Efecto de diferentes temperaturas en la germinación de dos especies de Dahlia

The temperature values at which seeds germinate can serve as a reference for proposing planting or establishment sites. This research evaluated the effect of eight temperatures on the germination of Dahlia coccinea Lehm. and Dahlia campanulata Saar, P. D. Sørensen and Hjert. The hypothesis was that, because the Dahlia species studied have contrasting distributions, it is expected that one of them will show the widest temperature range for the germination of its seeds. The collection was carried out in the Tlalpuente Ecological Reserve, Tlalpan, Mexico City, in 2023. The experimental units were Petri dishes containing two absorbent paper discs moistened with distilled water and 25 seeds of D. coccinea or D. campanulata. The treatments were incubation temperatures (5, 10, 15, 20, 25, 30, 35 and 40 ±2 °C). The number of germinated seeds was recorded for 15 days. D. coccinea had the highest germination percentage (93.6%) and speed (4 seeds day-1) at 25 °C, with cardinal temperatures of 3.3, 24.1 and 35.3 °C. In contrast, D. campanulata had a wider range, as it had an average germination of 90% from 10 to 25 °C, with 8 seeds day-1 and cardinal temperatures of 2.3, 22.5 and 38.4 °C. D. campanulata seeds were the ones that germinated over a wider range of temperatures, so this species has a better chance of success when grown outside its natural habitat.