Impact of River Water and Bottom Sediment Pollution on Accumulation of Metal(loid)s and Arsenic Species in the Coastal Plants Stuckenia pectinata L., Galium aparine L., and Urtica dioica L.: A Chemometric and Environmental Study.

The role of water and bottom sediment pollution of a river subjected to a strong industrial anthropo-pressure in coastal plants was investigated. The work presented the influence of polluted environment on accumulation of metal(loid)s (including arsenic and its species) in Stuckenia pectinata L., Galium aparine L., and Urtica dioica L. The study provided important information on the contents of organic and inorganic arsenic species in selected plants and their response to heavy metal and arsenic contamination. The As(III), As(V), AB (arsenobetaine), MMA (monomethylarsonic acid), and DMA (dimethylarsinic acid) ions were successfully separated on the Hamilton PRP-X100 column with high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) techniques. The Pollution Load Index and geo-accumulation Index (Igeo) values clearly indicate significant pollution of the examined ecosystem with heavy metals. The chemometric analysis with the concepts of (Dis)similarity Analysis, Cluster Analysis, and Principal Component Analysis helped to visualize the variability of the As species concentrations and to analyse correlations between sampling point locations and analyte contents.

The Anthelmintic Ingredient Moxidectin Negatively Affects Seed Germination of Three Temperate Grassland Species.

In animal farming, anthelmintics are regularly applied to control gastrointestinal nematodes. There is plenty of evidence that also non-target organisms, such as dung beetles, are negatively affected by residues of anthelmintics in faeces of domestic ungulates. By contrast, knowledge about possible effects on wild plants is scarce. To bridge this gap of knowledge, we tested for effects of the common anthelmintic formulation Cydectin and its active ingredient moxidectin on seed germination. We conducted a feeding experiment with sheep and germination experiments in a climate chamber. Three wide-spread plant species of temperate grasslands (Centaurea jacea, Galium verum, Plantago lanceolata) were studied. We found significant influences of both, Cydectin and moxidectin, on germination of the tested species. Across species, both formulation and active ingredient solely led to a decrease in germination percentage and synchrony of germination and an increase in mean germination time with the formulation showing a more pronounced response pattern. Our study shows for the first time that anthelmintics have the potential to negatively affect plant regeneration. This has practical implications for nature conservation since our results suggest that treatments of livestock with anthelmintics should be carefully timed to not impede endozoochorous seed exchange between plant populations.

Estimating economic thresholds for site-specific weed control using manual weed counts and sensor technology: an example based on three winter wheat trials.

BACKGROUND: Precision experimental design uses the natural heterogeneity of agricultural fields and combines sensor technology with linear mixed models to estimate the effect of weeds, soil properties and herbicide on yield. These estimates can be used to derive economic thresholds. Three field trials are presented using the precision experimental design in winter wheat. Weed densities were determined by manual sampling and bi-spectral cameras, yield and soil properties were mapped. RESULTS: Galium aparine, other broad-leaved weeds and Alopecurus myosuroides reduced yield by 17.5, 1.2 and 12.4 kg ha(-1) plant(-1) m(2) in one trial. The determined thresholds for site-specific weed control with independently applied herbicides were 4, 48 and 12 plants m(-2), respectively. Spring drought reduced yield effects of weeds considerably in one trial, since water became yield limiting. A negative herbicide effect on the crop was negligible, except in one trial, in which the herbicide mixture tended to reduce yield by 0.6 t ha(-1). Bi-spectral cameras for weed counting were of limited use and still need improvement. Nevertheless, large weed patches were correctly identified. CONCLUSION: The current paper presents a new approach to conducting field trials and deriving decision rules for weed control in farmers' fields.

Indigenous arbuscular mycorrhizal fungal assemblages protect grassland host plants from pathogens.

Plant roots can establish associations with neutral, beneficial and pathogenic groups of soil organisms. Although it has been recognized from the study of individual isolates that these associations are individually important for plant growth, little is known about interactions of whole assemblages of beneficial and pathogenic microorganisms associating with plants.We investigated the influence of an interaction between local arbuscular mycorrhizal (AM) fungal and pathogenic/saprobic microbial assemblages on the growth of two different plant species from semi-arid grasslands in NE Germany (Mallnow near Berlin). In a greenhouse experiment each plant species was grown for six months in either sterile soil or in sterile soil with one of three different treatments: 1) an AM fungal spore fraction isolated from field soil from Mallnow; 2) a soil pathogen/saprobe fraction consisting of a microbial community prepared with field soil from Mallnow and; 3) the combined AM fungal and pathogen/saprobe fractions. While both plant species grew significantly larger in the presence of AM fungi, they responded negatively to the pathogen/saprobe treatment. For both plant species, we found evidence of pathogen protection effects provided by the AM fungal assemblages. These results indicate that interactions between assemblages of beneficial and pathogenic microorganisms can influence the growth of host plants, but that the magnitude of these effects is plant species-specific.

Climbing plants: attachment and the ascent for light.

How do vines climb upward and harvest sunlight? A detailed study of one species (Galium aparine L.) shows that leaf hairs (trichomes) provide one solution that solves both tasks simultaneously.

Performance of potential non-crop or wild species under OECD 208 testing guideline study conditions for terrestrial non-target plants.

The inclusion of 52 potential non-crop or wild species in new OECD guidelines for terrestrial non-target plant (TNTP) testing led to a ring test conducted by four laboratories experienced in regulatory testing. Species selected had shown potential to meet validity criteria of emergence for TNTP studies in a previous evaluation of the 52 species. OECD 208 guideline conditions were applied, with and without seed pretreatments recommended to enhance germination. These species were Abutilon theophrasti (L.) Medic., Avena fatua L., Fallopia convolvulus (L.) Adans., Galium aparine L., Ipomoea hederacea (L.) Jacq. and Veronica persica Poir. Only I. hederacea met the validity criterion of 70% emergence in all laboratories and showed a low variability in biomass. Of the other species, none led to 70% emergence in all four laboratories. The recommended pretreatments did not have a major impact on emergence. Biomass was also investigated with A. theophrasti, A. fatua, Centaurea cyanus L., I. hederacea and Rumex crispus L. Variability of biomass, a key parameter in TNTP regulatory studies, exceeded normal biomass variability of crop species used for TNTP studies. The addition of a thin layer of quartz sand to the soil surface resulted in improved emergence of C. cyanus, G. aparine and V. persica; however, such a procedure, while routine in screening studies to improve germination, is a deviation from the TNTP guidelines. These initial studies indicate that some species could meet the emergence criteria for TNTP testing. However, there is a need for further studies on seed source, seed quality and conditions for uniform emergence before their use in routine regulatory testing.

Mechanical adaptations of cleavers (Galium aparine).

BACKGROUND AND AIMS: Cleavers (Galium aparine) is a fast-growing herbaceous annual with a semi-self-supporting, scrambling-ascending growth habit. Mature plants often use upright species for support. It is common in hedgerows and on waste ground. This study aims to characterize the mechanical behaviour of the stem and roots of cleavers and relate this to the arrangement of structural tissue, the net microfibrillar orientations in the cell walls, and plant growth habit. METHODS: The morphology and mechanics of mature cleavers was investigated using plants grown in pots and ones collected from the grounds at the University of Lincoln, Lincoln, UK. Tensile tests were carried out on the stem and the basal section of the first-order lateral roots. The net orientation of cellulose microfibrils in the cell walls was investigated using polarized light microscopy. KEY RESULTS: Results show that the basal regions of the stem and first-order lateral roots were highly extensible. Breaking strains of 24 +/- 7% were recorded for the stem base and 28 +/- 6% for the roots. Anatomical observations showed that the lower stem (base + 100 mm) was circular in cross-section with a solid central core of vascular tissue, whereas further up the stem the transverse section showed a typical four-angled shape with a ring-like arrangement of vascular tissue and sclerenchyma bundles in the corners. The net orientation of wall microfibrils in the secondary xylem diverges from the longitudinal by between 8 and 9 degrees . CONCLUSIONS: The basal region of the stem of cleavers is highly extensible, but the mechanism by which the stem is able to withstand such high breaking strains is unclear; reorientation of the cellulose fibrils in the stem along the axis of loading is not thought to be responsible.

On the mechanism of selectivity of the corn herbicide BAS 662H: a combination of the novel auxin transport inhibitor diflufenzopyr and the auxin herbicide dicamba.

BAS 662H, a 1:2.5 combination of the semicarbazone-type auxin transport inhibitor diflufenzopyr and the auxin herbicide dicamba, is used as a post-emergence herbicide in corn. The combination has been observed to provide more effective broadleaf weed control and improved tolerance in corn than typical rates of dicamba used alone. In order to analyze this phenomenon, the uptake, translocation, metabolism and action of both compounds, applied alone and in combination, were investigated in Amaranthus retroflexus L, Galium aparine L and corn (Zea mays L). When plants at the third-leaf stage were foliarly treated with diflufenzopyr and dicamba equivalent to field rates of 100 and 250 gha-1, respectively, diflufenzopyr synergistically increased dicamba-induced 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activity and ethylene formation in G aparine and even more in A retroflexus, followed by accumulations of (+)-abscisic acid (ABA) in the shoot tissue within 20 h. This correlated with subsequent growth inhibition, hydrogen peroxide overproduction and progressive tissue damage. Diflufenzopyr also enhanced the activity of other auxin herbicides, such as quinclorac and picloram, and of the synthetic auxin, 1-naphthaleneacetic acid. After foliar and root application of [14C]diflufenzopyr, alone or as BAS 662H, considerably lower tissue concentrations and systemic translocation of radioactivity beyond treated plant parts were found in corn, compared to G aparine and particularly A retroflexus. Furthermore, diflufenzopyr decreased foliar uptake of [14C]dicamba by c 50% selectively in corn, compared to the treatment alone. Metabolism of [14C]diflufenzopyr was more rapid in corn than in the weed species. In combination, the two compounds had no mutual effect on their metabolic degradation. In BAS 662H, diflufenzopyr synergizes the herbicidal activity of dicamba in sensitive weed species. In corn this effect is prevented by a more rapid metabolism of diflufenzopyr, coupled with lower uptake and translocation. Selectivity of BAS 662H is additionally favoured by a higher crop tolerance to dicamba because of reduced foliar uptake of this herbicide in corn under the influence of diflufenzopyr.