Modelos predictivos de desarrollo apical en trigo (Triticum aestivum L.), por características morfológicas externas

En el trigo (Triticum aestivum L.), el ápice en estado de doble lomo y de espiguilla terminal diferenciada, marcan los límites del período oportuno para realizar ciertas prácticas agronómicas. El objetivo del presente trabajo consistió en probar el ajuste de modelos de regresión lineal, que relacionan los estados de desarrollo apical con la altura del eje principal. Se utilizaron los cultivares Buck Charrúa, Buck Poncho, Buck Yapeyú y Buck Guaraní, medidos y disectados desde que se insinuó el estado In (Nerson) hasta el estado IX (Nerson). Se estimaron las ecuaciones de regresión entre las dos variables mencionadas, para cada cultivar y en su conjunto. Además se contrastó la altura del  eje principal con estado III (Nerson) y estado IX (Nerson) a fin de identificar la causa de la diferencia. No se encontró un modelo que relacione satisfactoriamente estado de desarrollo apical con altura del eje principal, aplicable para las condiciones climáticas locales.Director: Ing. Agr. Daniel R. Alí. Cátedra de Terapéutica Vegetal. Facultad de Agronomía Universidad Nacional de La Pampa.Codirector: lng. Agr. Fernando D. García. Cátedra de Terapéutica Vegetal

Modelos predictivos de desarrollo apical en trigo (Triticum aestivum L.), por características morfológicas externas

En el trigo (Triticum aestivum L.), el ápice en estado de doble lomo y de espiguilla terminal diferenciada, marcan los límites del período oportuno para realizar ciertas prácticas agronómicas. El objetivo del presente trabajo consistió en probar el ajuste de modelos de regresión lineal, que relacionan los estados de desarrollo apical con la altura del eje principal. Se utilizaron los cultivares Buck Charrúa, Buck Poncho, Buck Yapeyú y Buck Guaraní, medidos y disectados desde que se insinuó el estado In (Nerson) hasta el estado IX (Nerson). Se estimaron las ecuaciones de regresión entre las dos variables mencionadas, para cada cultivar y en su conjunto. Además se contrastó la altura del  eje principal con estado III (Nerson) y estado IX (Nerson) a fin de identificar la causa de la diferencia. No se encontró un modelo que relacione satisfactoriamente estado de desarrollo apical con altura del eje principal, aplicable para las condiciones climáticas locales. Director: Ing. Agr. Daniel R. Alí. Cátedra de Terapéutica Vegetal. Facultad de Agronomía Universidad Nacional de La Pampa. Codirector: lng. Agr. Fernando D. García. Cátedra de Terapéutica Vegetal

Cove-edged graphene nanoribbons with incorporation of periodic zigzag-edge segments

Structurally precision graphene nanoribbons (GNRs) are promising candidates for next-generation nanoelectronics due to their intriguing and tunable electronic structures. GNRs with hybrid edge structures often confer them unique geometries associated with exotic physicochemical properties. Herein, a novel type of cove-edged GNRs with periodic short zigzag-edge segments is demonstrated. The bandgap of this GNR family can be tuned using an interplay between the length of the zigzag segments and the distance of two adjacent cove units along the opposite edges, which can be converted from semiconducting to nearly metallic. A family member with periodic cove-zigzag edges based on N = 6 zigzag-edged GNR, namely 6-CZGNR-(2,1), is successfully synthesized in solution through the Scholl reaction of a unique snakelike polymer precursor (10) that is achieved by the Yamamoto coupling of a structurally flexible S-shaped phenanthrene-based monomer (1). The efficiency of cyclodehydrogenation of polymer 10 toward 6-CZGNR-(2,1) is validated by FT-IR, Raman, and UV–vis spectroscopies, as well as by the study of two representative model compounds (2 and 3). Remarkably, the resultant 6-CZGNR-(2,1) exhibits an extended and broad absorption in the near-infrared region with a record narrow optical bandgap of 0.99 eV among the reported solution-synthesized GNRs. Moreover, 6-CZGNR-(2,1) exhibits a high macroscopic carrier mobility of ∼20 cm2 V–1 s–1 determined by terahertz spectroscopy, primarily due to the intrinsically small effective mass (m*e = m*h = 0.17 m0), rendering this GNR a promising candidate for nanoelectronics

Cove-Edged Graphene Nanoribbons with Incorporation of Periodic Zigzag-Edge Segments

Structurally precision graphene nanoribbons (GNRs) are promising candidates for next-generation nanoelectronics due to their intriguing and tunable electronic structures. GNRs with hybrid edge structures often confer them unique geometries associated with exotic physicochemical properties. Herein, a novel type of cove-edged GNRs with periodic short zigzag-edge segments is demonstrated. The bandgap of this GNR family can be tuned using an interplay between the length of the zigzag segments and the distance of two adjacent cove units along the opposite edges, which can be converted from semiconducting to nearly metallic. A family member with periodic cove-zigzag edges based on N = 6 zigzag-edged GNR, namely 6-CZGNR-(2,1), is successfully synthesized in solution through the Scholl reaction of a unique snakelike polymer precursor (10) that is achieved by the Yamamoto coupling of a structurally flexible S-shaped phenanthrene-based monomer (1). The efficiency of cyclodehydrogenation of polymer 10 toward 6-CZGNR-(2,1) is validated by FT-IR, Raman, and UV-vis spectroscopies, as well as by the study of two representative model compounds (2 and 3). Remarkably, the resultant 6-CZGNR-(2,1) exhibits an extended and broad absorption in the near-infrared region with a record narrow optical bandgap of 0.99 eV among the reported solution-synthesized GNRs. Moreover, 6-CZGNR-(2,1) exhibits a high macroscopic carrier mobility of ∼20 cm2 V-1 s-1 determined by terahertz spectroscopy, primarily due to the intrinsically small effective mass (m*e = m*h = 0.17 m0), rendering this GNR a promising candidate for nanoelectronics

Genetic association mapping identifies single nucleotide polymorphisms in genes that affect abscisic acid levels in maize floral tissues during drought

In maize, water stress at flowering causes loss of kernel set and productivity. While changes in the levels of sugars and abscisic acid (ABA) are thought to play a role in this stress response, the mechanistic basis and genes involved are not known. A candidate gene approach was used with association mapping to identify loci involved in accumulation of carbohydrates and ABA metabolites during stress. A panel of single nucleotide polymorphisms (SNPs) in genes from these metabolic pathways and in genes for reproductive development and stress response was used to genotype 350 tropical and subtropical maize inbred lines that were well watered or water stressed at flowering. Pre-pollination ears, silks, and leaves were analysed for sugars, starch, proline, ABA, ABA-glucose ester, and phaseic acid. ABA and sugar levels in silks and ears were negatively correlated with their growth. Association mapping with 1229 SNPs in 540 candidate genes identified an SNP in the maize homologue of the Arabidopsis MADS-box gene, PISTILLATA, which was significantly associated with phaseic acid in ears of well-watered plants, and an SNP in pyruvate dehydrogenase kinase, a key regulator of carbon flux into respiration, that was associated with silk sugar concentration. An SNP in an aldehyde oxidase gene was significantly associated with ABA levels in silks of water-stressed plants. Given the short range over which decay of linkage disequilibrium occurs in maize, the results indicate that allelic variation in these genes affects ABA and carbohydrate metabolism in floral tissues during drought