SigmaTransformed transforms the measured sigma value at a specific
temperature to an estimate of sigma at another temperature. This useful in
comparitive seed testing protocol to compare seed longevities among species
tested at different temperatures
(Probert et al. 2009)
.
SigmaTransformed(sigma, temp1, temp2, temp.coeff = c(0.0329, 0.000478))
| sigma | The inverse of slope from the seed viability equation
(σ), estimated at
temperature |
|---|---|
| temp1 | The temperature at which |
| temp2 | The temperature at which the transformed σ is to be estimated in °C. |
| temp.coeff | The species-specific temperature coefficients (CH and CQ.) as a numeric vector of length 2. |
The transformed value of
σ at temperature
temp2.
The transformation is based on the effect of temperature on seed longevity (σ) (identified by storage experiment with constant moisture content and varying temperature) which is as follows.
logσ = β − CHt − CQt2
Where, CH and CQ are the species-specific temperature coefficients, t is the temperature and β is the constant associated with moisture relations of seed longevity.
Ellis RH, Roberts EH (1980). “Improved equations for the prediction of seed longevity.” Annals of Botany, 45(1), 13--30.
Probert RJ, Daws MI, Hay FR (2009). “Ecological correlates of ex situ seed longevity: A comparative study on 195 species.” Annals of Botany, 104(1), 57--69.
SigmaTransformed(250, 60, 45)#> [1] 4408.492