AOBPreview published online on September 26, 2007
Annals of Botany, doi:10.1093/aob/mcm214
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ecology of Achene Dimorphism in Leontodon saxatilis
University of Hamburg, Biocenter Klein Flottbek and Botanical Garden, Section Ecology and Biology of Useful Plants, Ohnhorststr. 18, 22609 Hamburg, Germany
* E-mail markus.braendel{at}botanik.uni-hamburg.de
Received: 4 June 2007 Returned for revision: 10 July 2007 Accepted: 20 July 2007
Backround and Aims Leontodon saxatilis: produces two morphologically distinct achenes (morphs) in a single capitulum: one row of dark brown achenes without a pappus lies at the edge (‘peripheral achenes’; 0·74 ± 0·18 mg) while the inner ones are light brown with a pappus (‘central achenes’; 0·38 ± 0·07 mg). The hypothesis that achene heteromorphism in L. saxatilis widens its ecological amplitude was tested.
Key Results: Achenes of both morphs germinated over the same range of temperatures (6–33 °C) but the central achenes showed significantly higher germination percentages, and the two also differed significantly in their annual dormancy cycle, with the peripheral achenes showing greater dormancy for part of the year. Seedlings from the two morphs did not differ significantly in total biomass after 2 and 4 weeks of growth, neither did they differ significantly in root and shoot weight and root:shoot ratio. Plants from both morphs growing at different regimes of soil moisture, nutrients and competition did not differ significantly in their number of achenes per capitulum. While the number of central achenes varied, that of peripheral achenes remained constant at approx. 13. Drier soil led to an increase in the number of central achenes in plants from both morphs.
Conclusions: The peripheral achenes can replace the mother plant in the following growing season, whereas the central achenes are well adapted for wind dispersal and thus for colonization of new sites. However, the extent of variation in germination characteristics was similar to that found in seed populations of homomorphic plants, which suggests that germination percentage and other growth characteristics do not contribute to widening the ecological amplitude. The habitat of most heteromorphic species, the morphs of which differ greatly in germination and/or growth characteristic, are deserts or highly disturbed areas where such differences are highly advantageous, but in the moderate habitat of L. saxatilis the differences may prove a disadvantage.
Key words: Achene morphology, Asteraceae, dormancy cycle, germination, Leontodon saxatilis, seed heteromorphism, seedling growth
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Kochankova and B. Mandak How do population genetic parameters affect germination of the heterocarpic species Atriplex tatarica (Amaranthaceae)? Ann. Bot., June 1, 2009; 103(8): 1303 - 1313. [Abstract] [Full Text] [PDF]
|
|