Deciphering the Germination Behavior of Sesame Cultivars: The Interplay of Hydrothermal Time Model Parameters and Seed Fatty Acid Profiles

Seed germination is a critical developmental stage susceptible to environmental factors, such as temperature and soil water potential, which directly influence germination percentage and rate. To gain deeper insight into these interactions, this study re-analyzed data from a previously published germination experiment involving six distinct sesame (<i>Sesamum indicum</i> L.) cultivars with varied fatty acid profiles. Germination was recorded across eight constant temperatures (10-45 °C) and seven water potential levels (0 to -1.2 MPa), using thermal time, hydrotime, and hydrothermal time models. No germination occurred at -1.0 or -1.2 MPa. The highest thermal time constant, θT(g), was observed at -0.8 MPa across all cultivars, and germination rates declined as water potential decreased. Hierarchical clustering based on principal component analysis grouped the cultivars into three distinct clusters. Cluster 1, containing two cultivars, exhibited the highest base temperatures (above 13 °C), which correlated with high arachidic and low linolenic acid content. The three cultivars in cluster 2 showed the highest hydrothermal time constants (θHT(g) = 760-2495 MPa·°C·h) and contrasting palmitic and stearic acid profiles. The single cultivar in cluster 3 had the lowest base water potential, the highest oleic acid content, and the highest percentage of linoleic acid. These findings underscore the significant role of seed fatty acid composition in stress tolerance, with 'Darab1' showing superior drought resistance and 'Dashtestan2' showing greater resilience to high temperatures. These modeling and multivariate analyses provide deeper insights into germination mechanisms and offer valuable guidance for selecting cultivars adapted to specific climatic conditions.