Horacio Maroder

Universidad Nacional de Luján, Luján, Buenos Aires, Argentina

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Publications (7)20.03 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.
    Physiologia Plantarum 03/2013; · 3.26 Impact Factor
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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.
    Journal of Experimental Botany 03/2012; 63(10):3631-42. · 5.79 Impact Factor
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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.
    Annals of Botany 03/2010; 105(6):1027-34. · 3.45 Impact Factor
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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.
    Biocell: official journal of the Sociedades Latinoamericanas de Microscopía Electronica ... et. al 01/2007; 31(3). · 0.73 Impact Factor
  • H. L. MARODER
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    ABSTRACT: Studies on the physiological effects of dalapon in Cynodon dactylon (L.) Pers. were carried out. Field and glasshouse experiments showed that dalapon is freely translocated in the aerial organs and from these to the rhizomes. No transformation of the herbicide was detected during 72 h following application. In rhizomes as well as in stolons, dalapon caused growth inhibition and necrosis of buds while root growth was apparently not affected. This differential susceptibility was confirmed by culturing node explants in nutrient solution containing dalapon. Although dalapon killed aerial organs, most rhizomes were capable of recovery even when a high dose was applied. These results are discussed.Effets physiologiqius du dalapon sur Cynodon dactylon (L.) Pers.Résumé. L'autetu- a étudié les effets physiologiques du dalapon sur Cynodon dactylon (L.) Pers. Des expériences au champ et en serre ont montri que le dalapon migre librement dans les organes aériens et de ceux-ci vers les rhizomes. Aucune transformation de l'herbicide ne fut détectéc dans les 72 heures qui suivirent l'application. Dans Ies rhizomes, comme dans les stolons, le dalapon provoqua une inhibition de la croissance et la nécrose des bourgeons alors que la croissance des racines n'était apparemment pas affectée. Cette differénce de sensibility fut confimée par la culture d'explantats de noeuds dans une solution nutritive contenant du dalapon. Bien que les oérianes ariens aient été tués par le dalapon, la plupart des rhizomes furent capables de repousser, même aprés application d'une dose dlcvée, Ces résultats font l'objet d'unc discussion.Physiologische Einflüsse von Dalapon bei Cynodon dactylon (L.) Pers.Zusammenfassung. Es wurden Untersuchungen auf die physiologische Wirkung von Daiapon bei Cynodon dactylon (L.) Pers. Durchgeführt. Freiland-und Gewachshausversuche zeigten, dass Dalapon in den oberirdischen Pflanzenteilen frei beweglich ist und von dort in die Rhizome transportiert wird. In der Zeit bis 72 h nach der Behandlung konnte keine Umwandlung des Herbizids festgestellt werden. In Rhizomen als auch in Stolonen verursachte Dalapon Wuchshemmung und Nekrosen an den Knospen, während das Wurzelwachstum offemichtlich nicht beeinträchtigt wurde. Diese unlerschiedliche Empfindlichkeit wurde durch Kultivieren von Nodienexplantaten Ln einer Nährlösung die Dalapon enthiett bestätigt. Wenngleich Dalapon die oberirdischen Pflanzenteile abtötete, vermochten sich die meisten Rhizome zu erholen, auch wenn cine hohe AufWandmenge angewandt wurde. Die Ergebnisse werden diskutiert.
    Weed Research 07/2006; 13(1):19 - 23. · 2.02 Impact Factor
  • 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.
    Trees 04/2003; 17(3):193-199. · 1.87 Impact Factor
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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.
    Botanical Journal of the Linnean Society 11/2002; 140(3):273 - 281. · 2.70 Impact Factor