Germination response of <i>Apocynum venetum</i> seeds to temperature and water potential

Abstract

Apocynum venetum (commonly known as luobuma or rafuma) is a shrub that is nature to Eurasia. It is economically important for sand fixation, forage production, honey production, medicine, fiber and fuel. Rapid and uniform seed germination is critical for successful crop establishment and vegetation restoration. The purpose of this study was to determine the germination responses of A. venetum seeds to temperature and water availability using hydrotime, thermal time and hydrothermal model analysis. Seed germination was relatively high for A. venetum from 25 °C to 30 °C. The base (T_b), optimum (T_o) and ceiling temperatures (T_c(50)) of A. venetum seed germination were 16.6, 27.0 and 45.9 °C, respectively. Values of base water potential (Ψ_b(g)) shifted to zero with increasing temperature, which was reflected in the greater effect of low Ψ on germination for temperatures above 30 °C. Hydrotime analysis suggested that T_b may not be independent of Ψ, and Ψ_b(g) may change as a function of temperature at temperatures below 30 °C. The interaction effects of Ψ and temperature reduced the ability of the hydrothermal time model to predict germination performance across temperature and Ψ conditions.