Seed germination of 14 wetland species in response to duration of cold-wet stratification and outdoor burial depth

Abstract

Effects of cold-wet stratification periods (0, 5, and 10 wk) and temperature fluctuation at different outdoor burial depths (0, 5, and 10 cm) on seed germination were examined in 14 wetland species from the temperate region of central China, with the aim of improving germination for rehabil- itation. Prior to cold-wet stratification, only seeds of 1 species, Eclipta prostrata, germinated to a high percentage (>90%), and a few seeds (<20%) germinated in 10 species. Five wk of stratification signif- icantly promoted germination in 6 species, but only 2 species germinated ≥50%. Ten wk of stratifica- tion significantly promoted germination in 11 species, and 6 species germinated ≥50%. In general, seeds of perennials required longer stratification periods than those of annuals to come out of dor- mancy. Burial significantly enhanced germination percentages in 7 species. Time to 50% of germina- tion (t50) values indicated that 11 species germinated much faster after burial treatments than after stratification treatments. During 1 wk of continuous monitoring, the mean amplitude of daily temper- ature fluctuations at 0 cm was much higher than that at the other 2 depths. Even though 8 species differed significantly in germination percentages at different burial depths, their optimal germination varied in relation to burial depth. The results suggest that cold-wet stratification for 10 wk or outdoor burial for 5 wk could significantly improve seed germinability of most temperate wetland plants.