols might be involved.

Evaluation of the sorption properties of a Mexican organo clinoptilolite-rich tuff for phenol and 4-chlorophenol.

A Mexican clinoptilolite-rich tuff was modified with the hexadecyltrimethyl ammonium (HDTMA) and used for the sorption of phenol and 4-chlorophenol. Whereas the zeolitic tuff had no affinity for phenol and 4-chlorophenol, the modified zeolite removed these organic compounds. The sorption behavior from aqueous solutions was studied by means of batch type and column experiments and isotherms were determined. It was found that the uptake was higher for 4-chlorophenol than for phenol.

Role of red carotenoids in photoprotection during winter acclimation in Buxus sempervirens leaves.

The red leaf coloration of several plant species during autumn and winter is due to the synthesis of phenolic compounds such as anthocyanins or red carotenoids. The latter occur very rarely and are non-ubiquitous and taxonomically restricted compounds. The present study shows that the leaves of common box ( Buxus sempervirens L.) accumulate red carotenoids (eschscholtzxanthin, monoanhydroeschscholtzxanthin, anhydroeschscholtzxanthin) as a response to photoinhibitory conditions during winter acclimation. These compounds are produced in a coordinated manner with the operation of other photoprotective systems: accumulation and sustained deepoxidation of VAZ pigments with a concomitant decrease in maximal photochemical efficiency, accumulation of alpha-tocopherol and a gradual decrease on chlorophyll content. All these processes were reversed when the photosynthetic tissues were transferred from photoinhibitory winter conditions to room temperature for 9 days. Buxus leaves showed a large degree of phenotype variation in the degree of reddening, ranging from green to orange. The differences in colour pattern were mainly due to differences in the accumulation of red carotenoids and xanthophyll esters. Red pigments were mainly anhydroeschscholtzxanthin and esters of eschscholtzxanthin. Conversely to fruit or petal chromoplasts, the plastids of red leaves in this species are not the terminal differentiated state but are able to redifferentiate again to chloroplasts. Their photoprotective role during winter as a light screen system or as antioxidants, in a similar way to other red pigments, and their implications on the wide ecological tolerance of this evergreen species are discussed.

[The relation between the HLA-DRB1*1501 allele and the severity of multiple sclerosis in a sample of the Spanish population from the Balearic Islands: the influence exerted by sex]. / Relación entre el alelo HLA-DRB1*1501 y la gravedad de la esclerosis múltiple en una muestra de población española perteneciente a las Islas Baleares: influencia del sexo.

INTRODUCTION: There is some controversy about the possible relation between HLA-DR2 (DRB1*1501-DRB5*0101-DQA1*0102-DQB1*0602) and the severity of multiple sclerosis (MS), which could be due, at least in part, to methodological differences among the different studies dealing with this subject and/or to a lack of phenotypic homogeneity within the series of patients. AIMS: This study aims to contribute information about the possible relation between DR2 (more specifically the HLA-DRB1*1501 allele) and the severity of MS. PATIENTS AND METHODS: We conducted a study of 43 individuals with clinically defined MS, whose degree of severity was determined using Kurtzke's EDSS, and 107 controls from a similar ethnic origin. DETERMINATIONS: HLA typing by PCR-SSO and PCR-SSP, analysis of oligoclonal IgG bands in CSF by isoelectric focusing, and quantification of the intrathecal synthesis of IgG (IgG index, IgG ratio, Reiber's formula and Tourtellotte's formula). STATISTICS: Chi2 test, Mann-Whitney test and Kendall correlation coefficient. RESULTS: DRB1*1501 is associated with the presence of MS only in females and with lower severity of the disease only in males. These associations do not appear to depend on any kind of effect exerted by DRB1*1501 on the intrathecal synthesis of IgG that differs between the two sexes. CONCLUSIONS: The absence of a relation between DRB1*1501 and the severity of MS reported in many studies could be due to not stratifying the patients according to sex. Our findings emphasise how important it is in genetic studies of complex traits to reduce the phenotypic heterogeneity of patients as much as possible.

Glyphosate effects on phenolic metabolism of nodulated soybean (Glycine max L. merr.).

Glyphosate is a herbicide that blocks the shikimic acid pathway. Three Bradyrhizobium japonicum strains with different sensitivities to glyphosate were used to test the effect of this herbicide on the phenolic metabolism of nodulated soybeans and on the bacteroid nitrogenase activity. Glyphosate caused an inhibition in the bacteroid nitrogenase activity that was related with the sensitivity of the nodule-forming strains. Both leaves and nodules accumulated huge amounts of shikimate and phenolic acids (mainly protocatechuic acid), indicating that the herbicide was translocated to the nodule and disturbed phenolic metabolism. However, this accumulation was not clearly related to the sensitivity of the different strains. Bacteroids from control plants were incubated with the same concentration of shikimate, and phenolic acid accumulated in glyphosate-treated plants. Despite the high levels found in nodules, they were not responsible for the decrease of the nitrogenase activity. Glyphosate by itself caused a small inhibition of the bacteroid nitrogenase activity.