小麦叶片衰老态势核磁共振分析

Investigating Senescence Status of Wheat Leaves by Nuclear Magnetic Resonance

建立了小麦的核磁共振活体检测体系,通过监测小麦叶片的T2弛豫特性、含水率以及叶绿素含量在灌浆中后期的日序变化,发现从叶片衰老初期至降解期,T2弛豫谱幅度和含水率变化不明显,平均T2弛豫时间持续增大,而叶绿素含量逐渐减小;到叶片衰亡期,T2弛豫谱幅度、含水率、平均T2弛豫时间以及叶绿素含量均迅速减小至最小值。由此可见,小麦叶片的T2弛豫谱幅度与含水率具有正相关关系,而平均T2弛豫时间与生理活性有关。最后根据叶片的T2弛豫特性,分析了核磁共振T2弛豫谱、磁共振T1加权成像以及T2加权成像等方法在评价小麦叶片衰老态势方面的特点。

Nuclear magnetic resonance（NMR） technique has been broadly used in probing plant water relations.However,the relationship between NMR parameters and photosynthetic traits is still not clear.An NMR system was constructed to perform non-imaging relaxation measurement or magnetic resonance imaging on wheat non-invasively and non-destructively.It was found that from the onset of leaf senescence to the degradation stage,the average T2relaxation time（T2,mean） increased gradually and the chlorophyll content decreased,while the amplitude（A） of T2relaxation spectrum and water content kept stable.When wheat leaves approached cell death,all of the above mentioned NMR and physiological parameters decreased to its minimum value.It was deduced that A and the water content of wheat leaves were linearly correlated.On the other hand,T2,meanwas related with leaf senescence status.Therefore, non-imaging T2relaxation technique was thought a fast and powerful method to estimate the senescence status of wheat leaf.In addition,T1weighted imaging and T2weighted imaging could represent leaf physiological status directly based on the relaxation property.T1weighted imaging was comparatively time-saving,whereas T2weighted imaging was much more sensitive to leaf aging.