Seed germination of high mountain Mediterranean species: altitudinal, interpopulation and interannual variability

Abstract

The germination response of 20 species from high altitude Mediterranean climates, most of them rare endemics, was studied. Our main goal was to model the germination response of a complete set of Iberian high mountain species. The effect of temperature and other parameters, such as spatial and temporal short gradients, on germination were also evaluated. Some seed features (mass and size) were also related to the germination response. Finally, we tested the effect of cold-wet stratification pretreatment when germination was low under natural conditions. Seeds were collected at four locations from 1,900 to 2,400 m a.s.l. in the Sierra de Guadarrama (Spanish Central Range) over two consecutive growing seasons (2001)(2002) and submitted to different temperatures and a constant photoperiod of 16 h light/8 h darkness. Most plants readily germinate without treatment, reaching an optimum at relatively high temperatures in contrast to lowland Mediterranean species. Seeds seem to be physiologically prepared for rapid germination even though these plants usually face very intense summer droughts after ripening and dispersal. Germination was also highly variable among altitudes, populations and years, but results were inconsistent among species. Such flexibility could be interpreted as an efficient survival strategy for species growing under unpredictable environments, such as the Mediterranean climate. Finally cold-wet stratification increased germination capacity in five of nine dormant species, as widely reported for many arctic, boreal and alpine species. In conclusion, high mountain Mediterranean species do not differ from alpine species except that a relatively high number of species are ready to germinate without any treatment.

Dormancy and germination in Rosa multibracteata Hemsl. & E. H. Wilson

“…Warm plus cold stratification appears to be another effective method to break dormancy in rose achenes (Semeniuk and Stewart, 1966;Svejda, 1968;Densmore and Zasada, 1977); in the present study, the method proved significantly better than either of the stratifications alone for stimulating both the percentage and the rate of germination. Contrary to several other reports that germination percentage increases with incubation temperature (Baskin et al, 2002;Lohengrin and Arroyo, 2000;Gimé nez-Benavides et al, 2005), our results show that high temperatures inhibit germination. In our study, warm plus cold stratification did not break the dormancy fully; about 50% of the achenes remained dormant.…”

Effect of Chemical and Physical Treatments on Seed Germination ofErica australis

“…Different letters indicate significant differences (p < 0.05) between treatments. Cold-stratification, generally in the range of 1-10 °C, is effective for breaking seed dormancy in a number of species (Bewley & Black 1994) and our results also support this conclusion for E. australis, even if for other Mediterranean species this treatment did not play a crucial role (Giménez-Benavides et al 2005, Luna et al 2008. A stratification time of 60 days is useful for removing embryo dormancy in many plants (Bewley & Black 1994); in E. australis, 15 days of wet cold-stratification were sufficient to break dormancy, although final germination increased approximately three-fold when time of stratification was duplicated.…”

Variation in Seed and Seedling Traits among Fifteen Chinese Provenances of Magnolia officinalis

“…The inter-population variability in germinability can be due to environmental differences or to genetic variation. Indeed, inter-population seed dormancy variability can serve as an adaptation strategy in unpredictable environments (Cruz et al, 2003;Giménez-Benavides, 2005). Cultivation is an ongoing artificially selected process that occurs over time as humans select and cultivate wild plants (Hancock, 2004).…”