Rhynchelytrum Repens Research Articles

Chemical composition and digestibility of hays of three grasses ammonized with urea

<p class="Default">This study aimed to evaluate the effect of ammoniation with urea on the chemical composition and in vitro digestibility of <em>Rhynchelytrum repens</em>, <em>Aristida setifolia</em> and <em>Eleusine indica</em> grasses. The experimental design was completely randomized, with a 3×2 factorial treatment (hay of three species, treated with or without urea) and five replications. The contents of dry matter, crude protein, neutral detergent fiber, acid detergent fiber, mineral matter, lignin, total carbohydrates and digestibility were evaluated in the grass (R. repens, A. setifolia e E. indica). The treatment with urea affected (<em>p</em> < 0.05) most of the variables analyzed in grass hays. Hay treated with urea showed an increase in crude protein levels and the highest value was observed for the hay of Eleusine indica grass. Rhynchelytrum repens grass hay presented the highest fiber value in acid detergent, with and without urea. An increase in vitro dry matter digestibility was observed after the use of urea. It is concluded that ammonization with 5% urea improves the nutritional values of hay in Rhynchelytrum repens, Aristida setifolia and Eleusine indica grasses, increasing the levels of protein, minerals and digestibility.</p>

Paper Spray Mass Spectrometry on the Analysis of Phenolic Compounds in Rhynchelytrum repens: A Tropical Grass with Hypoglycemic Activity.

The characterization of plant compounds with pharmacological activity is a field of great relevance in research and development. As such, identification techniques with the goal of developing new drugs or even validating the bioactive properties of extracts must be explored in order to further expand the knowledge of plant extract composition. Most works in this field employ HPLC, when exploring non-structural and cell wall carbohydrates from Rhynchelytrum repens. Phenolic compounds were studied by classical chromatography techniques and UV-vis spectrophotometry, with C-glycosylated flavonoids being detected but with no further details regarding the chemical structure of these compounds. In this work we employ paper spray ionization mass spectrometry (PS-MS) for the evaluation of the chemical profile of R. repens methanol extract. Positive ionization mode identified 15 compounds, belonging to flavonoids, fatty acids, and other classes of compounds; negative mode ionization was able to identify 20 compounds comprising the classes of quinic acids, stilbenes and flavonoids. PS-MS proved effective for the evaluation of R. repens extracts, making it possible to identify a total of thirty-five compounds. The bioactive properties attributed to R. repens were confirmed by the identification and characterization of compounds identified by PS-MS.

Influence of soil physical factors on productivity of herbaceous forage species in Kivaa and Ntugi rangelands in Eastern Kenya

Rangelands are extensive tracts of land with natural vegetation which is the main forage resource for domestic and wild ungulates. This study investigated the influence of soil texture, bulk density, and moisture content on the production of herbaceous forage species biomass in Kivaa and Ntugi rangelands in Eastern Kenya. Stratified random sampling was used where one out of four blocks of the target rangelands was picked and three belt transects established. Along the belt transects, ten experimental plots of 5 metres by 5 metres were established at intervals of 5 metres. Key forage species were identified using a structured questionnaire administered to key informants. Soil samples were collected from the experimental plots and analyzed for soil texture, bulk density and moisture content. Forage samples were collected and dry matter weight determined. The data collected were analyzed using both descriptive and inferential statistics especially tabulation and regression respectively. The study identified the most valuable forage species namely, Dichanthium annulatum, Themeda triandra, Cenchrus ciliaris, Rhynchelytrum repens, Digitaria abyssinica, Chloris roxburghiana and Cyperus rotundus. Soils in Ntugi ranged from clay loam to sandy clay while those from Kivaa ranged from silty loam to sandy loam. There was higher moisture content in soils in Ntugi than soils in Kivaa (t = 7.71, P ≤ 0.05). Soil moisture content had significant influence on herbage production in both Kivaa (R= 0.968, P ≤ 0.05) and Ntugi (R = 0.962, P ≤ 0.05). Soil bulk density significantly influenced forage grass species herbage production in Ntugi in 2014 (R= 0.513, P ≤ 0.05) and in 2016 ((R = 0.632, P ≤ 0.05). This study concluded that soil texture, bulk density and moisture content significantly influenced herbaceous forage production in the two rangelands. The study recommends use of rotational grazing systems combined with proper stocking rates to maintain moderate soil bulk density and good levels of soil moisture for the herbaceous forage species to continue producing adequate biomass while maintaining residual foliage for continued primary production.

Host weed species range of Meloidogyne ethiopica whitehead (Tylenchida: Meloidogynidae) found in Brazil

Meloidogyne ethiopica is considered to be one of the most economically important emerging nematode species, reported to cause crop losses to several hosts worldwide. The significance of this species is due to its high virulence and degree of polyphagia, in addition to persisting on weed hosts within agricultural fields. This study evaluated the host status of 36 different weed species, confirming the polyphagia habit of M. ethiopica and indicating which plant species may be alternative hosts for this plant nematode. Weed species were inoculated with 5000 eggs and second-stage juveniles (J2) of M. ethiopica, with gall index (GI), nematode/g root (Nem/g), and reproduction factor (RF) value determined following 60 days post inoculation. The data obtained indicate that many weed species may be excellent hosts for M. ethiopica. Plants deemed susceptible (RF ≥ 1.0) were: Acanthospermum australe, Amaranthus deflexus, A. hybridus, A. spinosus, A. viridis, Bidens pilosa, B. subalternans, Cardiospermum halicacabum, Commelina benghalensis, Cynodon dactylon, Euphorbia heterophylla, Galinsoga parviflora, Ipomoea grandifolia, I. nil, I. purpurea, Leonurus sibiricus, Nicandra physaloides, Oxalis corniculata, Portulaca oleracea, Raphanus raphanistrum, Sida rhombifolia, Solanum americanum, S. pseudocapsicum, S. sisymbriifolium, Sonchus oleraceus and Talinum paniculatum, representing 72.2% of the species assessed. The species Conyza bonariensis, Cyperus rotundus, Digitaria horizontalis, D. insularis, Echinochloa colonum, Eleusine indica, Lolium multiflorum, Polygonum hydropiperoides, Rhynchelytrum repens and Senecio brasiliensis were resistant to M. ethiopica (RF < 1.0). Based on the new host records presented, it is vital that control of weed species within agricultural fields are considered as part of effective management of M. ethiopica.

Evaluación de semilla de pastos cosechados en caminos y campos de cultivos

The physiological and physical quality of the grass seed Sporobolus aeroides , Bouteloua curtipendula , Briza minor , Bromus mollis , Chencrus ciliaris , Rhynchelytrum repens , Eragrostis curvula , Bouteloua gracilis , Setaria geniculata, Leptochloa filiformis , Bothriochloa perforata y Digitaria californica collected in Soledad de Graciano Sanchez, SLP in the years 2013, 2014 and 2015. The percentage of germination (PGER), dead seed (DS), seedling dry weight (SDW), seedling height (SH), analytical purity (AP), thousand seed weight (TSW) and volumetric weight (VW) were evaluated. The largest PGER was for Pega Ropa 2014 with 91.7%, and the minimum in Banderita 2014 with 23.2%. For DS Popotillo Plateado 2013 showed the highest percentage (9.5%). For SDW, Carretero grass 2014 presented the highest value with 0.6266 g for 20 seedlings. For SH, Punta Blanca grass 2014 presented the highest value with 15.25 mm. For AP for the year 2013 the Alcalino grass obtained a 100%, Plumilla 2013 presented 69.66%, in 2014 the Alcalino grass showed 100% and Buffel the lowest with 65%. For VW the Alcalino 2015 showed the highest value with 64.32 kg hl -1 . It is concluded that the evaluation of the seeds showed variability in quality.

Effect of Cover Crops, and the Management Thereof, on the Weed Spectrum in a Drip-irrigated Vineyard: 2. Weeds Growing From Grapevine Berry Set to Post-harvest

A five-year trial (2009 to 2013) was executed in a drip-irrigated seven-year-old Shiraz/101-14 Mgt vineyard established on a sandy to sandy clay loam soil at Blaauwklippen Farm (33°58’S, 18°50’E) near Stellenbosch, South Africa. Fourteen treatments, consisting of two management practices applied to five cover crop species, as well as winter-growing weeds (no cover crop) and winter-growing weeds (no cover crop) with nematicide applied in the vine row, were applied. The weeds and cover crop species were eithercontrolled chemically (CC) or mechanically (MC) during grapevine bud break, followed by full-surface chemical control during berry set (for both CC and MC treatments). Rhynchelytrum repens (Natal redtop)dominated the post-harvest pre-treatment weed spectrum in all the treatments except Eruca sativa cv. Nemat (Nemat) (MC). This species lost its post-harvest dominance from 2010 onwards. It seems that the relatively low summer rainfall during the 2010/2011 season allowed Anagallis arvensis to appear in April 2011 and dominate some of the treatments, which coincided with the disappearance of Cynodon dactylon (common couch) and Polygonum aviculare (prostrate knotweed). Digitaria sanguinalis, common couch and prostrate knotweed seemed to establish better during late summer where MC was applied. The pre-treatment average post-harvest weed stand of 5.53 t/ha was reduced to 0.53 t/ha within one season, illustrating the benefit of full-surface chemical weed control applied during grapevine berry set.

Evaluation of the Allelopathic Potential of Fifteen Common Malaysian Weeds

The use of allelopathy concept in weed management has received attentions to minimize extensively the reliance on herbicide applications on the agriculture industry in Malaysia. A laboratory study was conducted to evaluate the allelopathic potential of 15 Malaysian common weed species of different morphological characteristics (broadleaves, sedges and grasses). They were screened using the Sandwich method (from leaf litter leachate) and the Dish pack method (for testing the presence and content of volatile compounds in weeds). Among the 15 weed species tested, the leaf litter leachate of Centrosema pubescens was observed to be the most sensitive plant material inhibiting the growth of lettuce radicle (84%) and hypocotyl (55%) in the Sandwich bioassay compared to the control. This was followed by Asystasia gangentica (81%) and Cynodon dactylon (80%) inhibiting the lettuce radicle growth. In the Dish pack bioassay, Rhynchelytrum repens demonstrated maximum inhibition on the radicle and hypocotyl elongations by 44% and 29%, respectively, (over control) at 41 mm distance from the source well. Meanwhile, at the same distance, Cynodon dactylon was observed to have the least inhibitory effect on lettuce radicle growth by 12%. The results presented can be utilized as benchmark information for further research on the identification and isolation of allelochemicals for weed control strategies.

Reproduction of Pratylenchus zeae on Weeds

ABSTRACT Weeds can be hosts of root-lesion nematode (Pratylenchus spp.), maintaining or increasing their population in the soil. The objective of this study was to evaluate the reaction of 25 weeds species to the nematode Pratylenchus zeae. The weed plants were individually inoculated with 1,000 individuals of P. zeae and maintained in a greenhouse for 90 days. After this period, eggs and nematodes were extracted, quantified, and the reproduction factor (RF = final population/initial population) was calculated. All tested weeds were susceptible (RF&gt;1) to P. zeae, and the species Brachiaria decumbens, Rhynchelytrum repens, Digitaria insularis, D. horizontalis, B. brizantha were the most susceptible to this parasite.

Edaphic and seasonal heterogeneity of seed banks in agricultural fields of a tropical dry forest region in southern Mexico

The slash-and-burn agriculture practiced across tropical dry regions results in the elimination of native vegetation. Upon field abandonment, the seed bank becomes a potentially important mechanism of natural regeneration at early successional stages. Soil properties and climate seasonality may affect seed bank characteristics, thus we analyzed the effects of these two factors on seed bank density and composition in agricultural fields of a seasonally dry tropical region of southern Mexico. Soil cores were collected for the rainy and the dry seasons in order to assess changes occurring in the seed bank from the time of harvest to the moment when succession could potentially start (the next rainy season). The 12 studied fields comprised three different soil types recognized by local inhabitants: sandy and stony, silty, and clayey soils, locally known as cascajo, black soil, and red soil, respectively. At each field 20 soil cores (8 cm diameter, 4.5 cm depth) were collected and mixed to form four pooled samples, which were placed in a greenhouse to induce germination. A total of 4,422 seedlings (2,291 seeds m-2) representing 40 species were recorded. The most abundant species were, in decreasing order, Melanthera nivea, Rhynchelytrum repens, Waltheria indica, Amaranthus scariosus, Digitaria bicornis , and Cenchrus pilosus . Herbs were the prevailing growth form (&gt; 80% of total richness). No clear pattern was observed in the seed bank related to soil type; however, seed bank characteristics tended to be associated with the time of use of the agricultural fields, a variable that was not controlled in the study. Seed bank species richness was significantly larger in the dry season, and although seed density showed a similar trend, it was not significant. The studied seed banks contain no elements of the regional primary tropical dry forest, which suggests that seed banks in deforested areas cannot guarantee their maintenance beyond forested areas.

Effect of nitrogen on the sporulation of arbuscular mycorrhizal fungi colonizing several gramineous plant species

We examined the effect of nitrogen on sporulation of arbuscular mycorrhizal (AM) fungi colonizing gramineous plant species growing in a volcanic deposit with a nitrogen deficit. Five gramineous species (Saccharum spontaneum, Rhynchelytrum repens, Miscanthus sinensis, Paspalum notatum, and Eragrostis curvula) growing in a volcanic deposit on Mount Fugendake, Japan, were inoculated with the AM fungus Glomus etunicatum with or without the application of nitrate nitrogen (20 mg N kg soil–1). The AM dependent species (M. sinensis and P. notatum) which showed growth response to the inoculation increased sporulation with nitrogen addition. However, the species that did not depend on AM for their growth (S. spontaneum and E. curvula) showed decreased or non-increased sporulation with nitrogen application. This trend was also found for Glomus etunicatum in a dual-inoculation experiment with Glomus etunicatum and Gigaspora margarita. These indicate that the effect of nitrogen on the sporulation of AM fungi differed among gramineous species and that in some species nitrogen may suppress the sporulation.

Preparation, characterization, and biological properties of β-glucans

β-Glucans are soluble fibers with physiological functions, such as, interference with absorption of sugars and reduction of serum lipid levels. β-glucans are found in different species, such as, Rhynchelytrum repens, Lentinus edodes, Grifola frondosa, Tremella mesenterica, Tremella aurantia, Zea may, Agaricus blazei, Phellinus baummi, Saccharomyces cerevisae (yeast), and Agaricus blazei murell (mushroom). Analysis of the fractions reveals the presence of arabinose, glucose, xylose, and traces of rhamnose and galactose. The presence of β-glucan in these fractions is confirmed by hydrolyzing the polymers with endo-β-glucanase from Bacillus subtilis, followed by high-performance liquid chromatography (HPLC) analysis of the characteristic oligosaccharides produced. The 4 M KOH fractions from different tissues are subjected to gel permeation chromatography on Sepharose 4B, with separation of polysaccharides, with different degrees of polymerization, the highest molecular mass (above 2000 kDa) being found in young leaves. The molecular mass of the leaf blade polymers is similar (250 kDa) to that of the maize coleoptiles β-glucan used for comparison. The 4 M KOH fraction injected into rats with streptozotocin-induced diabetes has shown hypoglycemic activity, reducing blood sugar to normal levels for approximately 24 hours. This performance is better than that obtained with pure β-glucan from barley, which decreases blood sugar levels for about four hours. These results suggest that the activity of β-glucans is responsible for the use of this plant extract as a hypoglycemic drug in folk medicine.

Major and trace element distributions around active volcanic vents determined by analyses of grasses: implications for element cycling and bio-monitoring

Samples of grass were collected at Masaya Volcano (Nicaragua; Rhynchelytrum repens and Andropogon angustatus) and the Piton de La Fournaise (around the April 2007 eruptive vent, La Reunion; Vetiveria zizanioides) to investigate the controls on major and trace element concentrations in plants around active volcanic vents. Samples were analysed using inductively coupled plasma mass spectrometry for a wide range of elements, and atomic absorption spectroscopy for Hg. At Masaya, As, Cu, Mo, Tl and K concentrations in both grass species showed a simple pattern of variability consistent with exposure to the volcanic plume. Similar variability was found in A. angustatus for Al, Co, Cs, Hg and Mg. At the Piton de La Fournaise, the patterns of variability in V. zizanioides were more complex and related to variable exposures to emissions from both the active vent and lava flow. These results suggest that exposure to volcanic emissions is, for many elements, the main control on compositional variability in vegetation growing on active volcanoes. Thus, vegetation may be an important environmental reservoir for elements emitted by volcanoes and should be considered as part of the global biogeochemical cycles.

Chemical composition and dry matter digestion of some native and cultivated grasses in Mexico

The objective of the study was to quantify differences in nutritive value, over four seasons, of native grasses such as &lt;i&gt;Bouteloua curtipendula, Bouteloua trifida, Brachiaria fasciculata, Chloris ciliata, Digitaria insularis, Leptochloa filiformis, Panicum hallii, Panicum obtusum, Paspalum unispicatum, Setaria grisebachii, Setaria macrostachya, Tridens eragrostoides, Tridens muticu&lt;/i&gt;s and naturalized &lt;i&gt;chrus ciliaris&lt;/i&gt; and &lt;i&gt;Rhynchelytrum repens&lt;/i&gt; that are used as forages for grazing beef cattle. &lt;i&gt;Cenchrus ciliaris&lt;/i&gt; was included as a reference grass of good nutritional quality. Plants were collected in autumn 2001 and in winter, spring and summer 2002. The nutritive value was assessed in terms of nutrient content, effective rumen degradable dry matter (EDDM), metabolizable energy (ME) and metabolizable protein (MP). Most grasses had crude protein (CP) content comparable to the reference &lt;i&gt;C. ciliaris&lt;/i&gt; grass (grand mean = 120 g/kg) and some of them had a higher content (140 g/kg). Cell wall (NDF) and lignin contents were lower in &lt;i&gt;C. ciliaris&lt;/i&gt; (650 g/kg, 30, respectively) than in the other grasses (mean = 700 g/kg, 60, respectively). All grasses had less EDDM (mean = 420 g/kg) than &lt;i&gt;C. ciliaris&lt;/i&gt; (470 g/kg). All grasses had the ME content (mean = 5.6 MJ/kg DM) that was lower for maintenance requirements of growing beef cattle. Conversely, mean MP values (67 g/kg DM) were sufficient. Lower content of P (annual mean = 120 g/kg DM), Na (0.3) and Cu (40 mg/kg DM) was detected in all grasses to meet the requirements of growing cattle. All grasses, in all seasons, had sufficient CP and MP content to meet the maintenance requirements of growing beef cattle. Higher levels of EDDM occurred in summer and autumn. Because of their good nutritional quality, grasses such as &lt;i&gt;B. fasciculata, C. ciliata, P. hallii, P. obtusum, S. grisebachii, S. macrostachy&lt;/i&gt; and &lt;i&gt;T. eragrostoides&lt;/i&gt; can be considered as good forages for ruminants.

Patterns of Plant Composition in Fragments of Globally Imperiled Pine Rockland Forest: Effects of Soil Type, Recent Fire Frequency, and Fragment Size

Maintaining native plant diversity through fire management is challenging in the wildland-urban interface. In subtropical South Florida, fragments of fire-dependent, globally imperiled pine rockland forest are scattered throughout urban areas. To determine the effects of recent fire frequency, major soil type, and fragment size on species composition, we measured understory vascular plant presence and cover in 162 plots distributed among 16 publicly-owned pine rockland preserves in 1995 and 2003. Fragments received either 0, 1, or > 1 burn(s) between sampling periods. Native plant richness was very high overall. Major soil type, which varies regionally and is associated with latitude and elevation, strongly influenced the assemblage of species present at a given site. Native species cover was significantly different across different burn categories. Fragment size was positively associated with plant species richness, but small fragments had high variance in the total number of native plant species they supported, with some having nearly as many plant species as the largest fragment. Examining trends over time for rare native and invasive non-native plant species revealed the spread of the invasive grass Rhynchelytrum repens (Willd.) C.E. Hubb. and showed no major decreases in rare plant species. In general, this study provided encouraging results for managers of small urban forest fragments, showing that they can maintain high levels of native plant diversity, even when fire occurs infrequently.

In vitro evaluation of germination and growth of five plant species on medium supplemented with hydrocarbons associated with contaminated soils

The effect of a hydrocarbon mixture (HCM) of three polycyclic aromatic hydrocarbons (PAH) and Maya crude oil on germination, growth and survival of four grasses ( Bouteloua curtipendula, Cenchrus ciliaris, Echinochloa crusgalli and Rhynchelytrum repens) was studied and compared to a control ( Festuca arundinacea) under in vitro conditions. The species were cultured on MS medium with different HCM initial concentrations. Germination was not affected for any assayed concentration; however, the length of the stems and roots decreased when HCM increased and the survival of the four species also diminished. Except for F. arundinacea, a direct link between hydrocarbon concentration and plant survival was observed. In vitro studies are clean and easy to handle techniques allowing isolation of the plant activity from that derived from associations with microorganisms in non-sterile cultures. To our knowledge, this is the first work towards phytoremediation assisted by in vitro plant cultivation.

Competitive Effects of the Invasive Grass Rhynchelytrum repens (Willd.) C.E. Hubb. on Pine Rockland Vegetation

The widely invasive grass Rhynchelytrum repens (Willd.) C.E. Hubb. invades globally-imperiled pine rockland forests of South Florida. To examine whether its spread into and persistence in undisturbed areas pose a threat to native species, we investigated whether the presence of R. repens was associated with a decline in the diversity and abundance of native pine rockland understory plants. We showed R. repens density class was strongly associated with a reduction in native species diversity, with high density (20% cover) plots having five fewer species than low density (0.2%) ones. When we separated species by functional groups, we found that graminoids were affected much more than other native species, with R. repens cover explaining 23% of the variation in graminoid diversity. Rhynchelytrum repens is indeed causing harm to pine rockland diversity, and we recommend that land managers take action to: (1) treat infestations before they reach 30% cover, and (2) remove infestations of any density adjacent to natural areas.

Hypoglycemic activity of polysaccharide fractions containing ß-glucans from extracts of Rhynchelytrum repens (Willd.) C.E. Hubb., Poaceae

Beta-glucans are soluble fibers with physiological functions, such as interference with absorption of sugars and reduction of serum lipid levels. The objective of the present study was to analyze the distribution of beta-glucans in different tissues of the African grass species Rhynchelytrum repens and also to evaluate their hypoglycemic activity. Leaf blades, sheaths, stems, and young leaves of R. repens were submitted to extraction with 4 M KOH. Analysis of the fractions revealed the presence of arabinose, glucose, xylose, and traces of rhamnose and galactose. The presence of beta-glucan in these fractions was confirmed by hydrolyzing the polymers with endo-beta-glucanase from Bacillus subtilis, followed by HPLC analysis of the characteristic oligosaccharides produced. The 4 M KOH fractions from different tissues were subjected to gel permeation chromatography on Sepharose 4B, with separation of polysaccharides with different degrees of polymerization, the highest molecular mass (above 2000 kDa) being found in young leaves. The molecular mass of the leaf blade polymers was similar (250 kDa) to that of maize coleoptile beta-glucan used for comparison. The 4 M KOH fraction injected into rats with streptozotocin-induced diabetes showed hypoglycemic activity, reducing blood sugar to normal levels for approximately 24 h. This performance was better than that obtained with pure beta-glucan from barley, which decreased blood sugar levels for about 4 h. These results suggest that the activity of beta-glucans from R. repens is responsible for the use of this plant extract as a hypoglycemic drug in folk medicine.

Effects of irradiance on non-structural carbohydrates, growth, and hypoglycemic activity of Rhynchelytrum repens (Willd.) C.E. Hubb. (Poaceae)

Irradiance is a crucial factor in plant development. Different radiant energy levels cause different responses related to plant growth and the production and distribution of dry matter. Considering the relationship between light availability and metabolism of carbohydrates and derived compounds, the aim of this work was to assess the effects of irradiance on non-structural carbohydrate contents and composition, as well as on the hypoglycemiant activity of Rhynchelytrum repens, a pantropical grass species popularly used for diabetes treatment. Plants of R. repens growing under natural irradiance (NI) showed increased content of total soluble carbohydrate (TSC), higher fluctuations in starch content (SC) and higher number of tillers. The flowering process of these plants was preceded by an increase in sucrose. However, their water content was low when compared to that of plants cultivated under low irradiance (LI). The ratio root/aerial organs and SC showed no significant differences in plants grown under LI, although TSC increased and a lower number of tillers were observed during the experimental period. In both conditions, sucrose was the ubiquitous sugar and seemed to be involved in the flowering process. A reduction in the blood sugar level was observed through the intra-peritoneal (IP) administration of the precipitate of aqueous extracts obtained from plants growing in both conditions of light; the supernatant fraction showed no hypoglycemic effect.

Comportamento de espécies herbáceas em misturas de solo com diferentes graus de contaminação com metais pesados

O objetivo deste trabalho foi avaliar, em casa de vegetação, o comportamento de espécies herbáceas em relação ao excesso de Cd e Zn no solo. O gradiente de contaminação foi estabelecido a partir de mistura de solo contaminado com solo sem contaminação em diferentes proporções. As sementes foram semeadas em tubetes contendo 250 mL de solo, e após 90 dias as plantas foram colhidas e avaliadas. A maioria das espécies apresentou redução no crescimento com aumento da contaminação do solo e elevadas concentrações de Cd e Zn na matéria seca da parte aérea (MSPA), na mistura com 15% de solo contaminado. A espécie Pffafia sp. mostrou-se tolerante à contaminação, crescendo em misturas de solo contendo até 90 mg kg-1 de Cd e 1.450 mg kg-1 de zinco. Além disso, apresentou concentração superior a 100 mg kg-1 de Cd na MSPA, sendo considerada hiperacumuladora desse metal. Sida glaziovii, Bidens pilosa, Rhynchelytrum repens, Cenchrus echinatus e Nicandra physaloides, por sua vez, foram severamente afetadas pela contaminação, ao contrário de Trifolium repens, Euchlaena mexicana, Cynodon dactylon, Avena strigosa, Cenchrus ciliares e Cyperus sp. que apresentaram crescimento satisfatório. As espécies avaliadas mostram-se promissoras para estudos adicionais sobre a reabilitação de áreas contaminadas com metais pesados.

Reassessment of Revegetation Strategies for Kaho'olawe Island, Hawai'i

This work investigates 2 US Army Construction Engineering Research Laboratory revegetation experiment sites (Phase I and II) on Kaho'olawe Island, Hawai'i (USA) to determine the long-term success of several revegetation strategies and to identify species that are best suited for future restoration activities in the highly eroded central plateau region of the island. Only the Phase I treatments receiving the highest rates of phosphorus and nitrogen fertilizer and the Phase II strategy (moderately high fertilization and landscaping) produced enough cover to begin providing protection from erosion processes. Buffelgrass (Cenchrus ciliaris L.), glycine (Neonotonia wightii (Wight &Arnott) Verdc.), Natal redtop (Rhynchelytrum repens (Willd.) Hubb.), and siratro (Macroptilium atropurpureum (DC) Urb.) appear to be resilient to the harsh island conditions, which include strong winds, low annual rainfall, acute erosion, and a nutrient-depleted soil profile. Although all 4 species offer some protection against erosional processes, none are particularly desirable for long-term restoration of the island. Glycine and siratro, both of which volunteer readily in planting sites, are considered invasive in that they may smother other more desirable species, particularly less competitive natives. Finally, native woody species are shown to have difficulty in surviving on the island without special attention to planting and maintenance. DOI:10.2458/azu_jrm_v53i1_ziegler