Quantification of soybean seed germination response to seed deterioration under PEG-induced water stress using hydrotime concept

This experiment was arranged to investigate the ability of hydrotime model (theta (H)) for estimating soybean seed germination (cv. 'JK') under different accelerated aging periods (AAP, 0, 24, 48, and 72 h) at each of the following water potentials (psi, 0, - 0.12, - 0.24, and - 0.36 MPa). Results indicated that both germination percentage (GP) and germination rate (GR) significantly influenced by psi, AAP, and their interactions (P < 0.01). GP and GR decreased by 62.6 and 47.3% with longer AAP from 0 to 72 h and by 90.7 and 81.5% with lower psi from zero to - 0.36 MPa as compared to the control, respectively. Therefore, the effect of psi on GP and GR was more than AAP. The theta (H) value was constant (similar to 6.71 MPa h(-1)) till 50.6 h AAP and then linearly declined with the rate of 0.1545 MPa h(-1) per hour increase in AAP until 72 h (similar to 50% lower than its initial value). The psi (b(50)) value was - 0.343 MPa in the control and then increased (became more positive) by similar to 70% until 72 h AAP (- 0.104 MPa). In general, GP and GR of soybean declined with the increasing psi (b(50)) which can be due to cell membrane damage and reduce the activity of enzymes and organelles during AAP. Based on our findings, the theta (H) model could describe well these relationships and their parameters can nicely be used for simulating soybean seed germination under this condition.