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1 June 2006 In vitro development of vegetative propagules in Splachnum ampullaceum: brood cells and chloronematal bulbils
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The formation of specialized vegetative propagules like brood cells, gemmae and bulbils often occurs in bryophytes, and the propagule's capacity to remain viable, even when desiccated, contribute to form soil propagule banks. With the aim to prove the presence of vegetative propagules in Splachnum ampullaceum Hedw., never found in European Splachnaceae, we studied their formation and further development in vitro. The effect of different concentrations of abscisic acid (ABA)—an endogenous growth regulator in mosses—on brood cell germination was also examined. Vegetative forms were induced on protonematal explants of S. ampullaceum cultured in vitro with two different mineral media. Brood cells and chloronematal bulbils occurred on protonematal cultures maintained on the same culture medium for long periods of time. Brood cells developed new chloronematal filaments when they were transferred to a new medium. We found that S. ampullaceum is able to form in vitro brood cells, characterized by spherical thick-walled cells with lipid droplets in their cytoplasm, and chloronematal bulbils that consist of a multicellular propagule with a verrucose surface. The effects of ABA on S. ampullaceum cultured in vitro indicate a direct relationship between its concentration on media and brood cell formation, which may presumably indicate that desiccation tolerance in S. ampullaceum is induced by ABA. Growth retardant effects were also shown on explants cultured in the presence of the aforementioned regulator. Vegetative propagules, brood cells and chloronematal bulbils, are present in S. ampullaceum and they are probably developed as a desiccation tolerance strategy and as a faster way to spread the colonization on the substratum. Such structures constitute an inconspicuous phase of the life cycle.
Rubén Mallón, Juan Reinoso and Juan Rodríguez-Oubiña and María Luz González "In vitro development of vegetative propagules in Splachnum ampullaceum: brood cells and chloronematal bulbils," The Bryologist 109(2), (1 June 2006).[215:IVDOVP]2.0.CO;2
Received: 30 June 2005; Accepted: 1 November 2005; Published: 1 June 2006

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