Short communication. Secondary dormancy in Diplotaxis erucoides: a possible adaptative strategy as an annual weed

The germination of stored Diplotaxis erucoides seed was studied under controlled conditions of temperature and light by conducting germination tests over three years after collection. The D. erucoides seed was not dormant at harvest, but secondary dormancy appeared during storage as indicated by reduced germination 12 months after collection (from 92% down to 39%). This could be overcome by prolonged storage or by the use of gibberellic acid. Such shifts between dormancy and non-dormancy can be interpreted in terms of the soil seed bank dynamics in relation to intraspecific competition and/or with its adaptation as an annual weed in periodically disturbed soil in cultivated areas.Se estudió la evolución de la germinación/dormición de semillas de Diplotaxis erucoides mediante ensayos periódicos en condiciones controladas (temperatura y luz), durante tres años desde el momento de su recolección. Las semillas recién recolectadas no presentaron dormición, pero a los 12 meses apareció una dormición secundaria (la germinación disminuyó de un 92% a un 32%), desapareciendo posteriormente durante el almacenamiento o mediante aplicaciones exógenas de ácido giberélico. Los cambios entre estado no durmiente y durmiente de las semillas se interpretan como una dinámica de las semillas en el banco del suelo, como posible estrategia relacionada con la competición intraespecífica y su adaptación como mala hierba anual

Short communication. Secondary dormancy in Diplotaxis erucoides: a possible adaptative strategy as an annual weed

The germination of stored Diplotaxis erucoides seed was studied under controlled conditions of temperature and light by conducting germination tests over three years after collection. The D. erucoides seed was not dormant at harvest, but secondary dormancy appeared during storage as indicated by reduced germination 12 months after collection (from 92% down to 39%). This could be overcome by prolonged storage or by the use of gibberellic acid. Such shifts between dormancy and non-dormancy can be interpreted in terms of the soil seed bank dynamics in relation to intraspecific competition and/or with its adaptation as an annual weed in periodically disturbed soil in cultivated areas.Se estudió la evolución de la germinación/dormición de semillas de Diplotaxis erucoides mediante ensayos periódicos en condiciones controladas (temperatura y luz), durante tres años desde el momento de su recolección. Las semillas recién recolectadas no presentaron dormición, pero a los 12 meses apareció una dormición secundaria (la germinación disminuyó de un 92% a un 32%), desapareciendo posteriormente durante el almacenamiento o mediante aplicaciones exógenas de ácido giberélico. Los cambios entre estado no durmiente y durmiente de las semillas se interpretan como una dinámica de las semillas en el banco del suelo, como posible estrategia relacionada con la competición intraespecífica y su adaptación como mala hierba anual

Dormancy breaking and germination of Adenocarpus desertorum, Astragalus gines-lopezii and Hippocrepis grosii (Fabaceae) seeds, three threatened endemic Spanish species

The effectiveness of different presowing treatments for removing hardseededness in Adenocarpus desertorum, Astragalus gines-lopezii and Hippocrepis grossi, three endemic and threatened perennial leguminous species of Spain, was evaluated. Untreated seeds of all three species were germinated over a range of constant (15, 20 and 25°C) and alternating temperatures (15/25 and 20/30°C) under a 16-hour light photoperiod. A considerable fraction of these seeds had physical dormancy caused by a water-impermeable seed coat. Germination was studied for seeds subjected to different presowing treatments: dry heat, hot water, ultra-low freezing, liquid nitrogen, freeze-thaw and mechanical scarification. The most effective method for promoting germination of Adenocarpus desertorum (two populations) and Astragalus gines-lopezii (two populations) was mechanical scarification with pliers. The highest germination percentages of H. grosii were reached by seeds mechanically scarified and also by seeds stored in an ultra-low freezer for 24 hours. Our data provided useful information in germination protocols for ex situ propagation of these three endemic and threatened species, being the first report on seed germination behaviour of Adenocarpus desertorum and Hippocrepis grosii