S. Dussert et al., Quantitative estimation of seed desiccation sensitivity using a quantal response model: application to nine species of the genus Coffea L., SEED SCI R, 9(2), 1999, pp. 135-144
Seed desiccation sensitivity was studied in nine species of the genus Coffe
a by measuring seed viability after equilibration over various saturated sa
lt solutions. A quantal response model based on the logistic distribution w
as developed in order to describe the typical S-shaped patterns observed. T
he closeness of fit or the desiccation sensitivity model was shown, and the
assumption that seed desiccation sensitivity follows a continuous distribu
tion within species was verified. For each species, the water content at wh
ich 50% of initial viability was reached, WC50, and a specific parameter de
scribing the intra-specific variability, beta, were calculated using a non-
linear regression. A simplified water sorption model was developed which al
lowed easy calculation of water activity and water potential corresponding
to WC50 (a(w50) and Psi(50)) for relative humidities ranging between 10 and
100%. Distribution of WC50 and Psi(50) (or a(w50)) in the genus Coffea was
homogeneous within the following intervals: from 0.05 to 0.38 g H2O.g(-1)
dw for WC50 and from -168 to -11 MPa for Psi(50). Different classifications
of the coffee species studied as regards to their desiccation sensitivity
were obtained depending on whether WC50 or Psi(50) was used for classificat
ion. The continuum for desiccation sensitivity observed within the nine spe
cies studied confirmed that coffee is an appropriate material for studying
desiccation sensitivity.