Dynamic changes in morphology and composition during seed development in Xanthoceras sorbifolium Bunge

The seed oil of Xanthoceras sorbifolium Bunge is widely recognized as a promising material for high-grade edible oil and biodiesel. No effort has been made to identify the accumulation dynamics of its fatty acid composition and content during seed development, nor to provide a basis for determining the optimal harvest time for each potential use. In this study, the dynamic changes in morphological traits, oil content, fatty acid composition and other components during the seed development of X. sorbifolium were investigated. Seed diameter increased rapidly within 50 days after anthesis (DAA) and then increased slowly. The seed weight peaked on 65 DAA and then decreased. It took 75–80 days for the seeds to ripen completely. Seed kernel oil accumulated rapidly from 45 DAA to 55 DAA, and the oil content peaked on 70 DAA. Twelve fatty acids were detected in seed kernel oil, including four saturated and eight unsaturated fatty acids. With the accumulation of seed oil content, the non-structural carbohydrate content of the seed kernels gradually decreased, providing raw material and energy for seed oil synthesis. The temperature during this period was also observed. The effective accumulated temperature exceeding biological zero temperature (EATk) and the effective accumulated temperature exceeding 10 ℃ (EAT10) were calculated. During 70–75 DAA when EAT10 and EATk reached 1016.1 ℃ and 1567.6 ℃, respectively, the transverse and longitudinal diameters of the seeds were 16.65–17.15 mm and 19.73–19.98 mm, respectively. Based on their fatty acid composition and content, the seeds harvested during this period are recommended for the production of edible oil. For biodiesel production, the suggested harvest time is 60 DAA, when EAT10 and EATk were 876.6 ℃ and 1376.1 ℃, respectively, and the transverse and longitudinal diameters of seeds were approximately 16.33 mm and 19.08 mm, respectively.