Journal
ANNALS OF BOTANY
Volume 112, Issue 9, Pages 1815-1827Publisher
OXFORD UNIV PRESS
DOI: 10.1093/aob/mct240
Keywords
Amphi-basicarpic annual; Ceratocarpus arenarius; cold desert; conceptual model; diaspore heteromorphism; physiological dormancy; seed dispersal; seed germination
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Funding
- Scientific Research Program of the Higher Education Institution of Xinjiang, China [FSRPHEXJ 2011S12]
- National Natural Science Foundation of China [31160093, U1130301]
- Key Program for International S & T Cooperation Projects of China [2010ZR002]
- Early Scientific Research Foundation of Xinjiang Agricultural University of China [XJAU201002]
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Several studies have demonstrated trade-offs between depth of seed dormancy and dispersal ability for diaspore-dimorphic species. However, relatively little is known about trade-offs between these two life history traits for a species that produces more than two diaspore morphs. The aim of this study was to investigate the relationship between seed dormancy and dispersal in Ceratocarpus arenarius, an amphi-basicarpic cold desert annual that produces a continuum of dispersal unit morphs. A comparison was made of dispersal and dormancy breaking/germination responses of dispersal units from ground level (a), the middle of the plant canopy (c) and the top of the plant canopy (f). Various features of the morphology and mass of dispersal units and fruits (utricles) were measured. The role of bracteoles in diaspore dispersal by wind, settlement onto the soil surface and dormancy/germination was determined by comparing responses of intact dispersal units and fruits. Movement of dispersal units by wind and animals, seed after-ripening, germination phenology and the presence of water-soluble germination inhibitors in bracteoles were tested using standard procedures. Dispersal units a, c and f differed in morphology and mass; in the majority of cases, extremes were exhibited by a and f, with c being intermediate. Overall, relative dispersal ability was f c a, whereas relative intensity of dormancy was a c f. Bracteoles increased dispersal distance by wind, enhanced settlement of diaspores onto the soil surface and mechanically inhibited germination. The results provide evidence for a model in which there is a continuous inverse-linear relationship between diaspore dispersal ability and depth of dormancy. Thus, dispersal unit heteromorphism of C. arenarius results in a continuum, from no dispersal ability/high dormancy (dispersal unit a) to high dispersal ability/low dormancy (unit f), which may be a bet-hedging strategy in the cold desert environment.
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