Horacio Maroder

Universidad Nacional de Luján, Luján, Buenos Aires, Argentina

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Publications (7)17.07 Total impact

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    ABSTRACT: In willow seeds, photooxidative damage is mainly restricted to the outer cotyledonary tissues, significantly reducing normal germination. Here we analyzed the damage generated in cotyledonary tissues and investigated whether the increase in ROS generation in seedlings from photooxidized seeds can affect the morphogenetic capacity of the shoot apical meristem. Seeds were photooxidized under different light intensities and the evolution of the damage during seedling growth was studied by light and transmission electron microscopies. The level of lipid peroxidation and changes in antioxidant capacity were measured following the time course of superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase enzyme activities, and the effect of photooxidative stress on the genesis of new leaf primordia and lateral roots were examined. Early and active endocytosis and autophagy, changes in chloroplast morphology, as well as the accumulation and diffusion of ROS all play important roles in the early cell death observed in cotyledonary tissues. Following germination, seedlings from photooxidized seeds anticipated the emergence of first leaves, which complemented the altered functionality of the damaged cotyledons.
    No preview · Article · Mar 2013 · Physiologia Plantarum
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    ABSTRACT: Salix nigra seeds subjected to increased humidification show a decrease in normal germination (NG) during early imbibition followed by a recovery in that parameter at increasing imbibition times. Since photo-oxidized seeds contain high levels of reactive oxygen species (ROS), it is possible to infer that the atypical decrease in NG is a consequence of a higher ROS mobilization at early imbibition and the subsequent recovery from an increase in antioxidant activity. In this study, several oxidative stress indicators were evaluated in photo-oxidized seeds subjected to priming. ROS production was studied using electronic spin resonance spectroscopy, spontaneous chemiluminescence (SCL), spectrophotometry (with XTT), and histochemical (with DAB and NBT) and cytochemical (with CeCl(3)) techniques. Four indicators of molecular damage were monitored: lipid peroxidation, pigment destruction, protein oxidation, and membrane integrity. Antioxidant activity was evaluated by changes in the enzymes SOD, CAT, APX, and POX. The results revealed that the decrease in NG at the beginning of priming occurs by an oxidative burst, as determined by increases in both SCL and superoxide anion radical (O2(·-)) Such oxidative burst generates lipid peroxidation, protein oxidation, and a decrease in both pigment content and enzyme activities. With increasing hydration, damages are progressively reversed and NG restored, which coincides with the increased activity of antioxidant defences. It is proposed that these novel observations regarding the occurrence of an oxidative burst are related to the high basal ROS levels and the high membrane content retained in the mature embryo tissues.
    Preview · Article · Mar 2012 · Journal of Experimental Botany
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    ABSTRACT: Salix nigra seeds are desiccation-tolerant, as are orthodox seeds, although in contrast to other orthodox seeds they lose viability in a few weeks at room temperature. They also differ in that the chloroplasts of the embryo tissues conserve their chlorophyll and endomembranes. The aim of this paper was to investigate the role of chlorophyll in seed deterioration. Seeds were aged at different light intensities and atmospheric conditions. Mean germination time and normal and total germination were evaluated. The formation of free radicals was assessed using electronic spin resonance spectroscopy, and changes in the fatty acid composition from phospholipids, galactolipids and triglycerides using gas-liquid chromatography. Membrane integrity was studied with electronic spin resonance spin probe techniques, electrolyte leakage and transmission electron microscopy. Light and oxygen played an important role in free-radical generation, causing a decrease in normal germination and an increase in mean germination time. Both indices were associated with a decrease in polyunsaturated fatty acids derived from membrane lipids as phospholipids and galactolipids. The detection of damage in thylakoid membranes and an increase in plasmalemma permeability were consistent with the decrease in both types of lipids. Triglycerides remained unchanged. Light-induced damage began in outermost tissues and spread inwards, decreasing normal germination. Salix nigra seeds were very susceptible to photooxidation. The thylakoid membranes appeared to be the first target of the photooxidative process since there were large decreases in galactolipids and both these lipids and the activated chlorophyll are contiguous in the structure of that membrane. Changes in normal germination and mean germination time could be explained by the deteriorative effects of oxidation.
    Preview · Article · Mar 2010 · Annals of Botany
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    VÍCTOR PANZA · VERÓNICA LÁINEZ · SARA MALDONADO · HORACIO L. MARODER
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    ABSTRACT: Information on desiccation sensitivity of Euterpe edulis seeds under two drying rates is pre- sented. The sensitivity was studied during the course of germination and normal germination. The water content was evaluated for both seeds and embryos. Results showed the following: (a) For both drying treat- ments and for both germination and normal germination, desiccation sensitivity values were higher for mea- surements based on the water content of the embryo than for those of the seed. (b) For both drying treatments, desiccation sensitivity were higher for normal germination than for germination based on both the embryo and seed water contents. (c) Under the slow drying treatment and for measurements based on the seed water content, critical water content was visible for normal germination but not for germination; (d) Critical water contents for germination and normal germination were more clearly established in the fast drying treatment than they were in the slow drying method based on both the embryo and seed water contents. Critical water contents were not associated with changes in electrolyte leakage, which suggests that conductivity is not a good indicator of physiological seed quality. From the beginning of both drying treatments, changes in nuclei and vacuoles were observed, but, when seed water content was reduced to below critical values, the cells became severely plasmolyzed, the vacuoles highly distorted, and the nuclei formed an almost homogeneous mass with the chromatin and the nucleoplasm, which suggests irreversible DNA damages.
    Preview · Article · Dec 2007 · Biocell: official journal of the Sociedades Latinoamericanas de Microscopía Electronica ... et. al
  • Horacio Maroder · Imelda Prego · Sara Maldonado
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    ABSTRACT: Mature seeds of Salix alba L. and Salix matsudana Koidz. are exendospermous and consist of an embryo and a seed coat. Ultrastructural studies show the presence of protein bodies, lipid bodies, chloroplasts, and a nucleus in the cells of most of the embryo tissues. Protein bodies always contain two or more globoid crystals. Energy-dispersive X-ray analysis of globoid crystals revealed the presence of P, K, Mg and Ca as the main constituents in all tissues. The chloroplasts present well-developed grana and, frequently, starch grains in the stroma. In cells of apical meristems, plastid endomembranes are non-organised in grana and deposits of phytoferritin are present in the stroma. Some cells of the subdermal layers of the cotyledons and hypocotyl-radicle axis present a large central vacuole and a narrow peripheral band of cytoplasm within which the protein bodies are scarce. Seeds of the two species studied here have recently been characterised as orthodox with short viability. The present study was carried out in an attempt to advance in the characterisation of these seeds as part of a comprehensive study of Salicaceae seeds.
    No preview · Article · Apr 2003 · Trees
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    ABSTRACT: Seed tissues of Araucaria angustifolia (Bertol.) Kuntze were investigated using histochemistry, transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. Moisture content and water status in tissues were also evaluated. In the embryo, TEM studies revealed the presence of one to several central vacuoles and a peripheral layer of cytoplasm in cells from different tissues of the cotyledons and axis. In the cytoplasm, lipid bodies, starch grains, mitochondria and a nucleus are evident. In most tissues, vacuoles contain proteins, indicating that the storage proteins are highly hydrated. In cells of the root cap, proteins are stored in discrete protein bodies. Both protein storage vacuoles and discrete protein bodies have inclusions of crystal globoids. EDX analysis of globoids revealed the presence of P, K and Mg as the main constituents and traces of S, Ca and Fe. In the root and shoot meristems, deposits of phytoferritin are present in the stroma of proplastids. The gametophyte consists of cells characterized by relatively thin cell walls and one to several nuclei per cell. Protein and lipid bodies are present, although starch is the most conspicuous reserve. Immediately after shedding, moisture content is approximately 145% (dry weight) for the embryo and 95% (dry weight) for the gametophyte. Calorimetric studies reveal that axes and cotyledons have a very high content of freezable water, corresponding to types 5 and 4, i.e. dilute and concentrated (or capillary) solution, respectively. The results are discussed in relation to the behaviour of the species, which has been categorized as recalcitrant. © 2002 The Linnean Society of London. Botanical Journal of the Linnean Society, 2002, 140, 273−281.
    No preview · Article · Nov 2002 · Botanical Journal of the Linnean Society
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    ABSTRACT: Seeds of Salix nigra and Populus nigra were stored at 25 °C. After 6 days normal germination dropped to 4%. Soluble carbohydrates were determined by HPAEC-PAD in fresh and stored seeds of the two species. Sucrose was the main sugar with much lesser amounts of glucose and fructose and a peak of oligosaccharide was detected, which was purified by gel permeation chromatography. Analysis of the monosaccharide components and of the NMR spectra showed that it was constituted by α-L-arabinofuranose, β-D-xylopyranose and uronic acid, and it was esterified by a phenolic acid. Analysis of the cell wall monosaccharide constituents was performed on fresh and stored seeds. Arabinose was the main sugar, with galactose, xylose, glucose, rhamnose and uronic acid also present. The content of these monosaccharides did not significantly vary on storage.
    No preview · Article · Jan 2002 · Anales des la Asociacion Quimica Argentina