A Nuclear Magnetic Resonance Study of Water in Cold-acclimating Cereals

Abstract

Continuous wave nuclear magnetic resonance (NMR) studies indicated that the line width of the water absorption peak (AP%) from crowns of winter and spring wheat (Titicum aestivum L.) increased during cold acclimation. There was a negative correlation between Air and crown water content, and both of these parameters were correlated with the lowest survival temperature at which 50% or more of the crowns were not killed by freezing (LT5o). Regression analyses indicated that APS and water content account for similar variability in LT5w Slow dehydration of unacclimated winter wheat crowns by artificial means resulted in similarly correlated changes in water content and A4Y. Rapid dehydration of unacclimated crowns reduced water content but did not influence AP%. The incubation of unacclimated winter wheat crowns in a sucrose medium reduced water content and increased Au's. The increase in AP% appears to be dependent in part on a reduction in water content and an increase in solutes.Longitudinal (TO) and transverse (T2) relaxation times of water protons in cereals at different stages of cold acclimation were measured using pulse NMR methods. The T, and T2 signals each demonstrated the existence of two populations of water, one with a short and one with a long relaxation time. During the first 3 weeks of acclimation, the long T2 decreased significantly in winter-hardy cereals, and did not change in a spring wheat until the 5th week of hardening. There was no change in the long T, until the 3rd week of hardening for the winter cereals and until the 7th week of hardening for the spring wheat. No simple relationship could be established between T, or T2 and cold hardiness. Neither continuous wave or pulsed NMR spectroscopy can be used as a diagnostic tool in predicting the cold hardiness of winter wheats. An increase in AvA or a reduction in relaxation times does not provide evidence for ordering of the bulk of the cell water.water content and an increase in hydrophilic compounds such as sugars (17), proteins (24), and nucleic acids (23). These hydrophilic compounds could affect the physical state of water which in turn would affect the amount of water which crystallizes at any given subzero temperature.Continuous wave NMR studies on animal tissue have shown that line width (Av½, one-half maximum amplitude of the water absorption peak) is significantly broader than in pure water (6,15). This has led to the suggestion that cellular water consists of several populations, including a "bound" or unfreezable fraction (1,5,6 MATERIALS AND METHODS CONTINUOUS WAVE NMR MEASUREMENTSThe physical state of water in plant cells has long been a subject of interest in relation to cold hardiness (16,17,22). NMR3 provides one method of studying water and water interactions in intact biological systems (1,2,6,11,18,19 Samples for analysis were stripped to two leaves and 3-cm sections were cut from just above the base. Studies of the effect of sample shape and spinning rate on line width showed that crooked samples had a line width ...

Detection of Pre-Harvest Sprouting in Rice Seeds by Using 1H-NMR

“…The dynamic states of water in biological tissues were considered to reflect physiological changes. The components of T1 and T2 have been shown to arise from distinct populations of water in plant tissues (Gusta et al, 1979;Belton and Ratcliffe 1985;Isobe et al, 1999;Iwaya-Inoue and Nonami 2003). Thus, the NMR technique is expected to provide a novel, sensitive and direct method of characterizing water status in seeds.…”

Characterization of Heat Injury in Grapes Using 1H Nuclear Magnetic Resonance Methods

“…Although little is known about the effect of high temperatures on membranes, many studies suggest that the cell membranes are the locus of injury and that disintegration of cell membranes is associated with heat injury (3,15,18,21,28). There is overwhelming evidence that high temperature can disrupt membrane structure and, thus, the membrane-associated functions (3,22,24 (9,20,26) and to characterize heat and freezing injury in some plant tissues (19,21).…”

“…T22 of tissue water have been widely used to study water status in plant tissues (9,20,26) and to characterize heat and freezing injury in some plant tissues (19,21).…”

Some plant leaves have orientation-dependent EPR and NMR spectra

“…One well documented exception is in the spectrum of dogwood stems, which have orientation-dependent patterns caused by geometrical effects of the sample shape (3). Previous 1H NMR studies of plant tissue have concentrated on the effects of freezing (4). Spin-lattice (tj) and spin-spin (t0) relaxation times have also been measured; for example, exchange times between water compartments were determined in ivy bark (5).…”