Germination response of Oat (Avena sativa L.) to temperature and salinity using halothermal time model

Seed germination is a complex physiological process influenced by abiotic stresses such as drought, temperature, salinity along with other biological and physical means. Halothermal time model (HaloTT) permitted quantitative assessment of seed germination at different water potential (ψ) and temperature (T). The present study aimed to evaluate the reliability of HaloTT model and to find cardinal temperature values for seed germination of Oats under various Ts and ψs. Avena sativa L. Var. Swan seeds were incubated at seven constant Ts under five various ψs prepared through sodium chloride (NaCl) at Plant Physiology Lab., University of Peshawar, Pakistan. The cardinal Ts measured through HaloTT model for Oats seed germination were 10, 30 and 40 °C for the base (Tb), optimum (To) and ceiling (Tc) temperatures correspondingly in distilled water (0 MPa). The maximum halotime constant (θHalo) was recorded as 48 MPa °Ch−1 at 30 °C in distilled water (0 MPa). The highest value of halotime and thermal time of germination rate was observed at -2.0 MPa at 40 °C. Germination percentage (GP), germination rate index (GRI), germination energy (GE), coefficient of velocity of germination (CVG), timson germination index (TGI), mean germination rate (MGR) and coefficient of variation of germination time (CVt) was observed maximum in 0 MPa at 30 °C, while minimum in -2.0 MPa at 40 °C. Contrarily the high rate of mean germination time (MGT) and time to 50 % germination (T50 %) was reported in -2.0 MPa and -1.5 MPa at 10 and 40 °C, while in distilled water (0 MPa) is lowest at 25 and 30 °C. Thus, we concluded that HaloTT model precisely interpret germination responses to various ψs across different Ts and may be used as an accurate and simple method to predict germination parameters under natural field conditions.