Characterization of water status in primed seeds of tomato (Lycopersicon esculentum Mill.) by sorption properties and NMR relaxation times

Abstract

The enhanced laboratory and field emergence characteristics of osmo- and halo-primed tomato seeds (cv. Pusa Ruby) were related to changes in hydration–dehydration kinetics, modified sorption properties and nuclear magnetic resonance (NMR) relaxation behaviour of humidified and imbibed seeds. Water sorption isotherms were constructed for primed and unprimed seeds by equilibrating to different water activities (aw) at 25°C. Analysis of the isotherms by the D'Arcy–Watt equation revealed that priming reduced the number of strong binding sites and the associated water content, and increased significantly the number of weak binding sites and the associated water content. This redistribution of water, which increased the availability of seed water, may be the reason for the higher speed of germination of primed seeds. The changes in transverse relaxation time (T2) of seed water and its components, measuredin vivousing nuclear magnetic resonance spectroscopy, showed interesting differences between primed and unprimed seeds. With an increase in humidification time, the T2of primed seeds could be resolved into three components with varying mobilities, while the control seeds had only two components until 10 d of humidification. During imbibition, the third component appeared after 2 and 6 h in primed and control seeds, respectively. This component disappeared after the germination process started in all treatments. The third fraction, with very low molecular mobility, which accounted for about 40% of the proton population, was assigned to hydration water of macromolecules. Hence, we propose that better performance of primed seeds may be attributed to the modifications of seed water-binding properties and reorganization of seed water during imbibition, so as to increase the macromolecular hydration water required for various metabolic activities related to the germination process.

Seed Priming: New Comprehensive Approaches for an Old Empirical Technique

“…In particular, magnetic resonance imaging (MRI) has revealed a precise spatial distribution of water within tissues of germinating seeds and different patterns between species [125,127,128] highlighting the tight control of water transport. Water status of primed seeds was characterized by Nagarajan et al [129] in study on tomato halo-and osmopriming. Nagarajan et al [129] pointed out that better performance of primed seeds may be attributed to the modifications of seed water-binding properties and reorganization of seed water during imbibition, so as to increase the macromolecular hydration water required for various metabolic activities related to the germination process.…”

Water properties in fern spores: sorption characteristics relating to water affinity, glassy states, and storage stability

“…Some studies suggest that seed longevity may be inversely correlated with the water associated with D'ArcyWatt weak binding sites or the proportion of water in weak compared with strong binding sites (Sun et al, 1997;Nagarajan et al, 2005). If true, this would suggest that fern spores are relatively long-lived compared with other germplasm and that spores of P. setiferum have the shortest life span of the fern species studied.…”

“…Chemical affinity for water has been linked to stress tolerance in plant tissues (Levitt, 1980;Rascio et al, 1992;Vertucci and Stushnoff, 1992) and seed storage physiology (Vertucci and Leopold, 1987b;Vertucci and Roos, 1990;Vertucci et al, 1994;Sun et al, 1997;Eira et al, 1999;Dussert et al, 1999;Lyall et al, 2003;Pukacka et al, 2003;Hor et al, 2005;Nagarajan et al, 2005). Indeed, the mechanistic understanding of protection from dehydration and freezing stresses often invokes accumulation of highly hydrophilic substances such as sugars and heat-soluble proteins (Close, 1997;Bryant et al, 2001) that may increase the chemical affinity of water within cells.…”

“…Here water interactions with fern spores are studied using water sorption isotherms. Classical applications of water sorption isotherm models reveal the chemical affinity of materials for water (Rockland, 1969;Vertucci and Leopold, 1987a, b;Oksanen and Zografi, 1990;Costantino et al, 1998;Lyall et al, 2003;Nagarajan et al, 2005). More recent interpretations have also used isotherm shape to account for structural relaxation within amorphous solids (glasses) during plasticization by water (Zhang and Zografi, 2000).…”

Pulse productivity : physiological constraints /

“…In Bangladesh and India, crop from primed seeds flowered and matured earlier and gave higher yield as compared to that from non-primed seeds (Harris and Kumar Rao, 2005). The better performance of primed seeds has been attributed to the modification in the seed water binding properties and reorganization of seed water during imbibition, so as to increase the macromolecular mobility related to germination process (Nagarajan et al, 2005). Seed priming is reported to induce respiration (Smok et al, 1993) and enhance the synthesis of protein, RNA and DNA during priming (Bray, 1995).…”