Misunderstanding on germination sensu stricto leads us to a false positive germination-dormancy balance in diaspores of Paepalanthus chiquitensis Herzog (Eriocaulaceae), a threatened everlasting flowering species

Although germination sensu stricto and germination-dormancy balance are essential to each other, few reports demonstrate the effects of their relationship on patterns of seed-seedling transition. We studied this relationship by using diaspores of Paepalanthus chiquitensis, a threatened everlasting flowering species. We assessed three aspects: (a) water dynamics in germinating diaspores, (b) thermal stimulation (35, 40, 50, 60 and 70 degrees C for 30 min) and (c) imbibition (4 hr) in growth stimulators (100, 200 or 300 mg center dot L-1 GA(3); 0.1% KNO3). Our findings demonstrate that there are no barriers in the diaspore for diffusion. Additionally, there is high variability in diaspore permeability, and the germination of the species has two steps divided into five stages. These stages were defined by inflections on velocity in water dynamics, which ranged from -0.05 to 0.05 g center dot hr(-1), where only the last stage (Phase V) is associated with the second step of germination sensu stricto. The imbibition phase was the shortest germination phase (1.3 hr), whereas the predominantly biochemical phase was the longest (5 days after sowing [DAS]). Germinability was high (77.5-86.5%), with high daily embryo protrusion (2.46-3.03 diaspores center dot day(-1)). Protocorm emergence marked the end of the first step of germination sensu stricto (9 DAS), and first protocorm rupture (11 DAS) marked the end of the second step. The growth stimulus only concentrated the germination process, showing that the diaspores do not have primary dormancy. Knowing these diaspores' peculiarities during germination sensu stricto avoids a false positive statement on the existence of diaspore dormancy.

Automated summary

The study on the relationship between germination sensu stricto and germination-dormancy balance in Paepalanthus chiquitensis diaspores showed that there are no diffusion barriers present, high variability in diaspore permeability, and two steps of germination divided into five stages based on water dynamics velocity. The shortest phase was the imbibition phase (1.3 hr), while the longest phase was the biochemical phase (5 days after sowing). Germinability was high, with daily embryo protrusion rate between 2.46-3.03 diaspores per day. The growth stimulators only concentrated the germination process, indicating no primary dormancy in the diaspores.