Ultrastructural Changes in Leaves of Cichorium during Somatic Embryogenesis |
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Authors: | Verdus Marie-Claire; Dubois Therese; Dubois Jean; Vasseur Jacques |
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Institution: | Laboratoire de Physiologie cellulaire: Signaux et Régulations, Université de Rouen, URA CNRS 203, BP 118, 76134 Mont Saint Aignan and Laboratoire de Physiologie de la différenciation et Biotechnologies végétales, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France |
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Abstract: | A detailed electron microscopy study of early cellular eventsduring somatic embryogenesis in leaves of Cichorium is described.Leaves on in-vitro grown plantlets were sectioned and put at35°C, in darkness, in an agitated liquid induction medium.No sign of embryogenic predetermination, such as thick cellwall, dense cytoplasm and enlarged nucleus, could be seen inany cell before treatment. Perivascular cells were the firstto react. Addition of glycerol (330 mM) allowed the arrest ofembryogenic cells at an activated stage. The main events werea thickening of the wall, with extracellular secretion and anaccumulation of Ca2+ in the vacuole, demonstrated by an antimonateprocedure. After 5 d, leaves were transferred to glycerol-freemedium where multicellular proembryos could be observed. Theyshowed reduced vacuoles, cortical microtubules, numerous multivesicularbodies and lipid globules. The embryoid cells were lined alongthe mesophyll lacunae by an extracellular secretion with a tubularstructure; histochemical tests proved its complex lipo-glyco-proteicnature.Copyright 1993, 1999 Academic Press Cichorium, extracellular tubular protein, somatic embryogenesis, vacuolar calcium |
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