Germination niche of the permanent wetland specialist, Parnassia grandifolia DC

Abstract

Temperate wetland species often require light and warm temperatures for seed germination. However, recent studies indicate that species which specialize on permanently saturated wetlands that are maintained by groundwater discharge (fens, seeps and mountain springs), rather than wetlands with surfacewater-driven hydrologic regimes, diverge from the typical wetland germination niche by germinating at cool temperatures and lacking photoblastic seeds. We conducted laboratory experiments that manipulated stratification conditions (non-stratified versus cold stratification in light and darkness), thermal regime (15/6, 25/15 and 35/208C), and light (14 h photoperiod versus continuous darkness) to test whether seeds of the North American calcareous fen specialist Parnassia grandifolia diverged from the typical temperate wetland germination niche. After 30 d, fresh seeds were conditionally dormant and could only germinate to high percentages in light at 25/158C. During 16 weeks of incubation, non-stratified seeds germinated to low percentages (, 40%) at all thermal regimes in darkness. In contrast, cold-stratified seeds germinated to high percentages in both light and darkness at all thermal regimes, although germination was incomplete (no cotyledon emergence) at 35/208C. Further, seeds did not require light during cold stratification to germinate to high percentages when incubated in light or darkness. Thus, seeds diverged from the typical temperate wetland germination syndrome in lacking a light and warm temperature requirement for germination. Our results reinforce previous work from European fens and Mediterranean wetlands. This indicates that multiple germination strategies are found in fen wetlands that are maintained by the continuous or near-continuous discharge of cool groundwater.

Local climate explains degree of seed dormancy in Hypericum elodes L. (Hypericaceae)

“…Although it is less common in Mediterranean ephemeral wetlands (Carta et al . ) and fens (Albrecht & Long ), this response could be viewed as a typical germination syndrome of wetland species (Grime et al . ; Pons & Schröder ; Probert ; Schütz & Rave ), usually interpreted as a mechanism to detect a fall in the water table at the beginning of the favourable warm season, or as a sensing mechanism for gaps in the vegetation cover (Pons ).…”

Linking seed germination and plant height: a case study of a wetland community on the eastern Tibet Plateau

“…; Fernández‐Pascual et al . ; Albrecht & Long ). Seeds of many temperate wetland species require cold stratification to break dormancy and high temperature, temperature fluctuation and light for germination, which are known as the ‘typical wetland germination requirement (TWGR)’ (Grime et al .…”

“…; Fernández‐Pascual et al . , ; Albrecht & Long ), and only a few studies have been done at the community level (Grime et al . ; Shipley & Parent ).…”

“…In addition to timing of dormancy break, the temperature requirements for germination play a role in regulating the time of germination and thus help determine the germination niche of a species (Fern andez-Pascual et al 2013;Albrecht & Long 2014). Seeds of some species, e.g.…”

“…In wetlands with seasonal flooding, the water table and temperature usually determine optimal germination timing. Thus, how seed germination of wetland species is adapted to a habitat with an annual flooding period and a cold winter is a research topic of considerable interest to ecologists (Carta et al 2013;Fern andez-Pascual et al 2013;Albrecht & Long 2014). Seeds of many temperate wetland species require cold stratification to break dormancy and high temperature, temperature fluctuation and light for germination, which are known as the 'typical wetland germination requirement (TWGR)' (Grime et al 1981;Baskin et al 1989;Albrecht & Long 2014;Baskin & Baskin 2014).…”