Why are Chloris gayana leaves shorter in salt-affected plants? Analyses in the elongation zone

Reduced hydraulic conductance calculated from growth data was suggested to be the main reason for reduced leaf expansion in salt-stressed Chloris gayana (Rhodes grass). In this work, xylem vessel cross-sections and wall enzyme activities were analysed to re-examine the effects of salinity on leaf growth in this species. Maximal segmental growth rates were 20% lower and the growth zone was 23% shorter in leaves from salinized plants than in controls; however, growth rates between 0 mm and 15 mm from the ligule were similar in both types of leaves. Xylem cross-sectional areas in this region were about 65% smaller in leaves of salinized plants, suggesting that hydraulic restrictions in the leaves of salinized plants were much higher than overall growth reductions. Extractable xyloglucan endotransglucosylase activity in this zone was twice as high in leaves of salinized plants as in leaves of controls. Nevertheless, the activity of the extracted enzyme was not affected by up to 1 M NaCl added to the reaction medium. Therefore, increased xyloglucan endotransglucosylase activity under salinity may be due to a promotion of transcription of XTH (xyloglucan endotransglucosylase/hydrolases) genes and/or translation of preformed transcripts. These results suggest that, as in drought stress, increased activity of cell wall enzymes associated with wall loosening may contribute to the maintenance of growth under saline conditions despite hydraulic restrictions.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Ortega, Leandro Ismael. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); ArgentinaFil: Fry, Stephen C. University of Edinburgh. Institute of Molecular Plant Sciences. The Edinburgh Cell Wall Group; Gran BretañaFil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); Argentina

Benefits of Additional Runway Crossings on Parallel Runway Operations

As the air transportation industry expands, airports face numerous challenges to manage the increasing traffic. Among these problems, runway crossings are a considerable source of ground traffic inefficiency and risk. Building end-around taxiways are the only strategy to avoid crossings, but these are not always feasible, and therefore airport planners must find alternatives. This study consisted of a simulation over an airport that currently requires a vast amount of its arrivals to go through runway crossings in order to reach the apron; the airport simulation software utilized was the Total Airspace and Airport Modeler (TAAM). The process began with a thorough validation of a baseline model against the historical data of the airport, followed by the design and simulation of three alternatives, which had one, two, and three runway crossings subsequently added. The simulation also included two flight schedules resembling the operations of 2016 and 2026, in order to forecast the impact of the additional crossings in the upcoming years. Finally, an analysis with ANOVAs and t-tests of the simulation outputs revealed significant decreases in arrival and departure taxi times, along with no significant changes in runway or sequencing delay

Cellular Causes for Leaf Elongation Reductions under Salinity in \u3cem\u3ePanicum coloratum\u3c/em\u3e

Soil salinity is a growing constraint to crop and forage production worldwide and has driven the quest for salt-tolerant germplasm. Perennial forage grasses are regarded as choice alternative for the productive use of saline areas as well as for mitigating salinity in these areas (Ridley and Pannell 2005). Panicum coloratum L. is a C4 perennial grass native to tropical Africa, adapted to a wide range of rainfall conditions which makes it attractive as a forage for semiarid areas (Jones 1985). In forage grasses, yield is directly related to leaf area expansion and duration and the purpose of this work was to analyse the underlying cellular causes for reduced leaf growth under saline conditions. Kinematic studies on the spatial distribution of cell lengths, along with information on leaf elongation rates, can be used to calculate the contribution of cell expansion and division to leaf growth (Silk et al. 1989) and provide a first insight to the causes of stress-associated reductions in leaf expansion (Rymen et al. 2010). While kinematic analyses have been performed in several grass species, including perennial grasses (Volenec and Nelson 1981, Schnyder et al. 1987, Fiorani et al. 2000), to determine, for example, the association between leaf growth, meristematic activity and cell expansion, however, the contribution of alterations in cell division and expansion to salt-associated reductions in leaf size of a perennial forage grass had not been explored before

Early Ontogenetic Responses of Six Commercial Chloris Gayana Cultivars to Salinity

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 in 100 and 200 mM NaCl solutions. Growth of all the cultivars was reduced at high salinities, more markedly in cv. Boma, where stolon production was also affected. This cultivar was the most susceptible to frost and had lower Na and higher K accumulation in leaf tissues

La salinidad : Una oscura amenaza para la agricultura

El presente escrito es una síntesis de la conferencia con la que fui incorporada a la Academia Nacional de Agronomía y Veterinaria en abril del 2017. En consecuencia, la bibliografía abarca principalmente hasta fines de 2016, aunque algunas citas son más recientes. Contiene muchos elementos del capítulo que escribimos Andrés Rodríguez y yo (Taleisnik y Rodríguez, 2017) en el libro "Ambientes salinos y alcalinos de la Argentina. Recursos y aprovechamiento productivo" (Taleisnik y Lavado 2017).Academia Nacional de Agronomía y Veterinari

Variabilidad en sorgo para tolerancia a la alcalinidad en suelos: mecanismos fisiológicos y estrategias para incrementar la disponibilidad de nutrientes

El objetivo general de este proyecto es contribuir a la incorporación productiva de zonas afectadas por alcalinidad, identificando genotipos de sorgo con tolerancia a esa condición, avanzando en el conocimiento de las causas de tal tolerancia y evaluando prácticas de fertilización biológica para incrementar la productividad en tales ambientes.El mismo cuenta ya con financiamiento de FONCYT (PICT 2016 1136). Se presenta en esta convocatoria a fin de gestionar las evaluaciones a campo. En los campos de la UCC existen algunos manchones de suelos alcalinos (y no alcalinos), propicios para la evaluación de las respuesas de genotipos de sorgo a la alcalinidad del sustrato en condiciones de cultivo a campo. Esta actividad es fundamental para validar la fenotipificación que realizamos paralelamente en condiciones controladas. La comparación de los resultados de ensayos realizados bajo condiciones controladas y a campo nos permitirá la identificación inequívoca de materiales con respuestas contrastantes a la alcalinidad, que serán objeto del trabajo de investigación acerca de los mecanismos fisiológicos subyacentes.Fil: Taleisnik, Edith Liliana. Universidad Católica de Córdoba. Facultad de Ciencias Agropecuarias; Argentin

Tipburn in salt-affected lettuce (Lactuca sativa L.) plants results from local oxidative stress

Tipburn in lettuce is a physiological disorder expressed as a necrosis in the margins of young developing leaves and is commonly observed under saline conditions. Tipburn is usually attributed to Ca 2+ deficiencies, and there has very limited research on other mechanisms that may contribute to tipburn development. This work examines whether symptoms are mediated by increased reactive oxygen species (ROS) production.Two butter lettuce (Lactuca sativa L.) varieties, Sunstar (Su) and Pontina (Po), with contrasting tipburn susceptibility were grown in hydroponics with low Ca 2+ (0.5mM), and with or without 50mM NaCl. Tipburn symptoms were observed only in Su, and only in the saline treatment. Tipburn incidence in response to topical treatments with Ca 2+ scavengers, Ca 2+ transport inhibitors, and antioxidants was assessed. All treatments were applied before symptom expression, and evaluated later, when symptoms were expected to occur. Superoxide presence in tissues was determined with nitro blue tetrazolium (NBT) and oxidative damage as malondialdehyde (MDA) content. Superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities were assayed.Under control and saline conditions, tipburn could be induced in both varieties by topical treatments with a Ca 2+ scavenger (EGTA) and Ca 2+ transport inhibitors (verapamil, LaCl 3) and reduced by supplying Ca 2+ along with a ionophore (A 23187). Tipburn symptoms were associated with locally produced ROS. O 2 - and oxidative damage significantly increased in leaf margins before symptom expression, while topical antioxidant applications (Tiron, DPI) reduced symptoms in treated leaves, but not in the rest of the plant. Antioxidant enzyme activity was higher in Po, and increased more in response to EGTA treatments, and may contribute to mitigating oxidative damage and tipburn expression in this variety.Fil: Carassay, Luciano Raul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa; ArgentinaFil: Bustos, Dolores Angela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Golberg, Alberto Daniel. Universidad Nacional de La Pampa; ArgentinaFil: Taleisnik, Edith. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Fitopatología y Fisiología Vegetal; Argentin

Decreased reactive oxygen species concentration in the elongation zone contributes to the reduction in maize leaf growth under salinity

Reactive oxygen species (ROS) in the apoplast of cells in the growing zone of grass leaves are required for elongation growth. This work evaluates whether salinity‐induced reductions in leaf elongation are related to altered ROS production. Studies were performed in actively growing segments (SEZ) obtained from leaf three of 14‐d‐old maize (Zea mays L.) seedlings gradually salinized to 150 mM NaCl. Salinity reduced elongation rates and the length of the leaf growth zone. When SEZ obtained from the elongation zone of salinized plants (SEZs) were incubated in 100 mM NaCl, the concentration where growth inhibition was approximately 50%, O2•– production, measured as NBT formazan staining, was lower in these than in similar segments obtained from control plants. The NaCl effect was salt‐specific, and not osmotic, as incubation in 200 mM sorbitol did not reduce formazan staining intensity. SEZs elongation rates were higher in 200 mM sorbitol than in 100 mM NaCl, but the difference could be cancelled by scavenging or inhibiting O2•– production with 10 mM MgCl2 or 200 µM diphenylene iodonium, respectively. The actual ROS believed to stimulate growth is •OH, a product of O2•– metabolism in the apoplast. SEZs elongation in 100 mM NaCl was stimulated by a •OH‐generating medium. Fusicoccin, an ATPase stimulant, and acetate buffer pH 4, could also enhance elongation in these segments, although both failed to increase ROS activity. These results show that decreased ROS production contributes to the salinity‐associated reduction in grass leaf elongation, acting through a mechanism not associated with pH changes.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Rodriguez, Andrés Alberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); ArgentinaFil: Córdoba, Alicia R. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); ArgentinaFil: Ortega, Leandro Ismael. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); ArgentinaFil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); Argentin

Woody perennials for environments affected by salinity. A synopsis of the argentine contribution on this topic

La salinidad es una preocupación en la Argentina que, ocupa el tercer lugar después de Rusia y Australia en cuanto a la superficie del suelo afectado por la salinidad. El propósito de esta revisión es indicar la contribución de los científicos argentinos en el tema general de las plantas leñosas perennes y la salinidad. Quedan expresamente excluidos de esta revisión los estudios de la vegetación de lugares salinos y las investigaciones realizadas sobre especies no leñosas. En Argentina, la atención se ha centrado particularmente en la tolerancia a la salinidad de los árboles del bosque nativo, en especial en los miembros del género Prosopis, en los efectos de la forestación sobre el agua y la salinidad del suelo, y en los microorganismos que interactúan con árboles y arbustos en condiciones salinas. Además de estos temas específicos, se ha trabajado sobre la tolerancia a la salinidad en otros árboles y en arbustos del género Atriplex.Salinity is a concern in Argentina, which ranks third after Russia and Australia in soil surface affected by this condition. The purpose of this review is to point to the contribution of Argentine scientists to research on woody perennials in relation to salinity. Studies on the vegetation of saline areas in Argentina and on the responses of non-woody plants are beyond the scope of this review. In Argentina, attention has focused mainly on the salt tolerance of native forest trees, especially in members of the genus Prosopis, on the effects of afforestation on water and soil salinity and on microorganisms interacting with trees and shrubs under saline conditions. Besides these specific topics, there has been some work on salt tolerance of other trees and in Atriplex shrubs.Fil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Estudios Agropecuarios - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Estudios Agropecuarios; ArgentinaFil: López Lauenstein, Diego Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Estudios Agropecuarios - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Estudios Agropecuarios; Argentin