Letteratura scientifica selezionata sul tema "Eragrostis curvula"
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Articoli di riviste sul tema "Eragrostis curvula"
1
Carballo, Jose, Diego Zappacosta, Juan Pablo Selva, Mario Caccamo e Viviana Echenique. "Eragrostis curvula, a Model Species for Diplosporous Apomixis". Plants 10, n. 9 (31 agosto 2021): 1818. http://dx.doi.org/10.3390/plants10091818.
Testo completoAbstract (sommario):
Eragrostis curvula (Schrad.) Ness is a grass with a particular apomictic embryo sac development called Eragrostis type. Apomixis is a type of asexual reproduction that produces seeds without fertilization in which the resulting progeny is genetically identical to the mother plant and with the potential to fix the hybrid vigour from more than one generation, among other advantages. The absence of meiosis and the occurrence of only two rounds of mitosis instead of three during embryo sac development make this model unique and suitable to be transferred to economically important crops. Throughout this review, we highlight the advances in the knowledge of apomixis in E. curvula using different techniques such as cytoembryology, DNA methylation analyses, small-RNA-seq, RNA-seq, genome assembly, and genotyping by sequencing. The main bulk of evidence points out that apomixis is inherited as a single Mendelian factor, and it is regulated by genetic and epigenetic mechanisms controlled by a complex network. With all this information, we propose a model of the mechanisms involved in diplosporous apomixis in this grass. All the genetic and epigenetic resources generated in E. curvula to study the reproductive mode changed its status from an orphan to a well-characterised species.
2
Rabau, T., B. Longly e B. P. Louant. "Ontogenèse des sacs embryonnaires non réduits chez Eragrostis curvula". Canadian Journal of Botany 64, n. 8 (1 agosto 1986): 1778–85. http://dx.doi.org/10.1139/b86-237.
Testo completoAbstract (sommario):
The apomictic reproductive mode by diplospory is cytologically analysed in Eragrostis curvula (Schrad.) Nees, a tetraploid forage grass. The genesis of unreduced embryo sacs is followed; two kinds of sacs are then distinguished: (i) a monopolar one with a typical oogonial complex and a polar nucleus at the micropylar end; (ii) a bipolar one with an egg cell and two polar nuclei at the micropylar end, and some antipodial cells at the chalazal end. Monopolar sacs are 3 times more frequent than bipolar ones. Traces of sexuality are noted in E. curvula but with a low frequency. A chronology of female development is established according to stages of male development. This should make possible an early distinction and allow a useful comparison between diplospory and sexuality within the genus Eragrostis.
3
Johnston, W. H., e V. F. Shoemark. "Establishment and persistence of palatable taxa of Eragrostis curvula complex in southern New South Wales". Australian Journal of Experimental Agriculture 37, n. 1 (1997): 55. http://dx.doi.org/10.1071/ea96025.
Testo completoAbstract (sommario):
Summary. Spring sowings in cultivated plots at Wagga Wagga in 1980 and 1982, and Cowra and Colinroobie in 1980 and 1981 examined the establishment and persistence of Eragrostis curvula (Schrad.) Nees complex cv. Consol and accession 4660, Cenchrus ciliaris L. cv. American and Phalaris aquatica L. cv. Sirocco. Cenchrus ciliaris was short-lived and not frost-hardy. Competition and dry conditions reduced establishment of all species, nevertheless E. curvula established reliably. In 1 experiment where conditions were not immediately favourable for germination, E. curvula demonstrated a capacity to delay establishment until conditions improved. Competition from cool-season plants reduced persistence, particularly in the first year and when conditions were dry. Surviving E. curvula plants were generally long lived. At Cowra, the density of E. curvula was enhanced by regular mowing, but mowing reduced the density of P. aquatica. Presence of Trifolium subterraneum L. reduced the density of E. curvula while P. aquatica was unaffected. A second experiment at Colinroobie, sown in October 1987 examined the effects of mowing and fertiliser application on establishment and persistence of E. curvula cv. Consol and accession 4660. Fertiliser increased competition by cool-season annual species, reducing establishment and persistence of E. curvula, while regular mowing improved its persistence. In an experiment sown at Wagga Wagga in October 1989, E. curvula cv. Consol establishment was very low (<1 plant/m2) in undisturbed annual pasture and in the absence of cultivation, herbicide (glyphosate at 530 g a.i./ha) and mowing with herbage removal provided the best conditions for establishment.
4
DI RENZO, M. A., M. A. IBAÑEZ, N. C. BONAMICO e M. M. POVERENE. "Estimation of repeatability and phenotypic correlations in Eragrostis curvula". Journal of Agricultural Science 134, n. 2 (marzo 2000): 207–12. http://dx.doi.org/10.1017/s0021859699007522.
Testo completoAbstract (sommario):
Eragrostis curvula (Schrad.) Nees s. lat., a highly polymorphic polyploid complex, can be considered as one of the most important warm season perennial grasses for the semi-arid regions of central Argentina. In apomictically propagated and perennial plants such as weeping lovegrass, where successive measurements can be done across time, repeatability estimates provide an indication of the degree of influence of permanent effects on the phenotypic variation and allow prediction of future performance from past records. Analysis of variance of the experiment showed highly significant variation (P < 0·01) for the main factors in all four traits. Although there was very high variability between cuts, hybrids of E. curvula exhibited considerable inter-entry variability, in particular for those traits determining forage yield. Repeatability calculated in this experiment was highest for the crown diameter (0·86), leaf length (0·84) and dry matter (0·84), while in panicle number (0·66) it was lowest. Repeatability estimates for the vegetative characteristics indicate small effects of temporal environment. The four traits studied, including panicle number with their moderate repeatability, do not require an essentially different number of observations to obtain measures at the same level of accuracy. For vegetative characters two harvests provided 98% of the accuracy of the total obtained with four cuts, and for panicle number the same percentage was obtained for three harvests. This stability of performance is a desirable characteristic for grass cultivars. Patterns of trait associations were also described. Because leaf length is closely associated with dry matter and has high repeatability, to use leaf length as an indirect evaluation criterion should be almost as efficient as direct evaluation for aerial biomass yield. Reliable estimates of parameters such as repeatability and phenotypic correlation are needed for prediction of production values and for the design of efficient improvement programmes. For genotype evaluation additional research is required to quantify the extent of genotype × environment interaction across years and localities of semi-arid regions.
5
Johnston, W. H., T. B. Koen e V. F. Shoemark. "Water use, competition and a temperate-zone C4 grass (Eragrostis curvula (Schrad.) Nees. complex) cv. Consol". Australian Journal of Agricultural Research 53, n. 6 (2002): 715. http://dx.doi.org/10.1071/ar98115.
Testo completoAbstract (sommario):
The effects of a perennial C4 grass (Eragrostis curvula [Schrad.] Nees. complex cv. Consol) and winter-growing annual pasture on the soil water deficit (SWD) was assessed at 2 sites near Wagga Wagga, NSW. At Site A, newly sown E. curvula-Trifolium subterraneum L. pasture was compared with an annual pasture containing Lolium rigidum Gaud. and T. subterraneum. A mature E. curvula pasture sown 10 years previously was compared with an adjacent volunteer annual pasture at Site B. The annual pasture at Site A had little effect on the SWD at 120 cm depth, but it developed an appreciable SWD at 60 cm on 2 occasions when spring rainfall was well below average. This deficit was not evident the following autumn. When E. curvula was present in the pasture, it developed a substantial SWD at 120 cm in summer and autumn. This represented a significant realignment of the water balance that had the potential to reduce deep drainage. The size of the SWD in autumn determined how rapidly soils reached field capacity in winter. At Site B, E.�curvula consistently created a deficit of between 108 and 124 mm to 100 cm depth in autumn, compared with 2-106 mm for the annual pasture. The soil profile under E. curvula did not reach field capacity until 60-100 days later than the annual pasture. The annual pasture at Site B had a minimal effect on the SWD at 100 cm in 3 of the 4 years of the study. The camping behavior of sheep at Site A caused E. curvula to succumb to competition from T. subterraneum, Hordeum leporinum Link, and Cryptostemma calendula (L.) Druce. Competitive interactions between T.�subterraneum cv. Junee and Eragrostis curvula cv. Consol were therefore investigated in a glasshouse study using the de Wit replacement series methodology. Pots were watered to weight and water usage was recorded under 2 levels of watering [low (restricted watering) and high (watered to field capacity)] that were applied after an establishment period of 6 weeks. Pots were harvested after a further c.12 weeks and above- and below-ground yield of each species determined. T. subterraneum tended to use water up to the limit of its supply, and as water became less available and in response to increasing atmospheric water demand in spring, it frequently wilted. E. curvula rarely wilted; it exhibited water-saving strategies, including leaf waxing and leaf rolling in the heat of the day in response to increasing water demand without necessarily exhausting its water supply. Both species used water more efficiently (dry matter/kg water used) when its supply was limited. The water use efficiency of monoculture T. subterraneum was greater than that of slowly growing E. curvula, and both species used water most efficiently when growing alone. T. subterraneum was highly competitive against E. curvula. Competition resulted from its out-of-phase growth compared with E. curvula. E. curvula has the potential to markedly affect on the water balance. However, it is vulnerable to competition. Managing the flush of growth in spring is an important issue in maintaining a balance between E. curvula and winter-growing annual species.
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Johnston, WH. "Palatability to sheep of the Eragrostis curvula complex. 2. Selection of palatable taxa". Australian Journal of Experimental Agriculture 28, n. 1 (1988): 47. http://dx.doi.org/10.1071/ea9880047.
Testo completoAbstract (sommario):
Relative palatability of 12 previously selected taxa of Eragrostis curvula complex was assessed using a visual rating scale of 0 (not grazed) to 10 (completely grazed). Visual ratings were converted to ranks and the most and least palatable lines were compared over 19 grazing assessments in trials at Wagga Wagga, Temora and Orange, New South Wales. Three highly palatable and 2 acceptably palatable accessions were identified. The importance of palatability in the E. curvula complex is discussed.
7
Johnston, W. H., P. S. Cornish, T. B. Koen e V. F. Shoemark. "Eragrostis curvula (Schrad.) Nees. complex pastures in southern New South Wales, Australia: a comparison of Eragrostis curvula cv. Consol and Medicago sativa L. cv. Nova under intensive rotational management". Australian Journal of Experimental Agriculture 45, n. 10 (2005): 1255. http://dx.doi.org/10.1071/ea04080.
Testo completoAbstract (sommario):
The productivity, carrying capacity and liveweight performance of wether sheep grazing pastures of Eragrostis curvula cv. Consol and Medicago sativa cv. Nova, which were also sown with annual grasses and Trifolium subterraneum, were compared under an intensive 4-paddock rotational grazing regime in a ‘put-and-take’ grazing experiment at Wagga Wagga, New South Wales from November 1993 to August 1996. The productivity of the pastures was broadly similar, with production peaks of >1000 kg/ha in winter and >3000 kg/ha in spring and summer in paddocks that had been spelled for 6 weeks. Although annual species contributed a high proportion of the total herbage mass in spring, over the remainder of the year, both pastures were dominated by their respective perennials. E. curvula maintained an average plant density of approximately 20 plants/m2. The density of M. sativa declined noticeably during the 3 years, and at the end of the experiment M. sativa plants in 1 replicate of the experiment were killed by rising groundwater and dryland salinity. The long-term average stocking rate of E. curvula and M. sativa pastures were similar (12.1 v. 12.5 sheep/ha) and both pastures were capable of sustaining high stocking rates for lengthy periods in spring and summer. Sheep grazing M. sativa tended to be heavier than animals grazing E. curvula, and they produced, on average, 1.1 kg (or 21%) more wool. However, M. sativa was more difficult to establish and its costs for weed and insect control were higher. Therefore, although it was more productive, it might not have been the most economically viable of the 2 pastures. The implications of the findings were discussed within a whole-farm context and it was concluded that E. curvula has a complimentary role to M. sativa for sowing on landscapes and in situations to which M. sativa is poorly adapted.
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Campbell, MH, JJ Dellow, MJ Keys e AR Gilmour. "Use of herbicides for selective removal of Eragrostis curvula (Schrad.) Nees from a Phalaris aquatica pasture". Australian Journal of Experimental Agriculture 25, n. 3 (1985): 665. http://dx.doi.org/10.1071/ea9850665.
Testo completoAbstract (sommario):
In the main experiment, the effectiveness of tetrapion, glyphosate and 2,2-DPA in selectively removing Eragrostis curvula from a Phalaris aquatica pasture was determined by applying each at three rates in July 1980, September 1980, December 1980 and March 1981 near Braidwood, New South Wales. Auxiliary experiments were conducted from April 1981 to April 1983 to determine the reliability of herbicide effect on E. curvula. Tetrapion (2.25 and 3.375 kg/ha a.i.) was the most effective herbicide in killing E. curvula and promoting P. aquatica and Trifolium subterraneum. It was more selective when applied in September 1980 and December 1980 than when applied in July 1980 or March 198 1. Re-infestation by E. curvula seedlings in the 3 years after spraying with tetrapion amounted to a maximum of 3% of ground cover. In the auxiliary experiments, tetrapion was effective on all nine occasions of application, which demonstrated its reliability and effectiveness at any time of the year. Glyphosate (1.08 and 1.62 kg/ha a.i.) was effective in killing E. curvula in March 1981 but this result could not be repeated in March 1982 or March 1983 or in nine other applications at other times in these years. 2,2-DPA (maximum rate 22.2 kg/ha a.i.) was ineffective in killing E. curvula at four times of application. Recovery of the P. aquatica pasture after treatment declined in the order: tetrapion >2,2-DPA>glyphosate.
9
Burson, Byron L., e Paul W. Voigt. "Cytogenetic Relationships between the Eragrostis curvula and E. lehmanniana Complexes". International Journal of Plant Sciences 157, n. 5 (settembre 1996): 632–37. http://dx.doi.org/10.1086/297384.
Testo completo
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Rodrigo, Juan Manuel, Diego Carlos Zappacosta, Juan Pablo Selva, Ingrid Garbus, Emidio Albertini e Viviana Echenique. "Apomixis frequency under stress conditions in weeping lovegrass (Eragrostis curvula)". PLOS ONE 12, n. 4 (18 aprile 2017): e0175852. http://dx.doi.org/10.1371/journal.pone.0175852.
Testo completoTesi sul tema "Eragrostis curvula"
1
Ncanana, Sandile Welcome. "Biolistic-mediated transformation of Eragrostis Curvula with the HSP 12 gene". Thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/6771.
Testo completoAbstract (sommario):
Bibliography: leaves 91-107.Eragrostis curvula is a desiccation sensitive monocotyledonous plant and an economically important forage grass in southern Africa. This species has a potential to be improved for drought and salt resistance among other important agronomic traits. In this study, E. curvula was used as a model system to explore the feasibility of producing pasture grasses with increased tolerance to water deficit. To date, no reports have been published on transformation of this species. This study reports the transformation of E. curvula with Saccharomyces cerevisiae Hsp 12 gene using biolistic-mediated transformation. Firstly, a tissue culture protocol was established for E. curvula that was suitable for transformation studies. Although this species has been previously regenerated in vitro using inflorescence tissues, this study established new protocols that utilize leaf and seed as source of material. The aim of which was to find the best regenerable tissue that could be used for transformation studies. Plant regeneration was achieved from shoot explants cultured on MS medium supplemented with either 0.5 mg/I thidiazuron (TDZ) or 0.5 mg/I 6-benzylaminopurine (BAP) through the process of direct organogenesis. It was found that TDZ was the most effective cytokinin. Plant regeneration was also achieved from callus induced from immature leaves on MS medium supplemented with 2 mg/I 2,4- 0,0.01 mg/I BAP and 6 % (w/v) sucrose. Histological experiments performed gave clear evidence that plant regeneration from callus was through a process of indirect organogenesis. The regeneration protocol was combined with an optimized biolistic mediated transformation protocol using the PDS-I00/He apparatus of which both shoot explants and callus were used as target tissues. In the molecular aspect of the study, the Hsp 12 gene was ligated in the Sac I restriction site of pCAMBIAUbeeQ vector. The successful cloning of the Hsp 12 gene was confirmed by PCR and restriction endonuclease digestion. The resultant vector pCAMBIAUbeeQ Hsp 12 was purified and subsequently used for biolistic transformation of E. curvula. The regenerable shoot explants and callus tissue were bombarded with DNA (pCAMBIAUBeeQHsp12) coated on gold particles. As a comparative study, Agrobacterium tumefaciens was transformed with pCAMBIAUBeeQHsp12 vector for subsequent transformation of Nicotiana tabacum. Transient expression of GUS gene in transformed E. curvula shoot explants was visualized 72 h after bombardment. Optimized conditions for expression of GUS gene were gold micro projectiles, 7 cm travel distance and helium pressure of 9100 kPa. Transformed tissues were cultured on the regeneration medium without antibiotic selection. Putative transformants were generated and the presence of Hsp 12 gene was verified by PCR and its expression at RNA level was confirmed by RT-PCR. The presence of Hsp 12 protein in the transformed plants was analyzed using SDS-PAGE and MALDI-TOF peptide mass spectrometry.
2
Johnston, William Henry, University of Western Sydney, of Science Technology and Environment College e School of Environment and Agriculture. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia". THESIS_CSTE_EAG_Johnston_W.xml, 2003. http://handle.uws.edu.au:8081/1959.7/29.
Testo completoAbstract (sommario):
This thesis examines the hypothesis that, in southern New South Wales and northeast Victoria, Australia, palatable taxa of E. curvula offer advantages that complement those of the species that are traditionally sown in temperate pastures in a landscape context.This hypothesis was based on a review of literature showing that, prior to European settlement, the vegetation, the landscape and the climate were broadly in balance, and the wateruse pattern of the vegetation of southeastern Australia resulted in water being used more-or-less completely by the end of summer. This maximised the capacity of the soil to take up and store water during autumn and winter.Three grazing experiments and one spaced-plant species evaluation study were used to assess the role of summer-growing, C4 Eragrostis curvula in pastures in the temperate zone of southeastern Australia.Issues relating to pasture production and the productivity of wool-growing sheep were investigated. Factors affecting the sustainability of the pastures and their potential on and off site impacts were emphasised.Modelling was used to explore issues of water use, arising from the grazing experiments. It is concluded that the persistence, production, water use patterns, and the adaptability of palatable varieties of E. curvula make it a useful and complementary addition to the range of species that are currently available for use as sown pastures in southern Australia.Doctor of Philosophy (PhD)
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Johnston, William Henry. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia /". View thesis View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030506.100204/index.html.
Testo completo
4
Van, der Willigen Clare. "Comparisons of the resurrection grass, Eragrostis nindensis, with the related desiccation-sensitive species, E. curvula". Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/6104.
Testo completoAbstract (sommario):
Bibliography: leaves 100-133.Desiccation tolerance of the inner leaves of Eragrostis nindensis is compared with the desiccation sensitivity of the outer leaves, as well as those of the closely related species, E. curvula. Both E. nindensis and E. curvula dehydrate to a relative water content (RWC) ofless than 5% in two weeks. Photosynthetic activity in E. curvula is maintained down to 40% RWC, after which further drying results in a sudden irreversible breakdown of the photosynthetic system and its pigments.
5
Willigen, Clare Vander. "Comparisons of the resurrection grass, Eragrostis nindensis, with the related desiccation-sensitive species, E. curvula". Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/11403.
Testo completoAbstract (sommario):
Bibliography: leaves 100-133.Desiccation tolerance of the inner leaves of Eragrostis nindensis is compared with the desiccation sensitivity of the outer leaves, as well as those of the closely related species, E. curvula. Both E. nindensis and E. curvula dehydrate to a relative water content (RWC) ofless than 5% in two weeks. Photosynthetic activity in E. curvula is maintained down to 40% RWC, after which further drying results in a sudden irreversible breakdown of the photosynthetic system and its pigments.
6
Skinner, Amy. "Investigating the effect of Glomus etunicatum colonization on structure and phloem transport in roots of Eragrostis curvula (Umgeni)". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1003796.
Testo completoAbstract (sommario):
The symbiotic unit of an arbuscular mycorrhizal fungus and its host is able toachieve and maintain far higher inflow of nutrients than non-mycorrhizal roots. The colonization strategy of the mycobiont within the plant is intrinsic to the symbiosis with respect to both structural adaptations and nutrient exchange. An investigation into the effect of Glomus etunicatum colonization on the structure and phloem transport in Eragrostis curvula (Umgeni) allowed for greater insight into the dynamic of the symbiosis. The combined use of stains (such as Trypan Blue, Chlorazol Black, Safranin and Fast Green), and techniques, (such as freeze-microtome transverse sectioning and permanent slide preparations) contributed to a successful general observation of an intermediate colonization strategy using light microscopy methods. However, clarity into structural detail of mycorrhizal forms required electron microscopy studies. The SEM method used with freeze fracture was a relatively quick and simple method allowing for the observation of surface and internal features. The TEM method allowed for highresolution images providing insight into the variations in the apoplasmic compartmental form, and how this may relate to the function of the symbiosis with regard to fungal coils or arbuscules. The apoplasmic nature of mycorrhizas was substantiated and no symplasmic connections were found between symbionts. Fluorescence studies demonstrated that 5,6-carboxyfluorescein was transported through the phloem into the roots of E. curvula, but remained predominantly in the root phloem. Unloading only occurred in optimal nutrient exchange areas of meristimatic lateral or apical growth regions. It was not possible, using fluorescence techniques and related equipment available, to conclusively establish if there were symplasmic connections between the mycobiont and its host or if bidirectional transfer of nutrients occurred at the same interface.
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Hely, Sara Elizabeth Lorraine Biological Earth & Environmental Sciences Faculty of Science UNSW. "The responses of C4 invasive grass Eragrostis curvula and C3 native grass Austrodanthonia Racemosa under elevated CO2 and water limitation". Awarded by:University of New South Wales, 2008. http://handle.unsw.edu.au/1959.4/35671.
Testo completoAbstract (sommario):
The concentration of atmospheric carbon dioxide (CO2) in the atmosphere has increased by 35% since pre-industrial levels. Projections for the next 100 years indicate an increase to levels between 490 and 1260 parts per million by volume (ppm) of CO2, equating to a 75 % to 350 % increase in concentration since the year 1750. Associated with this increase in [CO2] will be a 1.4 to 5.8?? C increase in lower atmospheric temperature. While past research has attempted to address the effects of such climatic changes on individual plant responses, predictions of plant responses at the ecosystem level are still highly uncertain. Difficulties lie in the enormous variation of plant responses to climate change variables among and within species, and between and within environmental conditions. Past research assumed that plants using either the C3 or C4 metabolic pathways would respond differently but predictably to climate-change variables based on their metabolic pathway. Recent evidence has suggested however, that the added interactions of external environmental variables and species-specific sensitivities to climate change make it difficult to predict plant and ecosystem responses to climate change. To investigate the mechanisms behind responses of Australian grasses to climate change, 2 pot experiments was conducted using growth cabinets to compare the effect of elevated CO2 and water-limitation on the invasive C4 grassland plant, Eragrostis curvula (E. curvula), native Australian C3 grassland plant, Austrodanthonia racemosa (A. racemosa), and wheat species, Triticum aestivum (T. aestivum). The experiment was run at ambient levels of CO2 maintained at 390 ppm compared to elevated levels of 740 ppm. Imposed restrictions to water supply consisted of gradually drying the soil down to 30 % available soil water (ASW) followed by re-wetting to 50 % ASW. Well-watered conditions for the experiment consisted of gradually drying the soil down to 50 % ASW, followed by rewetting to 95 % ASW. Plants were grown in mixtures and monocultures, consisting of 9 plants equally spaced in a grid design. The three significant findings of the thesis were that: 1) the metabolic pathway (C3 versus C4) was not always an accurate predictor of biomass accumulation under elevated CO2 in the plants studied. Previous research suggested that CO2-stimulation of photosynthesis in C3 plants would lead to greater increases in biomass under elevated CO2 compared to C4 plants, though both C3 and C4 plants could benefit from any reduction in stomatal conductance under dry conditions at elevated CO2. The results from the experiments in this thesis showed a strongly significant biomass response to elevated CO2 in both dry and wet conditions for C4 grass E. curvula. The C3 grass A. racemosa in dry conditions, did not. It was speculated that without the CO2-induced water conservation effect, the C3 grass experienced photosynthetic down-regulation and this precluded a positive biomass response under elevated CO2. 2) the magnitude and direction of biomass response to elevated CO2 was dependant on factors such as resource-availability and the phenotypic variability of the plants species. 3) critical analysis of results from this thesis, combined with past research on plant responses under elevated CO2 showed a tendency for researchers to repeatedly test plants from the Poaceae family, or close relatives of the Poaceae family. As a result, when past data were corrected for this lack of independence, there was no relationship between the evolution of the C3 and C4 metabolic pathway and biomass response to elevated CO2. Instead, other factors (such as growth rate, plant height, leaf number, etc) were presented as being more important in determining biomass response. These observations were supported by results found in this thesis.
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Mynhardt, Herman. "Effect of nitrogen and energy supplementation on intake, digestibility and rumen fermentation efficiency in sheep fed poor quality Eragrostis curvula hay". Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/63291.
Testo completoAbstract (sommario):
The overall aim of the study was to study the effects of starch and urea
supplementation on roughage intake, digestibility, and microbial nitrogen synthesis (MNS) in
sheep fed low-quality Eragrostis curvula hay (< 3% CP, 80% NDF; DM basis).
In Trial 1, urea partially substituted the rumen degradable nitrogen (RDN) fraction of
sunflower meal (SFM). Neutral detergent fibre (NDF) digestibility was higher in the
treatments where urea substituted 45% and 60% of the RDN fraction of SFM. Treatment did
not affect roughage intake, rumen ammonia nitrogen (RAN), MNS or efficiency of MNS
(EMNS), suggesting that urea could substitute up to 60% of the RDN supplemented by SFM
in sheep fed low-quality E. curvula hay.
In Trial 2, the quantities of urea and starch supplemented to sheep differed. Urea
supplementation did not affect roughage intake and digestibility, however, MNS: available
Nitrogen intake (MNS:NI) improved from 2.21 to 0.88 as urea supplemented increased from
10.4 g urea/sheep/day to 32.4 g urea/sheep/day. Microbial N synthesis increased up to the
highest level of starch supplemented (280 g/sheep/day). It was concluded that urea
supplementation, as high as 26.4 g urea/sheep/day, coupled with starch supplementation,
between 240 g and 280 g starch/sheep/day, could be supplemented to sheep (50 kg BW)
consuming low-quality E. curvula hay.
In Trial 3, RDN and energy supplementation patterns differed in sheep fed lowquality
E. curvula hay. Treatment did not affect roughage or N intake; however, roughage
digestibility was higher in treatments where starch was supplemented, at least partly, during
the morning (08h00) supplementation period. Urinary N excretion, MNS and EMNS were
generally higher in the treatments where starch was supplemented twice daily. It was
concluded that, while the most optimal rumen pH was achieved in the treatment where both
urea and starch was supplemented twice daily, the supplementation frequency of starch was
the more important parameter, compared to urea, stimulating roughage digestibility, MNS
and EMNS in sheep fed low-quality E. curvula hay. To conclude this research, a meta-analysis was conducted to study the importance of
supplemental starch and/or urea on N efficiency in sheep fed low-quality E. curvula hay.
Starch or urea supplementation did not affect roughage intake or digestibility. Starch
supplementation affected MNS linearly while urea supplementation influenced RAN linearly
and MNS:NI inversely, with MNS:NI decreasing as urea supplementation increased. A strong
correlation was observed between starch: available CP and RAN, with RAN increasing
exponentially as the ratio of starch to available CP decreased below 2:1. It was concluded that
urea and starch supplementation, up to 0.5 g urea/kg BW and 2.2 g starch/kg BW
respectively, were necessary to optimise N efficiency in sheep grazing low-quality E. curvula
hay.Thesis (PhD)--University of Pretoria, 2017.
Red Meat Producers Organization
Animal and Wildlife Sciences
PhD
Unrestricted
9
Yasui, Simone-Louise Emiko. "Managing the community: Assessing the efficacy of invasive plant control strategies in Australian grassy ecosystems from deserts to dairy country". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213051/1/Simone-Louise_Yasui_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis investigated how management affects plants, seedbanks, and rhizospheric bacterial communities in grasslands. Control strategies studied reduced invasive grass cover in desert grasslands even though the invader holds unique root-associations with bacteria. Seedbank stores of invaders were high in both desert and dairy-country grasslands suggesting control strategies should also reduce seedbanks.
10
Johnston, William H. "The role of Eragrostis curvula (Schrad.) Nees. complex in temperate pastures in southeastern Australia". Thesis, 2003. http://handle.uws.edu.au:8081/1959.7/29.
Testo completoAbstract (sommario):
This thesis examines the hypothesis that, in southern New South Wales and northeast Victoria, Australia, palatable taxa of E. curvula offer advantages that complement those of the species that are traditionally sown in temperate pastures in a landscape context.This hypothesis was based on a review of literature showing that, prior to European settlement, the vegetation, the landscape and the climate were broadly in balance, and the wateruse pattern of the vegetation of southeastern Australia resulted in water being used more-or-less completely by the end of summer. This maximised the capacity of the soil to take up and store water during autumn and winter.Three grazing experiments and one spaced-plant species evaluation study were used to assess the role of summer-growing, C4 Eragrostis curvula in pastures in the temperate zone of southeastern Australia.Issues relating to pasture production and the productivity of wool-growing sheep were investigated. Factors affecting the sustainability of the pastures and their potential on and off site impacts were emphasised.Modelling was used to explore issues of water use, arising from the grazing experiments. It is concluded that the persistence, production, water use patterns, and the adaptability of palatable varieties of E. curvula make it a useful and complementary addition to the range of species that are currently available for use as sown pastures in southern Australia.
Capitoli di libri sul tema "Eragrostis curvula"
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Mentz, A. M., A. Hassen, W. A. Van Niekerk, H. Mynhardt e R. Coertze. "The effect of substituting urea for a commercial slow release urea as supplement to sheep fed a poor quality Eragrostis curvula hay". In Energy and protein metabolism and nutrition in sustainable animal production, 99–100. Wageningen: Wageningen Academic Publishers, 2013. http://dx.doi.org/10.3920/978-90-8686-781-3_23.
Testo completo