Quantifying Osmotic Stress and Temperature Effects on Germination and Seedlings Growth of Fenugreek ( Trigonella foenum - graecum L.) via Hydrothermal Time Model

Germination models are really useful in predicting seed germination, attributed to their application in economic crop management. Hence, we evaluated cardinal temperatures (Ts), seed germination behavior, and model coefficients of fenugreek under varying temperatures (Ts; 10, 20, 30, and 40 °C) and water potentials (ψ s 0, −0.01, −0.02, and −0.05 MPa). We observed that the maximum and minimum hydrotime constant ( θ H) values at 20 °C, respectively. The base water potential at 50 percentiles (Ψb 50) exhibited an asymmetrical pattern with the highest (−0.9 MPa) value computed at 40 °C and the lowest (−0.13 MPa) at 10 °C. Furthermore, the ceiling temperature (TC), base temperature (Tb), and optimal temperature (To) of Fenugreek were determined to be 34.5 °C, 7.8 °C, and 18 °C, respectively. In addition, we observed that germination index, germination rate index, germination percentage, germination energy, Timson germination index, seed vigor index I and II, and root-shoot ratio are at their highest values at 20 °C and lowest at −0.05 MPa at 40 °C. Based on our findings, we suggest that the hydrothermal time model (HTT) can be used to explore the independent and synergistic effects of both T and ψ on the germination of seeds in different environmental conditions. The obtained model coefficients indicate that fenugreek is temperature-sensitive and suitable for agriculture in irrigated regions.