Competitive Interactions Between Palatable And Unpalatable Grasses: Effects Of Selective Defoliations Of The Palatable Grasses,
2024
Universidad Nacional del Sur, Bahia Blanca, Argentina
Competitive Interactions Between Palatable And Unpalatable Grasses: Effects Of Selective Defoliations Of The Palatable Grasses, R A. Distel, A S. Moretto
IGC Proceedings (1997-2023)
Selective herbivory of the palatable species appears to be a dominant mechanisms contributing to species competitive replacement in grasslands. Selective herbivory of the palatable species allows unpalatable species to realize a competitive advantage within the community. To test this hypothesis we compare the competitive ability of the unpalatable grasses Stipa trichotoma or S. gyneriodes in the presence of nondefoliated and defoliated plants of the palatable grass S. clarazii. The three species are native to a temperate semiarid grassland of Argentina. The response variables estimated in S.trichotoma and S.gynerioides, at both plant and tiller levels, were higher (P < 0.05) in the presence of defoliated than in the presence of undefoliated plants of S.clarazii. These results support the hypothesis that selective herbivory of the palatable species confers unpalatable species a competitive advantages, contributing to species competitive replacement within the community.
Allelopathic Interactions Among Forage Grasses And Legumes,
2024
EMBRAPA-CPATU
Allelopathic Interactions Among Forage Grasses And Legumes, A P.S Souza Filho, T De J.D. Rodrigues, L.R. De A. Rodrigues, R A. Reis
IGC Proceedings (1997-2023)
Aqueous extracts at 10% were prepared with the shoots of the grasses Brachiaria brizantha cv. Marandú, B. decumbens, B. humidicola, and of the legumes Calopogonium mucunoides, Leucaena leucocephala, Stylosanthes guianensis cv. Mineirão. The effects of the extracts were evaluated on the germination and on the radicleelongation of the forages. The pH, the electric conductivity and the osmotic potential of the extracts were determined. The germination and radicle biossays were conducted in germination chambers, with controlled temperature and photoperiod. The pH and the presence of ions did not contribute to the effects observed. The extracts of the legumes tended …
Early Ontogenetic Responses Of Six Commercial Chloris Gayana Cultivars To Salinity,
2024
IFFIVE
Early Ontogenetic Responses Of Six Commercial Chloris Gayana Cultivars To Salinity, E Taleisnik, H Perez, G Peyrano, C Arias
IGC Proceedings (1997-2023)
Some physiological aspects relevant to pasture establishment under saline conditions were evaluated in six cultivars of Chloris gayana . Two tetraploid cultivars: Boma and Callide, and four diploid ones: Bell, Katambora, Pioneer and a local accession of Pioneer, were analyzed. The effect of salinity on seedling emergence, the number of stolons per plant and frost tolerance were evaluated in the field, while effects on germination, early vegetative growth, regrowth after clipping, ion accumulation and stolon rooting were assessed in the greenhouse. Salinity had a negative effect on seedling emergence. Saline solutions delayed or altogether inhibited germination, but seeds retained viability …
Interpreting Indicators Of A Transfer Of N From Legume To Grass In Competition Studies,
2024
The University of Adelaide
Interpreting Indicators Of A Transfer Of N From Legume To Grass In Competition Studies, P G. Tow
IGC Proceedings (1997-2023)
The transfer of N from legume to grass in mixtures is important for regulating competition. In competition studies which include both monocultures and mixtures, N transfer should be detectable by grass N measurements but may be masked by competitive reductions in grass growth. In the study reported here, whole plant DM and N were measured in Panicum maximum var trichoglume and Neonotonia wightii grown in monocultures and additively in mixtures. While competition reduced whole grass plant DM and N in mixture relative to monoculture, higher grass shoot % N and N yield in the mixture at early harvests appeared reliable …
A Comparison Of Production And Soils In Modified Mixed Prairie Community,
2024
Agriculture and Agri-Food Canada Research Center
A Comparison Of Production And Soils In Modified Mixed Prairie Community, S W. Porter, W D. Willms, J F. Dormaar, B H. Ellert, H H. Janzen
IGC Proceedings (1997-2023)
This study examined the effects of reseeding a Stipa-Agropyron- Bouteloua community to monocultures of crested wheatgrass (Agropyron cristatum (L.) Geartn.), Russian wild rye grass (Elymus junceus Fisch.), and wheat (Triticum aestivum L.) on above and below ground biomass and indicators of soil quality. Summer fallowed wheat produced 10817 kg ha-1 and 4090 kg ha-1 of above ground below ground biomass respectively whereas the native community produced 3191 kg ha-1 above ground and 13013 kg ha-1 of below ground biomass. However wheat, crested wheatgrass and Russian wildrye grass generally showed a lower biological index, phosphatase and dehydrogenase activity.
Nitrogen Use Efficiency Of Timothy Populations,
2024
Agriculture and Agri-food Canada
Nitrogen Use Efficiency Of Timothy Populations, G Belanger, C Murray, R Michaud, F Gastal, J E. Richards
IGC Proceedings (1997-2023)
The objective of this study was to determine the variability in N use efficiency among field-grown timothy (Phelum pratense L.) populations. Shoot biomass and N uptake were measured at the end of the spring growth cycle on six timothy populations fertilized with three N rates at two sites in Eastern Canada. The variability in shoot biomass among populations was similar under limiting and nonlimiting N conditions. The ranking of the populations, however, differed under limiting and non-limiting N conditions, and also between the two sites under limiting N conditions. The differences in shoot biomass among populations under highly N …
Characterization Of The Leaf Anatomy Of Panicum Virgatum Germplasm,
2024
North Carolina State University at Raleigh
Characterization Of The Leaf Anatomy Of Panicum Virgatum Germplasm, D S. Fisher, J C. Burns, J P. Pienaar
IGC Proceedings (1997-2023)
Both the yield and digestibility of C4 grasses have been related to anatomical characteristics. The objectives of the current work were to test switchgrass with varied yield and digestibility for variation in anatomical measurements and to develop a method of graphically representing the anatomy. Six accessions were established in replicated field plots and the lamina were sampled, dehydrated and embedded for anatomical study. Midrib dimensions were excluded from study but perimeters of primary and secondary vascular bundles in the lamina were measured. Lamina thickness was determined at the primary bundle, secondary bundle and at the minimum between the bundles. The …
Relation Of Root And Shoot Morphology Of Grass Seedlings,
2024
University of Nebraska - Lincoln
Relation Of Root And Shoot Morphology Of Grass Seedlings, L E. Moser, A J. Smart
IGC Proceedings (1997-2023)
Grass seedling establishment is dependent on adventitious root development. However, evaluating the establishment status of a seeding by excavating a population of seedlings and determining root morphology is difficult and generally will not be undertaken. Based on both field and greenhouse studies we have found that root and shoot morphological development is closely related within species, for intermediate wheatgrass, [Thinopyrum intermedium (Host) Barkw. and D.R. Dewey], smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman) seedling populations. Easily observable developmental stages of seedling shoots were related to adventitious root development. …
Dispersion Of Artificial Tracers In Ventilated Caves,
2024
Swiss Institute for Speleology and Karst Studies (SISKA), La Chaux-de-Fonds, Switzerland
Dispersion Of Artificial Tracers In Ventilated Caves, Claudio Pastore, Eric Weber, Frédéric Doumenc, Pierre-Yves Jeannin, Marc Lütscher
International Journal of Speleology
Artificial CO2 was used as a tracer along ventilated karst conduits to infer airflow and investigate tracer dispersion. In the karst vadose zone, cave ventilation is an efficient mode of transport for heat, gases and aerosols and thus drives the spatial distribution of airborne particles. Modelling this airborne transport requires geometrical and physical parameters of the conduit system, including the cross-sectional areas, the airflow and average air speed, as well as the longitudinal dispersion coefficient which describes the spreading of a solute. Four gauging tests were carried out in one mine (artificial conduit) and two ventilated caves (natural conduits). …
Effect Of Lowered Light Quality (R:Fr Ratio) At Targeted Organs On Branching Of Trifolium Repens,
2024
Palmerston North, New Zealand
Effect Of Lowered Light Quality (R:Fr Ratio) At Targeted Organs On Branching Of Trifolium Repens, M J.M Hay, Ch Robin, P C.D Newton, A Cresswell, J Tilbrook
IGC Proceedings (1997-2023)
This report examined results from four similarly conducted experiments using Trifolium repens in which the R:FR ratio but not the photosynthetically active radiation (PAR) of incident light was altered at specific organ(s) of several successive phytomers or just at a single phytomer. Results indicate the local response to lowered R:FR light treatment was similar irrespective of the number of phytomers treated. This response pattern provides the means whereby plants can initiate strong localised responses to a heterogeneous light environment.
Theoretical And Observed Relationships Between Defoliation And Partitioning In Grasses,
2024
Macaulay Land Research Institute, Scotland
Theoretical And Observed Relationships Between Defoliation And Partitioning In Grasses, C P.D. Birch, B Thornton
IGC Proceedings (1997-2023)
A model is presented that analyses the potential effect of vertebrate grazing on the partitioning of grasses. Its conclusions are: 1) When grazing is sufficiently frequent and severe, grasses can increase their net increase in biomass by partitioning growth to reserves. 2) Partitioning growth to reserves greatly reduces leaf growth between defoliations. After repeated clipping, dryland browntop (Agrostis castellana) and red fescue (Festuca rubra) allocated a smaller proportion of growth between defoliations to leaves than ryegrass (Lolium perenne) or rough meadow-grass (Poa trivialis). Browntop and fescue achieved less leaf growth than ryegrass …
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds,
2024
The Norwegian Crop Research Institute, Norway
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds, Lars T. Havstad
IGC Proceedings (1997-2023)
Seedlings of Festuca pratensis Huds. (cv. Salten) were raised at three different light intensities (141, 85 or 28 (mol m-2s-1 ) for 7 weeks after emergence and then either left uncut or defoliated 40 or 80% of total leaf area, before transfer to primary induction (6°C, natural short days) for 12, 15 or 18 weeks. Percentage of heading plants was more affected by the duration of primary induction than by light intensity and defoliation prior to induction. The results lend no support to the existence of a juvenile stage in seedlings of Festuca pratensis. Defoliation had less influence on …
Water Use Efficiency In Chilean And Argentine Humid Temperate Grass-Legume Pastures,
2024
Universidad Nacional de Centro
Water Use Efficiency In Chilean And Argentine Humid Temperate Grass-Legume Pastures, H G. Landi, M H. Wade, V Garcia De Cortazar, D E. Dalla Valle
IGC Proceedings (1997-2023)
At two sites in Argentina and Chile five levels of water input were applied to four sown pastures of varying ages during spring and summer. The pastures consisted principally of C3 grasses and legumes, some of which were sown such as Lolium perenne, Trifolium repens, Dactylis glomerata. Dry matter (DM) production was measured and related to the estimated total evapotranspiration (ET): responses were both highly linear. Both responses to ET and absolute yields were higher at the Argentinian than at the Chilean site: respectively 10.7 and 15.2 kg DM/mm water evapotranspired. Nevertheless the calculated indices of sensitivity (Ky) of Doorenbos …
Effects Of Accelerate Ageing And Low Temperatures On Germination Of Range Grasses,
2024
Universidad Nacional del Sur
Effects Of Accelerate Ageing And Low Temperatures On Germination Of Range Grasses, C Cabeza, R E. Brevedan, M G. Klich, M A. Varillas
IGC Proceedings (1997-2023)
Accelerated ageing and cold tests were used to determine the seed vigour of different valuable forage grasses from the temperate semiarid region of Argentina (Piptochaetium napostaense, Poa ligularis, Stipa longiglumis, Stipa tenuis, Digitaria californica, Pappophorum subbulbosum, Setaria leiantha, Sorghastrum pellitum, Trichloris crinita). In general, warm season species showed greater vigour than cool season species.
Leaf Anatomy And Ultrastructure Of Poa Ligularis After Defoliation And Water Stress,
2024
Universidad Nacional del Sur
Leaf Anatomy And Ultrastructure Of Poa Ligularis After Defoliation And Water Stress, M G. Klich, R E. Brevedan, S C. Villamil
IGC Proceedings (1997-2023)
The objective of this study was to determine the effect of defoliation and water stress on leaf anatomy and the mesophyll cell ultrastructure of Poa ligularis. Anatomical differences were detected mainly at epidermal level. Under water stress, leaf roughness was enhanced since the epidermal-cell surface contours became conspicuous. Under defoliation the microscopic roughness decreased as a result of fewer epicuticular wax crystals being formed. Defoliation produced an enhancement of the interlamellar spaces in the irrigated plantís chloroplast. Under no defoliation conditions, chloroplast structure was not affected by water stress. When subjected to water stress, lightly defoliated plants presented chloroplasts …
Effects Of Water Stress On Germination And Seedling Growth Of Lovegrass Species,
2024
Universidad Nacional del Sur
Effects Of Water Stress On Germination And Seedling Growth Of Lovegrass Species, R E. Brevedan, M G. Klich, E E. Sanchez
IGC Proceedings (1997-2023)
Seeds of seven cultivars of lovegrass species Ermelo, Morpa and Tanganyika weeping lovegrass (Eragrostis curvula var. curvula, Don Eduardo INTA (E. curvula var. robusta), Cochise lovegrass (E. lehmanniana x E. trichophera), A-68 Lehmann lovegrass (E. lehmanniana Nees) and Catalina boer lovegrass (E. curvula var. conferta) were germinated at different water potentials. Total germination percentage differed within cultivars according to water availability, although there were no great differences between the germination of the cultivars within any given water potential. The only exception was Don Eduardo INTA which had lower germination values. A marked …
Leaf Growth And Anatomy During Winter Droughting Of Tetrachne Dregei Plants,
2024
Universidad Nacional del Sur
Leaf Growth And Anatomy During Winter Droughting Of Tetrachne Dregei Plants, M G. Klich, R E. Brevedan, H Laborde
IGC Proceedings (1997-2023)
The purpose of this work was to study the leaf growth and anatomy of Tetrachne dregei plants when they were subjected to a winter drought period. Plants were grown in semicontrolled conditions under two soil moisture regimes: irrigated and non-irrigated. Anatomical characterization was made using optical and scanning electron microscopy. No differences were found in stomatal index, stomatal length and epidermal cell size, between irrigated and non-irrigated plants. The adaxial epidermis of water stressed plants was more pubescent. Leaf abaxial epidermis of non-irrigated plants showed more intercostal plates of crystallized epicuticular wax than that of the irrigated ones. Leaf tissue …
The Interaction Between Root Distribution And Pasture Growth During Water Deficit,
2024
AgResearch, NZ
The Interaction Between Root Distribution And Pasture Growth During Water Deficit, D J. Barker, N Dymock
IGC Proceedings (1997-2023)
Quantification of water-limited pasture growth is of interest in agriculture since it allows prediction of impaired animal production during drought, and is the basis for scheduling irrigation. Experimental work on two dairy pastures 25 km south-west of Palmerston North, New Zealand found 50% of root mass was in the top 2.3 cm of soil. Soil moisture was, similarly, not uniformly distributed down the soil profile and dried most rapidly in the top 20†cm of soil. Leaf appearance rate was more strongly correlated with water status nearer the soil surface (r = 0.52 & 0.63 for 0-5 & 10-15 cm depth, …
Effects Of Phytohormone On Lateral Bud Elongation And Acidinvertase Activity During The Regrowth Of Sorghum Bicolor M.,
2024
Chiba University
Effects Of Phytohormone On Lateral Bud Elongation And Acidinvertase Activity During The Regrowth Of Sorghum Bicolor M., H Nojima, Y Takasaki, A Isoda
IGC Proceedings (1997-2023)
The relationships of phytohormone and sucrose metabolism in the stem ofoesorghum after cutting were studied using the stem disks treated with various plantoegrowth regulators The release of buds after incubating was accelerated by 6-benzyladenoprine riboside (6- BAR) treatment. But, on abcisic acid (ABA) andoeindole acetic acid (IAA ) treatment the release of buds was retarded. The length ofoeelongated buds on all hormonal treatments was shorter than the non-treated at the end of incubated period tested. Invertase activities were stimulated on all hormonal treatments. On 6-BAR treatment, invertase activities were the highest. But there were no relationships between invertase activities and …
Management Of Tall Wheatgrass Based On The Leaf Appearance During Spring,
2024
UNMdP, Argentina
Management Of Tall Wheatgrass Based On The Leaf Appearance During Spring, S Laplace, M A. Brizuela, M S. Cid
IGC Proceedings (1997-2023)
The objectives of this study were to determine the date of transition from vegetative to reproductive stage at different defoliation frequencies in tall wheatgrass (Thinopyrum ponticum). In addition, we assessed the relationship between the spring temperatures and the rate of leaf appearance. To meet both objectives we had defoliated and undefoliated plant plots at Balcarce Experiment Station, Argentina. The different defoliation treatments (every 7, 14, 21 and 28 days) delayed or avoided the manifestation of the reproductive stage. The apexes of undefoliated plants began to rise on October 12, while defoliated ones slowed that elevation or the same …
