Influencia del nitrógeno en el aborto de flores y frutos de la soja y en su rendimiento en distintos niveles del canopeo

El objeto de este estudio fue lograr un mejor conocimiento de la influencia del nitrógeno sobre el aborto de flores y frutos durante la floración y cuajado de frutos, y sobre el rendimiento de semilla, en diferentes niveles del canopeo.Tema: El rendimiento de especies de gran cultivo: características ecofisiológicas y su manipulación genéticaAcademia Nacional de Agronomía y Veterinari

Effects of Water Stress on Germination and Seedling Growth of Lovegrass Species

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 fall in germination was registered as from -0.6 MPa, which became practically non-existent at -1.5 MPa . Root and shoot length was measured on all cultivars of Eragrostis curvula var. curvula and shortening was observed when the water potential was reduced

Forage Quality of Mixtures of \u3ci\u3eBromus wildenowii\u3c/i\u3e and \u3ci\u3eB. parodii\u3c/i\u3e Influenced by Nitrogen Fertilization or Alfalfa Interseeding

Under good soil fertility conditions, Bromus wildenowii Kunth and Bromus parodii Covas et Itria are two high producing forage grasses. The objective of this study was to evaluate the effect of nitrogen fertilization or the association with alfalfa (Medicago sativa L) on yield and forage quality of mixtures of both grasses during the establishment year. Nitrogen fertilizer (300 kg ha-1) was broadcasted in three 100 kg N dosis. Nitrogen fertilization or alfalfa intercropping did not increase dry matter yield. Tiller density and crude protein content of grass forage were increased by nitrogen application. Intercropped alfalfa increased N content of grasses mixture. In vitro dry matter disappearance, neutral detergent fiber and lignin content were not affected by treatments

Influencia del nitrógeno en el aborto de flores y frutos de la soja y en su rendimiento en distintos niveles del canopeo

El objeto de este estudio fue lograr un mejor conocimiento de la influencia del nitrógeno sobre el aborto de flores y frutos durante la floración y cuajado de frutos, y sobre el rendimiento de semilla, en diferentes niveles del canopeo.Tema: El rendimiento de especies de gran cultivo: características ecofisiológicas y su manipulación genéticaAcademia Nacional de Agronomía y Veterinari

Leaf Growth and Anatomy During Winter Droughting of Tetrachne Dregei Plants

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 distribution was not affected by the different moisture regimes. The effect of water deficit was neither detected on plant height, nor on leaf width and length. Except for the enhanced adaxial pubescence and abaxial wax crystal content, no other xeroplastic changes were noticed

Leaf Anatomy and Ultrastructure of Poa Ligularis After Defoliation and Water Stress

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 with a bellowed outer membrane, irregular thylacoid distribution and the disorganization of peripheral grana. Severely defoliated plants showed disorganized internal chloroplast membranes and even the disappearance of the grana. No breakdown or disappearance of chloroplast external membranes was detected under the imposed growing conditions, suggesting that no irreversible changes were induced

Effects of Accelerate Ageing and Low Temperatures on Germination of Range Grasses

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

Yield and Forage Quality in Alfalfa-Weeping Lovegrass Mixtures

Little is known about the relative performance of weeping lovegrass in mixtures with alfalfa. Our objective was to compare the productivity and forage quality of monocultures and binary mixtures of the species. Mixtures always gave higher yields than any of the monocultures and the highest was obtained in the mixture with the largest proportion of alfalfa. In the second year weeping lovegrass N concentration in the mixtures were higher than in monoculture. Weeping lovegrass did not affect the alfalfa N concentration. There was not differences in the NDF, for between these species

Evapotranspiration and energy balance measurements over a soybean field in the semiarid sowthwestern region of Buenos Aires province (Argentina)

Fil: Cargnel, M. D. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Orchansky, A. L. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Fil: Brevedan, R. E. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Fil: Baioni, S. S. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires´, Argentina.Fil: Fioretti, M. N. Universidad Nacional del Sur. Departamento de Agronomía. Bahía Blanca, Buenos Aires, Argentina.Two field experiments were carried out in a semiarid region of Argentina over a soybean (Glycine max L. Merrill) field. The sites of study were San Adolfo (39˚ 23’ S, 62˚ 22’ W, 22 m.a.s.l.) and Nueva Roma (38˚ 29’ S, 62˚ 39’ W, 70 m.a.s.l.). Soybeans were planted on Jan 4 (San Adolfo) and Nov 27 (Nueva Roma) in 0.75 m wide rows and at 400000 pl/ha during two consecutive growing seasons. Energy balance and evapotranspiration (ET) were estimated during the reproductive stages from full bloom (R2) to full maturity (R8). In Nueva Roma ET or latent heat flux (LE) was estimated using the Bowen ratio-energy balance (BREB) (LEb) and the Priestley -Taylor equation (LEPT) with αPT=1.26, 48 h after irrigation or rain. Both methods could be used to predict ET since the ratio LEb/LEPT ranged between 0.83 and 0.95. The observed Bowen ratio values were almost 0 during and after rain and increased to approximately 0.45 several days after rain. In San Adolfo LE was estimating using the Priestley -Taylor equation. For both sites the regression analysis for comparison available energy (Rn-G) and LE using BREB or LEPT indicated that, approximately 90% of the available energy was consumed by LE without detecting significative advective conditions.tbls., grafs