we have studied the timing of preprophase band ( ppb ) development in the division cycle of onion ( allium cepa l. ) root-tip cells by combinations of immunofluorescence microscopy of microtubules , microspectrophotometry of nuclear dna , and autoradiography of [ ( 3 ) h ] thymidine incorporation during pulse-chase experiments .
C0007634
cells
C0026046
microtubules