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Germination ecology of the holoparasite Cuscuta epithymum

Published online by Cambridge University Press:  01 March 2008

Klaar Meulebrouck*
Affiliation:
Division Forest, Nature and Landscape, KULeuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium
Els Ameloot
Affiliation:
Division Forest, Nature and Landscape, KULeuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium
Jozef A. Van Assche
Affiliation:
Laboratory of Plant Ecology, KULeuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium
Kris Verheyen
Affiliation:
Laboratory of Forestry, Ghent University, Geraardsbergse Steenweg 267, B-9090 Melle-Gontrode, Belgium
Martin Hermy
Affiliation:
Division Forest, Nature and Landscape, KULeuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium
Carol C. Baskin
Affiliation:
Department of Biology and Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40506-0225, USA
*
*Correspondence Fax: +32 16 32 97 60 Email: [email protected]

Abstract

Little is known about the seed ecology of annual holoparasites, such as Cuscuta (dodders), and how germination is timed to occur when seedlings can attach to a host. Seeds of Cuscuta epithymum, which is a rare and often threatened species in dry heaths of north-western Europe, were water-impermeable (physically dormant) at maturity in late summer. An 8-week period at 5°C, followed by incubation at 23, 15/6 or 30/20°C, resulted in 15–30% germination. Thus, in nature, only part of the seed population exposed to low winter temperatures and a subsequent warm spring potentially becomes water-permeable and can germinate in spring. When scarified seeds were cold-stratified at 5°C for 8 weeks and then incubated at 23°C, essentially all the viable seeds (c. 65%) germinated. It is concluded that seeds have a combination of physical (PY) and physiological (PD) dormancy (the first to be reported in the Convolvulaceae), which is interpreted as a double safety mechanism preventing germination at unfavourable times or places. After PY and PD were broken, seeds did not require light or fluctuating temperatures for germination. Some loss of PD (afterripening) can occur before PY is broken. These data indicate that a portion of the seed crop remains physically dormant in spring and potentially forms a persistent seed bank, a strategy that eliminates the risk of a total reproductive failure in a particular bad year.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2008

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