Effect of burial on the germination of Opuntia tomentosa's (Cactaceae, Opuntioideae) seeds

• Published in: Journal of arid environments 2009-04, Vol.73 (4), p.421-427
• Main Authors: Olvera-Carrillo, Y., Márquez-Guzmán, J., Sánchez-Coronado, M.E., Barradas, V.L., Rincón, E., Orozco-Segovia, A.
• Format: Article
• Language: English
• Subjects: Buried seeds; Cactaceae; cacti and succulents; dormancy breaking; Funicular envelope; gibberellins; light; Opuntia; Opuntia tomentosa; Physiological dormancy; Positive photoblastism; seed germination; Seed heterogeneity; seed scarification; Soil fungi; temperature
• ISSN: 0140-1963; 1095-922X
• DOI: 10.1016/j.jaridenv.2008.12.011

Opuntia tomentosa seeds have physiological dormancy and a permeable but hard funicular envelope that restricts water uptake and embryo growth. Dormancy break, germination, and changes in the funiculus were compared in laboratory-stored seeds and in those buried for 7 months at different microsites and later exhumed and stored in the laboratory. The funicular envelopes of both lots were examined with a scanning electron microscope (SEM). Seeds in both lots were: scarified with H 2SO 4 (0, 45, 60 and 90 min), treated with gibberellins (0, 1000 and 2000 ppm) and germinated at the same ages (0, 2, 4, 7, and 10 months after exhumation) at 24 °C. Light effect was determined at 24 °C and 20–35 °C. In laboratory-stored seeds germination was low. Exhumed seeds germinated in ∼50%, the remaining ones required scarification and gibberellins, but lost dormancy two months later. Gibberellins reduced germination heterogeneity, and scarification reduced germination; the adverse effect of scarification was offset by gibberellins. Exhumed seeds germinated mainly in darkness at 20–35 °C and partially in far red light at both temperatures. SEM showed that fungi eroded the funiculus reducing its resistance. O. tomentosa could form a seed bank, ensuring its survival under heterogeneous environments.