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 ofM. alejandrae and seeds from site with higher humidity will have increased germination percentage. Study species: Magnolia alejandrae. Study sites and dates: El Farallon in the Jaumave municipality and Los San Pedros in the Guemez 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 C) and fluctuating temperatures (8/18 C) and two populations (El Farallon and Los San Pedros) on the germination ofM. 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 degrees C) enhanced germination ofM. alejandrae more than constant temperature (18/18 degrees C). Conclusions: M. alejandrae seeds respond differentially to light quality and temperature, which has important implications in the reforestation and conservation of the species.