Light Effect on Seed Germination of Four Mammillaria Species From the Tehuacán-Cuicatlán Valley, Central Mexico

Seed germination of 4 species of Mammillaria (Cactaceae) from the Tehuacán-Cui-catlán Valley in central México were compared at 4 light treatments (red, far-red, white light, and darkness) at 25°C and at 2 light treatments (white light and darkness) at 2 alternating temperatures (15/30°C and 20/35°C). Seeds were positive photoblastic, but germinated at far-red light. For all species, best germination results were obtained at 25°C with white and red light, and there were no significant differences among treatments. Higher germination percentages were obtained at 25°C than at alternating temperatures. None of the species exhibited any morphophysiological mechanisms of dormancy.