Light quality and temperature fluctuation promote the germination of Magnolia alejandrae (Magnoliaceae, sect. Macrophylla), a critically endangered species endemic to northeast Mexico

Abstract

Background: Magnolia alejandrae is a critically endangered species and endemic to the Sierra Madre Oriental in northeastern Mexico. The abiotic requirements for its germination, such as light and temperature, are unknown. Hypotheses: White light and temperature fluctuations will promote the germination of M . alejandrae and seeds from site with higher humidity will have increased germination percentage. Study species: Magnolia alejandrae . Study sites and dates: El Farallón in the Jaumave municipality and Los San Pedros in the Güémez municipality, Tamaulipas, Mexico. May-June 2019. Methods: Four light-quality treatments (white, red, far-red and darkness) were evaluated, along with two temperature treatments: constant (18/18 ºC) and fluctuating temperatures (8/18 ºC) and two populations (El Farallón and Los San Pedros) on the germination of M . alejandrae . We used twenty seeds of the study species per experimental unit with five repetitions for each treatment. Results: Light quality influenced the germination of M . alejandrae seeds, having the highest germination (76 %) under white light, followed by 45 % under red light, 9 % under far-red and 5 % in darkness, demonstrating that the seeds of this species are neutral photoblastic. Temperature fluctuation (8/18 °C) enhanced germination of M . alejandrae more than constant temperature (18/18 °C). Conclusions: M . alejandrae seeds respond differentially to light quality and temperature, which has important implications in the reforestation and conservation of the species.