Physically damage seeds of non-woody plants before sowing: freshwater wetlands
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 3
Background information and definitions
Damaging, weakening or softening the coating of seeds before planting can help to break seed dormancy and encourage germination. For species with physical dormancy, damage to the seed coat can increase its permeability to water and gases, which are essential for germination. For a database of seed dormancy class by species, see Baskin & Baskin (2014).
This action includes mechanically damaging seeds (e.g. by rubbing them with sandpaper or nicking them with a knife) and removing excess tissues from around the seed (e.g. the sac-like perigynia around sedge seeds). To be summarized as evidence for this action, studies must have explicitly compared the performance of treated and untreated seeds. Studies that simply report the performance of treated seeds are not summarized here. Studies do not have to be in flooded/saturated soils, as long as they involve wetland-characteristic species.
Baskin C.C. & Baskin J.M. (2014) Seeds: Ecology, Biogeography and Evolution of Dormancy and Germination, Second Edition. Academic Press.
Supporting evidence from individual studies
A replicated, controlled study in the early 1990s in a laboratory in Colorado, USA (Thullen & Eberts 1995) found that rubbing hardstem bulrush Scirpus acutus seeds with sandpaper had no significant effect on their germination rate. Germination rates did not significantly differ between seeds that had been rubbed between sandpaper before incubation (0–11% germination) and seeds that had not been rubbed (0–14% germination). Methods: Thirty-two sets of 10–50 hardstem bulrush seeds were incubated in flasks of fresh water at 10/25°C or 18/22°C (night/day temperatures). Of these, 16 sets had been rubbed 20 times with sandpaper immediately before incubation, whilst 16 sets had not. All seeds had been collected in August 1991 from two wild populations, stored in the laboratory for >5 months, and sterilized immediately before the experiment. The study does not clearly report the length of monitoring (probably between six and twelve weeks).Study and other actions tested
A replicated, randomized, controlled study in 1994–1995 in a greenhouse in Florida, USA (Ponzio 1998) found that rubbing sawgrass Cladium jamaicense seeds with sandpaper had no significant effect on their germination rate. Germination rates did not significantly differ between seeds rubbed with sandpaper then soaked in water (44% germinated) and seeds only soaked in water (44% germinated). For reference, the germination rate of seeds that were neither rubbed nor soaked was 55%. Methods: In September 1994, three-year-old sawgrass seeds were sprinkled onto 18 trays of sterilized soil (100 seeds/tray). Six trays were planted with seeds rubbed with sandpaper for one minute then soaked in water for 24 h. Six trays were planted with seeds only soaked in water. Six trays were planted with untreated seeds (neither rubbed nor soaked). The trays were placed in random positions in a greenhouse and watered daily until no more germination occurred.Study and other actions tested
A replicated, randomized, paired, controlled study in 1997 in a laboratory in Utah, USA (Jones et al. 2004) found that removing the sac-like coating of sedge Carex spp. seeds before sowing never reduced the germination rate, although the precise effect depended on light conditions after sowing. In three of three comparisons involving seeds germinating in light, exposed seeds had a higher germination rate (43–95%) than seeds still in their sac (26–88%). In two of three comparisons involving seeds germinating in the dark, exposed seeds had a statistically similar germination rate (2–12%) to seeds still in their sac (1–8%). In the other comparison, exposed seeds had a higher germination rate (40%) than seeds still in their sac (31%). Methods: Two-year-old seeds of beaked sedge Carex utriculata and Nebraska sedge Carex nebracensis were sown into a total of 384 petri dishes (192 dishes/species; 32 seeds/dish), then incubated in the laboratory. In 192 random dishes, the sac-like coating of the seeds had been removed by tumbling the seeds in sandpaper. In the other 192 dishes, the coating had not been removed. Dishes were allocated to various other treatments (including germination in light vs dark, and different pre- and post-sowing temperature regimes). Each incubator shelf received four random dishes of each treatment combination. Germination rates, as a percentage of viable seeds, were recorded for each dish 36 days after sowing.Environmental effects on germination ofStudy and other actions tested