Rapid and noninvasive tools to understand lipid role in seed storage: dsc and ft-ir

ANTONIO MOLINA-GARCÍA; VANESA IXTAÍNA; GUIDI GUADALUPE; LORENA DELADINO; ALINE SCHNEIDER-TEIXEIRA

Conferencia; Cryobyology 2021- Virtual conference; 2021

Differential Scanning Calorimetry (DSC), a classic biophysical technique for characterizing thermal transitions in the triacylglycerol phase of dry seeds, has shown links to storage behavior. Though a powerful tool, DSC has some limitations. Fourier Transform Infrared (FT-IR) spectroscopy provides fast and valuable physicochemical information due to its sensitivity to hydrogen bonds, being an option for accurate analysis of changes in lipid structures. Lipid´s absorptivity in the infrared region allows higher pathlengths than other methods. Tomato seeds deterioration for different varieties stored for 5-31 years at the COMAV Plant Germplasm Bank (Valencia, Spain) was studied using traditional (germination and tetrazolium test) and non-traditional (DSC and FT-IR) techniques, to rapidly identify the accessions physiological status. Samples exhibited an exothermic event (-110 to -57 °C), attributed to lipid crystallization and at least two lipids melting peaks (-50 to 5 °C). Melting peak temperature differed among accessions whereas devitrification energy decreased with storage time, with exception of samples harvested in 1999, showing anomalous results. FT-IR spectra from whole seeds were processed by Principal Components Analysis (PCA), where two principal components explained 89.5% of the total variance. PC1 (71%) was positively correlated with the peak at 1600 cm-1 related to the Amide I zone, denoting any dissimilarities in protein structure, whereas PC2 was strongly related to lipid peaks. Also, to evaluate the degree of unsaturation in stored samples, specific FT-IR absorbance ratios were calculated, estimating iodine values: one of the accessions showed higher values (p