Characterization of wheat (Triticum aestivum) and soybean (Glycine max) seeds under accelerated ageing conditions by proton nuclear magnetic spectroscopy

Inferences on the quality of seeds are made based on many standard seed tests. The non-destructive Nuclear Magnetic Resonance (NMR) spectroscopic techniques can be effective in characterising the seed status. In the present study, seeds of wheat and soybean were subjected to accelerated ageing and seed quality was characterized by both classical seed tests and the proton NMR relaxation times. Under ageing conditions (100% RH both at 35° and 45°C), the spin-spin relaxation time (T₂) of the seed decreased with time in both wheat and soybean, and there were decreases in the seed protein and starch contents. The conductivity of the seed leachate increased and the accumulation of soluble sugars increased in both species with ageing. The decreases in T₂ were more rapid at high temperature (45°C) than at 35°C, even more so in soybean than in wheat seeds. In addition, the trend of changes in spin-spin relaxation time (T₂) values could be related to the loss of seed viability, as evaluated by percentage germination. At least three different fractions of spin-spin relaxation (due to non- or slowly exchanging water protons) could be identified. The pattern of changes in NMR spin-spin relaxation time (T₂) of both seed species during ageing suggests that loss of viability due to high temperature and high moisture content is closely linked to the irreversible loss of membrane integrity and cellular machinery.