A method to monitor seed germination that combines isothermal calorimetry and imbibition measurements is reported. Individual seeds of three cultivars of soybean seeds (A7636RG, Munasqa and DM5.8RR) and one of radish were used. Imbibition curves were performed on individual seeds in a germination chamber at 25 °C. Calorimetric specific thermal power (p)–time (t) curves of germination were also obtained at 25 °C for 10 or more individual seeds after 30 min of equilibration of the system. Calorimetric experiments of germination in 5 mM KCN were performed to estimate specific imbibitions enthalpies (Δih). The p–t curves could be extrapolated to t = 0 by relating the rate of water uptake as determined from imbibitions curves with p values. Then, p–t curves were integrated to determine the specific metabolic enthalpies Δh which in turn were related to the water content (WC) of seeds at the corresponding times. The method allows determination of specific enthalpy change due to germination, Δgh, which apparently is species related. Besides, the standard deviation (SD) of the Δgh value gives an indication of seed quality. On the other hand, the water content that seeds need to germinate and the moment at which seeds are fully imbibed can also be determined. This is very important when breeding new cultivars for water stress tolerance. The water content needed for each cultivar to germinate was 74, 57, 35 and 64% for soybean seeds cvs. A7636RG, Munasqa, DM5.8RR and radish, respectively.
1. Jann, RC, Amen, RD. What is germination? 1977 Kahn, AA eds. The physiology and biochemistry of seed dormancy and germination North Holland Publishing Company Amsterdam 157–178.
2. Al-Ani, A, Bruzau, F, Raimond, P, Saint-Ges, V, Leblang, JM, Pradet, A. Germination, respiration, and adenylate energy charge of seeds at various oxygen partial pressures. Plant Physiol 1985 79:885–890 .
3. Sigstad, EE, Prado, FE. A microcalorimetric study of Chenopodium quinoa Willd seed germination. Thermochim Acta 1999 326:159–164 .
4. Bradford, KJ. A water relations analysis of seed germination rates. Plant Physiol. 1990;94:840–849 .
5. Bewley, JD, Black, M Seeds: physiology of development and germination 1994 2 Plenum Press New York, London.
6. Criddle, RS, Breidenbach, RW, Hansen, LD. Plant calorimetry: how to quantitatively compare apples and oranges. Thermochim Acta 1991 193:67–90 .
7. Wadsö, I. Trends in isothermal microcalorimetry. Chem Soc Rev. 1997;26:79–86 .
8. Zhou, P-J, Hu, Y-C, Wang, C-X, Song, Z-H, Wang, T-Z, Qu, S-S, Zhou, H-T, Zhu, Y-GJ. Determination of the thermogenesis curves and studies of the thermodynamics and thermokinetics of seed germination. Biochem Biophys Methods 1999 38:171–180 .
9. Sigstad, EE, Schabes, FI. Isothermal microcalorimetry allows detection of ‘aquaporines’ in quinoa seeds. Thermochim Acta 2000 349:95–101 .
10. Sigstad, EE, García, CI. A microcalorimetric analysis of quinoa seeds with different initial water content during germination at 25 °C. Thermochim Acta 2001 366:149–155 .
11. Sigstad, EE, Schabes, FI. Loss of germinability of quinoa seeds during storage. A microcalorimetric study. Biocell 2004 28:47.
12. Schabes, FI, Sigstad, EE. Microcalorimetric studies of quinoa (Chenopodium quinoa Willd.) seed germination under saline stress conditions. Thermochim Acta 2005 428:71–77 .
13. Schabes, FI, Sigstad, EE. Optimizing conditions to study seed germination by calorimetry using soybean (Glycine max (L.) Merr.) seeds. Thermochim Acta 2006 450:96–101 .
14. Paschal, EH, Ellis, MA. Variation in seed quality characteristics of tropically grown soybean. Crop Sci 1978 18:837–840 .
15. Ports, HC, Uangpatra, J, Hairstone, HG, Delouche, JC. Some influence of hardseededness on soybean seed quality. Crop Sci 1978 18:221–224 .
16. Hartwig, EE, Potts, HC. Development and evaluation of impermeable seed-coats for preserving soybean seed quality. Crop Sci 1987 27:506–508 .
17. Panobianco M , Vieira RD, Krzyzanowski FC. In: Research results of Embrapa soybean. Methodology for the selection of soybean genotypes with resistant seeds to mechanical damages—relation with lignin content. Londrina; 1997. p. 142–2. (EMBRAPA-CNPSo. Documentos, 104).
18. Suriyong S , Vearasilk S, Krittigamas N, Thanapornpoonpong S-N. Pre-emergence effect to imbibition of soybean seeds. In: Conference on international agricultural research, Deutscher Tropentag 2002, Witzenhausen, Germany, October 2002.
19. Vertucci, CW, Leopold, C. Bound water in soybean seed and its relation to respiration and imbibition damage. Plant Physiol 1984 75:114–117 .