In vivo ¹³C NMR metabolite profiling: potential for understanding and assessing conifer seed quality

High-resolution ¹³C MAS NMR spectroscopy was used to profile a range of primary and secondary metabolites in vivo in intact whole seeds of eight different conifer species native to North America, including six of the Pinaceae family and two of the Cupressaceae family. In vivo ¹³C NMR provided information on the total seed oil content and fatty acid composition of the major storage lipids in a non-destructive manner. In addition, a number of monoterpenes were identified in the ¹³C NMR spectra of conifer seeds containing oleoresin; these compounds showed marked variability in individual seeds of Pacific silver fir within the same seed lot. In imbibed conifer seeds, the ¹³C NMR spectra showed the presence of considerable amounts of dissolved sucrose presumed to play a protective role in the desiccation-tolerance of seeds. The free amino acids arginine and asparagine, generated as a result of storage protein mobilization, were detected in vivo during seed germination and early seedling growth. The potential for NMR to profile metabolites in a non-destructive manner in single conifer seeds and seed populations is discussed. It is a powerful tool to evaluate seed quality because of its ability to assess reserve accumulation during seed development or at seed maturity; it can also be used to monitor reserve mobilization, which is critical for seedling emergence.