Leading trait dimensions in flood-tolerant plants.

BACKGROUND AND AIMS: While trait-based approaches have provided critical insights into general plant functioning, we lack a comprehensive quantitative view on plant strategies in flooded conditions. Plants adapted to flooded conditions have specific traits (e.g. root porosity, low root/shoot ratio and shoot elongation) to cope with the environmental stressors including anoxic sediments, and the subsequent presence of phytotoxic compounds. In flooded habitats, plants also respond to potential nutrient and light limitations, e.g. through the expression of leaf economics traits and size-related traits, respectively. However, we do not know whether and how these trait dimensions are connected. METHODS: Based on a trait dataset compiled on 131 plant species from 141 studies in flooded habitats, we quantitatively analysed how flooding-induced traits are positioned in relation to the other two dominant trait dimensions: leaf economics traits and size-related traits. We evaluated how these key trait components are expressed along wetness gradients, across habitat types and among plant life forms. KEY RESULTS: We found that flooding-induced traits constitute a trait dimension independent from leaf economics traits and size-related traits, indicating that there is no generic trade-off associated with flooding adaptations. Moreover, individual flooding-induced traits themselves are to a large extent decoupled from each other. These results suggest that adaptation to stressful environments, such as flooding, can be stressor specific without generic adverse effects on plant functioning (e.g. causing trade-offs on leaf economics traits). CONCLUSIONS: The trait expression across multiple dimensions promotes plant adaptations and coexistence across multifaceted flooded environments. The decoupled trait dimensions, as related to different environmental drivers, also explain why ecosystem functioning (including, for example, methane emissions) are species and habitat specific. Thus, our results provide a backbone for applying trait-based approaches in wetland ecology by considering flooding-induced traits as an independent trait dimension.

Global patterns of the leaf economics spectrum in wetlands.

The leaf economics spectrum (LES) describes consistent correlations among a variety of leaf traits that reflect a gradient from conservative to acquisitive plant strategies. So far, whether the LES holds in wetland plants at a global scale has been unclear. Using data on 365 wetland species from 151 studies, we find that wetland plants in general show a shift within trait space along the same common slope as observed in non-wetland plants, with lower leaf mass per area, higher leaf nitrogen and phosphorus, faster photosynthetic rates, and shorter leaf life span compared to non-wetland plants. We conclude that wetland plants tend to cluster at the acquisitive end of the LES. The presented global quantifications of the LES in wetland plants enhance our understanding of wetland plant strategies in terms of resources acquisition and allocation, and provide a stepping-stone to developing trait-based approaches for wetland ecology.

Communication Aspects of Visible Light Positioning (VLP) Systems Using a Quadrature Angular Diversity Aperture (QADA) Receiver.

Visible light positioning (VLP) is a promising indoor localization system in which light emitting diode (LED) luminaires are used as positioning beacons. Data communication is an essential aspect of any VLP system, as each luminaire must transmit information about its own location to the receiver. The quadrature angular diversity aperture (QADA) is a new receiver designed specifically for VLP systems using angle-of-arrival estimation. Previous QADA research has focused only on positioning and assumed error-free communication. In this paper, we investigate, via simulations and experiment, the actual communication characteristics of a VLP system that uses a QADA receiver. We calculate the signal-to-noise ratio and bit-error-rates for a range of scenarios and demonstrate the impact of the dimensions of the receiver. We show that reliable communication is assured in typical operating scenarios, proving that communication will not be a limiting factor when using QADA in VLP systems.

Indoor Visible Light Positioning: Overcoming the Practical Limitations of the Quadrant Angular Diversity Aperture Receiver (QADA) by Using the Two-Stage QADA-Plus Receiver.

Visible light positioning (VLP), using LED luminaires as beacons, is a promising solution to the growing demand for accurate indoor positioning. In this paper, we introduce a two-stage receiver that has been specifically designed for VLP. This receiver exploits the advantages of two different VLP receiver types: photodiodes and imaging sensors. In this new receiver design a quadrant angular diversity aperture (QADA) receiver is combined with an off-the-shelf camera to form a robust new receiver called QADA-plus. Results are presented for QADA that show the impact of noise and luminaire geometry on angle of arrival estimation accuracy and positioning accuracy. Detailed discussions highlight other potential sources of error for the QADA receiver and explain how the two-stage QADA-plus can overcome these issues.

High angular resolution visible light positioning using a quadrant photodiode angular diversity aperture receiver (QADA).

The increasing use of white LEDs for indoor illumination provides a significant opportunity for Visible Light Positioning (VLP). The challenge is to design a small, unobtrusive sensor that can be incorporated into mobile devices to provide accurate measurements for triangulation. We present experimental results for a novel angle of arrival (AOA) detector that has been designed for use in a VLP system. The detector is composed of a transparent aperture in an opaque screen that is located above a quadrant photodiode (PD), separated by a known vertical distance. Light passing through the aperture from an LED casts a light spot onto the quadrant PD. The position of this spot, coupled with knowledge of the height of the aperture above the quadrant PD, provides sufficient information to determine both the incident and polar angles of the light. Experiments, using a prototype detector, show that detector is capable of accurate estimation of AOA. The root mean square errors (rMSE) were less than 0.11° for all the measured positions on the test bed, with 90% of positions having an rMSE of less than 0.07°.

Infant feeding knowledge, perceptions and practices among women with and without HIV in Johannesburg, South Africa: a survey in healthcare facilities.

BACKGROUND: South Africa has a history of low breastfeeding rates among women with and without Human Immunodeficiency Virus (HIV). In this study, we assessed infant feeding knowledge, perceptions and practices among pregnant and postpartum women with and without HIV, in the context of changes in infant feeding and Prevention of Mother-to-Child Transmission of HIV (PMTCT) guidelines. METHODS: This was a cross-sectional survey conducted from April 2014 to March 2015 in 10 healthcare facilities in Johannesburg, South Africa. A total of 190 pregnant and 180 postpartum women (74 and 67, respectively, were HIV positive) were interviewed using a semi-structured questionnaire. Multiple regression analyses assessed factors associated with an intention to exclusively breastfeed, and exclusive breastfeeding of infants less than six months of age. RESULTS: Women with HIV had better overall knowledge on safe infant feeding practices, both in general and in the context of HIV infection. There were however gaps in knowledge among women with and without HIV. Information from healthcare facilities was the main source of information for all groups of women in the study. A greater percentage of women without HIV 80.9% (93/115), reported an intention to exclusively breastfeed, compared to 64.9% (48/74) of women with HIV, p = 0.014. Not having HIV was positively associated with a reported intention to breastfeed, Adjusted Odds Ratio (AOR) 3.60, 95% CI 1.50, 8.62. Other factors associated with a reported intention to exclusively breastfeed were prior breastfeeding experience and higher knowledge scores on safe infant feeding practices in the context of HIV infection. Among postpartum women, higher scores on general knowledge of safe infant feeding practices were positively associated with reported exclusive breastfeeding, AOR 2.18, 95% CI 1.52, 3.12. Most women perceived that it was difficult to exclusively breastfeed and that cultural factors were a barrier to exclusive breastfeeding. CONCLUSIONS: While a greater proportion of women are electing to breastfeed, HIV infection and cultural factors remain an important influence on safe infant feeding practices. Healthcare workers are the main source of information, and highlight the need for accurate and consistent messaging for both women with and without HIV.

Aerenchymatous phellem in hypocotyl and roots enables O2 transport in Melilotus siculus.

• Aerenchymatous phellem (secondary aerenchyma) has rarely been studied in roots. Its formation and role in internal aeration were evaluated for Melilotus siculus, an annual legume of wet saline land. • Plants were grown for 21 d in aerated or stagnant (deoxygenated) agar solutions. Root porosity and maximum diameters were measured after 0, 7, 14 and 21 d of treatment. Phellem anatomy was studied and oxygen (O(2)) transport properties examined using methylene blue dye and root-sleeving O(2) electrodes. • Interconnecting aerenchymatous phellem developed in hypocotyl, tap root and older laterals (but not in aerial shoots), with radial intercellular connections to steles. Porosity of main roots containing phellem was c. 25%; cross-sectional areas of this phellem were threefold greater for stagnant than for aerated treatments. Root radial O(2) loss was significantly reduced by complete hypocotyl submergence; values approached zero after disruption of hypocotyl phellem below the waterline or, after shoot excision, by covering hypocotyl phellem in nontoxic cream. • Aerenchymatous phellem enables hypocotyl-to-root O(2) transport in M. siculus. Phellem increases radially under stagnant conditions, and will contribute to waterlogging tolerance by enhancing root aeration. It seems likely that with hypocotyl submerged, O(2) will diffuse via surface gas-films and internally from the shoot system.

Reasons for the presence or absence of convective (pressurized) ventilation in the genus Equisetum.

• The very high rates of convective ventilation reported recently in Equisetum telmateia (up to 120 cm(3) min(-1); internal wind speed, 10 cm s(-1)) prompted this study of a further eight species for the presence or absence of convection and the possible reasons for this. • Convection rates were examined in relation to anatomical pathways, internal resistance to applied pressurized gas flow and stomata. • Only species with interconnecting cortical aerenchyma in branches (when present), shoots and rhizomes induced convection. Rapid humidity-induced convection (HIC) occurred in E. palustre (up to 13 cm(3) min(-1)), with slower rates in E. × schaffneri and E. ramosissimum (≤ 6 and 3 cm(3) min(-1), respectively). Excised shoots of E. hyemale and E. fluviatile showed the potential for HIC (≤ 0.5 and 0.15 cm(3) min(-1), respectively), but not into the rhizomes. High rates were linked to low internal gas flow resistance. No convection was detected in E. scirpoides, E. sylvaticum or E. arvense due to the extremely high resistance to pressure flow, for example, from intercalary meristems and, in the last two, to nonaerenchymatous branches. • Of the nine Equisetum species studied so far, four showed through-flow convection; the other species must rely solely on diffusion for underground aeration in wet soils.

Record rates of pressurized gas-flow in the great horsetail, Equisetum telmateia. Were Carboniferous Calamites similarly aerated?

Significant pressurized (convective) ventilation has been demonstrated in some flowering wetland plants, for example water-lilies and reeds, but not previously in nonflowering plants. Here we investigated convective flows in the great horsetail, Equisetum telmateia, and the possibility that convections aerated the massive rhizomes of the Calamites, extinct giant horsetails of the Carboniferous. Convection in E. telmateia was examined in relation to induction sites, anatomical pathways, relative humidity (RH), external wind-speed, diurnal effects, rhizome resistance and pressure-gradients. A mathematical model, incorporating Calamite aeration anatomy, was applied in assessing potentials for convective aeration. Individual shoots of E. telmateia generated extremely high rates of humidity-induced convection: < or = 120 cm(3) min(-1) (internal wind-velocity: 10 cm s(-1)) with rates proportional to branch numbers and 1/RH. Flows passed through branches, stem and rhizome via low-resistance lacunae (vallecular canals) and vented via stubble. Stomata supported internal pressures up to 800 Pa. Anatomically, E. telmateia resembles the Calamites and modelling predicted possible flows of 70 l min(-1) per Calamite tree. This is the first demonstration of significant convective flow in a nonflowering species, indicating that plant ventilation by a type of 'molecular gas-pump' may date back 350 million yr or more. Stomatal form and low-resistance pathways may facilitate high flow rates.

Effects of oil on internal gas transport, radial oxygen loss, gas films and bud growth in Phragmites australis.

BACKGROUND AND AIMS: Oil pollution of wetlands is a world-wide problem but, to date, research has concentrated on its influences on salt marsh rather than freshwater plant communities. The effects of water-borne light oils (liquid paraffin and diesel) were investigated on the fresh/brackish wetland species Phragmites australis in terms of routes of oil infiltration, internal gas transport, radial O(2) loss (ROL), underwater gas films and bud growth. METHODS: Pressure flow resistances of pith cavities of nodes and aerenchyma of leaf sheaths, with or without previous exposure to oil, were recorded from flow rates under applied pressure. Convective flows were measured from living excised culms with oiled and non-oiled nodes and leaf sheaths. The effect of oil around culm basal nodes on ROL from rhizome and root apices was measured polarographically. Surface gas films on submerged shoots with and without oil treatment were recorded photographically. Growth and emergence of buds through water with and without an oil film were measured. KEY RESULTS: Internodes are virtually impermeable, but nodes of senesced and living culms are permeable to oils which can block pith cavity diaphragms, preventing flows at applied pressures of 1 kPa, natural convective transport to the rhizome, and greatly decreasing ROL to phyllospheres and rhizospheres. Oil infiltrating or covering living leaf sheaths prevents humidity-induced convection. Oil displaces surface gas films from laminae and leaf sheaths. Buds emerge only a few centimetres through oil and die. CONCLUSIONS: Oil infiltrates the gas space system via nodal and leaf sheath stomata, reducing O(2) diffusion and convective flows into the rhizome system and decreasing oxygenation of phyllospheres and rhizospheres; underwater gas exchange via gas films will be impeded. Plants can be weakened by oil-induced failure of emerging buds. Plants will be most at risk during the growing season.

Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems.

We show using simulations that a combination of Orthogonal Frequency Division Multiplexing (OFDM) and Optical Single Sideband Modulation (OSSB) can be used to adaptively compensate for chromatic dispersion in ultra-long-haul 10 Gbps Standard Single-Mode Fiber (S-SMF) links. Additionally, for optical noise limited systems with Forward-Error Correction, OFDM can tolerate an Optical Signal to Noise Ratio (OSNR) 0.5 dB higher than NRZ systems providing the optical carrier is suppressed.

Rice: sulfide-induced barriers to root radial oxygen loss, Fe2+ and water uptake, and lateral root emergence.

BACKGROUND AND AIMS: Akagare and Akiochi are diseases of rice associated with sulfide toxicity. This study investigates the possibility that rice reacts to sulfide by producing impermeable barriers in roots. METHODS: Root systems of rice, Oryza sativa cv. Norin 36, were subjected to short-term exposure to 0.174 mm sulfide (5.6 ppm) in stagnant solution. Root growth was monitored; root permeability was investigated in terms of polarographic determinations of oxygen efflux from fine laterals and the apices of adventitious roots, water uptake, anatomy and permeability to Fe2+ using potassium ferricyanide. KEY RESULTS: Both types of root responded rapidly to the sulfide with immediate cessation of growth, decreased radial oxygen loss (ROL) to the rhizospheres and reduced water uptake. Profiles of ROL measured from apex to basal regions of adventitious roots indicated that more intense barriers to ROL than normal were formed around the apices. Absorption of Fe2+ appeared to be impeded in sulfide-treated roots. In adventitious roots, deposition of lipid material (suberisation) and thickenings of walls within the superficial cell layers were obvious within a week after lifting the treatment and could prevent the emergence of laterals and commonly result in their upward longitudinal growth within the cortex. Death of laterals sometimes occurred prior to emergence; emergent laterals eventually died. In adventitious roots, blockages formed within the vascular and aeration systems in response to the sulfide. CONCLUSIONS: In both adventitious and lateral roots, sulfide-induced cell wall suberization and thickening of the superficial layers were correlated with reduced permeability to O2, water and Fe2+. This study sheds light on some of the symptoms of diseases such as Akiochi. The results correlate with the authors' previous findings on the effects on roots of sulfide and lower organic acids in Phragmites and of acetic acid in rice.

Stem photosynthesis not pressurized ventilation is responsible for light-enhanced oxygen supply to submerged roots of alder (Alnus glutinosa).

BACKGROUND AND AIMS: Claims that submerged roots of alder and other wetland trees are aerated by pressurized gas flow generated in the stem by a light-induced thermo-osmosis have seemed inconsistent with root anatomy. Our aim was to seek a verification using physical root-stem models, stem segments with or without artificial roots, and rooted saplings. METHODS: Radial O2 loss (ROL) from roots was monitored polarographically as the gas space system of the models, and stems were pressurized artificially. ROL and internal pressurization were also measured when stems were irradiated and the xylem stream was either CO2 enriched or not. Stem photosynthesis and respiration were measured polarographically. Stem and root anatomy were examined by light and fluorescence microscopy. KEY RESULTS: Pressurizing the models and stems to

10Gbit/s Multimode Fiber Link using Power-Efficient Orthogonal-Frequency-Division Multiplexing.

Orthogonal Frequency Division Multiplexing (OFDM) can provide electronic dispersion compensation of optical paths. However, it requires a high bias to convert bipolar electrical signals to unipolar optical signals, so is inefficient in optical power for a given electrical signal to noise ratio. We present a novel method of transmitting OFDM signals over multimode fibers that increases electrical SNR by 7 dB for a given optical power. Using simulations, we show a 1.8 dB sensitivity benefit over 10 Gbit/s NRZ (Non-Return to Zero) and demonstrate compensation of intermodal dispersion in a 300-m multimode fiber that cannot support NRZ.

Chlorophyll development in mature lysigenous and schizogenous root aerenchymas provides evidence of continuing cortical cell viability.

The'greening'of mature aerenchymatous adventitious roots of Phragmrtes auttralis (Cav.) Trin. ex Steudel, rice, maize, Atorm calamus L., and Epilobium hirsutum L., when exposed to light was found to be due to chloroplast development in the cortex. In Phragmites, maize and rice, which are characterized by lysigenous cortical aerenchymos, chlomplasts developed not only in normally intact cortical cell layers adjacent to the exodermis/hypodermis and endodermis, but also in isolated radial cellular strands (and isolated cells) between the lacunae, cells which had failed to collapse during the active phase of aerenchyma development. The observation provides conclusive evidence for the continuing viability and the potential for active metabolism of the non-lysed cells of lysigenous aerenchymas. In Acortis and Epitobium, chloroplast development occurred in the cells of the schisogettmts cortical aerenchymas. In Phragmites, chloroplasts also developed in the non-aerenchymatous cortex of illuminated fine basal lateral roots.