Germination and emergence of Neslia paniculata (L.) Desv.

Abstract Seed characteristics, either in size or in structure, can affect germination, hence the emergence of a plant species. In the present work germination and emergence of Neslia paniculata , a Brassicaceae species that produces fruits containing one seed covered by a hard fruit coat, was studied. Germination experiments of seed with and without the fruit coat were performed at constant temperatures from 5 to 23 °C under controlled conditions and germination was measured daily. Additionally, seeds were sown in the field and emergence was periodically followed in three sites: Almenar (Spain), Morris (USA) and Riga (Latvia). Both germination and emergence were modelled with Boltzmann and Weibull mathematical functions. Neslia paniculata is a winter species adapted to low temperatures, with low base temperatures for germination (0.79 °C) and emergence (-3.6 °C). Seeds present both physiological and physical dormancy, the latter provoked by a thick fruit coat that prevents the seed from germinating unless it is degraded. In contrast to other Brassicaceae species studied ( Camelina microcarpa ; Thlaspi arvense ), N. paniculata emergence lacked a response to light. This might have been caused by its fruit coat rendering the embryo non-sensitive to light. For this same reason the best emergence models were developed using a hydrothermal time basis. The relatively larger seed size of N. paniculata species explains the need for considering moisture in the soil at deeper layers (8–10 cm) compared to other Brassicaceae (4–6 cm in C. microcarpa and 4–8 cm in T. arvense ), as their radicles can elongate deeper before emergence occurs. The factors to be considered for germination and emergence models are seed dormancy characteristics, either physical, physiological or both, seed size, which allow seedlings to reach deeper moist soil layers prior to emergence, and their seed position in the soil, which determines the temperature for germination. This research deepens in the knowledge of the germination and emergence biology of N. paniculata , with new models for parametrizing these stages, which can help in either germination laboratory studies and field emergence predictions, either for control or conservation purposes.