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This study evaluated the physiological and anatomical traits of two contrasting maize hybrids subjected to high density sowing in order to explain yield stability through yield component analysis and the relation between the grain yield capacities per plant according to individual growth. Experiment factors were two commercially important maize hybrids: DK190MGRR2 and DK670MG, which behave differently under stress, and two levels of plant density: 7 and 11 plant/m2 high and recommended density to favour the conditions of water stress respectively. The experiment was carried out in the west of Argentina under rainfed conditions and five replications. Physiological parameters (pigments and endogenous content of phytohormones, injury of cell membranes, yield components) and anatomical parameters (stomatal bevhaviour, foliar and peduncles anatomy, xylem and phloem area in vascular bundles) were analyzed. In this study, both maize hybrids showed a differential response to both sowing densities. The DK670 showed an increased yield (24 and 10 % at 7 and 11 plant/m2 , respectively) due to enhanced individual yield components. This hybrid was differentiated by a higher stomatal density (7±1 in the abaxial side) and pigment amount (20%, mainly chl a) which led to a better photosynthetic ability. In addition, this hybrid showed the capacity to compensate damages derived from stress, mesophyll leaf thickness and closer bundles associated with tolerance to drought, and abundance in endogenous phytohormones to cope with stress. The description of these characteristics in response to different plant densities is novel results, especially those related to anatomical analysis under the different treatments. This research shows that the ability of hybrids to take advantage of abundance of resources at lower populations is an imperative need for over-seasonal potential yield accomplishment. This could help select more appropriate management practices and contribute to production areas. Fil: Travaglia, Claudia Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Espósito, Gabriel. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentina Fil: Balboa, Guillermo. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentina Fil: Masciarelli, Oscar Alberto. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fortuna, Julieta. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina Fil: Cardozo, Paula Gabriela. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Reinoso, Herminda Elmira. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina

In this work, the response of the halophytic shrub Prosopis strombulifera to lowering an osmotic potential ( o) to -1.0, -1.9, and -2.6 MPa generated by NaCl, Na2SO4, and the iso-osmotic combination of them was studied at 6, 12, and 24 h after reaching such values in the growing media. By analyzing the content of abscisic acid (ABA) and related metabolites and transpiration rates, we observed that ABA content varied depending on type of salt, salt concentration, organ analyzed, and age of a plant. ABA content in leaves was much higher than in roots, presumably because of rapid biosynthesis and transport from roots. Leaves of Na2SO4-treated plants had the highest ABA content at o -2.6 MPa (24 h) associated with sulfate toxicity symptoms. Significant content of ABA-glucose ester (ABA-GE) was found in both the roots and leaves, whereas only low content of phaseic acid (PA) and dihydrophaseic acid (DPA). The roots showed high ABA-GE accumulation in all treatments. The highest content of free ABA was correlated with ABA-GE glucosidase activity. The results show that ABA-GE and free ABA work together to create a specific stress signal. Fil: Llanes, Analia Susana. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Catedra de Fisiologia Vegetal; Argentina Fil: Masciarelli, Oscar Alberto. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Catedra de Fisiologia Vegetal; Argentina Fil: Ordóñez, Roxana Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina Fil: Isla, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Quimica del Noroeste; Argentina Fil: Luna, Maria Virginia. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Catedra de Fisiologia Vegetal; Argentina

Fluorescent Pseudomonas spp. isolated from the roots of healthy tomato plants were screened for their antagonistic activities against Sclerotium rolfsii, Alternaria alternata and Fusarium solani, three phytopathogenic fungi of tomato and pepper. They were tested for phosphate solubilization ability and production of siderophores, hydrolytic enzymes, indole 3-acetic acid and hydrogen cyanid. The isolates were also characterized based on biochemical (API 20NE test) and genotypic (ERIC-PCR fingerprinting) features. A Pseudomonas sp. strain denoted PCI2 was chosen as a potential candidate for controlling tomato damping-off caused by Sclerotium rolfsii. PCI2 was identified at the genus level with a 16S rDNA partial sequence analysis and its phylogenetic relationship with previously characterized Pseudomonas species was determined. PCI2 clustered with the P. putida species. Growth chamber studies resulted in statistically significant increases in plant stand (29%) as well as in root dry weight (58%). PCI2 was able to establish itself and survive in tomato rhizosphere after 40 days, following planting of bacterized seeds. PCI2 is a potential biological control agent that may contribute to the protection of tomato plants against damping-off caused by S. rolfsii. Fil: Pastor, Nicolás Alejandro. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Biología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Reynoso, Maria Marta. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Microbiología e Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Tonelli, Maria Laura. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Masciarelli, Oscar Alberto. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Rosas, Susana Beatriz. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Biología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Rovera, Marisa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Microbiología e Inmunología; Argentina