Hydrothermal time analysis of Ceratonia siliqua L. germination requirements under different abiotic constraints.

Abstract

Reforestation projects are considered key climate change mitigation strategies, especially while considering native tree species as Ceratonia siliqua. The aims of this study were to evaluate the seed germination responses of three Tunisian accessions of Ceratonia siliqua, (Ichkeul (A1), Melloulech (A2), and Matmata (A3)), to temperature, water and salt stresses and their combination on germination aptitude. To overcome integumentary inhibition, we tested the different physical and chemical pre-treatments. Then, we subjected the seeds to different concentrations of NaCl and PEG (0 to -2 MPa), at different temperatures (from 10 to 35 °C). Results showed that the best pretreatment is soaking the seeds with 98% sulfuric acid for 20 minutes at 24 °C. The highest germination rate was observed at a temperature of 20 °C for A1 and 25 °C for A2 and A3. Using the hydrothermal time model, we found that the base water potential (Ψb), showed lower values in optimal range temperature (-2,19 MPa). All Ceratonia siliqua accessions showed a greater sensitivity to drought stress in germination and root growth in comparison with salt stress. The Ichkeul accession showed faster germination and better tolerance to stress. In conclusion, Ceratonia siliqua is thus recommended for restoration programs in arid and semi-arid ecosystems.