Ramin Piri, Farzad Sharifzadeh, Naser Majnounhosseini,
Volume 11, Issue 1 (9-2024)
Abstract
Extended abstract
Introduction: Currently, temperature and salinity stresses are spreading globally, which have a detrimental impact on the performance of various plants, particularly during seed germination and seedling growth stages. Therefore, the objective of this laboratory study was to examine the influence of temperature treatments and salinity levels on germination characteristics and initial seedling growth of kochia.
Materials and Methods: In the first experiment, temperature at nine levels (1, 5, 10, 15, 20, 25, 30, 35, and 40°C), and in the second experiment, salinity (osmotic potential at six levels (no stress, -0.4, -0.8, -1.2, -1.6, and -1.8 MPa) were considered as experimental treatments. In order to determine the cardinal temperatures (base, optimal, and ceiling) of germination in kochia seeds, non-linear regression models including the segmented, dent-like, and modified beta models were used.
Results: In the first experiment, the response of kochia germination rate was predicted by a segmented function with R2, RMSE, and AIC (Akaike) values of 0.92, 1.32, and 65.69, respectively, which indicates the high accuracy and precision of this model in predicting the cardinal temperatures of kochia seed germination compared with the other two models. In this model, the estimated base temperature for germination was 0.7°C, the optimal temperature was 20°C, and the ceiling temperature was 44.3°C. In the second experiment, salinity stress negatively affected the characteristics of seed germination in kochia, including germination percentage, germination rate, percentage of normal seedlings, seedling length, and seedling vigor index. The highest germination percentage of kochia seeds was observed under salt-free conditions with 88.66%, which decreased to 13% under -1.8 MPa salinity conditions.
Conclusions: In general, the results showed that the segmented model is more efficient and accurate than the other two models in predicting germination of kochia seeds under different temperature treatments. Also, increasing levels of salinity stress significantly reduced germination potential and seedling growth of kochia seeds, so that at a stress level of -1.8 MPa, germination rate decreased by 75% compared with stress-free condition.
Highlights:
- The cardinal temperatures (base, optimum, and ceiling temperatures) of kochia seed germination were determined.
- This research introduced 1°C temperature and -1.8 MPa of salinity level as low temperature stress and critical salinity, respectively.
