Investigation of changes in water status and distribution of Quercus acutissima seeds during desiccation using LF-NMR and MRI methods

Abstract

Background The Quercus acutissima seed is a typical temperate recalcitrant seed; storing the seeds for longer than a year after maturation and shedding is challenging because they are sensitive to water loss. Therefore, research on the Q.acutissima seed water loss site and the dynamic changes in seed water status during desiccation can offer a theoretical foundation for the storage of these seeds safely as well as a reference for the mechanism study of recalcitrant seeds. Results The site of water loss in Q.acutissima seeds was explored using nuclear magnetic resonance imaging combined with the results of scanning electron microscopy of the seed coat. The results showed that the micropyle and the scar were identified as the main water loss sites of Q.acutissima seeds. The LF-NMR tests indicated that water in the Q. acutissima seeds exists in three states: free water, immobile water, and bound water. The effects of each water status on seed vigor were also analyzed with the changes in seed germination rate during desiccation. During desiccation, both the bound and free water of Q.acutissima seeds were lost significantly, resulting in the death of the seeds. Finally, the relationship between the transverse relaxation signal and the water content of Q.acutissima seeds during drying is established, providing a foundation for quick and nondestructive assessment of Q.acutissima seed water content. Conclusion Rapid and non-destructive monitoring of the drying process of Q. acutissima seeds is made possible by MRI and NMR technology. By conducting them, we can determine the sites of water loss, the migration rules of different water statuses during seed drying, and the relationship between the causes of seed desiccation sensitivity and changes in water status.