Rojas-Aréchiga, Mariana , Golubov, Jordan , Romero, Oscar , Mandujano, Maria .
Effect of light and temperature on the germination of two endangered species of cacti.
Several factors apart from humidity, like light and temperature may regulate seed germination in plants inhabiting desertic areas. For cacti species, the effect that light and temperature has upon germination has been studied obtaining diverse results. It has been demonstrated that light promotes germination in many cacti species, while other species germinate either in light or in darkness. Cacti seeds respond in a wide range of temperatures, with optimum results between 18 and 34 Â°C. Several constant and alternating temperatures have been studied and alternating temperatures have been use to determine if they can substitute for light requirement.
We studied the effect of white light and darkness and of 25 Â°C and 15/25 Â°C on the germination of two endangered cacti species: Obregonia denegrii Fric, Zivot & PrÃrode and Turbinicarpus valdezianus (H. Moeller) Glass & R.A. Foster. Seeds were collected from the fruits and sown on July 2006 inside Petri dishes with agar at 1% and put inside germination chambers at 25 Â° and 15/25 Â°C. We used 25 seeds in five replicates. For white light treatment, seeds were put under fluorescent and incandescent lamps that provide a R:FR= 1.73, and for darkness treatments, seeds were wrapped in two foils of aluminum paper and were not opened until the experiment finished (30 days). A seed was considered germinated when the radicle appeared. Germination percentages were arcsine square root transformed to make an ANOVA to test for significant differences between treatments.
Seeds were positive photoblastic and both species obtained their maximum germination percentage at 25 Â°C, although for T. valdezianus we found no significant differences between both temperature treatments. The alternating temperature used did not substitute the light requirement for germination. The light requirement is an important characteristic for seeds that have the potential to form a seed soil bank.
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1 - Insttituto de Ecología, UNAM, Ecología de la Biodiversidad, Circuito Exterior, Ciudad Universitaria, México, D.F., D.F., 04510, México
2 - Universidad Autónoma Metropolitana-Xochimilco, El Hombre y su Ambiente, Calzada del Hueso 1100, Col. Villa Quietud, Coyoacán, México, D.F., D.F., 04960, México
3 - Universidad Nacional Autonoma de Mexico, Instituto de Ecologia, Ciudad Universitaria, A.P. 70-275, Mexico, D.F., 04510, Mexico
Presentation Type: Poster:Posters for Topics
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM