In order to investigate the catholicness of microtubule cycle in higher plants,changes of microtubule orientation in cell division cycle of Sagittaria sagittifolia L.,root tips were detected by the inverted fluorescence microscope and laser scanning confocal microscope,through the techniques of enzymatic digestion and separation of root tip cells after fixation,coomassie brilliant blue staining and indirect immunofluorescence microscopy.The results have shown that a large number of cells without cell walls and their aggregates of S.sagittifolia L.root tips can be gained by enzymatic digestion and separation.Abundant protein and nuclear chromosomes at different mitotic stage can be observed by coomassie brilliant blue staining.Under the observation of immunofluorescence microscopy,there are four basic types of microtubule organization,namely,interphase cortical microtubule,preprophase band microtubule,spindle microtubule and phragmoplast microtubule,which constitute the typical microtubule cycle in dividing cells of higher aquatic plants.The changing similarity between the microtubule cycles of higher aquatic and terrestrial plants has provided a new instance for the notion of plant microtubule cycles.