Water availability shifts the optimal temperatures for seed germination: A modelling approach

Abstract

Hydrothermal time (HTT) models have been widely applied to describe the germination responses of seeds to temperature and water. Some HTT models assume that the thermoinhibition of germination is caused by an upward shift in base water potential Ψb(g) that only happens above the optimum temperature To, and that To is a parameter independent of the water stress level. However, the available data suggest that these assumptions may be invalid in practice. We introduce a new HTT model that uses a log-logistic distribution for Ψb(g) and assumes a linear increase in Ψb(g) across both sub- and supra-optimal temperature ranges. We also provide explicit mathematical solutions for estimating To and ot..