Characterization of water uptake and distribution in chickpea (Cicer arietinum L.) seeds during germination by NMR spectroscopy
Experiments were conducted to characterize the changes in water status during imbibition by nuclear magnetic resonance (NMR) spectroscopy in chickpea seeds exposed to static magnetic fields of 100 mT for 1 h. Water uptake during seed germination showed three phases with rapid initial hydration phase I, followed by lag phase II and steady hydration phase III. Comparative analysis of the hydration pattern showed that water uptake was more in phase II and III in magnetically exposed than unexposed seeds. The longitudinal relaxation time (T1) of seed water showed significantly higher values and hence higher molecular mobility of cellular water in magnetically exposed seeds as compared to unexposed seeds. Analysis of transverse relaxation time (T2) revealed a three component of water in germinating chickpea seeds. Interesting observation found in this study was the early appearance of hydration water with least mobility and higher values of relaxation times of cytoplasmic bulk water and hydration water in magnetically treated over untreated seeds. Early hydration of macromolecules, membranes, greater molecular mobility of bulk and hydration water fractions in magnetically exposed seeds may be responsible for quicker germination and appearance of early seedling vigour in chickpea. Activities of enzymes related to germination process such as α-amylase, dehydrogenase and protease were higher in magnetically exposed seeds as compared to unexposed seeds. Moreover, a significant correlation between the relaxation time of cytoplasmic bulk water and the activities of germination related enzymes supported our conclusion that this fraction of water plays a major role in the metabolism of germination process.
Key words: Cicer arietinum L., imbibition, nuclear magnetic resonance, longitudinal relaxation time (T1), transverse relaxation time (T2), germination enzymes.