In the North American northern Great Plains region, despite its non-native status the perennial Altai wildrye Leymus angustus (indigenous to Asia) is recommended for stabilising and remediation of salt affected soils. Establishment success by sowing is however, highly variable, perhaps due to fluctuating environmental extremes in the seedbed (temperature extremes and moisture deficits are major factors that influence germination, growth and seedlings survival on the Plains). This study investigated the effect of temperature and moisture on Altai wildrye germination, seed solute leakage and seedling growth.
Seeds (approximately 10 months old; from Agriculture Canada Research Station, Saskatchewan, Canada) were subjected to five pretreatments(applied to seeds placed on a filter paper disc in Petri dishes): stratification (5º C); stratification plus drying (30º C); stratification plus freezing (-10º C); cool-dry storage (5º C); and laboratory storage.
Stratification entailed adding 7 mL of distilled water to the petri dishes and incubating seeds in the dark at 5º C for 48 h.
After pre-treatment, seeds were incubated at 10 and 20º C in a gradient of six osmotic potentials (i.e. moisture conditions): -0.10, -0.35, -0.69, -0.99, -1.22 and -1.59 MPa. Samples of 25 seeds subject to each pre-treatment were assessed for solute leakage. Samples of 50 seeds were assessed for etiolated seedling growth (seedlings grown for 5 days at 15ºC in darkness).
Germination was higher and more rapid over the range of osmotic potentials at 20º C than at 10º C with germination poorest in the stratification + freezing pretreatment. In the absence of water stress, leakage of solutes was 21% lower (ranging 0.50-0.54) from stratified seeds than unstratified (i.e. cool dry and lab storage) seeds (0.65-0.68). Leakage at -0.48 MPa (range 0.86-0.87) was similar across pretreatments.
Reduced germination and seedling growth was apparent in stratified seeds subjected to freezing. Root growth (averaging 14.9 mg) and shoot growth (averaging 6.4 mg) of these seedlings was reduced by 34 and 76% respectively at -0.48 MPa, compared to the other pretreatments.
Results of this study (and others) indicate that minimizing seedbed temperature extremes could improve Altai wildrye germination and seedling growth.
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