Water Absorption Characteristics of the Ormosia hosiei Seeds by Nuclear Magnetic Resonance Technique

To investigate the spatial and phase changes of water in the Ormosia hosiei seeds during the water absorption and germination process, MRI technology was employed to observe their water absorption sites and the path of water movement during the water absorption process, and NMR technology was employed to get the transverse relaxation time T₂ to explore the changes in water phase during the water absorption and germination process of the seeds. The results showed that the micropyle was the main water absorption site of the Ormosia hosiei seeds. After water entered through the micropyle, part of the water moved toward the end of the cotyledon through the gap between the seed coat and cotyledon as well as the vascular bundles in the hilum, while another part of the water was absorbed by the radicle and diffused toward the center of the cotyledon. The fitting results showed that the peak area (S) of the NMR relaxation spectrum had a significant linear relationship with the moisture mass (x, g) of the Ormosia hosiei seeds: S=8841.6x-5440, R²=0.9967. During the process of seed water absorption and germination, the various phases of water were in dynamic change. The content of bound water and intracellular water first increased and then decreased, but their proportion overall showed a declining trend. The content and proportion of extracellular free water both showed an increasing trend that was initially rapid and then slowed down. By X₁₀, the proportion reached 69.7%, and the water mobility within the seeds continued to increase. Magnetic resonance technology accurately presented the spatial distribution and phase changes of water in the Ormosia hosiei seeds during the water absorption process, systematically revealing their water absorption characteristics.