A Nuclear Magnetic Resonance Study of Water in Cold-acclimating Cereals.
A Nuclear Magnetic Resonance Study of Water in Cold-acclimating Cereals.
复制标题
冷驯化谷物中水的核磁共振研究。
作者：
L. Gusta;D. Fowler;P. Chen
连续波核磁共振研究表明，冬小麦和春小麦冠层的吸水峰(Deltav(1/2))的线宽。在冷驯化过程中增加。Deltav(1/2)与树冠含水率呈负相关，这两个参数都与树冠不被冻死的最低生存温度(LT(50))相关。回归分析表明，Deltav(1/2)和含水率在LT(50)中的变异性相似。用人工方法对未驯化的冬小麦冠层进行缓慢脱水处理后，水分含量和Deltav(1/2)的变化趋势相似。未驯化树冠的快速脱水可降低水分含量，但不影响Deltav(1/2)。未驯化的冬小麦冠部在蔗糖介质中培养，降低了水分含量，增加了Deltav(1/2)。Deltav(1/2)的增加似乎部分依赖于水分含量的减少和溶液的增加。用脉冲核磁共振方法测量了不同冷驯化阶段谷物中水质子的纵向(T(1))和横向(T(2))弛豫时间。T(1)和T(2)信号分别表明存在两个种群的水，一个具有较短的松弛时间，另一个具有较长的松弛时间。在驯化的前3周，耐冬性谷类作物的长T(2)显著降低，而春小麦的长T(2)直到锻炼第5周才发生变化。在冬粮硬化第3周和春小麦硬化第7周之前，长T(1)没有变化。T(1)或T(2)与抗寒性之间不存在简单的关系。无论是连续波谱还是脉冲核磁共振谱都不能作为预测冬小麦抗寒性的诊断工具。Deltav(1/2)的增加或弛豫时间的缩短并不能提供大量细胞水有序的证据。
Continuous wave nuclear magnetic resonance (NMR) studies indicated that the line width of the water absorption peak (Deltav(1/2)) from crowns of winter and spring wheat (Triticum aestivum L.) increased during cold acclimation. There was a negative correlation between Deltav(1/2) 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 (LT(50)). Regression analyses indicated that Deltav(1/2) and water content account for similar variability in LT(50). Slow dehydration of unacclimated winter wheat crowns by artificial means resulted in similarly correlated changes in water content and Deltav(1/2). Rapid dehydration of unacclimated crowns reduced water content but did not influence Deltav(1/2). The incubation of unacclimated winter wheat crowns in a sucrose medium reduced water content and increased Deltav(1/2). The increase in Deltav(1/2) appears to be dependent in part on a reduction in water content and an increase in solutes.Longitudinal (T(1)) and transverse (T(2)) relaxation times of water protons in cereals at different stages of cold acclimation were measured using pulse NMR methods. The T(1) and T(2) 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 T(2) 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(1) 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(1) or T(2) 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 Deltav(1/2) or a reduction in relaxation times does not provide evidence for ordering of the bulk of the cell water.