Viability assessment and estimation of the germination potential of charophyte oospores: testing for site and species specificity

Ecology of charophytes – permanent pioneers and ecosystem engineers

“…After the period of primary dormancy, the oospore becomes susceptible to triggers that induce germination. Hilhorst (1993) developed a physiological model of dormancy, which has been shown to be applicable for charophytes as well (Holzhausen et al 2017). Oospores can enter into a secondary dormancy if the germination 'window' is not available in any one year (Sokal and Stross 1986).…”

“…Proctor 1967;Casanova and Brock 1996;Lambert 2013;Lambert et al 2013) can stimulate germination via synthesis of gibberellins (Hilhorst 1993;Vleeshouwers et al 1995;Penfield and King 2009) when irradiance conditions are favourable (Sabbatini et al 1987;van den Berg et al 1998a;Matheson et al 2005; Kalin and Smith 2007;Sederias and Coleman 2007;2009). The specific conditions required for breaking dormancy and induction of germination, differ among species (for a detailed discussion see: Holzhausen et al 2017).…”

Re-Establishment Techniques and Transplantations of Charophytes to Support Threatened Species

“…Oospores collected while still situated on the plants are often in primary dormancy, which is broken after the winter or if the oospores are exposed to low temperatures for a longer time period (stratification); contrarily, oospores taken from sediments can germinate immediately (Takatori and Imahori 1971 [ 33 ], Sederias and Colman 2007 [ 34 ], Skurzyński and Bociąg 2009 [ 32 ]). Such oospores, however, have far lower germination success than bulbils, as they are in a secondary dormancy, which prevents them from germinating under unsuitable conditions (Stross 1989 [ 35 ], Holzhausen et al, 2017 [ 36 ]). Species-specific conditions of temperature, redox potential, and light are required to break dormancy and initiate germination (Casanova and Brock 1996 [ 37 ], Bonis and Grillas 2002 [ 16 ], de Winton et al, 2004 [ 38 ], Kalin and Smith 2007 [ 39 ], Skurzyński and Bociąg 2009 [ 32 ], Holzhausen et al, 2017 [ 36 ]).…”

“…Such oospores, however, have far lower germination success than bulbils, as they are in a secondary dormancy, which prevents them from germinating under unsuitable conditions (Stross 1989 [ 35 ], Holzhausen et al, 2017 [ 36 ]). Species-specific conditions of temperature, redox potential, and light are required to break dormancy and initiate germination (Casanova and Brock 1996 [ 37 ], Bonis and Grillas 2002 [ 16 ], de Winton et al, 2004 [ 38 ], Kalin and Smith 2007 [ 39 ], Skurzyński and Bociąg 2009 [ 32 ], Holzhausen et al, 2017 [ 36 ]). Oospores of species from temporary water bodies germinate far better after having been dried before (Sabbatini et al, 1987 [ 40 ], Casanova and Brock 1990 [ 41 ], 1996 [ 37 ], de Winton et al, 2004 [ 38 ]).…”

“…Even under favorable conditions, (re)establishment of macrophytes may fail because of lack of diaspores. Diaspore banks should therefore be investigated before lake restorations to estimate the potential for re-establishments (Rodrigo and Alonso-Guillen 2013 [ 121 ], Hussner et al, 2014 [ 79 ], Holzhausen et al, 2017 [ 36 ]). A shift of macrophyte species composition is often observed after successful lake restorations and is explained by the large differences in numbers and longevity of diaspores among these species (Bakker et al, 2013 [ 12 ]).…”