AOBPreview published online on September 3, 2008
Annals of Botany, doi:10.1093/aob/mcn158
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Germination of Dimorphic Seeds of the Desert Annual Halophyte Suaeda aralocaspica (Chenopodiaceae), a C4 Plant without Kranz Anatomy
1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
2 Department of Biology, University of Kentucky, Lexington, KY 40506, USA
3 Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA
4 Graduate University of Chinese Academy of Sciences, Beijing 100049, China
* For correspondence. E-mail zhenying{at}ibcas.ac.cn or dongming{at}ibcas.ac.cn
Received: 14 April 2008 Returned for revision: 6 June 2008 Accepted: 15 July 2008
Background and Aims: Suaeda aralocaspica is a C4 summer annual halophyte without Kranz anatomy that is restricted to the deserts of central Asia. It produces two distinct types of seeds that differ in colour, shape and size. The primary aims of the present study were to compare the dormancy and germination characteristics of dimorphic seeds of S. aralocaspica and to develop a conceptual model of their dynamics.
Methods: Temperatures simulating those in the natural habitat of S. aralocaspica were used to test for primary dormancy and germination behaviour of fresh brown and black seeds. The effects of cold stratification, gibberellic acid, seed coat scarification, seed coat removal and dry storage on dormancy breaking were tested in black seeds. Germination percentage and recovery responses of brown seeds, non-treated black seeds and 8-week cold-stratified black seeds to salt stress were tested.
Key Results: Brown seeds were non-dormant, whereas black seeds had non-deep Type 2 physiological dormancy (PD). Germination percentage and rate of germination of brown seeds and of variously pretreated black seeds were significantly higher than those of non-pretreated black seeds. Exposure of seeds to various salinities had significant effects on germination, germination recovery and induction into secondary dormancy. A conceptual model is presented that ties these results together and puts them into an ecological context.
Conclusions: The two seed morphs of S. aralocaspica exhibit distinct differences in dormancy and germination characteristics. Suaeda aralocaspica is the first cold desert halophyte for which non-deep Type 2 PD has been documented.
Key words: Borszczowia, cold desert halophyte, physiological seed dormancy, seed germination, Suaeda