SciCombinator

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Concept: Grass

58

The deposition of toxic munitions compounds, such as hexahydro-1, 3, 5-triniitro-1, 3, 5-trizaine (RDX), on soils around targets in live-fire-training ranges is an important source of groundwater contamination. Plants take up RDX but do not significantly degrade it. Reported here is the transformation of two perennial grass species, switchgrass (Panicum virgatum) and creeping bentgrass (Agrostis stolonifera), with the genes for degradation of RDX. These species possess a number of agronomic traits making them well-equipped for the uptake and removal of RDX from root zone leachates. Transformation vectors were constructed with xplA and xplB, which confer the ability to degrade RDX, and nfsI, which encodes a nitroreductase for the detoxification of the co-contaminating explosive 2, 4, 6-trinitrotoluene (TNT). The vectors were transformed into the grass species using Agrobacterium tumefaciens infection. All transformed grass lines showing high transgene expression levels removed significantly more RDX from hydroponic solutions and retained significantly less RDX in their leaf tissues than wild type plants. Soil columns planted with the best-performing switchgrass line were able to prevent leaching of RDX through a 0.5 m root zone. These plants represent a promising plant biotechnology to sustainably remove RDX from training range soil, thus preventing contamination of groundwater. This article is protected by copyright. All rights reserved.

Concepts: Gene, Agriculture, Plant, Soil, Poaceae, Agrobacterium, Grass, Agrostis

28

Parasitic plants have major impacts on plant community structure through their direct negative influence on host productivity and competitive ability. However, the possibility that these parasites may also have indirect impacts on community structure (via the mechanism of nutrient-rich litter input) while long hypothesized, has remained unsupported until now. Using the hemiparasite Rhinanthus minor, we established experimental grassland mesocosms to quantify the impacts of Rhinanthus litter and parasitism across two soil fertility levels. We measured the biomass and tissue nutrient concentration of three functional groups within these communities to determine their physiological response to resource abstraction and litter input by the parasite. We show that Rhinanthus alters the biomass and nutrient status of co-occurring plants with contrasting effects on different functional groups via the mechanism of nutrient-rich litter input. Critically, in the case of grass and total community biomass, this partially negates biomass reductions caused directly by parasitism. This demonstrates that the influence of parasitic plant litter on plant community structure can be of equal importance to the much-reported direct impacts of parasitism. We must consider both positive indirect (litter) and negative direct (parasitism) impacts of parasitic plants to understand their role in structuring plant communities.

Concepts: Fungus, Symbiosis, Parasitism, Mistletoe, Grass, Parasitic plant, Myco-heterotrophy, Rhinanthus

28

One of the most commonly employed water conservation strategies is to restrict lawn watering to limited times on specified days. Water managers typically assume that limiting the frequency and duration of lawn watering will reduce water use. Consequently, the effectiveness of water restrictions is often evaluated based on observed compliance to the specified schedule, whether or not actual reductions in water use are achieved. This assessment approach is more practical than quantifying the reduction in water use brought about by restrictions because quantification of lawn water use is hampered by difficulties in disaggregating the various components of residential water use. Dual meters to separately meter the portion of public supply devoted to lawn water use are rare, and for households that withdraw water from private wells, canals, or ponds for lawn watering, there is no record of such water use at all. As a consequence of this gap in water use data, compliance to a prescribed frequency of watering is often equated with effectiveness. In this paper we develop an alternative metric for evaluating the effectiveness of water restrictions and present a case study in a suburban area in Southeast Florida that illustrates some of the challenges of quantifying lawn water use and explores some of the limitations of day of the week water restrictions as a conservation strategy.

Concepts: Scientific method, Wavelength, Case study, Indian Reductions, Water conservation, Metre, Grass, Metric system

27

To compare the incidence, severity and nature of injuries sustained by Saudi National Team footballers during match-play and training on natural grass and 3rd generation (3G) artificial turf.

Concepts: Artificial turf, Grass

27

The purpose of this study was to investigate the interaction of skin with natural grass and artificial turf at clinical, histological and immunohistochemical level. Therefore, 14 male volunteers performed slidings on dry natural grass, wet natural grass and artificial turf. Directly and 24 h after the slidings, a clinical picture and a 3-mm punch biopsy of the lesion were taken. Paraffin sections (6 µm) were hematoxylin-eosin stained. Immunohistochemistry was performed for CD3, hBD-2, K16, K10, Ki67 and HSP70. Clinically, a sliding performed on artificial turf caused less erythema but more abrasion compared to natural grass. At histological level, artificial turf or dry natural grass damaged the stratum corneum the most. Directly after the sliding, CD3, hBD-2, K16, K10, Ki67 and HSP70 expression was normal. 24 h after a sliding on artificial turf or dry natural grass, an increase of K16, hBD-2 and HSP70 expression was observed. In this pilot study it was not possible to clearly distinguish between skin damage induced by a sliding on artificial turf and natural grass. However, small differences at clinical and histological level seem to exist. This demonstrates the potential of the skin as readout system to evaluate artificial turf systems and mechanical skin damage.

Concepts: Cancer, Biopsy, Anatomical pathology, Histology, Immunohistochemistry, Microtome, Artificial turf, Grass

25

This study quantified the mechanical interactions of 19 American football cleats with a natural grass and an infill-type artificial surface under loading conditions designed to represent play-relevant manoeuvres of elite athletes. Variation in peak forces and torques was observed across cleats when tested on natural grass (2.8-4.2 kN in translation, 120-174 Nm in rotation). A significant (p < 0.05) relationship was found between the peak force and torque on natural grass. Almost all of the cleats caused shear failure of the natural surface, which generated a divot following a test. This is a force-limiting cleat release mode. In contrast, all but one of the cleat types held fast in the artificial turf, resulting in force and torque limited by the prescribed input load from the test device (nom. 4.8 kN and 200 Nm). Only one cleat pattern, consisting of small deformable nubs, released on the artificial surface and generated force (3.9 kN) comparable to the range observed with natural grass. These findings (1) should inform the design of cleats intended for use on natural and artificial surfaces and (2) suggest a mechanical explanation for a higher lower-limb injury rate in elite athletes playing on artificial surfaces.

Concepts: Energy, Torque, Force, American football, Physics in medieval Islam, Artificial turf, Grass, Simple machine

23

Eighty-one cutaway peat production fields with a total area of about 9000 ha exist and were studied in Estonia in 2005-2015. Only a very small number of the fields (seven) have been restored-either afforested or used for growing berries. The re-vegetation of Estonian cutaway peat production fields is mainly the result of natural processes, which are generally very slow due to an unfavourable water regime or a too thin remaining peat layer. The fields are mostly covered by cotton grass and birches. Often sparse vegetation covers 15-20% of a peat field, but some fields have turned into heaths or grasslands with plant coverage up to 60%. However, due to changes in environmental (mainly hydrological) conditions and peat characteristics (mainly peat type), these areas can also be new niches for several species. A number of moss species new to or rare in Estonia, e.g. Pohlia elongata, Ephemerum serratum, Campylopus introflexus and Bryum oblongum, were recorded.

Concepts: Plant, Europe, Field, Grassland, Moss, Grass, The Field, Mosses

20

Many important crops are members of the Poaceae family, which develop root systems characterized by a high degree of root initiation from the belowground basal nodes of the shoot, termed the crown. Although this postembryonic shoot-borne root system represents the major conduit for water uptake, little is known about the effect of water availability on its development. Here we demonstrate that in the model C4 grass Setaria viridis, the crown locally senses water availability and suppresses postemergence crown root growth under a water deficit. This response was observed in field and growth room environments and in all grass species tested. Luminescence-based imaging of root systems grown in soil-like media revealed a shift in root growth from crown-derived to primary root-derived branches, suggesting that primary root-dominated architecture can be induced in S. viridis under certain stress conditions. Crown roots of Zea mays and Setaria italica, domesticated relatives of teosinte and S. viridis, respectively, show reduced sensitivity to water deficit, suggesting that this response might have been influenced by human selection. Enhanced water status of maize mutants lacking crown roots suggests that under a water deficit, stronger suppression of crown roots actually may benefit crop productivity.

Concepts: Agriculture, Wheat, Poaceae, Root, Maize, Zea, Grass, Poales

19

Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO2, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO2 (eCO2) through optimizing functioning of the root-soil interface. By using a labeling technique with (13)C and (15)N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO2. These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO2 effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO2. The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.

Concepts: Photosynthesis, Oxygen, Carbon dioxide, Bacteria, Eukaryote, Species, Pseudomonas, Grass

14

In Arabidopsis, development during flowering is coordinated by transport of the hormone auxin mediated by polar-localized PIN-FORMED1 (AtPIN1). However Arabidopsis has lost a PIN clade sister to AtPIN1, Sister-of-PIN1 (SoPIN1), which is conserved in flowering plants. We previously proposed that the AtPIN1 organ initiation and vein patterning functions are split between the SoPIN1 and PIN1 clades in grasses. Here we show that in the grass Brachypodium sopin1 mutants have organ initiation defects similar to Arabidopsis atpin1, while loss of PIN1 function in Brachypodium has little effect on organ initiation but alters stem growth. Heterologous expression of Brachypodium SoPIN1 and PIN1b in Arabidopsis provides further evidence of functional specificity. SoPIN1 but not PIN1b can mediate flower formation in null atpin1 mutants, although both can complement a missense allele. The behavior of SoPIN1 and PIN1b in Arabidopsis illustrates how membrane and tissue-level accumulation, transport activity, and interaction contribute to PIN functional specificity.

Concepts: Plant, Poaceae, Clade, Flower, Grass