SUMMARY Background and aims: The onion (Allium cepa var. cepa) is an allogamous species in which male-sterile lines have been developed. However, the structure of the flower and floral nectaries have only been briefly described. The objective of this study is to update the floral anatomy data, comparing the gynoecium and androecium of male-fertile and male-sterile lines, and to analyze the three-dimensional structure of the floral nectary. M&M: Conventional optical and scanning electron microscopy techniques were used. Results: Fertile and sterile male flowers have the same structural organization. The septal or gynopleural nectary is organized in three zones: 1) production area formed by the glandular tissue arranged radially in the septa of the ovary, 2) discharge zone: a small channel at the apex connects the nectariferous tissue with the pocket formed between the ovary wall and the overlying ridge, and 3) presentation and harvest zone, where the excreted nectar accumulates, formed between the widened base of the inner staminal filaments opposite the ovary. Conclusions: The only anatomical differences in the flowers sterile male lines are the lack of pollen production and the absence of dehiscence, despite having a normal stomium and anther wall. The floral nectaries of onion are a clear example of secondary presentation of nectar.

Resumen Introducción y objetivos: La cebolla (Allium cepa var. cepa) es una especie alógama, donde se han desarrollado líneas androestériles. La estructura floral y la de sus nectarios florales ha sido descrita de manera somera e incompleta. El objetivo del presente trabajo es actualizar los datos de la anatomía floral comparando líneas fértiles y androestériles y analizar la estructura tridimensional del nectario floral. M&M: Se utilizaron técnicas convencionales de microscopía óptica y electrónica de barrido. Resultados: Las flores fértiles y androestériles presentan la misma organización estructural. El nectario septal o ginopleural se organiza en tres zonas: 1) área productora formada por el tejido glandular dispuesto radialmente en los septos del ovario, 2) zona de descarga: un pequeño canal en el ápice conecta el tejido nectarífero con el bolsillo formado entre la pared del ovario y la cresta que los cubre, y 3) zona de presentación y cosecha, donde el néctar excretado se acumula, formada entre la base ensanchada de los filamentos estaminales internos y la base del ovario. Conclusiones: Las únicas diferencias anatómicas en las flores de las líneas androestériles y las fértiles radican en la falta de producción de granos de polen y la ausencia de dehiscencia, pese a presentar estomio y pared de anteras normales. Los nectarios florales de la cebolla son un claro ejemplo de presentación secundaria del néctar.

Abstract Green and variegated Benjamin fig (Ficus benjamina) often suffer from root restriction when grown in pots. While exogenous cytokinin applications have proven effective in reversing this stress, the possibility that exogenous auxins, either alone or in combination with cytokinin, may also be helpful has received little attention. In this work, we analyse the response of green and variegated Ficus benjamina rooted cuttings growing in small pots to exogenous supply of auxin and cytokinin at different concentrations, either in single or combined applications. Our results show that both benzyl aminopurine (BAP) and indole acetic acid (IAA), at the highest concentration tested (100 mg L-1) increased leaf development and plant biomass accumulation in green and variegated Ficus genotypes. However, exogenous IAA and BAP appeared to elicit differential plant morpho-physiological responses. While BAP tended to enhance leaf appearance more than IAA did, the latter promoted leaf expansion in a steadier manner than BAP, thus resulting in plants with less, but larger, leaves than those treated with cytokinin. Despite these differences in plant architecture, regression analysis suggests that hormonal-induced growth promotion was solely attributable to enhanced carbon assimilation. Rather unexpectedly, IAA promoted net assimilation and photosynthesis rates at least as effectively as cytokinin. Possible mechanisms involved in growth and development promotion by exogenous application of both hormones are discussed. Auxin treatment may help overcome root restriction in Ficus as effectively as cytokinin in terms of growth promotion, although differences in plant architecture may arise as compared with plants sprayed with the latter hormone.

Resumo Ficus Benjamina (Ficus benjamina) verde e variegado geralmente sofre de restrição no crescimento das raízes quando cultivado em vasos. Embora as aplicações de citocinina exógena tenham se mostrado eficazes na reversão desse estresse, a possibilidade de que auxinas exógenas, sozinhas ou em combinação com citocinina, também possam ser benéficas tem recebido pouca atenção. Neste trabalho, foi analisada a resposta de estacas enraizadas de Ficus benjamina verdes e variegadas cultivadas em pequenos vasos, em relação ao fornecimento exógeno de auxina e citocinina em diferentes concentrações, em aplicações únicas ou combinadas. Nossos resultados mostram que tanto a benzilaminopurina (BAP) quanto o ácido indol-acético (IAA), na maior concentração testada (100 mg L-1), aumentaram o desenvolvimento foliar e o acúmulo de biomassa vegetal nos genótipos de Ficus verde e variegado. No entanto, AIA e BAP exógenos parecem provocar respostas morfofisiológicas diferenciadas nas plantas. O uso de BAP teve a tendência de melhorar a aparência das folhas mais do que AIA, sendo que este promoveu a expansão foliar de maneira mais estável do que o BAP, resultando em plantas com menos folhas, porém maiores, do que as tratadas com citocinina. Apesar dessas diferenças na arquitetura da planta, a análise de regressão sugere que a promoção do crescimento induzida por hormônios foi atribuída exclusivamente ao aumento da assimilação de carbono. De forma bastante inesperada, o AIA promoveu assimilação líquida e taxas de fotossíntese pelo menos tão efetivamente quanto a citocinina. Possíveis mecanismos envolvidos na promoção do crescimento e desenvolvimento pela aplicação exógena de ambos os hormônios são discutidos. O tratamento com auxina pode ajudar a superar a restrição radicular em Ficus de forma tão eficaz quanto a citocinina em termos de promoção de crescimento, embora possam surgir diferenças na arquitetura da planta em comparação com plantas pulverizadas com o último hormônio.

Abstract Platelets are essential elements of human blood. In addition to their normal role, platelets are involved in causing myocardial infarction, stroke and other thrombotic disorders. Platelet activation in vivo, probably involves a combination of agonists. Garlic has beneficial effects due to its ability to inhibit platelet aggregation and thromboxane formation. The aim of this work was to evaluate the ability of garlic extracts to inhibit platelet aggregation induced by different agonists and their mixtures in different donors. Significant differences were found in platelet aggregation in response to each agonist (P ≤ 0.05). The highest antiaggregatory effect was observed with arachidonic acid and the lowest effect with collagen-arachidonic acid mixture. Interaction effects between donor and agonist (or mixtures) were detected. The study showed the potential of aqueous garlic extracts to prevent platelet aggregation induced by different agonist.

Resumen Las plaquetas son componentes esenciales de la sangre humana. Además de su rol normal, las plaquetas pueden estar involucradas en procesos que causan infarto de miocardio, apoplejía y otros trastornos trombóticos. La activación plaquetaria in vivo, invo lucra una combinación de agonistas. El ajo posee efectos beneficiosos debido a su capacidad para inhibir la agregación plaquetaria y la formación de tromboxano. El objetivo fue evaluar la capacidad de extractos acuosos de ajo de inhibir la agregación plaquetaria inducida por diferentes agonistas y sus mezclas en diferentes donantes. Se encontraron diferencias signi ficativas en la agregación plaquetaria en respuesta a cada agonista (P ≤ 0,05). El mayor efecto antiplaquetario se observó con el ácido araquidónico y el menor con la mezcla de colágeno y ácido araquidónico. Se evidenció efecto de interacción entre donante y agonista (o mezclas). El estudio muestra el potencial de los extractos acuosos de ajo para prevenir la agregación plaquetaria inducida por diferentes agonistas.

Resumo O Ficus (Ficus benjamina) é uma importante espécie de folhagem usada no paisagismo que compreende genótipos verdes e variegados. Estes últimos desenvolvem folhas com áreas foliares amarelas e brancas que podem impor menor atividade fotossintética, resultando em crescimento mais lento que os genótipos verdes. Em muitas espécies, o suprimento exógeno de citocinina em plantas cultivadas em vaso promove o crescimento, principalmente devido à maior fixação de carbono. Neste trabalho, analisamos o efeito da pulverização da citocinina 6-benzilaminopurina (BAP) no crescimento e desenvolvimento de genótipos verdes e variegados de Ficus benjamina. Foram realizadas dois experimentos em casa de vegetação, nos quais foram testados diferentes números de aplicações de BAP (Experimento 1) ou diferentes concentrações de BAP (Experimento 2). No experimento 2, as plantas foram cultivadas sob três intensidades de luz diferentes. A pulverização com BAP promoveram taxa de aparência foliar, expansão foliar e crescimento de plantas inteiras, e o efeito foi mais forte em variegadas do que em plantas verdes. A promoção da taxa de crescimento relativo pelo BAP foi associada ao aumento da taxa líquida de assimilação, e não à variação na proporção da área foliar. Por outro lado, o sombreamento teve impacto mais negativo no crescimento e desenvolvimento de plantas variegadas do que nas verdes. Plantas variegadas, diferentemente das verdes, desenvolveram folhas com alta área foliar específica sob a menor intensidade de luz. Isso levou a altos valores da razão de área foliar, o que ajudou a manter taxas de crescimento relativas próximas às das plantas sob sombreamento moderado.

Abstract Benjamin fig (Ficus benjamina) is an important foliage and landscape crop species comprising green and variegated genotypes. The latter develop leaves with yellow and white leaf areas which may impose lower photosynthetic activity, thus resulting in slower growth than green genotypes. In many species, the exogenous supply of cytokinin to pot-grown plants promotes growth, mainly due to enhanced carbon fixation. In this work, we analyze the effect of spraying the cytokinin 6-benzylaminopurine (BAP) on growth and development of green and variegated Ficus benjamina genotypes. Two experiments were carried out in a greenhouse, in which either different number of BAP applications (Experiment 1) or different BAP concentrations (Experiment 2) were tested. In Experiment 2, plants were grown under three different light intensities. BAP sprays promoted rate of leaf appearance, leaf expansion and whole-plant growth, and the effect was stronger in variegated than in green plants. The relative growth rate promotion by BAP was associated with increased net assimilation rate rather than with variation in the leaf area ratio. On the other hand, shading had a more negative impact on growth and development of variegated plants than in green ones. Variegated plants, unlike green ones, developed leaves with high specific leaf area under the lowest light intensity. This led to high leaf area ratio values, which helped to maintain relative growth rates close to those of plants under moderate shading.

Pollinators are required to produce onion seeds. This specie is one of the main vegetable crops. Two types of onion varieties are mainly grown worldwide: hybrids and open pollination (OP) cultivars. Although hybrids offer advantages to bulb growers, seed yields of hybrids are lower than OP cultivars and that is a significant problem. The influence of environmental factors (temperature, radiation, rainfall, relative humidity (RH) and wind speed) was determined, as well as bee attraction and seed production in three locations of the main onion seed production area in Argentina. Nine male sterile lines (MSL) and one OP were used. The results obtained showed a marked variability in the attraction of bees and seed production between the OP and MSL and within MLS. In addition, environmental factors such as minimun temperature or RH were determinant to modify bee foraging behavior, where values lower than 9°C and 22%, respectively, caused that bees stop their activity.

Los polinizadores son necesarios para producir semillas de cebolla. Esta especie es uno de los principales cultivos hortícolas. Dos tipos de variedades de cebolla se cultivan principalmente en todo el mundo: híbridos y cultivares de polinización abierta (PA). Aunque los híbridos ofrecen ventajas a los cultivadores de bulbos, los rendimientos de semillas de los híbridos son más bajos que los cultivares PA y eso es un problema importante. Se determinó la influencia de los factores ambientales (temperatura, radiación, precipitación, humedad relativa (HR) y velocidad del viento), así como la atracción de abejas y la producción de semillas en tres localidades, de principal zona productora de semillas de cebolla en Argentina. Se utilizaron nueve líneas androestériles (LAE) y una PA. Los resultados obtenidos mostraron una marcada variabilidad en la atracción de abejas y la producción de semillas entre la variedad PA y las LAE y dentro de las LAE. Además, los factores ambientales, como la temperatura mínima o HR, fueron determinantes para modificar el comportamiento de alimentación de las abejas, donde valores inferiores a 9°C y 22%, respectivamente, hicieron que las abejas detuvieran su actividad.

RESUMO Plantas trepadeiras (Epipremnum aureum) conduzidas suspensas, desenvolvem folhas maiores em comparação com plantas conduzidas sem suporte (rasteiras). Esse efeito pode ser visto, em parte, como uma resposta thigmomorfogênica; mas o efeito gravimorfogênico também pode estar envolvido, uma vez que o transporte polar de auxinas é afetado negativamente em plantas com hastes horizontais ou pendentes, o que pode resultar em um balanço hormonal alterado, a nível da planta como um todo. O presente trabalho teve como objetivo estudar como as auxinas e citocininas exógenas podem influenciar o crescimento de estacas enraizadas de E. aureum sob diferentes sistemas de condução. Estacas enraizadas de E. aureum foram cultivadas como trepadeiras em uma tábua de madeira vertical ou rasteiras sobre bancada em casa de vegetação ou suspensas em uma cesta. Todas as folhas de cada planta foram pulverizadas até escoamento à tarde, com quatro doses de ácido indol-3-acético (AIA), 7 dias após o transplante e, após uma semana, com quatro concentrações de benzilaminopurina (BAP), resultando em 16 tratamentos combinados com hormônios. A aplicação de IAA ou BAP a 50 mg L-1 em plantas rasteiras e suspensas, promoveu crescimento significativo mas, em plantas trepadeiras, observou-se, em geral, efeito negativo. Mudanças na assimilação líquida e taxas fotossintéticas, juntamente com coeficientes alométricos modificados, foram responsáveis por essas respostas. A maior promoção do crescimento por reguladores de crescimento exógenos, observada em plantas rasteiras ou suspensas em comparação com plantas trepadeiras, pode ser interpretada principalmente como uma resposta gravimorfogênica.

ABSTRACT Climbing Epipremnum aureum plants develop larger leaves than unsupported, hanging plants. This effect may be regarded, in part, as a thigmomorphogenic response, but gravimorphogenetic effect may also be involved, since polar auxin transport is known to be negatively affected in plants with horizontal or hanging stems, which may result in an altered hormone balance at the whole plant level. The present work was aimed at studying how exogenous auxins and cytokinins may influence growth of E. aureum rooted cuttings under different training systems. Rooted cuttings of E. aureum were cultivated either climbing on an upright wooden board or creeping on the glasshouse bench or hanging from a basket. All leaves of each plant were sprayed to run-off at sunset with four indole-3-acetic acid (IAA) doses 7 days after transplanting and one week later, with four benzylaminopurine (BAP) concentrations, rendering 16 hormone combination treatments. The application of IAA or BAP at 50 mg L-1 to creeping and hanging plants significantly promoted growth but, in climbing plants, a negative effect was generally observed. Changes in net assimilation and photosynthetic rates, together with modified allometric coefficients, accounted for these responses. The higher growth promotion by exogenous growth regulators observed in creeping or hanging plants compared to climbing plants, may be interpreted mostly as a gravimorphogenetic response.

Fusarium basal rot (FBR), which is caused predominantly by Fusarium oxysporum and F. proliferatum, is the main limiting factor of onion crops. Resistant cultivars obtained in other countries do not behave as such in Argentina crop fields. The cultivars Antártica-INTA, Grano de Oro-Seminis, Valcatorce-INTA and TW-2007 (reported as tolerant) were tested with five Fusarium spp. isolates, using four inoculum concentrations. Disease incidence was recorded along 28 days and the area under disease progress curve was calculated. Diverse epidemiological models were fitted to experimental data. There were significant differences in the resistance level among cultivars, with TW-2007 being the most tolerant. Local Fusarium isolates were the most virulent ones. The concentration of 10,000 microconidia/ gram was the most lethal for all isolates. The absence of resistance to Fusarium in the four cultivars tested was confirmed. Inoculum concentration and isolate are critical factors in screening for resistance to FBR. Breeding based on the selection of genotypes against low virulence strains of Fusarium spp. and the presence of more aggressive strains in local fields may be one of the causes why varieties reported as resistant or tolerant behave as susceptible in our environment.

Doubled haploid onion (Allium cepa L.) plants allow the production of completely homozygous lines for a later production of hybrids. The haploid plants are normally produced using in vitro gynogenesis. The obtained haploid plantlets must be treated with different agents for doubling chromosomes. It is necessary to adjust the concentration and the length of treatment of the doubling agent. In this case, the effect of 250 and 500 mg.L-1 colchicine and 15.2; 30 and 60 mg.L- 1 amiprophos-methyl during 24 and 48 h was assessed over the rate of onion haploid plantlets chromosome doubling. The best duplication treatment was 250 mg.L-1 colchicine for 48 h, which yielded 100% of doubled haploid plants. On the other hand, a positive correlation resulted from the ploidy level and stomatal size, and a negative correlation between the level of ploidy and stomatal density. Significant differences between the stomatal length, width and density in haploid and doubled haploid plantlets were observed. An economical and quick method to test ploidy level in onion plantlets is proposed through the measurement of stomatal size and density.

La producción de plantas dihaploides de cebolla (Allium cepa L.), permite obtener líneas completamente homocigotas para luego producir híbridos. A través de la ginogénesis in vitro se ha logrado producir plantas haploides, las cuales deben ser sometidas a tratamientos de duplicación de sus cromosomas, siendo necesario ajustar la concentración del agente duplicador y la duración del tratamiento. En este trabajo se evaluó el efecto de la aplicación de 250 y 500 mg.L-1 de colchicina y 15,2; 30 y 60 mg.L-1 de amiprofos-metil durante 24 y 48 h, sobre la tasa de duplicación de cromosomas en plántulas haploides de cebolla. El mejor tratamiento de duplicación fue 250 mg.L- 1 de colchicina, durante 48 h, logrando un 100% de plantas dihaploides. Por otra parte, se obtuvo una correlación positiva entre el nivel de ploidía y el tamaño de estomas y una correlación negativa entre el nivel de ploidía y la densidad estomática, registrándose diferencias significativas entre los valores promedio de largo, ancho y densidad de estomas para plantas haploides y dihaploides. Se propone un método económico y rápido para verificar el nivel de ploidía de las plántulas de cebolla mediante la medición del tamaño y densidad estomática.

The aim of this work was to explore the possibility of obtaining transgenic plants of onion varieties cultivated in Argentina, starting from calli induced from mature zygotic embryos, using two strains of Agrobacterium tumefaciens as transfection vectors. Mature embryos from three varieties of 'Valenciana' onion, Torrentina, Cobriza INTA and Grano de oro were in vitro cultivated for callus induction. After three to four months an average of 57.4% success for the three varieties was reached. Transformation was carried out with Agl1 or LBA 4404 A. tumefaciens strains, both carrying a binary vector containing the marker gene gus a and the selection gene nptII. Selection was done in callus induction medium containing 10 mgL-1 geneticin during three subcultures. At the end of the selection period, 342 portions of calli were recovered and transferred to regeneration medium. Of the selected calli evaluated by the expresión of the β-glucuronidase enzyme, 42% presented extensive blue areas or were completely blue. At the end of the first subculture in the regeneration medium, 54 calli were considered potentially organogenic because of the green areas observed. At the end of the wole regeneration period, just one normal plant was obtained, that was negative to PCR analysis using specific primers for gus a and nptII. All selected calli came from the Torrentina variety and the highest quantity of them were transformed with the strain LBA 4404.