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

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

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

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

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

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

Drought induces distinct growth response, protection, and recovery mechanisms in the maize leaf growth zone

Drought is the most important crop yield-limiting factor, and detailed knowledge of its impact on plant growth regulation is crucial. The maize (Zea mays) leaf growth zone offers unique possibilities for studying the spatiotemporal regulation of developmental processes by transcriptional analyses and methods that require more material, such as metabolite and enzyme activity measurements. By means of a kinematic analysis, we show that drought inhibits maize leaf growth by inhibiting cell division in the meristem and cell expansion in the elongation zone. Through a microarray study, we observed the down- regulation of 32 of the 54 cell cycle genes, providing a basis for the inhibited cell division. We also found evidence for an up- regulation of the photosynthetic machinery and the antioxidant and redox systems. This was confirmed by increased chlorophyll content in mature cells and increased activity of antioxidant enzymes and metabolite levels across the growth zone, respectively. We demonstrate the functional significance of the identified transcriptional reprogramming by showing that increasing the antioxidant capacity in the proliferation zone, by overexpression of the Arabidopsis (Arabidopsis thaliana) iron-superoxide dismutase gene, increases leaf growth rate by stimulating cell division. We also show that the increased photosynthetic capacity leads to enhanced photosynthesis upon rewatering, facilitating the often-observed growth compensation.Fil: Avramova, Viktoriya. Universiteit Antwerp; BélgicaFil: Abdelgawad, Hamada. University of Beni-Suef; EgiptoFil: Zhang, Zhengfeng. Central China Normal University; ChinaFil: Fotschki, Bartosz. Institute of Animal Reproduction and Food Research; PoloniaFil: Casadevall, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; ArgentinaFil: Vergauwen, Lucia. Universiteit Antwerp; BélgicaFil: Knapen, Dries. Universiteit Antwerp; BélgicaFil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guisez, Yves. Universiteit Antwerp; BélgicaFil: Asard, Han. Universiteit Antwerp; BélgicaFil: Beemster, Gerrit T. S.. Universiteit Antwerp; Bélgic

Tilting the scale towards Plant Science…in Argentina

Is Plant Science regarded as a socially valuable activity? Is the support to Plant Science adequate and effective? Can the current research enterprise provide effective support to the agricultural sector? This type of questions have driven the analyses included in this lecture. Investment in agriculturerelated research topics and specifically in Plant Science are examined in some Latin American countries and, particularly in Argentina. From a national perspective, the reasons to support plant science research may be related to the importance of agriculture in the national gross domestic product (GDP). In Latin America, the average contribution of agriculture to GDP is about 5 %. Plant-derived products contribute more than 40 % to Argentine exports. Food and agricultural research and development (R&D) spending relative to agricultural GDP in Latin America as a whole, and, specifically in Argentina, is only about 1 %, much lower than the high-income countries average of 2.5 %. Yet, in other parts of the world, return estimates to research investment in agriculture strongly indicate it is profitable, and that less-than-adequate funding can have long term negative effects on the country’s economy. Is Plant Science research innovative and are approaches dynamic and flexible? It has been concluded that continued food demand growth, in a scenery of increasing environmental concerns, requires redefining the research enterprise to meet these complex challenges. Measures towards this goal should include a redesign of higher education programs in agriculture to make them more attractive, stimulation of migration of research capacity from traditional to innovative topics, specifically by young, well trained scientists, increased attention targeted to site-specific research and stronger links with the private sector. Plant scientists can and should assume active roles in this transformation process.Fil: Taleisnik, Edith. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Inv. Agropecuarias. Instituto de Fisiologia y Recursos Geneticos Vegetales; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigaciones Agropecuarias; Argentin

Elongation growth in leaf blades of Chloris gayana under saline conditions

In Chloris gayana, salinity-associated yield decreases are due mainly to leaf area reductions. To understand the physiological basis for such reduction, the effects of salinity were studied on the spatial and temporal distribution of extension in the intercalary meristem at the leaf base, and on hydraulic conductance in that zone. C. gayana plants were grown on sand irrigated with Hoagland solution with the addition of 0 or 200 mmol/L NaCl, and all measurements were performed on tiller leaf four. In salinised plants, that leaf was 20 percnt; shorter than in controls. Extension in the blade expansion zone was studied by pricking through the leaf sheaths and analysing the displacement of the pricks. In salt-treated plants, maximum growth rates were depressed by 53 percnt; and the growth zone was shorter by approximately 10 mm, nevertheless, extension proceeded for a longer period than in control plants. The analysis of specific leaf areas in the expansion zone suggests the rate of dry matter deposition was lowered by salinity and estimations of tissue displacement time within that zone suggest cell wall maturity was delayed. Hydraulic conductance was reduced by salinity and this may be the main cause for reduced growth under salinity in Chloris gayana.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); Argentina.Fil: Taleisnik, Edith. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales (ex IFFIVE); Argentina