Using isothermal calorimetry and FT-Raman spectroscopy for step-by-step monitoring of maize seed germination: case study
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Using isothermal calorimetry and FT‑Raman spectroscopy for step‑by‑step monitoring of maize seed germination: case study Iwona Stawoska1 · Aleksandra M. Staszak2 · Iwona Ciereszko2 · Jakub Oliwa3 · Andrzej Skoczowski1 Received: 4 July 2019 / Accepted: 6 March 2020 © The Author(s) 2020
Abstract Thermoanalytical methods are widely used to study seed germination processes. Our research aimed to use them in order to monitor the germination of maize seeds. To this end, we employed—for the first time—the isothermal calorimetric method with full oxygen access. Dry seeds were placed in ampoules with threaded caps, filled with distilled water. Heat flow was recorded in microwatts at 20 °C for 72 h in order to determine changes in thermal power associated with germination. In parallel with these measurements, in the same time regime, we measured FT-Raman spectra, which allowed us to analyze how endosperm and embryo changed their chemical compositions during imbibition and germination. Spectra obtained for endosperm reflected chemical changes resulting from catabolic processes. We also analyzed variations in the secondary structure of proteins in the embryo accompanying germination. Decomposition of amide I bands proved that during germination and protein hydrolysis, the content of helical and β-sheet structures decreased. Furthermore, in the embryos of dry seeds, S-S linkages were in both gauche–gauche-trans and trans-gauche-trans conformations, but after imbibition, only gauche–gauche-trans conformation can be identified. Keywords Seed germination · FT-Raman spectroscopy · Decomposition · Secondary structure of proteins · Zea mays
Introduction Among the critical stages of plant life is seed germination. It is during this stage that the plant’s genetic pool is transferred to the environment, a critical process behind perpetuating the species. Germination ends the plant’s quiescent phase, making it metabolically active. To germinate, seeds need to complete the imbibition phase, in which colloids are hydrated, leading to enzymes becoming active and reserves being hydrolyzed. After that period, anabolic processes Iwona Stawoska and Aleksandra M. Staszak have contributed equally to this work. * Iwona Stawoska [email protected] 1
Institute of Biology, Pedagogical University of Cracow, Podchorążych 2, 30‑084 Kraków, Poland
2
Institute of Biology, University of Bialystok, Ciołkowskiego 1J, 15‑245 Białystok, Poland
3
Department of Chemistry and Biochemistry, Institute of Basic Sciences, University of Physical Education, Jana Pawła II 78, 31‑571 Krakow, Poland
start, and embryo radicle is growing. During reserve mobilization, stored materials are enzymatically decomposed to simpler components, which then serve as energy source for the embryo and forming seedlings. Germination ends when the radicle breaks the seed coat, a moment that marks the formation of a seedling and the beginning of its grow [1]. Isothermal calorimetry is used to monitor many biological processes, such as fermentation [2], microorgan
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