Journal of Experimental Botany, Vol 49, 1235-1244, Copyright © 1998 by Oxford University Press
M Bauer, S Meyer and P Allen
Bromus tectorum L. (cheatgrass) is an invasive winter
annual whose seeds lose dormancy through dry after-ripening. In this paper
a thermal after-ripening time model for simulating seed dormancy loss of
B. tectorum in the field is presented. The model
employs the hydrothermal time parameter mean base water potential
(
ARTICLES
A simulation model to predict seed dormancy loss in the field for Bromus tectorum L
Department of Agronomy and Horticulture, Brigham Young University, Provo, UT 84602, USA; Rocky Mountain Research Station, Forest Service, United States Department of Agriculture, Shrub Sciences Laboratory, 735 N 500 E, Provo, UT 84606, USA; Corresponding author
b(50)) as an index of dormancy status. Other parameters of the
hydrothermal time equation (the hydrothermal time constant 
HT,
the standard deviation of base water potentials 
b, and
the base temperature Tb) are held constant, while
b(50) is allowed to vary and accounts for changes in germination
time-course curves due to stage of after-ripening or incubation
temperature. To obtain hydrothermal time parameters for each of four
collections, seeds were stored dry at 20
C
for different intervals, then incubated in water (O MPA) or polyethylene
glycol (PEG) solutions (-0.5, -1.0, -1.5 MPa) at 15 and 25C. Germination data for the thermal after-ripening
time model were obtained from seeds stored dry in the laboratory at 10, 15,
20, 30, 40, and 50°C for 0 to 42 weeks, then incubated at two
alternating temperatures in water. Change in b(50) was
characterized for each collection and incubation temperature as a linear
function of thermal time in storage. Measurements of seed zone temperature
at a field site were combined with equations describing changes in
b(50) during after-ripening to make predictions of seed dormancy
loss in the field. Model predictions were compared with values derived from
incubation of seeds retrieved weekly from the field site. Predictions of
changes in b(50) were generally close to observed values,
suggesting the model is useful for simulating seed dormancy loss during
after-ripening in the field.Keywords: After-ripening,
cheatgrass, dormancy, hydrothermal time, thermal time.
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