Variation in dormancy and germination in three co-occurring perennial forest herbs

Abstract

Mesic deciduous forest herbs often disperse seed with morphophysiological dormancy (MPD) that prevents germination during unfavorable periods for seedling survival. However, for seeds of some species with MPD, seasonal separation of root and shoot emergence and variation in dormancy levels can complicate interpretation of seedling emergence timing in the field. We tested whether dormancybreak and germination requirements differed among co-occurring perennial forest herbs, Actaea racemosa, Hydrastis canadensis, and Sanguinaria canadensis, which are wild-harvested for their medicinal properties and known to have MPD. Seeds of all species exhibited a summer ? autumn ? winter requirement for seedling emergence in spring. However, species differed in seed-bank persistence due to variation in primary dormancy levels and stratification requirement of seeds. A. racemosa and H. canadensis can form short-term persistent seed bank, whereas S. canadensis can form a long-term persistent seed-bank, regardless of whether elaiosomes were removed from seeds prior to burial. A. racemosa seeds are dispersed in autumn with weak physiological dormancy, as seeds germinated to high rates at 15/6°C after 8 weeks. In contrast, most seeds of the summer dispersed species, H. canadensis and S. canadensis, require summer temperatures to overcome physiological dormancy. Consequently, seedling emergence is reduced and delayed by 1 year if seeds are not sown immediately following the period of natural dispersal. Seedling emergence was much lower in the field than in controlled conditions for all species, especially in the small-seeded A. racemosa. Interspecific variation in dormancy levels and germination traits must be considered when establishing populations for conservation purposes and in understanding recruitment limitation in perennial forest herbs.

Germination niche of the permanent wetland specialist, Parnassia grandifolia DC

“…Interestingly, the germination characteristics of P. grandifolia (and P. asarifolia ) are more similar to those of herbaceous perennials in the surrounding woodlands (i.e. cold stratification requirement, germination at low temperatures and in darkness) (Baskin and Baskin, 2001; Albrecht and McCarthy, 2011), rather than the more typical wetland germination niche described for species of prairie wetlands, fen grasslands and more open aquatic habitats. Schütz (1997) similarly found that woodland sedges ( Carex ) had cooler germination temperature thresholds than sedges from open wetlands, suggesting that germination characteristics in wetland plants are contingent on habitat-specific differences.…”

Drivers of a riparian forest specialist (Carex remota, Cyperaceae): It is not only a matter of soil moisture

“…On the contrary, we found that light that arrives through small gaps in the canopy and not directly from the sun seems to have a positive effect on C. remota germination. Previous studies ( Brändel and Schütz, 2005 ;Zukowski et al, 2010 ) have shown that sedge germination occurs when there is a very limited range of light and indirectly fl uctuating temperatures ( Albrecht and McCarthy, 2011 ). Germination strategies of forest plants are adapted to use such narrow windows in time ( Brändel and Schütz, 2005 ;ten Brink et al, 2013 ) so continuous censuses of seedlings and related measurements in soil conditions will clear up factors determining establishment processes that are critical for maintaining forest plant populations ( Harper, 1977 ).…”

Intermediate complex morphophysiological dormancy in seeds of Aconitum barbatum (Ranunculaceae)

“…Because the ripe embryo of the Ranunculaceae is typically tiny, this family may be in morphological or morphophysiological dormancy. For instance, seeds of Pulsatilla slavica have been suggested with MD [ 18 ]; seeds of Adonis vernalis [ 19 ], Anemone coronariab [ 20 ], Aquilegia oxysepala [ 21 ] show nondeep simple MPD; Seeds of Aconitella decipiens [ 19 ] were reported to have intermediate simple morphophysiological dormancy; seeds of Aconitum altaicum [ 19 ] show deep simple MPD; seeds of Actaea pachypoda [ 7 ], and A. racemosa [ 22 , 23 ] were reported to show deep simple epicotyl MPD, while seeds of Anemone ranunculoides [ 24 ] were reported to show nondeep simple epicotyl morphophysiological dormancy.…”