Ecological mechanisms involved in dormancy breakage in Ulex parviflorus seeds

• Published in: Plant ecology Vol. 183; no. 2; pp. 191 - 205
• Main Authors: Baeza, M. J, Vallejo, V. R
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.04.2006; Springer; Springer Nature B.V
• Subjects: Disturbance; Dormancy; Fabaceae; Germination; Hard-seed coats; Heat treatment; Mediterranean shrub; Plant ecology; Scarification; Seed banks; seed scarification; Seeds; Shrublands; Shrubs; Soil depth; Soil profiles; Soil seed banks; Soil temperature regimes; Soils; Testa; Ulex
• ISSN: 1385-0237; 1573-5052
• DOI: 10.1007/s11258-005-9016-0

Dormancy in the hard seed coats of Mediterranean species is considered a strategy that enables persistent seed banks to be formed in the soil. An important factor related to seed coat fracture and dormancy breakage in Mediterranean ecosystems is heat. Nevertheless, the effect of factors other than heat on dormancy breakage in these species has hardly been studied. To investigate the different ecological factors involved in germination, in the laboratory we applied several scarification treatments to seeds with chromatic polymorphism. We evaluated the effect of soil seed depth during experimental burns by sowing seeds at -1, -3 and -5 cm in the soil profile, and we also studied the effect of seed origin on the posterior germination of seeds from 4 and 10 year-old shrubs as well as from the soil seed bank. U. parviflorus shows clear chromatic polymorphism: its brown seeds present higher dormancy levels than its yellow seeds. The different techniques of dormancy breakage result in different degrees of germination; the highest degree of germination is generated by the mechanical treatment, followed by the acid and the heat treatments, in that order. The depth of the seeds in the soil determines the temperature thresholds and the residence times of these temperatures and whether they stimulate a massive germination at the -1 cm soil profile or only a slight germination at the -5 cm depth. Seeds recently produced by the plant show higher dormancy levels than seeds extracted from soil seed banks. Dormancy levels also depend on the shrubland age used for extracting the soil samples (3>9 years old). In effect, from the point of view of dormancy, the germination behaviour of U. parviflorus seeds seems to follow a multiresponse strategy based on different seed populations and involving both biological and abiotic processes to break dormancy.