Treat tree/shrub seeds with chemicals before sowing: freshwater wetlands

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

30%
Certainty

33%
Harms

13%

Calculating overall effectiveness category

Background information and definitions

Acids and bleach may weaken the seed coat, increasing its permeability to water and gases which are essential breaking dormancy and inducing germination (Baskin & Baskin 2014). They may also sterilize seeds, killing fungi that may otherwise reduce germination rates. Hormones are widely used in agriculture and horticulture to stimulate germination and growth (Small & Degenhardt 2018). Other molecules such as nitrates act as signals within plants and may stimulate germination (Alboresi et al. 2005).

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.

^{Alboresi A., Gestin C., Leydecker M.T., Bedu M., Meyer C. & Truong, H.N. (2005) Nitrate, a signal relieving seed dormancy in Arabidopsis. Plant, Cell & Environment, 28, 500–512.}

^{Baskin C.C. & Baskin J.M. (2014) Seeds: Ecology, Biogeography and Evolution of Dormancy and Germination, Second Edition. Academic Press.}

^{Small C.C. & Degenhardt D. (2018) Plant growth regulators for enhancing revegetation success in reclamation: a review. Ecological Engineering, 118, 43–51.}

Study locations

Key messages

Two studies evaluated the effects – on trees/shrubs typical of freshwater wetlands – of treating their seeds with chemicals before sowing. Both studies were in one laboratory in the USA.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

VEGETATION STRUCTURE

OTHER

Germination/emergence (2 studies): Two replicated, controlled studies in a laboratory in the USA found that soaking baldcypress Taxodium distichum seeds in weak sodium hydroxide increased their germination rate. One of the studies found that soaking in ethyl alcohol and/or hydrochloric acid reduced the germination rate. One of the studies found that soaking in stronger sodium hydroxide, or hydrogen peroxide and ethyl alcohol, had no significant effect on the germination rate.
Growth (1 study): One replicated, controlled study in a laboratory in the USA found that soaking baldcypress Taxodium distichum seeds in chemicals before sowing typically had no significant effect on the height of surviving seedlings, 30 days after germination. Soaking in ethyl alcohol, however, reduced seedling height.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, controlled study in 2004 in a laboratory in Florida, USA (Liu et al. 2009) found that soaking baldcypress Taxodium distichum seeds in sodium hydroxide NaOH increased their germination rate, but that soaking in hydrochloric acid HCl or ethyl alcohol reduced their germination rate. Seeds soaked in 1% NaOH then water had a higher germination rate (54% germinated) than seeds soaked only in water (47% germinated). Seeds soaked in other chemicals had a lower germination rate than the seeds soaked only in water. This was true for 1% HCl (34% germinated), 95% ethyl alcohol (7% germinated), ethyl alcohol then NaOH (0% germinated), and ethyl alcohol then HCl (7% germinated). After 30 days and in three of four comparisons, there was no significant difference in the height seedlings that had grown from seeds soaked in chemicals (9.3–10.5 cm) or seeds soaked only in water (8.3 cm). In the other comparison, seedlings that had grown from seeds soaked in ethyl alcohol were shorter (4.3 cm) than the seeds soaked only in water. Methods: In August 2004, baldcypress seeds were planted into trays of growing medium. There were three replicates (10 seeds/replicate) for each of six pre-sowing chemical treatments (each involving soaking for 5 min/chemical): NaOH; HCl; ethyl alcohol; ethyl alcohol then NaOH; ethyl alcohol then HCl; or no chemical. All seeds were then soaked in distilled water for 24 h before sowing. All seeds had been stored at 4°C for four months before the experiment started. Germinated seedlings were transplanted to individual pots of growing medium and measured after 30 days.
Study and other actions tested
Referenced paper
Liu G., Li Y., Hedgepeth M., Wan Y. & Roberts R.E. (2009) Seed germination enhancement for bald cypress [Taxodium distichum (L.) Rich.]. Journal of Horticulture and Forestry, 1, 22-26.
A replicated, controlled study in 2004–2005 in a laboratory in Florida, USA (Liu et al. 2009) found that soaking baldcypress Taxodium distichum seeds in weak sodium hydroxide NaOH increased their germination rate, but that soaking in stronger NaOH or hydrogen peroxide H₂O₂ + ethyl alcohol had no significant effect on their germination rate. Seeds soaked in 0.5% NaOH then water had a higher germination rate (45% germinated) than seeds soaked only in water (36% germinated). Seeds soaked in other chemicals had a statistically similar germination rate to seeds soaked only in water. This was true for 2% NaOH (33% germinated), 4% NaOH (36% germinated), 0.03% H₂O₂ + ethyl alcohol (36% germinated), and 0.3% H₂O₂ + ethyl alcohol (28% germinated). Methods: In November 2004, baldcypress seeds were planted into trays of growing medium. There were three replicates (12 seeds/replicate) for each of six pre-sowing chemical treatments: 0.5% NaOH for 24 h; 2% NaOH for 24 h; 4% NaOH for 24 h; 0.3% H₂O₂ + ethyl alcohol for 5 min; 0.03% H₂O₂ + ethyl alcohol for 5 min; or no chemical. All seeds were then soaked in distilled water for 24 h before sowing. All seeds had been stored at 4°C for four months before the experiment started.
Study and other actions tested
Referenced paper
Liu G., Li Y., Hedgepeth M., Wan Y. & Roberts R.E. (2009) Seed germination enhancement for bald cypress [Taxodium distichum (L.) Rich.]. Journal of Horticulture and Forestry, 1, 22-26.

Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

Actions	Effectiveness	Category
Soak tree/shrub seeds before sowing: brackish/saline wetlands Action Link	No evidence found (no assessment)	Synopsis Link
Physically damage tree/shrub seeds before sowing: brackish/saline wetlands Action Link	No evidence found (no assessment)	Synopsis Link
Heat tree/shrub seeds before sowing: brackish/saline wetlands Action Link	No evidence found (no assessment)	Synopsis Link