Seed Fatty Acid Changes Germination Response to Temperature and Water Potentials in Six Sesame ( Sesamum indicum L.) Cultivars: Estimating the Cardinal Temperatures

Seed fatty acid composition can influence seed quality, followed by seed germination and optimal seedling establishment. Therefore, to find out the role of seed fatty acids in changing the cardinal temperatures of six sesame cultivars germinated at different temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and water potentials (0, −0.2, −0.4, −0.6, −0.8, −1, and −1.2 MPa), an experiment was conducted. The dent-like, beta, and segmented models were used to analyze the data. The results showed that different cultivars at optimal temperatures show different reactions to environmental conditions; for example, the germination rate in Halil and Dashtestan2 cultivars followed the dent-like model, Darab1, Oltan, and Yellow-White followed the beta model, and Naz followed the segmented model. Based on the results, the average temperature in all water potentials of the base, sub-optimal, supra-optimum, and ceiling was determined as 12.6, 33.3, 38, and 43.9 °C, respectively, once the superior dent-like model was used. Using the superior beta model, the average temperatures in the base, optimum, and ceiling were 8.5, 31.2, and 50.5 °C. In contrast, when the segmented superior model was used, they were determined to be 7.6, 34, and 44.1 °C, respectively. According to the results, it can be stated that the Halil cultivar with more oleic acid and less linoleic acid has a higher base temperature and is more adapted to high temperatures for later cultivations. The Naz cultivar with a long biological clock is suitable for earlier cultivations. The ceiling temperature of these cultivars was also affected by the osmotic potential and decreased significantly with the increase in osmotic levels. Dashtestan2 cultivar with a high germination rate could be chosen for cultivation in water and high-temperature stress areas.