Hidayati, Siti , Walck, Jeffrey .
Seed dispersal and germination strategies of two Oenothera species (Onagraceae) in temperate North America.
Capsule dehiscence, seed dispersal, and seed dormancy-break and germination were examined for two Oenothera species in Tennessee: O. macrocarpa Nutt. and O. triloba Nutt. Capsules of O. macrocarpa opened during 60 d of alternating 1-d wet at 22oC and 3-d dry at 5 or 60oC, whereas those kept continuously dry remained closed. In the field, these capsules opened primarily in December and January. In contrast, O. triloba capsules opened within 20 min when wetted and closed within 18 h during drying. Opening and closing of capsules for O. triloba in nature corresponds to precipitation events. Fresh O. macrocarpa seeds collected in July 2000 and 2001 germinated to 0-3% at 15/6, 20/10, 25/15, 30/15, and 35/20oC in light, and cold-stratified seeds germinated to 89-100% at 20/10-35/20oC. Seeds removed from O. macrocarpa capsules that remained in the field did not germinate to high percentages until January or February. On the other hand, fresh O. triloba seeds collected in July 2000 germinated to 1% at 15/6oC and 95-100% at 20/10-35/20oC in light, and seeds retained in capsules in nature between August 2000 and 2001 germinated to high percentages. Thus, seeds of O. macrocarpa are dormant at maturity and require low (winter) temperatures to become nondormant; germination in the field occurs in early spring. Seeds of O. triloba are nondormant at maturity and can readily germinate following rainfall throughout the year. Capsules of both species opened by water absorption (hygrochasy), which is a feature usually found amongst plants of arid regions.
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1 - Middle Tennessee State University, Department of Biology, Murfreesboro, Tennessee, 37132
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM